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Sample records for airborne disease transmission

  1. Turbulent dispersivity under conditions relevant to airborne disease transmission between laboratory animals

    NASA Astrophysics Data System (ADS)

    Halloran, Siobhan; Wexler, Anthony; Ristenpart, William

    2014-11-01

    Virologists and other researchers who test pathogens for airborne disease transmissibility often place a test animal downstream from an inoculated animal and later determine whether the test animal became infected. Despite the crucial role of the airflow in modulating the pathogen transmission, to date the infectious disease community has paid little attention to the effect of airspeed or turbulence intensity on the probability of transmission. Here we present measurements of the turbulent dispersivity under conditions relevant to experimental tests of airborne disease transmissibility between laboratory animals. We used time lapse photography to visualize the downstream transport and turbulent dispersion of smoke particulates released from a point source downstream of a standard axial fan, thus mimicking the release and transport of expiratory aerosols exhaled by an inoculated animal. We demonstrate that the fan speed counterintuitively has no effect on the downstream plume width, a result replicated with a variety of different fan types and configurations. The results point toward a useful simplification in modeling of airborne disease transmission via fan-generated flows.

  2. Personalized ventilation as a control measure for airborne transmissible disease spread

    PubMed Central

    Pantelic, Jovan; Sze-To, Gin Nam; Tham, Kwok Wai; Chao, Christopher Y. H.; Khoo, Yong Chuan Mike

    2009-01-01

    The protective role of personalized ventilation (PV) against plausible airborne transmissible disease was investigated using cough droplets released from a ‘coughing machine’ simulating the human cough at different distances (1, 1.75 and 3 m) from the PV user. Particle image velocimetry was used to characterize and visualize the interaction between the cough-generated multiphase flow and PV-induced flow in the inhalation zone of the thermal breathing manikin. A dose–response model for unsteady imperfectly mixed environment was used to estimate the reduction in infection risk of two common diseases that can be transmitted by airborne mode. PV was able to both reduce the peak aerosol concentration levels and shorten the exposure time at all the examined injection distances. PV could reduce the infection risks of two diseases, influenza A and tuberculosis, by between 27 and 65 per cent. The protection offered by PV is less effective at a distance of 1.75 m than the other distances, as shown in the risk assessment results, as the PV-generated flow was blown off by the cough-generated flow for the longest time. Results of this study demonstrate the ability of desktop PV to mitigate the infection risk of airborne transmissible disease. PMID:19812074

  3. Personalized ventilation as a control measure for airborne transmissible disease spread.

    PubMed

    Pantelic, Jovan; Sze-To, Gin Nam; Tham, Kwok Wai; Chao, Christopher Y H; Khoo, Yong Chuan Mike

    2009-12-01

    The protective role of personalized ventilation (PV) against plausible airborne transmissible disease was investigated using cough droplets released from a 'coughing machine' simulating the human cough at different distances (1, 1.75 and 3 m) from the PV user. Particle image velocimetry was used to characterize and visualize the interaction between the cough-generated multiphase flow and PV-induced flow in the inhalation zone of the thermal breathing manikin. A dose-response model for unsteady imperfectly mixed environment was used to estimate the reduction in infection risk of two common diseases that can be transmitted by airborne mode. PV was able to both reduce the peak aerosol concentration levels and shorten the exposure time at all the examined injection distances. PV could reduce the infection risks of two diseases, influenza A and tuberculosis, by between 27 and 65 per cent. The protection offered by PV is less effective at a distance of 1.75 m than the other distances, as shown in the risk assessment results, as the PV-generated flow was blown off by the cough-generated flow for the longest time. Results of this study demonstrate the ability of desktop PV to mitigate the infection risk of airborne transmissible disease.

  4. Preventing Airborne Disease Transmission: Review of Methods for Ventilation Design in Health Care Facilities

    PubMed Central

    Aliabadi, Amir A.; Rogak, Steven N.; Bartlett, Karen H.; Green, Sheldon I.

    2011-01-01

    Health care facility ventilation design greatly affects disease transmission by aerosols. The desire to control infection in hospitals and at the same time to reduce their carbon footprint motivates the use of unconventional solutions for building design and associated control measures. This paper considers indoor sources and types of infectious aerosols, and pathogen viability and infectivity behaviors in response to environmental conditions. Aerosol dispersion, heat and mass transfer, deposition in the respiratory tract, and infection mechanisms are discussed, with an emphasis on experimental and modeling approaches. Key building design parameters are described that include types of ventilation systems (mixing, displacement, natural and hybrid), air exchange rate, temperature and relative humidity, air flow distribution structure, occupancy, engineered disinfection of air (filtration and UV radiation), and architectural programming (source and activity management) for health care facilities. The paper describes major findings and suggests future research needs in methods for ventilation design of health care facilities to prevent airborne infection risk. PMID:22162813

  5. Quantification of Shared Air: A Social and Environmental Determinant of Airborne Disease Transmission

    PubMed Central

    Wood, Robin; Morrow, Carl; Ginsberg, Samuel; Piccoli, Elizabeth; Kalil, Darryl; Sassi, Angelina; Walensky, Rochelle P.; Andrews, Jason R.

    2014-01-01

    Background Tuberculosis is endemic in Cape Town, South Africa where a majority of the population become tuberculosis infected before adulthood. While social contact patterns impacting tuberculosis and other respiratory disease spread have been studied, the environmental determinants driving airborne transmission have not been quantified. Methods Indoor carbon dioxide levels above outdoor levels reflect the balance of exhaled breath by room occupants and ventilation. We developed a portable monitor to continuously sample carbon dioxide levels, which were combined with social contact diary records to estimate daily rebreathed litres. A pilot study established the practicality of monitor use up to 48-hours. We then estimated the daily volumes of air rebreathed by adolescents living in a crowded township. Results One hundred eight daily records were obtained from 63 adolescents aged between 12- and 20-years. Forty-five lived in wooden shacks and 18 in brick-built homes with a median household of 4 members (range 2–9). Mean daily volume of rebreathed air was 120.6 (standard error: 8.0) litres/day, with location contributions from household (48%), school (44%), visited households (4%), transport (0.5%) and other locations (3.4%). Independent predictors of daily rebreathed volumes included household type (p = 0.002), number of household occupants (p = 0.021), number of sleeping space occupants (p = 0.022) and winter season (p<0.001). Conclusions We demonstrated the practical measurement of carbon dioxide levels to which individuals are exposed in a sequence of non-steady state indoor environments. A novel metric of rebreathed air volume reflects social and environmental factors associated with airborne infection and can identify locations with high transmission potential. PMID:25181526

  6. [Air-borne disease].

    PubMed

    Lameiro Vilariño, Carmen; del Campo Pérez, Victor M; Alonso Bürger, Susana; Felpeto Nodar, Irene; Guimarey Pérez, Rosa; Pérez Alvarellos, Alberto

    2003-11-01

    Respiratory protection is a factor which worries nursing professionals who take care of patients susceptible of transmitting microorganisms through the air more as every day passes. This type of protection covers the use of surgical or hygienic masks against the transmission of infection by airborne drops to the use of highly effective masks or respirators against the transmission of airborne diseases such as tuberculosis or SARS, a recently discovered disease. The adequate choice of this protective device and its correct use are fundamental in order to have an effective protection for exposed personnel. The authors summarize the main protective respiratory devices used by health workers, their characteristics and degree of effectiveness, as well as the circumstances under which each device is indicated for use. PMID:14705591

  7. Airborne Transmission of Bordetella pertussis

    PubMed Central

    Warfel, Jason M.; Beren, Joel; Merkel, Tod J.

    2012-01-01

    Pertussis is a contagious, acute respiratory illness caused by the bacterial pathogen Bordetella pertussis. Although it is widely believed that transmission of B. pertussis occurs via aerosolized respiratory droplets, no controlled study has ever documented airborne transmission of pertussis. We set out to determine if airborne transmission occurs between infected and naive animals, utilizing the baboon model of pertussis. Our results showed that 100% of exposed naive animals became infected even when physical contact was prevented, demonstrating that pertussis transmission occurs via aerosolized respiratory droplets. PMID:22807521

  8. The application of ultraviolet germicidal irradiation to control transmission of airborne disease: bioterrorism countermeasure.

    PubMed

    Brickner, Philip W; Vincent, Richard L; First, Melvin; Nardell, Edward; Murray, Megan; Kaufman, Will

    2003-01-01

    Bioterrorism is an area of increasing public health concern. The intent of this article is to review the air cleansing technologies available to protect building occupants from the intentional release of bioterror agents into congregate spaces (such as offices, schools, auditoriums, and transportation centers), as well as through outside air intakes and by way of recirculation air ducts. Current available technologies include increased ventilation, filtration, and ultraviolet germicidal irradiation (UVGI) UVGI is a common tool in laboratories and health care facilities, but is not familiar to the public, or to some heating, ventilation, and air conditioning engineers. Interest in UVGI is increasing as concern about a possible malicious release of bioterror agents mounts. Recent applications of UVGI have focused on control of tuberculosis transmission, but a wide range of airborne respiratory pathogens are susceptible to deactivation by UVGI. In this article, the authors provide an overview of air disinfection technologies, and an in-depth analysis of UVGI-its history, applications, and effectiveness. PMID:12690064

  9. The application of ultraviolet germicidal irradiation to control transmission of airborne disease: bioterrorism countermeasure.

    PubMed

    Brickner, Philip W; Vincent, Richard L; First, Melvin; Nardell, Edward; Murray, Megan; Kaufman, Will

    2003-01-01

    Bioterrorism is an area of increasing public health concern. The intent of this article is to review the air cleansing technologies available to protect building occupants from the intentional release of bioterror agents into congregate spaces (such as offices, schools, auditoriums, and transportation centers), as well as through outside air intakes and by way of recirculation air ducts. Current available technologies include increased ventilation, filtration, and ultraviolet germicidal irradiation (UVGI) UVGI is a common tool in laboratories and health care facilities, but is not familiar to the public, or to some heating, ventilation, and air conditioning engineers. Interest in UVGI is increasing as concern about a possible malicious release of bioterror agents mounts. Recent applications of UVGI have focused on control of tuberculosis transmission, but a wide range of airborne respiratory pathogens are susceptible to deactivation by UVGI. In this article, the authors provide an overview of air disinfection technologies, and an in-depth analysis of UVGI-its history, applications, and effectiveness.

  10. Investigation of airborne foot-and-mouth disease virus transmission during low-wind conditions in the early phase of the UK 2001 epidemic

    NASA Astrophysics Data System (ADS)

    Mikkelsen, T.; Alexandersen, S.; Astrup, P.; Champion, H. J.; Donaldson, A. I.; Dunkerley, F. N.; Gloster, J.; Sørensen, J. H.; Thykier-Nielsen, S.

    2003-02-01

    Foot-and-mouth disease (FMD) is a highly contagious viral disease of cloven-hoofed domesticated and wild animals. The highly contagious nature of FMD is a reflection of the wide range of host species, the enormous quantities of virus liberated by infected animals, the range of excretions and secretions which can be infectious, the stability of the virus in the environment, the multiplicity of routes of infection and the very small doses of the virus that can initiate infection. One of the mechanisms of spread is the carriage of droplets and droplet nuclei exhaled in the breath of infected animals. Such spread can be rapid and extensive, and it is known in certain circumstances to have transmitted disease over a distance of several hundred kilometres. During the 2001 FMD epidemic in the United Kingdom (UK), atmospheric dispersion models were applied in real time in order to assess the potential for atmospheric dispersion of the disease. The operational value of such modelling is primarily to identify premises which may have been exposed so that the human resources for surveillance and disease control purposes are employed most effectively. The paper describes the combined modelling techniques and presents the results obtained of detailed analyses performed during the early stages of the UK 2001 epidemic. This paper investigates the potential for disease spread in relation to two outbreaks (Burnside Farm, Heddon-on-the-Wall and Prestwick Hall Farm, Ponteland, Northumberland). A separate paper (Gloster et al., 2002) provides a more detailed analysis of the airborne disease transmission in the vicinity of Burnside Farm. The combined results are consistent with airborne transmission of disease to livestock in the Heddon-on-the Wall area. Local topography may have played a significant role in influencing the pattern of disease spread.

  11. Investigation of airborne foot-and-mouth disease virus transmission during low-wind conditions in the early phase of the UK 2001 epidemic

    NASA Astrophysics Data System (ADS)

    Mikkelsen, T.; Alexandersen, S.; Astrup, P.; Champion, H. J.; Donaldson, A. I.; Dunkerley, F. N.; Gloster, J.; Sørensen, J. H.; Thykier-Nielsen, S.

    2003-11-01

    Foot-and-mouth disease (FMD) is a highly contagious viral disease of cloven-hoofed domesticated and wild animals. The highly contagious nature of FMD is a reflection of the wide range of host species, the enormous quantities of virus liberated by infected animals, the range of excretions and secretions which can be infectious, the stability of the virus in the environment, the multiplicity of routes of infection and the very small doses of the virus that can initiate infection. One of the mechanisms of spread is the carriage of droplets and droplet nuclei exhaled in the breath of infected animals. Such spread can be rapid and extensive, and it is known in certain circumstances to have transmitted disease over a distance of several hundred kilometres. During the 2001 FMD epidemic in the United Kingdom (UK), atmospheric dispersion models were applied in real time in order to assess the potential for atmospheric dispersion of the disease. The operational value of such modelling is primarily to identify premises which may have been exposed so that the human resources for surveillance and disease control purposes are employed most effectively.

    The paper describes the combined modelling techniques and presents the results obtained of detailed analyses performed during the early stages of the UK 2001 epidemic. This paper investigates the potential for disease spread in relation to two outbreaks (Burnside Farm, Heddon-on-the-Wall and Prestwick Hall Farm, Ponteland, Northumberland). A separate paper (Gloster et al., 2002) provides a more detailed analysis of the airborne disease transmission in the vicinity of Burnside Farm.

    The combined results are consistent with airborne transmission of disease to livestock in the Heddon-on-the-Wall area. Local topography may have played a significant role in influencing the pattern of disease spread.

  12. Airborne transmission and precautions: facts and myths.

    PubMed

    Seto, W H

    2015-04-01

    Airborne transmission occurs only when infectious particles of <5 μm, known as aerosols, are propelled into the air. The prevention of such transmission is expensive, requiring N95 respirators and negative pressure isolation rooms. This lecture first discussed whether respiratory viral infections are airborne with reference to published reviews of studies before 2008, comparative trials of surgical masks and N95 respirators, and relevant new experimental studies. However, the most recent experimental study, using naturally infected influenza volunteers as the source, showed negative results from all the manikins that were exposed. Modelling studies by ventilation engineers were then summarized to explain why these results were not unexpected. Second, the systematic review commissioned by the World Health Organization on what constituted aerosol-generating procedures was summarized. From the available evidence, endotracheal intubation either by itself or combined with other procedures (e.g. cardiopulmonary resuscitation or bronchoscopy) was consistently associated with increased risk of transmission by the generation of aerosols. PMID:25578684

  13. Multicarrier airborne ultrasound transmission with piezoelectric transducers.

    PubMed

    Ens, Alexander; Reindl, Leonhard M

    2015-05-01

    In decentralized localization systems, the received signal has to be assigned to the sender. Therefore, longrange airborne ultrasound communication enables the transmission of an identifier of the sender within the ultrasound signal to the receiver. Further, in areas with high electromagnetic noise or electromagnetic free areas, ultrasound communication is an alternative. Using code division multiple access (CDMA) to transmit data is ineffective in rooms due to high echo amplitudes. Further, piezoelectric transducers generate a narrow-band ultrasound signal, which limits the data rate. This work shows the use of multiple carrier frequencies in orthogonal frequency division multiplex (OFDM) and differential quadrature phase shift keying modulation with narrowband piezoelectric devices to achieve a packet length of 2.1 ms. Moreover, the adapted channel coding increases data rate by correcting transmission errors. As a result, a 2-carrier ultrasound transmission system on an embedded system achieves a data rate of approximately 5.7 kBaud. Within the presented work, a transmission range up to 18 m with a packet error rate (PER) of 13% at 10-V supply voltage is reported. In addition, the transmission works up to 22 m with a PER of 85%. Moreover, this paper shows the accuracy of the frame synchronization over the distance. Consequently, the system achieves a standard deviation of 14 μs for ranges up to 10 m.

  14. Multicarrier airborne ultrasound transmission with piezoelectric transducers.

    PubMed

    Ens, Alexander; Reindl, Leonhard M

    2015-05-01

    In decentralized localization systems, the received signal has to be assigned to the sender. Therefore, longrange airborne ultrasound communication enables the transmission of an identifier of the sender within the ultrasound signal to the receiver. Further, in areas with high electromagnetic noise or electromagnetic free areas, ultrasound communication is an alternative. Using code division multiple access (CDMA) to transmit data is ineffective in rooms due to high echo amplitudes. Further, piezoelectric transducers generate a narrow-band ultrasound signal, which limits the data rate. This work shows the use of multiple carrier frequencies in orthogonal frequency division multiplex (OFDM) and differential quadrature phase shift keying modulation with narrowband piezoelectric devices to achieve a packet length of 2.1 ms. Moreover, the adapted channel coding increases data rate by correcting transmission errors. As a result, a 2-carrier ultrasound transmission system on an embedded system achieves a data rate of approximately 5.7 kBaud. Within the presented work, a transmission range up to 18 m with a packet error rate (PER) of 13% at 10-V supply voltage is reported. In addition, the transmission works up to 22 m with a PER of 85%. Moreover, this paper shows the accuracy of the frame synchronization over the distance. Consequently, the system achieves a standard deviation of 14 μs for ranges up to 10 m. PMID:25965683

  15. Some aspects of the airborne transmission of infection

    PubMed Central

    Clark, Raymond P.; de Calcina-Goff, Mervyn L.

    2009-01-01

    The relationship between the human body and the dissemination of potentially pathogenic particles and droplets is described. Airborne transmission of infection in operating theatres and a burns unit and the part played by the human microclimate and its interaction with ventilating air flows is discussed. The mechanisms by which different garment assemblies used for surgery can enhance particle dispersion are illustrated and the way that floor cleaning can increase the concentration of airborne organisms is described. The development of the successful use of ultra-clean air systems in orthopaedic implant surgery is reviewed. Relationships between contact and airborne transmission of disease are explored and ways by which containment strategies and metrics used in pharmaceutical and electronics manufacturing can be applied to the design and monitoring of healthcare areas is discussed. It is suggested that currently available techniques involving architectural, ventilation and operational aspects of healthcare provision, when properly applied, can markedly improve treatment outcomes that may otherwise be compromised by hospital-acquired infections involving both bacteria and viruses. PMID:19815574

  16. An assessment of the airborne route in hepatitis B transmission.

    PubMed

    Petersen, N J

    1980-01-01

    The experimental and epidemiologic evidence for airborne transmission of hepatitis B is inconclusive and our efforts to detect airborne HBsAg or blood in environments where hepatitis B transmission occurs have been uniformly unsuccessful. In the specific areas investigated: dialysis centers, laboratories, and dental operatories, other major routes of transmission that can explain the spread of hepatitis B invariably are present. Therefore, while airborne taansmission is theoretically possible and probably has occurred, at this time its contribution to the overfall hepatitis B problem cannot be quantitated. we fell comfortable in concluding that airborne HBV does not play a major role in hepatitis B transmission and that true airborne infections are probably rare. Because of the fine line airborne transmission from contract transmission via droplets, we feel it important to emphasize the need to take those precautions that protect against the latter. These include the use of gloves where surfaces become contaminated and masks and glasses to protect the eyes, nose and mouth where the possibility of spatter exists.

  17. Spatial dynamics of airborne infectious diseases.

    PubMed

    Robinson, Marguerite; Stilianakis, Nikolaos I; Drossinos, Yannis

    2012-03-21

    Disease outbreaks, such as those of Severe Acute Respiratory Syndrome in 2003 and the 2009 pandemic A(H1N1) influenza, have highlighted the potential for airborne transmission in indoor environments. Respirable pathogen-carrying droplets provide a vector for the spatial spread of infection with droplet transport determined by diffusive and convective processes. An epidemiological model describing the spatial dynamics of disease transmission is presented. The effects of an ambient airflow, as an infection control, are incorporated leading to a delay equation, with droplet density dependent on the infectious density at a previous time. It is found that small droplets (∼0.4μm) generate a negligible infectious force due to the small viral load and the associated duration they require to transmit infection. In contrast, larger droplets (∼4μm) can lead to an infectious wave propagating through a fully susceptible population or a secondary infection outbreak for a localized susceptible population. Droplet diffusion is found to be an inefficient mode of droplet transport leading to minimal spatial spread of infection. A threshold air velocity is derived, above which disease transmission is impaired even when the basic reproduction number R(0) exceeds unity.

  18. Spatial dynamics of airborne infectious diseases.

    PubMed

    Robinson, Marguerite; Stilianakis, Nikolaos I; Drossinos, Yannis

    2012-03-21

    Disease outbreaks, such as those of Severe Acute Respiratory Syndrome in 2003 and the 2009 pandemic A(H1N1) influenza, have highlighted the potential for airborne transmission in indoor environments. Respirable pathogen-carrying droplets provide a vector for the spatial spread of infection with droplet transport determined by diffusive and convective processes. An epidemiological model describing the spatial dynamics of disease transmission is presented. The effects of an ambient airflow, as an infection control, are incorporated leading to a delay equation, with droplet density dependent on the infectious density at a previous time. It is found that small droplets (∼0.4μm) generate a negligible infectious force due to the small viral load and the associated duration they require to transmit infection. In contrast, larger droplets (∼4μm) can lead to an infectious wave propagating through a fully susceptible population or a secondary infection outbreak for a localized susceptible population. Droplet diffusion is found to be an inefficient mode of droplet transport leading to minimal spatial spread of infection. A threshold air velocity is derived, above which disease transmission is impaired even when the basic reproduction number R(0) exceeds unity. PMID:22207025

  19. Aerobiology and Its Role in the Transmission of Infectious Diseases

    PubMed Central

    Fernstrom, Aaron; Goldblatt, Michael

    2013-01-01

    Aerobiology plays a fundamental role in the transmission of infectious diseases. As infectious disease and infection control practitioners continue employing contemporary techniques (e.g., computational fluid dynamics to study particle flow, polymerase chain reaction methodologies to quantify particle concentrations in various settings, and epidemiology to track the spread of disease), the central variables affecting the airborne transmission of pathogens are becoming better known. This paper reviews many of these aerobiological variables (e.g., particle size, particle type, the duration that particles can remain airborne, the distance that particles can travel, and meteorological and environmental factors), as well as the common origins of these infectious particles. We then review several real-world settings with known difficulties controlling the airborne transmission of infectious particles (e.g., office buildings, healthcare facilities, and commercial airplanes), while detailing the respective measures each of these industries is undertaking in its effort to ameliorate the transmission of airborne infectious diseases. PMID:23365758

  20. Role of mechanical ventilation in the airborne transmission of infectious agents in buildings.

    PubMed

    Luongo, J C; Fennelly, K P; Keen, J A; Zhai, Z J; Jones, B W; Miller, S L

    2016-10-01

    Infectious disease outbreaks and epidemics such as those due to SARS, influenza, measles, tuberculosis, and Middle East respiratory syndrome coronavirus have raised concern about the airborne transmission of pathogens in indoor environments. Significant gaps in knowledge still exist regarding the role of mechanical ventilation in airborne pathogen transmission. This review, prepared by a multidisciplinary group of researchers, focuses on summarizing the strengths and limitations of epidemiologic studies that specifically addressed the association of at least one heating, ventilating and/or air-conditioning (HVAC) system-related parameter with airborne disease transmission in buildings. The purpose of this literature review was to assess the quality and quantity of available data and to identify research needs. This review suggests that there is a need for well-designed observational and intervention studies in buildings with better HVAC system characterization and measurements of both airborne exposures and disease outcomes. Studies should also be designed so that they may be used in future quantitative meta-analyses.

  1. Airborne Transmission of Highly Pathogenic H7N1 Influenza Virus in Ferrets

    PubMed Central

    Finch, Courtney; Shao, Hongxia; Angel, Matthew; Chen, Hongjun; Capua, Ilaria; Cattoli, Giovanni; Monne, Isabella

    2014-01-01

    ABSTRACT Avian H7 influenza viruses are recognized as potential pandemic viruses, as personnel often become infected during poultry outbreaks. H7 infections in humans typically cause mild conjunctivitis; however, the H7N9 outbreak in the spring of 2013 has resulted in severe respiratory disease. To date, no H7 viruses have acquired the ability for sustained transmission among humans. Airborne transmission is considered a requirement for the emergence of pandemic influenza, and advanced knowledge of the molecular changes or signature required for transmission would allow early identification of pandemic vaccine seed stocks, screening and stockpiling of antiviral compounds, and eradication efforts focused on flocks harboring threatening viruses. Thus, we sought to determine if a highly pathogenic influenza A H7N1 (A/H7N1) virus with no history of human infection could become capable of airborne transmission among ferrets. We show that after 10 serial passages, A/H7N1 developed the ability to be transmitted to cohoused and airborne contact ferrets. Four amino acid mutations (PB2 T81I, NP V284M, and M1 R95K and Q211K) in the internal genes and a minimal amino acid mutation (K/R313R) in the stalk region of the hemagglutinin protein were associated with airborne transmission. Furthermore, transmission was not associated with loss of virulence. These findings highlight the importance of the internal genes in host adaptation and suggest that natural isolates carrying these mutations be further evaluated. Our results demonstrate that a highly pathogenic avian H7 virus can become capable of airborne transmission in a mammalian host, and they support ongoing surveillance and pandemic H7 vaccine development. IMPORTANCE The major findings of this report are that a highly pathogenic strain of H7N1 avian influenza virus can be adapted to become capable of airborne transmission in mammals without mutations altering receptor specificity. Changes in receptor specificity have been

  2. Airborne infectious disease and the suppression of pulmonary bioaerosols.

    PubMed

    Fiegel, Jennifer; Clarke, Robert; Edwards, David A

    2006-01-01

    The current understanding of airborne pathogen spread in relation to the new methods of suppressing exhaled bioaerosols using safe surface-active materials, such as isotonic saline, is reviewed here. We discuss the physics of bioaerosol generation in the lungs, what is currently known about the relationship between expired bioaerosols and airborne infectious disease and current methods of airborne infectious disease containment. We conclude by reviewing recent experiments that suggest the delivery of isotonic saline can significantly diminish exhaled aerosol--generated from airway lining fluid in the course of natural breathing. We also discuss these implications in relation to airborne infectious disease control.

  3. Effect of an electrostatic space charge system on airborne dust and subsequent potential transmission of microorganisms to broiler breeder pullets by airborne dust.

    PubMed

    Richardson, L J; Mitchell, B W; Wilson, J L; Hofacre, C L

    2003-01-01

    High levels of dust and microorganisms are known to be associated with animal confinement rearing facilities. Many of the microorganisms are carried by dust particles, thus providing an excellent vector for horizontal disease transmission between birds. Two environmentally controlled rooms containing female broiler breeder pullets (n = 300) were used to evaluate the effectiveness of an electrostatic space charge system (ESCS) in reducing airborne dust and gram-negative bacteria levels over an 8-wk period (starting when the birds were 10 wk old). The ESCS was used to evaluate the effectiveness of reducing airborne microorganism levels by charging airborne dust particles and causing the particles to be attracted to grounded surfaces (i.e., walls, floor, equipment). The use of the ESCS resulted in a 64% mean reduction in gram-negative bacteria. Airborne dust levels were reduced an average of 37% over a 1-wk period in the experimental room compared with the control room on the basis of samples taken every 10 min. The reductions of airborne dust and bacteria in this study are comparable with earlier results obtained with the ESCS in commercial hatching cabinets and experimental caged layer rooms, suggesting the system could also be applied to other types of enclosed animal housing. PMID:12713167

  4. Spread of Coxiella burnetii between dairy cattle herds in an enzootic region: modelling contributions of airborne transmission and trade.

    PubMed

    Pandit, Pranav; Hoch, Thierry; Ezanno, Pauline; Beaudeau, François; Vergu, Elisabeta

    2016-04-05

    Q fever, a worldwide zoonotic disease caused by Coxiella burnetii, is a looming concern for livestock and public health. Epidemiological features of inter-herd transmission of C. burnetii in cattle herds by wind and trade of cows are poorly understood. We present a novel dynamic spatial model describing the inter-herd regional spread of C. burnetii in dairy cattle herds, quantifying the ability of airborne transmission and animal trade in C. burnetii propagation in an enzootic region. Among all the new herd infections, 92% were attributed to airborne transmission and the rest to cattle trade. Infections acquired following airborne transmission were shown to cause relatively small and ephemeral intra-herd outbreaks. On the contrary, disease-free herds purchasing an infectious cow experienced significantly higher intra-herd prevalence. The results also indicated that, for short duration, both transmission routes were independent from each other without any synergistic effect. The model outputs applied to the Finistère department in western France showed satisfactory sensitivity (0.71) and specificity (0.80) in predicting herd infection statuses at the end of one year in a neighbourhood of 3 km around expected incident herds, when compared with data. The model developed here thus provides important insights into the spread of C. burnetii between dairy cattle herds and paves the way for implementation and assessment of control strategies.

  5. Spread of Coxiella burnetii between dairy cattle herds in an enzootic region: modelling contributions of airborne transmission and trade.

    PubMed

    Pandit, Pranav; Hoch, Thierry; Ezanno, Pauline; Beaudeau, François; Vergu, Elisabeta

    2016-01-01

    Q fever, a worldwide zoonotic disease caused by Coxiella burnetii, is a looming concern for livestock and public health. Epidemiological features of inter-herd transmission of C. burnetii in cattle herds by wind and trade of cows are poorly understood. We present a novel dynamic spatial model describing the inter-herd regional spread of C. burnetii in dairy cattle herds, quantifying the ability of airborne transmission and animal trade in C. burnetii propagation in an enzootic region. Among all the new herd infections, 92% were attributed to airborne transmission and the rest to cattle trade. Infections acquired following airborne transmission were shown to cause relatively small and ephemeral intra-herd outbreaks. On the contrary, disease-free herds purchasing an infectious cow experienced significantly higher intra-herd prevalence. The results also indicated that, for short duration, both transmission routes were independent from each other without any synergistic effect. The model outputs applied to the Finistère department in western France showed satisfactory sensitivity (0.71) and specificity (0.80) in predicting herd infection statuses at the end of one year in a neighbourhood of 3 km around expected incident herds, when compared with data. The model developed here thus provides important insights into the spread of C. burnetii between dairy cattle herds and paves the way for implementation and assessment of control strategies. PMID:27048416

  6. Amino acid substitutions in the neuraminidase protein of an H9N2 avian influenza virus affect its airborne transmission in chickens.

    PubMed

    Lv, Jing; Wei, Liangmeng; Yang, Yan; Wang, Bingxiao; Liang, Wei; Gao, Yuwei; Xia, Xianzhu; Gao, Lili; Cai, Yumei; Hou, Peiqiang; Yang, Huili; Wang, Airong; Huang, Rong; Gao, Jing; Chai, Tongjie

    2015-01-01

    Cases of H9N2 avian influenza virus (AIV) in poultry are increasing throughout many Eurasian countries, and co-infections with other pathogens have resulted in high morbidity and mortality in poultry. Few studies have investigated the genetic factors of virus airborne transmission which determine the scope of this epidemic. In this study, we used specific-pathogen-free chickens housed in isolators to investigate the airborne transmissibility of five recombinant H9N2 AIV rescued by reverse genetic technology. The results show that airborne transmission of A/Chicken/Shandong/01/2008 (SD01) virus was related to the neuraminidase (NA) gene, and four amino acid mutations (D368E, S370L, E313K and G381D) within the head region of the SD01 NA, reduced virus replication in the respiratory tract of chickens, reduced virus NA activity, and resulted in a loss of airborne transmission ability in chickens. Similarly, reverse mutations of these four amino acids in the NA protein of r01/NASS virus, conferred an airborne transmission ability to the recombinant virus. We conclude that these four NA residues may be significant genetic markers for evaluating potential disease outbreak of H9N2 AIV, and propose that immediate attention should be paid to the airborne transmission of this virus. PMID:25928577

  7. Dynamics of infectious disease transmission by inhalable respiratory droplets.

    PubMed

    Stilianakis, Nikolaos I; Drossinos, Yannis

    2010-09-01

    Transmission of respiratory infectious diseases in humans, for instance influenza, occurs by several modes. Respiratory droplets provide a vector of transmission of an infectious pathogen that may contribute to different transmission modes. An epidemiological model incorporating the dynamics of inhalable respiratory droplets is developed to assess their relevance in the infectious process. Inhalable respiratory droplets are divided into respirable droplets, with droplet diameter less than 10 microm, and inspirable droplets, with diameter in the range 10-100 microm: both droplet classes may be inhaled or settle. Droplet dynamics is determined by their physical properties (size), whereas population dynamics is determined by, among other parameters, the pathogen infectivity and the host contact rates. Three model influenza epidemic scenarios, mediated by different airborne or settled droplet classes, are analysed. The scenarios are distinguished by the characteristic times associated with breathing at contact and with hand-to-face contact. The scenarios suggest that airborne transmission, mediated by respirable droplets, provides the dominant transmission mode in middle and long-term epidemics, whereas inspirable droplets, be they airborne or settled, characterize short-term epidemics with high attack rates. The model neglects close-contact transmission by droplet sprays (direct projection onto facial mucous membranes), retaining close-contact transmission by inspirable droplets.

  8. [Climatic changes and transmissible diseases].

    PubMed

    Amat-Roze, J M

    1998-01-01

    Transmissible disease geography can be defined as the study of the spatial expression of pathogenic processes. The three main elements implicated in this study are environmental conditions affecting biophysical dynamics, political, economic, social, and cultural events, and evolution of pathogenic agents under the influence of the first two factors. A number of pathogenic areas or regions can be delimited in function of different combinations of these factors. These territories are subject to rapid change and variation. Meteorological changes and cycles are contributing factors. However the underlying mechanisms appear to be increasingly affected by human activity. Several disturbing signs have been attributed to man including desertification, drought, and global warming, but the cause-and-effect relationship is unsure. Much research is in progress but resulting data remains contradictory except insofar as to confirm the complexity of atmospheric phenomena. The natural geography of transmissible diseases is affected by these variations but it is mainly the expression of the dialogue between man and nature.

  9. Ionizing air affects influenza virus infectivity and prevents airborne-transmission.

    PubMed

    Hagbom, Marie; Nordgren, Johan; Nybom, Rolf; Hedlund, Kjell-Olof; Wigzell, Hans; Svensson, Lennart

    2015-01-01

    By the use of a modified ionizer device we describe effective prevention of airborne transmitted influenza A (strain Panama 99) virus infection between animals and inactivation of virus (>97%). Active ionizer prevented 100% (4/4) of guinea pigs from infection. Moreover, the device effectively captured airborne transmitted calicivirus, rotavirus and influenza virus, with recovery rates up to 21% after 40 min in a 19 m(3) room. The ionizer generates negative ions, rendering airborne particles/aerosol droplets negatively charged and electrostatically attracts them to a positively charged collector plate. Trapped viruses are then identified by reverse transcription quantitative real-time PCR. The device enables unique possibilities for rapid and simple removal of virus from air and offers possibilities to simultaneously identify and prevent airborne transmission of viruses. PMID:26101102

  10. Ionizing air affects influenza virus infectivity and prevents airborne-transmission

    PubMed Central

    Hagbom, Marie; Nordgren, Johan; Nybom, Rolf; Hedlund, Kjell-Olof; Wigzell, Hans; Svensson, Lennart

    2015-01-01

    By the use of a modified ionizer device we describe effective prevention of airborne transmitted influenza A (strain Panama 99) virus infection between animals and inactivation of virus (>97%). Active ionizer prevented 100% (4/4) of guinea pigs from infection. Moreover, the device effectively captured airborne transmitted calicivirus, rotavirus and influenza virus, with recovery rates up to 21% after 40 min in a 19 m3 room. The ionizer generates negative ions, rendering airborne particles/aerosol droplets negatively charged and electrostatically attracts them to a positively charged collector plate. Trapped viruses are then identified by reverse transcription quantitative real-time PCR. The device enables unique possibilities for rapid and simple removal of virus from air and offers possibilities to simultaneously identify and prevent airborne transmission of viruses. PMID:26101102

  11. Airborne Transmission of Influenza A/H5N1 Virus Between Ferrets

    PubMed Central

    Herfst, Sander; Schrauwen, Eefje J. A.; Linster, Martin; Chutinimitkul, Salin; de Wit, Emmie; Munster, Vincent J.; Sorrell, Erin M.; Bestebroer, Theo M.; Burke, David F.; Smith, Derek J.; Rimmelzwaan, Guus F.; Osterhaus, Albert D. M. E.; Fouchier, Ron A. M.

    2016-01-01

    Highly pathogenic avian influenza A/H5N1 virus can cause morbidity and mortality in humans but thus far has not acquired the ability to be transmitted by aerosol or respiratory droplet (“airborne transmission”) between humans. To address the concern that the virus could acquire this ability under natural conditions, we genetically modified A/H5N1 virus by site-directed mutagenesis and subsequent serial passage in ferrets. The genetically modified A/H5N1 virus acquired mutations during passage in ferrets, ultimately becoming airborne transmissible in ferrets. None of the recipient ferrets died after airborne infection with the mutant A/H5N1 viruses. Four amino acid substitutions in the host receptor-binding protein hemagglutinin, and one in the polymerase complex protein basic polymerase 2, were consistently present in airborne-transmitted viruses. The transmissible viruses were sensitive to the antiviral drug oseltamivir and reacted well with antisera raised against H5 influenza vaccine strains. Thus, avian A/H5N1 influenza viruses can acquire the capacity for airborne transmission between mammals without recombination in an intermediate host and therefore constitute a risk for human pandemic influenza. PMID:22723413

  12. Transmission of ebola virus disease: an overview.

    PubMed

    Rewar, Suresh; Mirdha, Dashrath

    2014-01-01

    Ebola is a viral illness of which the initial symptoms can include a sudden fever, intense weakness, muscle pain and a sore throat, according to the World Health Organization (WHO). Airborne transmission of Ebola virus has been hypothesized but not demonstrated in humans. Ebola is not spread through the air or by water, or in general, by food. However, in Africa, Ebola may be spread as a result of handling bushmeat (wild animals hunted for food) and contact with infected bats. The disease infects humans through close contact with infected animals, including chimpanzees, fruit bats, and forest antelope. Ebola virus can be transmitted by direct contact with blood, bodily fluids, or skin of patients with or who died of Ebola virus disease. As of late October 2014, the World Health Organization reported 13,567 suspected cases and 4922 deaths, although the agency believes that this substantially understates the magnitude of the outbreak. Experimental vaccines and treatments for Ebola are under development, but they have not yet been fully tested for safety or effectiveness.

  13. An experimental hut study to quantify the effect of DDT and airborne pyrethroids on entomological parameters of malaria transmission

    PubMed Central

    2014-01-01

    Background Current malaria vector control programmes rely on insecticides with rapid contact toxicity. However, spatial repellents can also be applied to reduce man-vector contact, which might ultimately impact malaria transmission. The aim of this study was to quantify effects of airborne pyrethroids from coils and DDT used an indoor residual spray (IRS) on entomological parameters that influence malaria transmission. Methods The effect of Transfluthrin and Metofluthrin coils compared to DDT on house entry, exit and indoor feeding behaviour of Anopheles gambiae sensu lato were measured in experimental huts in the field and in the semi-field. Outcomes were deterrence - reduction in house entry of mosquitoes; irritancy or excito-repellency – induced premature exit of mosquitoes; blood feeding inhibition and effect on mosquito fecundity. Results Transfluthrin coils, Metofluthrin coils and DDT reduced human vector contact through deterrence by 38%, 30% and 8%, respectively and induced half of the mosquitoes to leave huts before feeding (56%, 55% and 48%, respectively). Almost all mosquitoes inside huts with Metofluthrin and Transfluthrin coils and more than three quarters of mosquitoes in the DDT hut did not feed, almost none laid eggs and 67%, 72% and 70% of all mosquitoes collected from Transfluthrin, Metofluthrin and DDT huts, respectively had died after 24 hours. Conclusion This study highlights that airborne pyrethroids and DDT affect a range of anopheline mosquito behaviours that are important parameters in malaria transmission, namely deterrence, irritancy/excito-repellency and blood-feeding inhibition. These effects are in addition to significant toxicity and reduced mosquito fecundity that affect mosquito densities and, therefore, provide community protection against diseases for both users and non-users. Airborne insecticides and freshly applied DDT had similar effects on deterrence, irritancy and feeding inhibition. Therefore, it is suggested that

  14. Prion diseases as transmissible zoonotic diseases.

    PubMed

    Lee, Jeongmin; Kim, Su Yeon; Hwang, Kyu Jam; Ju, Young Ran; Woo, Hee-Jong

    2013-02-01

    Prion diseases, also called transmissible spongiform encephalopathies (TSEs), lead to neurological dysfunction in animals and are fatal. Infectious prion proteins are causative agents of many mammalian TSEs, including scrapie (in sheep), chronic wasting disease (in deer and elk), bovine spongiform encephalopathy (BSE; in cattle), and Creutzfeldt-Jakob disease (CJD; in humans). BSE, better known as mad cow disease, is among the many recently discovered zoonotic diseases. BSE cases were first reported in the United Kingdom in 1986. Variant CJD (vCJD) is a disease that was first detected in 1996, which affects humans and is linked to the BSE epidemic in cattle. vCJD is presumed to be caused by consumption of contaminated meat and other food products derived from affected cattle. The BSE epidemic peaked in 1992 and decreased thereafter; this decline is continuing sharply owing to intensive surveillance and screening programs in the Western world. However, there are still new outbreaks and/or progression of prion diseases, including atypical BSE, and iatrogenic CJD and vCJD via organ transplantation and blood transfusion. This paper summarizes studies on prions, particularly on prion molecular mechanisms, BSE, vCJD, and diagnostic procedures. Risk perception and communication policies of the European Union for the prevention of prion diseases are also addressed to provide recommendations for appropriate government policies in Korea. PMID:24159531

  15. Prion Diseases as Transmissible Zoonotic Diseases

    PubMed Central

    Lee, Jeongmin; Kim, Su Yeon; Hwang, Kyu Jam; Ju, Young Ran; Woo, Hee-Jong

    2013-01-01

    Prion diseases, also called transmissible spongiform encephalopathies (TSEs), lead to neurological dysfunction in animals and are fatal. Infectious prion proteins are causative agents of many mammalian TSEs, including scrapie (in sheep), chronic wasting disease (in deer and elk), bovine spongiform encephalopathy (BSE; in cattle), and Creutzfeldt–Jakob disease (CJD; in humans). BSE, better known as mad cow disease, is among the many recently discovered zoonotic diseases. BSE cases were first reported in the United Kingdom in 1986. Variant CJD (vCJD) is a disease that was first detected in 1996, which affects humans and is linked to the BSE epidemic in cattle. vCJD is presumed to be caused by consumption of contaminated meat and other food products derived from affected cattle. The BSE epidemic peaked in 1992 and decreased thereafter; this decline is continuing sharply owing to intensive surveillance and screening programs in the Western world. However, there are still new outbreaks and/or progression of prion diseases, including atypical BSE, and iatrogenic CJD and vCJD via organ transplantation and blood transfusion. This paper summarizes studies on prions, particularly on prion molecular mechanisms, BSE, vCJD, and diagnostic procedures. Risk perception and communication policies of the European Union for the prevention of prion diseases are also addressed to provide recommendations for appropriate government policies in Korea. PMID:24159531

  16. Pneumococcal Disease: Risk Factors and Transmission

    MedlinePlus

    ... Foundation for Infectious Diseases Sepsis Risk Factors and Transmission Recommend on Facebook Tweet Share Compartir On this ... the brain and spinal cord) Who smoke cigarettes Transmission Pneumococcal bacteria spread from person-to-person by ...

  17. Sexual transmission of Lyme disease: challenging the tickborne disease paradigm.

    PubMed

    Stricker, Raphael B; Middelveen, Marianne J

    2015-01-01

    Lyme disease caused by the spirochete Borrelia burgdorferi has become a major worldwide epidemic. In this article, we explore the clinical, epidemiological and experimental evidence for sexual transmission of Lyme disease in animal models and humans. Although the likelihood of sexual transmission of the Lyme spirochete remains speculative, the possibility of Lyme disease transmission via intimate human contact merits further study.

  18. A qualitative exploration of social contact patterns relevant to airborne infectious diseases in northwest Bangladesh.

    PubMed

    Feenstra, Sabiena G; Nahar, Quamrun; Pahan, David; Oskam, Linda; Richardus, Jan Hendrik

    2013-12-01

    In South Asia, the burden of infectious diseases is high. Socioeconomically and culturally-defined social interaction patterns are considered to be an important determinant in the spread of diseases that are transmitted through person-to-person contact. Understanding of the contact patterns in this region can be helpful to develop more effective control measures. Focus group discussions were used in exploring social contact patterns in northwest Bangladesh. The patterns were assessed for perceived relevance to the spread of airborne infectious diseases, with special focus on diseases, like leprosy and tuberculosis, in which the role of social determinants is well-recognized. Highly-relevant social contact patterns inside the home and the neighbourhood, across age and sex groups, were reported in all group discussions. Outside the home, women and girls reported relevant contacts limited to the close neighbourhood while men mentioned high relevant contacts beyond. This implies that, in theory, infectious diseases can easily be transmitted across age and sex groups in and around the home. Adult men might play a role in the transmission of airborne infectious diseases from outside this confined area since only this group reported highly-relevant social contacts beyond the home. This concept needs further exploration but control programmes in the South Asian region could benefit from considering differences in social contact patterns by gender for risk assessments and planning of preventive interventions. PMID:24592583

  19. A Qualitative Exploration of Social Contact Patterns Relevant to Airborne Infectious Diseases in Northwest Bangladesh

    PubMed Central

    Nahar, Quamrun; Pahan, David; Oskam, Linda; Richardus, Jan Hendrik

    2013-01-01

    In South Asia, the burden of infectious diseases is high. Socioeconomically and culturally-defined social interaction patterns are considered to be an important determinant in the spread of diseases that are transmitted through person-to-person contact. Understanding of the contact patterns in this region can be helpful to develop more effective control measures. Focus group discussions were used in exploring social contact patterns in northwest Bangladesh. The patterns were assessed for perceived relevance to the spread of airborne infectious diseases, with special focus on diseases, like leprosy and tuberculosis, in which the role of social determinants is well-recognized. Highly-relevant social contact patterns inside the home and the neighbourhood, across age and sex groups, were reported in all group discussions. Outside the home, women and girls reported relevant contacts limited to the close neighbourhood while men mentioned high relevant contacts beyond. This implies that, in theory, infectious diseases can easily be transmitted across age and sex groups in and around the home. Adult men might play a role in the transmission of airborne infectious diseases from outside this confined area since only this group reported highly-relevant social contacts beyond the home. This concept needs further exploration but control programmes in the South Asian region could benefit from considering differences in social contact patterns by gender for risk assessments and planning of preventive interventions. PMID:24592583

  20. Airborne lidar measurements of smoke plume distribution, vertical transmission, and particle size.

    PubMed

    Uthe, E E; Morley, B M; Nielsen, N B

    1982-02-01

    Observations were made of a dense smoke plume downwind from a forest fire using the ALPHA-1 two-wavelength downward-looking airborne lidar system. Facsimile displays derived from lidar signatures depict plume dimensions, boundary layer height, and underlying terrain elevation. Surface returns are interpreted in terms of vertical transmission as function of cross-plume distance. Results show significantly greater plume attenuation at 0.53-microm wavelength than at 1.06-microm, indicating ~0.1-microm mean particle diameters or the presence of gaseous constituents that absorb the visible radiation. These results demonstrate the potential of multiple-wavelength airborne lidar for quantitative analysis of atmospheric particulate and gaseous constituents. PMID:20372478

  1. Possible Airborne Person-to-Person Transmission of Mycobacterium bovis - Nebraska 2014-2015.

    PubMed

    Buss, Bryan F; Keyser-Metobo, Alison; Rother, Julie; Holtz, Laura; Gall, Kristin; Jereb, John; Murphy, Caitlin N; Iwen, Peter C; Robbe-Austerman, Suelee; Holcomb, Melissa A; Infield, Pat

    2016-03-01

    Mycobacterium bovis, one of several mycobacteria of the M. tuberculosis complex, is a global zoonotic pathogen that primarily infects cattle. Humans become infected by consuming unpasteurized dairy products from infected cows; possible person-to-person airborne transmission has also been reported. In April 2014, a man in Nebraska who was born in Mexico was determined to have extensive pulmonary tuberculosis (TB) caused by M. bovis after experiencing approximately 3 months of cough and fever. Four months later, a U.S.-born Hispanic girl from a nearby town who had been ill for 4-5 months was also determined to have pulmonary TB caused by M. bovis. The only social connection between the two patients was attendance at the same church, and no common dietary exposure was identified. Both patients had pulmonary cavities on radiography and acid-fast bacilli (AFB) on sputum-smear microscopy, indicators of being contagious. Whole-genome sequencing results of the isolates were nearly indistinguishable. Initial examination of 181 contacts determined that 39 (22%) had latent infection: 10 (42%) of 24 who had close exposure to either patient, 28 (28%) of 100 who were exposed to one or both patients in church, and one (2%) of 57 exposed to the second patient at a school. Latent infection was diagnosed in six contacts on follow-up examination, 2 months after an initial negative test result, for an overall latent infection rate of 25%. No infected contacts recalled consuming unpasteurized dairy products, and none had active TB disease at the initial or secondary examination. Persons who have M. bovis TB should be asked about consumption of unpasteurized dairy products, and contact investigations should follow the same guidance as for M. tuberculosis TB. PMID:26938831

  2. A comprehensive breath plume model for disease transmission via expiratory aerosols.

    PubMed

    Halloran, Siobhan K; Wexler, Anthony S; Ristenpart, William D

    2012-01-01

    The peak in influenza incidence during wintertime in temperate regions represents a longstanding, unresolved scientific question. One hypothesis is that the efficacy of airborne transmission via aerosols is increased at lower humidities and temperatures, conditions that prevail in wintertime. Recent work with a guinea pig model by Lowen et al. indicated that humidity and temperature do modulate airborne influenza virus transmission, and several investigators have interpreted the observed humidity dependence in terms of airborne virus survivability. This interpretation, however, neglects two key observations: the effect of ambient temperature on the viral growth kinetics within the animals, and the strong influence of the background airflow on transmission. Here we provide a comprehensive theoretical framework for assessing the probability of disease transmission via expiratory aerosols between test animals in laboratory conditions. The spread of aerosols emitted from an infected animal is modeled using dispersion theory for a homogeneous turbulent airflow. The concentration and size distribution of the evaporating droplets in the resulting "Gaussian breath plume" are calculated as functions of position, humidity, and temperature. The overall transmission probability is modeled with a combination of the time-dependent viral concentration in the infected animal and the probability of droplet inhalation by the exposed animal downstream. We demonstrate that the breath plume model is broadly consistent with the results of Lowen et al., without invoking airborne virus survivability. The results also suggest that, at least for guinea pigs, variation in viral kinetics within the infected animals is the dominant factor explaining the increased transmission probability observed at lower temperatures.

  3. Critical Behavior in Cellular Automata Animal Disease Transmission Model

    NASA Astrophysics Data System (ADS)

    Morley, P. D.; Chang, Julius

    Using cellular automata model, we simulate the British Government Policy (BGP) in the 2001 foot and mouth epidemic in Great Britain. When clinical symptoms of the disease appeared in a farm, there is mandatory slaughter (culling) of all livestock in an infected premise (IP). Those farms in the neighboring of an IP (contiguous premise, CP), are also culled, aka nearest neighbor interaction. Farms where the disease may be prevalent from animal, human, vehicle or airborne transmission (dangerous contact, DC), are additionally culled, aka next-to-nearest neighbor interactions and lightning factor. The resulting mathematical model possesses a phase transition, whereupon if the physical disease transmission kernel exceeds a critical value, catastrophic loss of animals ensues. The nonlocal disease transport probability can be as low as 0.01% per day and the disease can still be in the high mortality phase. We show that the fundamental equation for sustainable disease transport is the criticality equation for neutron fission cascade. Finally, we calculate that the percentage of culled animals that are actually healthy is ≈30%.

  4. Ebola (Ebola Virus Disease): Transmission

    MedlinePlus

    ... Search The CDC Cancel Submit Search The CDC Ebola (Ebola Virus Disease) Note: Javascript is disabled or is ... message, please visit this page: About CDC.gov . Ebola (Ebola Virus Disease) About Ebola Questions & Answers 2014 ...

  5. Effect of electrostatic space charge on reduction of airborne transmission of Salmonella and other bacteria in broiler breeders in production and their progeny.

    PubMed

    Richardson, L J; Hofacre, C L; Mitchell, B W; Wilson, J L

    2003-01-01

    Salmonella in birds is a concern because of the human foodborne illness associated with the consumption of poultry meat and eggs. One of the methods of transmission of Salmonella within a flock can be by the air. Therefore, we used reduction of transmission of Salmonella to monitor the effectiveness of the electrostatic space charge system (ESCS). During the average broiler breeder laying cycle of 40 wk, a large amount of dust becomes airborne and accumulates on walls, ceiling, and equipment. Many microorganisms adhere to these dust particles, making dust an excellent vector for horizontal disease transmission between birds. We used two environmentally controlled rooms containing commercial broiler breeders to evaluate the effectiveness of an ESCS that produced a strong negative electrostatic charge to reduce airborne dust and, subsequently, microorganism levels. The ESCS caused the dust to become negatively charged, therefore moving to the grounded floor in the treatment room. The use of the ESCS resulted in a significant reduction (P < 0.0001, 61% reduction) in airborne dust concentration levels, which resulted in a significant reduction (P < 0.0001, 76% reduction) in total airborne bacteria and gram-negative bacteria (48% reduction) in the treatment room. Significant reductions (P < 0.05) of gram-negative bacteria (63% reduction) on the egg collection belts were also recorded in the treatment room, which resulted in a significant reduction (P < 0.0001) of gram-negative bacteria (28% reduction) on the eggshell surface. The ESCS treatment resulted in fewer Salmonella enteritidis-positive hens and their progeny from the treatment room due to reductions of dust and airborne bacteria. In addition, this significant reduction in bacteria on the eggshell surface should result in less bacteria in the day-old chicks, therefore better early chick livability. There was no significant difference (P > 0.05) in egg production, male or female body weights, mortality, or

  6. Transmissible Spongiform Encephalopathies (Prion Diseases)

    MedlinePlus

    ... when brain tissue is viewed under a microscope. Creutzfeldt-Jakob disease (CJD) is the most well-known of the ... and Worldwide NINDS Clinical Trials Organizations Column1 Column2 Creutzfeldt-Jakob Disease (CJD) Foundation Inc. 341 W. 38th Street, Suite ...

  7. A Comprehensive Breath Plume Model for Disease Transmission via Expiratory Aerosols

    NASA Astrophysics Data System (ADS)

    Halloran, S. K.; Wexler, A. S.; Ristenpart, W. D.

    2012-11-01

    The peak in influenza incidence during wintertime represents a longstanding unresolved scientific question. One hypothesis is that the efficacy of airborne transmission via aerosols is increased at low humidity and temperature, conditions that prevail in wintertime. Recent experiments with guinea pigs suggest that transmission is indeed maximized at low humidity and temperature, a finding which has been widely interpreted in terms of airborne influenza virus survivability. This interpretation, however, neglects the effect of the airflow on the transmission probability. Here we provide a comprehensive model for assessing the probability of disease transmission via expiratory aerosols between test animals in laboratory conditions. The spread of aerosols emitted from an infected animal is modeled using dispersion theory for a homogeneous turbulent airflow. The concentration and size distribution of the evaporating droplets in the resulting ``Gaussian breath plume'' are calculated as functions of downstream position. We demonstrate that the breath plume model is broadly consistent with the guinea pig experiments, without invoking airborne virus survivability. Moreover, the results highlight the need for careful characterization of the airflow in airborne transmission experiments.

  8. Airborne spread of foot-and-mouth disease - model intercomparison

    SciTech Connect

    Gloster, J; Jones, A; Redington, A; Burgin, L; Sorensen, J H; Turner, R; Dillon, M; Hullinger, P; Simpson, M; Astrup, P; Garner, G; Stewart, P; D'Amours, R; Sellers, R; Paton, D

    2008-09-04

    Foot-and-mouth disease is a highly infectious vesicular disease of cloven-hoofed animals caused by foot-and-mouth disease virus. It spreads by direct contact between animals, by animal products (milk, meat and semen), by mechanical transfer on people or fomites and by the airborne route - with the relative importance of each mechanism depending on the particular outbreak characteristics. Over the years a number of workers have developed or adapted atmospheric dispersion models to assess the risk of foot-and-mouth disease virus spread through the air. Six of these models were compared at a workshop hosted by the Institute for Animal Health/Met Office during 2008. A number of key issues emerged from the workshop and subsequent modelling work: (1) in general all of the models predicted similar directions for 'at risk' livestock with much of the remaining differences strongly related to differences in the meteorological data used; (2) determination of an accurate sequence of events is highly important, especially if the meteorological conditions vary substantially during the virus emission period; and (3) differences in assumptions made about virus release, environmental fate, and subsequent infection can substantially modify the size and location of the downwind risk area. Close relationships have now been established between participants, which in the event of an outbreak of disease could be readily activated to supply advice or modelling support.

  9. Mechanism and calculation of the niche effect in airborne sound transmission.

    PubMed

    Vinokur, Roman

    2006-04-01

    The goal is to interpret and calculate the "niche effect" for the airborne sound transmission through a specimen mounted inside an aperture in the wall between the source and receiving reverberation rooms. The low-frequency sound insulation is known to be worse for the specimen placed at the center than for the specimen mounted at either edge of the aperture. As shown, the aperture with a tested specimen can be simulated at low frequencies as a triple partition where the middle element is the specimen and the role of the edge leaves is played by the air masses entrained at the aperture edges. With a centrally located specimen, such a triple system is symmetric and has two main natural frequencies close together. In this case, the resonant transmission is higher than for the edge arrangement simulated as a double system with one natural frequency. Analogous resonant phenomena are known to reduce the low-frequency transmission loss for symmetric triple windows or solid walls with identical air gaps and lightweight boards on both sides. The theoretical results obtained for the mechanical and acoustical models are in a good agreement with the experimental data. PMID:16642835

  10. Identification, Characterization, and Natural Selection of Mutations Driving Airborne Transmission of A/H5N1 virus

    PubMed Central

    Linster, Martin; van Boheemen, Sander; de Graaf, Miranda; Schrauwen, Eefje J. A.; Lexmond, Pascal; Mänz, Benjamin; Bestebroer, Theo M.; Baumann, Jan; van Riel, Debby; Rimmelzwaan, Guus F.; Osterhaus, Albert D.M.E.; Matrosovich, Mikhail; Fouchier, Ron A. M.; Herfst, Sander

    2014-01-01

    SUMMARY Recently, A/H5N1 influenza viruses were shown to acquire airborne transmissibility between ferrets upon targeted mutagenesis and virus passage. The critical genetic changes in airborne A/Indonesia/5/05 were not yet identified. Here, five substitutions proved to be sufficient to determine this airborne transmission phenotype. Substitutions in PB1 and PB2 collectively caused enhanced transcription and virus replication. One substitution increased HA thermostability and lowered the pH of membrane fusion. Two substitutions independently changed HA binding preference from α2,3 linked to α2,6 linked sialic acid receptors. The loss of a glycosylation site in HA enhanced overall binding to receptors. The acquired substitutions emerged early during ferret passage as minor variants and became dominant rapidly. Identification of substitutions that are essential for airborne transmission of avian influenza viruses between ferrets and their associated phenotypes advances our fundamental understanding of virus transmission and will increase the value of future surveillance programs and public health risk assessments. PMID:24725402

  11. Breast milk transmission of viral disease.

    PubMed

    Stiehm, E R; Keller, M A

    2001-01-01

    Breast milk transmission of maternal viral infection is well established for CMV and HIV-1. In the case of CMV, this usually does not pose a risk to the infant since serious disease is prevented by placentally transferred maternal antibody. However, in HIV infection, breast-feeding increases the risk of maternal-fetal transmission by about 25% with late breast-feeding (after six months of age) constituting a particular risk. In other maternal viral diseases, e.g., other herpes viruses, parvovirus, hepatitis A, B and C, and rubella, the virus is often demonstrated in the breast milk, but transmission is very rare. The highest risk is during an acute viral infection at the time of birth, since the breast milk has a high titer of virus, and a lack of antibody to neutralize the organism. PMID:11795036

  12. Using special functions to model the propagation of airborne diseases

    NASA Astrophysics Data System (ADS)

    Bolaños, Daniela

    2014-06-01

    Some special functions of the mathematical physics are using to obtain a mathematical model of the propagation of airborne diseases. In particular we study the propagation of tuberculosis in closed rooms and we model the propagation using the error function and the Bessel function. In the model, infected individual emit pathogens to the environment and this infect others individuals who absorb it. The evolution in time of the concentration of pathogens in the environment is computed in terms of error functions. The evolution in time of the number of susceptible individuals is expressed by a differential equation that contains the error function and it is solved numerically for different parametric simulations. The evolution in time of the number of infected individuals is plotted for each numerical simulation. On the other hand, the spatial distribution of the pathogen around the source of infection is represented by the Bessel function K0. The spatial and temporal distribution of the number of infected individuals is computed and plotted for some numerical simulations. All computations were made using software Computer algebra, specifically Maple. It is expected that the analytical results that we obtained allow the design of treatment rooms and ventilation systems that reduce the risk of spread of tuberculosis.

  13. Droplets and modes of respiratory disease transmission

    NASA Astrophysics Data System (ADS)

    Bourouiba, Lydia

    2014-11-01

    Direct observation of violent expirations such as sneezes and coughs events reveal that such flows are multiphase turbulent buoyant clouds with suspended droplets of various sizes. The effects of ambient conditions indoors, such as moisture and temperature, coupled with the water content of such clouds are key in shaping the pathogen footprint emitted by potentially sick individuals. Such pathogen footprint can change the patterns of respiratory disease transmission. We discuss how the fluid dynamics of violent expirations can help inform how.

  14. Airborne Transmission of Melioidosis to Humans from Environmental Aerosols Contaminated with B. pseudomallei

    PubMed Central

    Lin, Hsi-Hsun; Liu, Pei-Ju; Ni, Wei-Fan; Hsueh, Pei-Tan; Liang, Shih-Hsiung; Chen, Chialin; Chen, Ya-Lei

    2015-01-01

    Melioidosis results from an infection with the soil-borne pathogen Burkholderia pseudomallei, and cases of melioidosis usually cluster after rains or a typhoon. In an endemic area of Taiwan, B. pseudomallei is primarily geographically distributed in cropped fields in the northwest of this area, whereas melioidosis cases are distributed in a densely populated district in the southeast. We hypothesized that contaminated cropped fields generated aerosols contaminated with B. pseudomallei, which were carried by a northwesterly wind to the densely populated southeastern district. We collected soil and aerosol samples from a 72 km2 area of land, including the melioidosis-clustered area and its surroundings. Aerosols that contained B. pseudomallei-specific TTSS (type III secretion system) ORF2 DNA were well distributed in the endemic area but were rare in the surrounding areas during the rainy season. The concentration of this specific DNA in aerosols was positively correlated with the incidence of melioidosis and the appearance of a northwesterly wind. Moreover, the isolation rate in the superficial layers of the contaminated cropped field in the northwest was correlated with PCR positivity for aerosols collected from the southeast over a 2-year period. According to pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) analyses, PFGE Type Ia (ST58) was the predominant pattern linking the molecular association among soil, aerosol and human isolates. Thus, the airborne transmission of melioidosis moves from the contaminated soil to aerosols and/or to humans in this endemic area. PMID:26061639

  15. Growth and airborne transmission of cell-sorted life cycle stages of Pneumocystis carinii.

    PubMed

    Martinez, Anna; Halliez, Marie C M; Aliouat, El Moukhtar; Chabé, Magali; Standaert-Vitse, Annie; Fréalle, Emilie; Gantois, Nausicaa; Pottier, Muriel; Pinon, Anthony; Dei-Cas, Eduardo; Aliouat-Denis, Cécile-Marie

    2013-01-01

    Pneumocystis organisms are airborne opportunistic pathogens that cannot be continuously grown in culture. Consequently, the follow-up of Pneumocystis stage-to-stage differentiation, the sequence of their multiplication processes as well as formal identification of the transmitted form have remained elusive. The successful high-speed cell sorting of trophic and cystic forms is paving the way for the elucidation of the complex Pneumocystis life cycle. The growth of each sorted Pneumocystis stage population was followed up independently both in nude rats and in vitro. In addition, by setting up a novel nude rat model, we attempted to delineate which cystic and/or trophic forms can be naturally aerially transmitted from host to host. The results showed that in axenic culture, cystic forms can differentiate into trophic forms, whereas trophic forms are unable to evolve into cystic forms. In contrast, nude rats inoculated with pure trophic forms are able to produce cystic forms and vice versa. Transmission experiments indicated that 12 h of contact between seeder and recipient nude rats was sufficient for cystic forms to be aerially transmitted. In conclusion, trophic- to cystic-form transition is a key step in the proliferation of Pneumocystis microfungi because the cystic forms (but not the trophic forms) can be transmitted by aerial route from host to host. PMID:24223207

  16. Chagas' Disease: Pregnancy and Congenital Transmission

    PubMed Central

    Hernández, Roberto

    2014-01-01

    Chagas disease is a chronic infection that kills approximately 12,000 people a year. Mass migration of chronically infected and asymptomatic persons has caused globalization of Chagas disease and has made nonvectorial infection, including vertical and blood-borne transmission, more of a threat to human communities than vectorial infection. To control transmission, it is essential to test all pregnant women living in endemic countries and all pregnant women having migrated from, or having lived in, endemic countries. All children born to seropositive mothers should be tested not only within the first month of life but also at ~6 months and ~12 months of age. The diagnosis is made by identification of the parasite in blood before the age of 6 months and by identification of the parasite in blood and/or positive serology after 10 months of age. Follow up for a year is essential as a significant proportion of cases are initially negative and are only detected at a later stage. If the condition is diagnosed and treated early, the clinical response is excellent and the majority of cases are cured. PMID:24949443

  17. Prevention of disease transmission during flexible laryngoscopy.

    PubMed

    Muscarella, Lawrence F

    2007-10-01

    The medical literature was reviewed to evaluate the risk of disease transmission and nosocomial infection associated with flexible laryngoscopes. These instruments have been reported to be contaminated with blood, body fluids, organic debris, and potentially pathogenic microorganisms during routine clinical use. Failure to reprocess properly a flexible laryngoscope may, therefore, result in patient-to-patient disease transmission. Different types of biocidal agents, including 70% isopropyl alcohol, quaternary ammonium compounds, and 2% glutaraldehyde have been reported to be used to disinfect flexible laryngoscopes. A logic, or algorithm, was developed to evaluate the adequacy of these and other types of biocidal agents used during instrument reprocessing. This review determined that flexible laryngoscopes are semicritical instruments that require high-level disinfection (or sterilization) to prevent nosocomial infection. Whereas 70% isopropyl alcohol, quaternary ammonium compounds, and other products that achieve intermediate-level or low-level disinfection are contraindicated for reprocessing flexible laryngoscopes, 2% glutaraldehyde and other products that achieve high-level disinfection (or sterilization) are recommended for reprocessing these instruments to prevent nosocomial infection. A formal set of step-by-step guidelines for reprocessing flexible laryngoscopes is provided. Use of a disposable sheath to cover and protect the flexible laryngoscope from contamination during clinical use is discussed.

  18. How Ambient Humidity May Affect the Transmission of Viral Infectious Diseases

    NASA Astrophysics Data System (ADS)

    Yang, Wan; Marr, Linsey; Elankumaran, Subbiah

    2013-04-01

    Viral infectious diseases such as influenza have been a great burden to public health. The airborne transmission route is an important venue for the spread of many respiratory viral diseases. Many airborne viruses have been shown to be sensitive to ambient humidity, yet the mechanisms responsible for this phenomenon remain elusive. A thorough understanding of this phenomenon may provide insight into the temporal and spatial distribution of diseases. For instance, studies have repeatedly suggested ambient humidity as an important environmental determinant in the transmission of influenza in temperate regions. Further, knowing how to optimize humidity so as to minimize virus survival may have practical implications for disease prevention. In this talk, we will discuss multiple mechanisms that may account for the association between humidity and viability of viruses in aerosols, including water activity, surface inactivation, salt toxicity, and conformational changes to the virus in response to varying pH. As a case study, we will discuss our work on the effect of relative humidity (RH) on survival of influenza A virus (IAV) and how it may contribute to the transmission patterns of seasonal flu around the world. We measured the change in viability of IAV in droplets at various RHs. Results suggest three potential regimes defined by humidity: physiological (~100% RH) with high viability, concentrated (~50% to near 100% RH) with lower viability, and dry (<~50% RH) with high viability. Based on these results, we propose a mechanistic basis for the dependence of IAV's transmission on humidity. In temperate regions, the increase in influenza activity in winter may be due to enhanced transmission via the aerosol route thanks to IAV's higher viability in droplets at low RH. In tropical regions, transmission could be enhanced due to high viability of IAV at extremely high RH (rainy season), as observed in our study, possibly through both the aerosol route and the contact

  19. Interrupting Chagas disease transmission in Venezuela.

    PubMed

    Aché, A; Matos, A J

    2001-01-01

    The interruption of vectorial transmission of Chagas disease in Venezuela is attributed to the combined effects of ongoing entomoepidemiological surveillance, ongoing house spraying with residual insecticides and the concurrent building and modification of rural houses in endemic areas during almost five decades. The original endemic areas which totaled 750,000 km(2), have been reduced to 365,000 km(2). During 1958-1968, initial entomological evaluations carried out showed that the house infestation index ranged between 60-80%, the house infection index at 8-11% and a house density index of 30-50 triatomine bugs per house. By 1990-98, these indexes were further reduced to 1.6-4.0%, 0.01-0.6% and 3-4 bugs per house respectively. The overall rural population seroprevalence has declined from 44.5% (95% C.I.: 43.4-45.3%) to 9.2% (95% C.I.: 9.0-9.4%) for successive grouped periods from 1958 to 1998. The annual blood donor prevalence is firmly established below 1%. The population at risk of infection has been estimated to be less than four million. Given that prevalence rates are stable and appropriate for public health programmes, consideration has been given to potential biases that may distort results such as: a) geographical differences in illness or longevity of patients; b) variations in levels of ascertainment; c) variations in diagnostic criteria; and d) variations in population structure, mainly due to appreciable population migration. The endemic areas with continuous transmission are now mainly confined to piedmonts, as well as patchy foci in higher mountainous ranges, where the exclusive vector is Rhodnius prolixus. There is also an unstable area, of which landscapes are made up of grasslands with scattered broad-leaved evergreen trees and costal plains, where transmission is very low and occasional outbreaks are reported.

  20. Space-time airborne disease mapping applied to detect specific behaviour of varicella in Valencia, Spain.

    PubMed

    Iftimi, Adina; Montes, Francisco; Santiyán, Ana Míguez; Martínez-Ruiz, Francisco

    2015-01-01

    Airborne diseases are one of humanity's most feared sicknesses and have regularly caused concern among specialists. Varicella is an airborne disease which usually affects children before the age of 10. Because of its nature, varicella gives rise to interesting spatial, temporal and spatio-temporal patterns. This paper studies spatio-temporal exploratory analysis tools to detect specific behaviour of varicella in the city of Valencia, Spain, from 2008 to 2013. These methods have shown a significant association between the spatial and the temporal component, confirmed by the space-time models applied to the data. High relative risk of varicella is observed in economically disadvantaged regions, areas less involved in vaccination programmes.

  1. Collection, Storage and Real-Time Transmission of Housekeeping and Instrument Data Aboard Manned NASA Airborne Science Platforms

    NASA Astrophysics Data System (ADS)

    Van Gilst, D. P.; Sorenson, C. E.

    2011-12-01

    Multi-instrument aircraft-based science campaigns require a baseline level of housekeeping service to record and distribute real time data, including timing signals, aircraft state and air data. As campaigns have become more sophisticated with greater integration between aircraft, ground instrumentation, satellites and forecasters in locations around the world, the scope of the services provided by the facility data systems on NASA's airborne science aircraft have increased to include situational awareness displays, real-time interchange of data between instruments and aircraft, and ingest of data to assist in real-time targeting of flights. As the scope of services has expanded, it has become increasingly important to provide standardized interfaces to experimenters to minimize integration complexity, and to make services sufficiently reliable for mission operations to depend upon them. Within the NASA airborne science program in recent years this has been provided by systems based around the core of the REVEAL/NASDAT system, with additional services including satellite communications, data display and ingest of outside data being provided by a mix of custom and COTS hardware and software. With a strong emphasis on transmission of data over industry standard IP and ethernet based networks, this system has been proven on numerous highly diverse missions on the DC-8 over the last 4 years and is being replicated on other NASA Airborne Science Platforms.

  2. Comparison of different detection methods for citrus greening disease based on airborne multispectral and hyperspectral imagery

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Citrus greening or Huanglongbing (HLB) is a devastating disease spread in many citrus groves since first found in 2005 in Florida. Multispectral (MS) and hyperspectral (HS) airborne images of citrus groves in Florida were taken to detect citrus greening infected trees in 2007 and 2010. Ground truthi...

  3. Relating phylogenetic trees to transmission trees of infectious disease outbreaks.

    PubMed

    Ypma, Rolf J F; van Ballegooijen, W Marijn; Wallinga, Jacco

    2013-11-01

    Transmission events are the fundamental building blocks of the dynamics of any infectious disease. Much about the epidemiology of a disease can be learned when these individual transmission events are known or can be estimated. Such estimations are difficult and generally feasible only when detailed epidemiological data are available. The genealogy estimated from genetic sequences of sampled pathogens is another rich source of information on transmission history. Optimal inference of transmission events calls for the combination of genetic data and epidemiological data into one joint analysis. A key difficulty is that the transmission tree, which describes the transmission events between infected hosts, differs from the phylogenetic tree, which describes the ancestral relationships between pathogens sampled from these hosts. The trees differ both in timing of the internal nodes and in topology. These differences become more pronounced when a higher fraction of infected hosts is sampled. We show how the phylogenetic tree of sampled pathogens is related to the transmission tree of an outbreak of an infectious disease, by the within-host dynamics of pathogens. We provide a statistical framework to infer key epidemiological and mutational parameters by simultaneously estimating the phylogenetic tree and the transmission tree. We test the approach using simulations and illustrate its use on an outbreak of foot-and-mouth disease. The approach unifies existing methods in the emerging field of phylodynamics with transmission tree reconstruction methods that are used in infectious disease epidemiology.

  4. A Cough Aerosol Simulator for the Study of Disease Transmission by Human Cough-Generated Aerosols

    PubMed Central

    Lindsley, William G.; Reynolds, Jeffrey S.; Szalajda, Jonathan V.; Noti, John D.; Beezhold, Donald H.

    2015-01-01

    Aerosol particles expelled during human coughs are a potential pathway for infectious disease transmission. However, the importance of airborne transmission is unclear for many diseases. To better understand the role of cough aerosol particles in the spread of disease and the efficacy of different types of protective measures, we constructed a cough aerosol simulator that produces a humanlike cough in a controlled environment. The simulated cough has a 4.2 l volume and is based on coughs recorded from influenza patients. In one configuration, the simulator produces a cough aerosol containing particles from 0.1 to 100 µm in diameter with a volume median diameter (VMD) of 8.5 µm and a geometric standard deviation (GSD) of 2.9. In a second configuration, the cough aerosol has a size range of 0.1–30 µm, a VMD of 3.4 µm, and a GSD of 2.3. The total aerosol volume expelled during each cough is 68 µl. By generating a controlled and reproducible artificial cough, the simulator allows us to test different ventilation, disinfection, and personal protection scenarios. The system can be used with live pathogens, including influenza virus, which allows isolation precautions used in the healthcare field to be tested without risk of exposure for workers or patients. The information gained from tests with the simulator will help to better understand the transmission of infectious diseases, develop improved techniques for infection control, and improve safety for healthcare workers and patients. PMID:26500387

  5. A Novel Method for Assessment of Light Transmissivity in Forest Canopy from Full-Waveform Airborne LiDAR Data

    NASA Astrophysics Data System (ADS)

    Milenković, Milutin; Wagner, Wolfgang; Hollaus, Markus; Ressl, Camillo; Pfeifer, Norbert

    2016-04-01

    Air- and space-borne 2D imaging in visible and infrared domain of electromagnetic spectrum have been proven to be a reliable remote sensing techniques for forest monitoring and mapping. However, in contrast to the ranging techniques, 2D imaging over forest can not distinguish backscattering contributing from scattering elements at different ranges, e.g. from the forest canopy and the forest floor. Light transmissivity is a wavelength and directionally depended physical parameter which quantifies loss of light while traveling trough forest canopy, and thus, figures as a parameter in radiative transfer models when the scattering from these forest components should be quantified. This work proposes a novel method to derive the transmissivity of forest canopy based on small-footprint, full-waveform airborne LiDAR data. The method explores the energy balance at the ground boundary in the water cloud model applied on individual Gaussian clusters. The transmissivity map derived by the method proposed showed plausible results in comparison with orthophotos and ground images.

  6. Space-time airborne disease mapping applied to detect specific behaviour of varicella in Valencia, Spain.

    PubMed

    Iftimi, Adina; Montes, Francisco; Santiyán, Ana Míguez; Martínez-Ruiz, Francisco

    2015-01-01

    Airborne diseases are one of humanity's most feared sicknesses and have regularly caused concern among specialists. Varicella is an airborne disease which usually affects children before the age of 10. Because of its nature, varicella gives rise to interesting spatial, temporal and spatio-temporal patterns. This paper studies spatio-temporal exploratory analysis tools to detect specific behaviour of varicella in the city of Valencia, Spain, from 2008 to 2013. These methods have shown a significant association between the spatial and the temporal component, confirmed by the space-time models applied to the data. High relative risk of varicella is observed in economically disadvantaged regions, areas less involved in vaccination programmes. PMID:26530821

  7. White Band Disease transmission in the threatened coral, Acropora cervicornis

    PubMed Central

    Gignoux-Wolfsohn, S. A.; Marks, Christopher J.; Vollmer, Steven V.

    2012-01-01

    The global rise in coral diseases has severely impacted coral reef ecosystems, yet often little is known about these diseases, including how they are transmitted. White Band Disease (WBD), for example, has caused unparalleled declines in live Acropora cover, spreading rapidly throughout the Caribbean by unknown means. Here we test four putative modes of WBD transmission to the staghorn coral Acropora cervicornis: two animal vectors (Coralliophila abbreviata and C. caribaea) and waterborne transmission to intact and injured coral tissues. Using aquarium-based infection experiments, we determine that C. abbreviata, but not C. caribaea, acts as both a vector and reservoir for transmission of the WBD pathogen. We also demonstrate waterborne transmission to injured, but not intact staghorn coral tissues. The combination of transmission by both animal vectors and through the water column helps explain how WBD is spread locally and across the Caribbean. PMID:23150775

  8. Analysis of a dengue disease transmission model.

    PubMed

    Esteva, L; Vargas, C

    1998-06-15

    A model for the transmission of dengue fever in a constant human population and variable vector population is discussed. A complete global analysis is given, which uses the results of the theory of competitive systems and stability of periodic orbits, to establish the global stability of the endemic equilibrium. The control measures of the vector population are discussed in terms of the threshold condition, which governs the existence and stability of the endemic equilibrium.

  9. Bat Predation by Cercopithecus Monkeys: Implications for Zoonotic Disease Transmission.

    PubMed

    Tapanes, Elizabeth; Detwiler, Kate M; Cords, Marina

    2016-06-01

    The relationship between bats and primates, which may contribute to zoonotic disease transmission, is poorly documented. We provide the first behavioral accounts of predation on bats by Cercopithecus monkeys, both of which are known to harbor zoonotic disease. We witnessed 13 bat predation events over 6.5 years in two forests in Kenya and Tanzania. Monkeys sometimes had prolonged contact with the bat carcass, consuming it entirely. All predation events occurred in forest-edge or plantation habitat. Predator-prey relations between bats and primates are little considered by disease ecologists, but may contribute to transmission of zoonotic disease, including Ebolavirus. PMID:27138290

  10. Human prion diseases: surgical lessons learned from iatrogenic prion transmission.

    PubMed

    Bonda, David J; Manjila, Sunil; Mehndiratta, Prachi; Khan, Fahd; Miller, Benjamin R; Onwuzulike, Kaine; Puoti, Gianfranco; Cohen, Mark L; Schonberger, Lawrence B; Cali, Ignazio

    2016-07-01

    The human prion diseases, or transmissible spongiform encephalopathies, have captivated our imaginations since their discovery in the Fore linguistic group in Papua New Guinea in the 1950s. The mysterious and poorly understood "infectious protein" has become somewhat of a household name in many regions across the globe. From bovine spongiform encephalopathy (BSE), commonly identified as mad cow disease, to endocannibalism, media outlets have capitalized on these devastatingly fatal neurological conditions. Interestingly, since their discovery, there have been more than 492 incidents of iatrogenic transmission of prion diseases, largely resulting from prion-contaminated growth hormone and dura mater grafts. Although fewer than 9 cases of probable iatrogenic neurosurgical cases of Creutzfeldt-Jakob disease (CJD) have been reported worldwide, the likelihood of some missed cases and the potential for prion transmission by neurosurgery create considerable concern. Laboratory studies indicate that standard decontamination and sterilization procedures may be insufficient to completely remove infectivity from prion-contaminated instruments. In this unfortunate event, the instruments may transmit the prion disease to others. Much caution therefore should be taken in the absence of strong evidence against the presence of a prion disease in a neurosurgical patient. While the Centers for Disease Control and Prevention (CDC) and World Health Organization (WHO) have devised risk assessment and decontamination protocols for the prevention of iatrogenic transmission of the prion diseases, incidents of possible exposure to prions have unfortunately occurred in the United States. In this article, the authors outline the historical discoveries that led from kuru to the identification and isolation of the pathological prion proteins in addition to providing a brief description of human prion diseases and iatrogenic forms of CJD, a brief history of prion disease nosocomial transmission

  11. Targeting Transmission Pathways for Emerging Zoonotic Disease Surveillance and Control

    PubMed Central

    Loh, Elizabeth H.; Zambrana-Torrelio, Carlos; Olival, Kevin J.; Bogich, Tiffany L.; Johnson, Christine K.; Mazet, Jonna A. K.; Karesh, William

    2015-01-01

    Abstract We used literature searches and a database of all reported emerging infectious diseases (EIDs) to analyze the most important transmission pathways (e.g., vector-borne, aerosol droplet transmitted) for emerging zoonoses. Our results suggest that at the broad scale, the likelihood of transmission occurring through any one pathway is approximately equal. However, the major transmission pathways for zoonoses differ widely according to the specific underlying drivers of EID events (e.g., land-use change, agricultural intensification). These results can be used to develop better targeting of surveillance for, and more effective control of newly emerged zoonoses in regions under different underlying pressures that drive disease emergence. PMID:26186515

  12. Infectious disease in animal metapopulations: the importance of environmental transmission

    PubMed Central

    Park, Andrew W

    2012-01-01

    Motivated by an array of infectious diseases that threaten wildlife populations, a simple metapopulation model (subpopulations connected by animal movement) is developed, which allows for both movement-based and environmental transmission. The model demonstrates that for a range of plausible parameterizations of environmental transmission, increased movement rate of animals between discrete habitats can lead to a decrease in the overall proportion of sites that are occupied. This can limit the ability of the rescue effect to ensure locally extinct populations become recolonized and can drive metapopulations down in size so that extinction by mechanisms other than disease may become more likely. It further highlights that, in the context of environmental transmission, the environmental persistence time of pathogens and the probability of acquiring infection by environmental transmission can affect host metapopulations both qualitatively and quantitatively. Additional spillover sources of infection from alternate reservoir hosts are also included in the model and a synthesis of all three types of transmission, acting alone or in combination, is performed revealing that movement-based transmission is the only necessary condition for a decline in the proportion of occupied sites with increasing movement rate, but that the presence of other types of transmission can reverse this qualitative result. By including the previously neglected role of environmental transmission, this work contributes to the general discussion of when dispersal by wild animals is beneficial or detrimental to populations experiencing infectious disease. PMID:22957148

  13. Infectious disease in animal metapopulations: the importance of environmental transmission.

    PubMed

    Park, Andrew W

    2012-07-01

    Motivated by an array of infectious diseases that threaten wildlife populations, a simple metapopulation model (subpopulations connected by animal movement) is developed, which allows for both movement-based and environmental transmission. The model demonstrates that for a range of plausible parameterizations of environmental transmission, increased movement rate of animals between discrete habitats can lead to a decrease in the overall proportion of sites that are occupied. This can limit the ability of the rescue effect to ensure locally extinct populations become recolonized and can drive metapopulations down in size so that extinction by mechanisms other than disease may become more likely. It further highlights that, in the context of environmental transmission, the environmental persistence time of pathogens and the probability of acquiring infection by environmental transmission can affect host metapopulations both qualitatively and quantitatively. Additional spillover sources of infection from alternate reservoir hosts are also included in the model and a synthesis of all three types of transmission, acting alone or in combination, is performed revealing that movement-based transmission is the only necessary condition for a decline in the proportion of occupied sites with increasing movement rate, but that the presence of other types of transmission can reverse this qualitative result. By including the previously neglected role of environmental transmission, this work contributes to the general discussion of when dispersal by wild animals is beneficial or detrimental to populations experiencing infectious disease.

  14. Epidemiology and Transmission Dynamics of West Nile Virus Disease

    PubMed Central

    Komar, Nicholas; Nasci, Roger S.; Montgomery, Susan P.; O'Leary, Daniel R.; Campbell, Grant L.

    2005-01-01

    From 1937 until 1999, West Nile virus (WNV) garnered scant medical attention as the cause of febrile illness and sporadic encephalitis in parts of Africa, Asia, and Europe. After the surprising detection of WNV in New York City in 1999, the virus has spread dramatically westward across the United States, southward into Central America and the Caribbean, and northward into Canada, resulting in the largest epidemics of neuroinvasive WNV disease ever reported. From 1999 to 2004, >7,000 neuroinvasive WNV disease cases were reported in the United States. In 2002, WNV transmission through blood transfusion and organ transplantation was described for the first time, intrauterine transmission was first documented, and possible transmission through breastfeeding was reported. This review highlights new information regarding the epidemiology and dynamics of WNV transmission, providing a new platform for further research into preventing and controlling WNV disease. PMID:16102302

  15. The main sceneries of Chagas disease transmission. The vectors, blood and oral transmissions - A comprehensive review

    PubMed Central

    Coura, José Rodrigues

    2015-01-01

    This review deals with transmission of Trypanosoma cruzi by the most important domestic vectors, blood transfusion and oral intake. Among the vectors, Triatoma infestans, Panstrongylus megistus, Rhodnius prolixus, Triatoma dimidiata, Triatoma brasiliensis, Triatoma pseudomaculata, Triatoma sordida, Triatoma maculata, Panstrongylus geniculatus, Rhodnius ecuadoriensis and Rhodnius pallescens can be highlighted. Transmission of Chagas infection, which has been brought under control in some countries in South and Central America, remains a great challenge, particularly considering that many endemic countries do not have control over blood donors. Even more concerning is the case of non-endemic countries that receive thousands of migrants from endemic areas that carry Chagas disease, such as the United States of America, in North America, Spain, in Europe, Japan, in Asia, and Australia, in Oceania. In the Brazilian Amazon Region, since Shaw et al. (1969) described the first acute cases of the disease caused by oral transmission, hundreds of acute cases of the disease due to oral transmission have been described in that region, which is today considered to be endemic for oral transmission. Several other outbreaks of acute Chagas disease by oral transmission have been described in different states of Brazil and in other South American countries. PMID:25466622

  16. The Ebb and Flow of Airborne Pathogens: Monitoring and Use in Disease Management Decisions.

    PubMed

    Mahaffee, Walter F; Stoll, Rob

    2016-05-01

    Perhaps the earliest form of monitoring the regional spread of plant disease was a group of growers gathering together at the market and discussing what they see in their crops. This type of reporting continues to this day through regional extension blogs, by crop consultants and more formal scouting of sentential plots in the IPM PIPE network (http://www.ipmpipe.org/). As our knowledge of plant disease epidemiology has increased, we have also increased our ability to detect and monitor the presence of pathogens and use this information to make management decisions in commercial production systems. The advent of phylogenetics, next-generation sequencing, and nucleic acid amplification technologies has allowed for development of sensitive and accurate assays for pathogen inoculum detection and quantification. The application of these tools is beginning to change how we manage diseases with airborne inoculum by allowing for the detection of pathogen movement instead of assuming it and by targeting management strategies to the early phases of the epidemic development when there is the greatest opportunity to reduce the rate of disease development. While there are numerous advantages to using data on inoculum presence to aid management decisions, there are limitations in what the data represent that are often unrecognized. In addition, our understanding of where and how to effectively monitor airborne inoculum is limited. There is a strong need to improve our knowledge of the mechanisms that influence inoculum dispersion across scales as particles move from leaf to leaf, and everything in between.

  17. The Ebb and Flow of Airborne Pathogens: Monitoring and Use in Disease Management Decisions.

    PubMed

    Mahaffee, Walter F; Stoll, Rob

    2016-05-01

    Perhaps the earliest form of monitoring the regional spread of plant disease was a group of growers gathering together at the market and discussing what they see in their crops. This type of reporting continues to this day through regional extension blogs, by crop consultants and more formal scouting of sentential plots in the IPM PIPE network (http://www.ipmpipe.org/). As our knowledge of plant disease epidemiology has increased, we have also increased our ability to detect and monitor the presence of pathogens and use this information to make management decisions in commercial production systems. The advent of phylogenetics, next-generation sequencing, and nucleic acid amplification technologies has allowed for development of sensitive and accurate assays for pathogen inoculum detection and quantification. The application of these tools is beginning to change how we manage diseases with airborne inoculum by allowing for the detection of pathogen movement instead of assuming it and by targeting management strategies to the early phases of the epidemic development when there is the greatest opportunity to reduce the rate of disease development. While there are numerous advantages to using data on inoculum presence to aid management decisions, there are limitations in what the data represent that are often unrecognized. In addition, our understanding of where and how to effectively monitor airborne inoculum is limited. There is a strong need to improve our knowledge of the mechanisms that influence inoculum dispersion across scales as particles move from leaf to leaf, and everything in between. PMID:27003505

  18. Transmission of occupational disease to family contacts.

    PubMed

    Knishkowy, B; Baker, E L

    1986-01-01

    As recognition of occupational illness increases, the scope of health problems related to work widens. An important area of concern is the worker's family, which has been shown to be at increased risk of disease attributable to the hazards previously thought to be relevant only to the worker. Such "para-occupational" disease occurs particularly in spouses and children through transport by the worker of hazardous materials from the worksite into the home. The most common vehicle has been contaminated work clothing brought home for cleaning. Outbreaks of severe illness caused by lead, beryllium, asbestos, and other compounds have been traced to home contamination by industrial dust. In this review, we describe reports of "para-occupational" illness that demonstrate the importance of early recognition by medical professionals of this cause of illness and of strict control of the dissemination of hazardous materials outside the workplace.

  19. Spatiotemporal relationships between disease development and airborne inoculum in unmanaged and managed Botrytis leaf blight epidemics.

    PubMed

    Carisse, O; Savary, S; Willocquet, L

    2008-01-01

    Comparatively little quantitative information is available on both the spatial and temporal relationships that develop between airborne inoculum and disease intensity during the course of aerially spread epidemics. Botrytis leaf blight and Botrytis squamosa airborne inoculum were analyzed over space and time during 2 years (2002 and 2004) in a nonprotected experimental field, using a 6 x 8 lattice of quadrats of 10 x 10 m each. A similar experiment was conducted in 2004 and 2006 in a commercial field managed for Botrytis leaf blight using a 5 x 5 lattice of quadrats of 25 x 25 m each. Each quadrat was monitored weekly for lesion density (LD) and aerial conidium concentration (ACC). The adjustment of the Taylor's power law showed that heterogeneity in both LD and ACC generally increased with increasing mean. Unmanaged epidemics were characterized in either year, with aggregation indices derived from SADIE (Spatial Analysis by Distance Indices). For LD, the aggregation indices suggested a random pattern of disease early in the season, followed by an aggregated pattern in the second part of the epidemic. The index of aggregation for ACC in 2002 was significantly greater than 1 at only one date, while it was significantly greater than 1 at most sampling dates in 2004. In both years and for both variables, positive trends in partial autocorrelation were observed mainly for a spatial lag of 1. In 2002, the overall pattern of partial autocorrelations over sampling dates was similar for LD and ACC with no significant partial autocorrelation during the first part of the epidemic, followed by a period with significant positive autocorrelation, and again no autocorrelation on the last three sampling dates. In 2004, there was no significant positive autocorrelation for LD at most sampling dates while for ACC, there was a fluctuation between significant and non-significant positive correlation over sampling dates. There was a significant spatial correlation between ACC at given

  20. Spatial Heterogeneity, Host Movement and Mosquito-Borne Disease Transmission

    PubMed Central

    Acevedo, Miguel A.; Prosper, Olivia; Lopiano, Kenneth; Ruktanonchai, Nick; Caughlin, T. Trevor; Martcheva, Maia; Osenberg, Craig W.; Smith, David L.

    2015-01-01

    Mosquito-borne diseases are a global health priority disproportionately affecting low-income populations in tropical and sub-tropical countries. These pathogens live in mosquitoes and hosts that interact in spatially heterogeneous environments where hosts move between regions of varying transmission intensity. Although there is increasing interest in the implications of spatial processes for mosquito-borne disease dynamics, most of our understanding derives from models that assume spatially homogeneous transmission. Spatial variation in contact rates can influence transmission and the risk of epidemics, yet the interaction between spatial heterogeneity and movement of hosts remains relatively unexplored. Here we explore, analytically and through numerical simulations, how human mobility connects spatially heterogeneous mosquito populations, thereby influencing disease persistence (determined by the basic reproduction number R0), prevalence and their relationship. We show that, when local transmission rates are highly heterogeneous, R0 declines asymptotically as human mobility increases, but infection prevalence peaks at low to intermediate rates of movement and decreases asymptotically after this peak. Movement can reduce heterogeneity in exposure to mosquito biting. As a result, if biting intensity is high but uneven, infection prevalence increases with mobility despite reductions in R0. This increase in prevalence decreases with further increase in mobility because individuals do not spend enough time in high transmission patches, hence decreasing the number of new infections and overall prevalence. These results provide a better basis for understanding the interplay between spatial transmission heterogeneity and human mobility, and their combined influence on prevalence and R0. PMID:26030769

  1. Deer density and disease prevalence influence transmission of Chronic Wasting Disease in White-tailed Deer

    USGS Publications Warehouse

    Samuel, Michael D.; Richards, Bryan J.; Storm, Daniel J.; Rolley, Robert E.; Shelton, Paul; Nicholas S. Keuler,; Timothy R. Van Deelen,

    2013-01-01

    Host-parasite dynamics and strategies for managing infectious diseases of wildlife depend on the functional relationship between disease transmission rates and host density. However, the disease transmission function is rarely known for free-living wildlife, leading to uncertainty regarding the impacts of diseases on host populations and effective control actions. We evaluated the influence of deer density, landscape features, and soil clay content on transmission of chronic wasting disease (CWD) in young (<2-year-old) white-tailed deer (Odocoileus virginianus) in south-central Wisconsin, USA. We evaluated how frequency-dependent, density-dependent, and intermediate transmission models predicted CWD incidence rates in harvested yearling deer. An intermediate transmission model, incorporating both disease prevalence and density of infected deer, performed better than simple density- and frequency-dependent models. Our results indicate a combination of social structure, non-linear relationships between infectious contact and deer density, and distribution of disease among groups are important factors driving CWD infection in young deer. The landscape covariates % deciduous forest cover and forest edge density also were positively associated with infection rates, but soil clay content had no measurable influences on CWD transmission. Lack of strong density-dependent transmission rates indicates that controlling CWD by reducing deer density will be difficult. The consequences of non-linear disease transmission and aggregation of disease on cervid populations deserves further consideration.

  2. Kingella kingae: Carriage, Transmission, and Disease

    PubMed Central

    2015-01-01

    SUMMARY Kingella kingae is a common etiology of pediatric bacteremia and the leading agent of osteomyelitis and septic arthritis in children aged 6 to 36 months. This Gram-negative bacterium is carried asymptomatically in the oropharynx and disseminates by close interpersonal contact. The colonized epithelium is the source of bloodstream invasion and dissemination to distant sites, and certain clones show significant association with bacteremia, osteoarthritis, or endocarditis. Kingella kingae produces an RTX (repeat-in-toxin) toxin with broad-spectrum cytotoxicity that probably facilitates mucosal colonization and persistence of the organism in the bloodstream and deep body tissues. With the exception of patients with endocardial involvement, children with K. kingae diseases often show only mild symptoms and signs, necessitating clinical acumen. The isolation of K. kingae on routine solid media is suboptimal, and detection of the bacterium is significantly improved by inoculating exudates into blood culture bottles and the use of PCR-based assays. The organism is generally susceptible to antibiotics that are administered to young patients with joint and bone infections. β-Lactamase production is clonal, and the local prevalence of β-lactamase-producing strains is variable. If adequately and promptly treated, invasive K. kingae infections with no endocardial involvement usually run a benign clinical course. PMID:25567222

  3. [Effect of parting surfaces on the transmission of airborne organisms at junctions between areas of different hygienic standards].

    PubMed

    Burchard, H U; Ohgke, H; Beckert, J

    1985-12-01

    Parting surfaces between areas having different standards of hygienic requirements, represent naturally the weak points in the hygienic conception of operating theatres. These boundary areas between the operation room on the one hand and the adjoining entrance lock for the staff on the other are of specific interest in this connection. While opening the connecting doors, dust particles may be whirled up due to turbulence, thermic, constructional and other effects, which are difficult to be identified and may then settle down directly on the operating area after reaching there from the entrance lock through the airways. Since bacteria are in most cases attached to particles, it may be assumed that each air flow loaded with dust particles is also a potential carrier of air-borne germs (contact germs----contaminated dust particles----air borne germs----settling germs). Therefore, the present paper is to be understood as a contribution towards the application of methods for identifying air-borne routes of infection in the operating area and finding ways and means for their elimination. In comparison with the investigations done by Esdorn and Kanz during simulated and operating activities respectively, the experiments described in this paper have been carried out while the operating theatre was not running. It is to be assumed that even under these tranquil conditions, parting surfaces appear to act as permanent disturbing factors. Transmission of germs from the entrance lock for the staff to the operating room is only then possible, if the doors suffer functional disturbance and the entrance lock is found hygienically in objectionable condition. Functional measures regarding construction aim, therefore, at the principle of clear-cut separation of the clean side from the unclean in the design and running of operating theatres, as specified in the guidelines of the Bundesgesundheitsamt. The constructional conception of entrance lock can contribute to achieving almost

  4. Zoonotic Transmission of Waterborne Disease: A Mathematical Model.

    PubMed

    Waters, Edward K; Hamilton, Andrew J; Sidhu, Harvinder S; Sidhu, Leesa A; Dunbar, Michelle

    2016-01-01

    Waterborne parasites that infect both humans and animals are common causes of diarrhoeal illness, but the relative importance of transmission between humans and animals and vice versa remains poorly understood. Transmission of infection from animals to humans via environmental reservoirs, such as water sources, has attracted attention as a potential source of endemic and epidemic infections, but existing mathematical models of waterborne disease transmission have limitations for studying this phenomenon, as they only consider contamination of environmental reservoirs by humans. This paper develops a mathematical model that represents the transmission of waterborne parasites within and between both animal and human populations. It also improves upon existing models by including animal contamination of water sources explicitly. Linear stability analysis and simulation results, using realistic parameter values to describe Giardia transmission in rural Australia, show that endemic infection of an animal host with zoonotic protozoa can result in endemic infection in human hosts, even in the absence of person-to-person transmission. These results imply that zoonotic transmission via environmental reservoirs is important. PMID:26733222

  5. Vector Blood Meals and Chagas Disease Transmission Potential, United States

    PubMed Central

    Dorn, Patricia L.; Hobson, Julia; de la Rua, Nicholas M.; Lucero, David E.; Klotz, John H.; Schmidt, Justin O.; Klotz, Stephen A.

    2012-01-01

    A high proportion of triatomine insects, vectors for Trypanosoma cruzi trypanosomes, collected in Arizona and California and examined using a novel assay had fed on humans. Other triatomine insects were positive for T. cruzi parasite infection, which indicates that the potential exists for vector transmission of Chagas disease in the United States. PMID:22469536

  6. Ecology and Transmission of Buruli Ulcer Disease: A Systematic Review

    PubMed Central

    Merritt, Richard W.; Walker, Edward D.; Small, Pamela L. C.; Wallace, John R.; Johnson, Paul D. R.; Benbow, M. Eric; Boakye, Daniel A.

    2010-01-01

    Buruli ulcer is a neglected emerging disease that has recently been reported in some countries as the second most frequent mycobacterial disease in humans after tuberculosis. Cases have been reported from at least 32 countries in Africa (mainly west), Australia, Southeast Asia, China, Central and South America, and the Western Pacific. Large lesions often result in scarring, contractual deformities, amputations, and disabilities, and in Africa, most cases of the disease occur in children between the ages of 4–15 years. This environmental mycobacterium, Mycobacterium ulcerans, is found in communities associated with rivers, swamps, wetlands, and human-linked changes in the aquatic environment, particularly those created as a result of environmental disturbance such as deforestation, dam construction, and agriculture. Buruli ulcer disease is often referred to as the “mysterious disease” because the mode of transmission remains unclear, although several hypotheses have been proposed. The above review reveals that various routes of transmission may occur, varying amongst epidemiological setting and geographic region, and that there may be some role for living agents as reservoirs and as vectors of M. ulcerans, in particular aquatic insects, adult mosquitoes or other biting arthropods. We discuss traditional and non-traditional methods for indicting the roles of living agents as biologically significant reservoirs and/or vectors of pathogens, and suggest an intellectual framework for establishing criteria for transmission. The application of these criteria to the transmission of M. ulcerans presents a significant challenge. PMID:21179505

  7. The Transmissibility of Sexually Transmitted Diseases in Sexually Abused Children.

    ERIC Educational Resources Information Center

    Hammerschlag, Margaret R.

    1998-01-01

    This paper summarizes what is known about, and research needs on, the transmissibility to sexually abused children of the following sexually transmitted diseases: gonorrhea, chlamydia trachomatis, human papillomavirus genital warts, condylomata acuminata, syphilis, bacterial vaginosis, trichomonas vaginalis, herpes simplex, and human…

  8. A Lagrangian particle model to predict the airborne spread of foot-and-mouth disease virus

    NASA Astrophysics Data System (ADS)

    Mayer, D.; Reiczigel, J.; Rubel, F.

    Airborne spread of bioaerosols in the boundary layer over a complex terrain is simulated using a Lagrangian particle model, and applied to modelling the airborne spread of foot-and-mouth disease (FMD) virus. Two case studies are made with study domains located in a hilly region in the northwest of the Styrian capital Graz, the second largest town in Austria. Mountainous terrain as well as inhomogeneous and time varying meteorological conditions prevent from application of so far used Gaussian dispersion models, while the proposed model can handle these realistically. In the model, trajectories of several thousands of particles are computed and the distribution of virus concentration near the ground is calculated. This allows to assess risk of infection areas with respect to animal species of interest, such as cattle, swine or sheep. Meteorological input data like wind field and other variables necessary to compute turbulence were taken from the new pre-operational version of the non-hydrostatic numerical weather prediction model LMK ( Lokal-Modell-Kürzestfrist) running at the German weather service DWD ( Deutscher Wetterdienst). The LMK model provides meteorological parameters with a spatial resolution of about 2.8 km. To account for the spatial resolution of 400 m used by the Lagrangian particle model, the initial wind field is interpolated upon the finer grid by a mass consistent interpolation method. Case studies depict a significant influence of local wind systems on the spread of virus. Higher virus concentrations at the upwind side of the hills and marginal concentrations in the lee are well observable, as well as canalization effects by valleys. The study demonstrates that the Lagrangian particle model is an appropriate tool for risk assessment of airborne spread of virus by taking into account the realistic orographic and meteorological conditions.

  9. Ebola virus disease in Africa: epidemiology and nosocomial transmission.

    PubMed

    Shears, P; O'Dempsey, T J D

    2015-05-01

    The 2014 Ebola outbreak in West Africa, primarily affecting Guinea, Sierra Leone, and Liberia, has exceeded all previous Ebola outbreaks in the number of cases and in international response. There have been 20 significant outbreaks of Ebola virus disease in Sub-Saharan Africa prior to the 2014 outbreak, the largest being that in Uganda in 2000, with 425 cases and a mortality of 53%. Since the first outbreaks in Sudan and Zaire in 1976, transmission within health facilities has been of major concern, affecting healthcare workers and acting as amplifiers of spread into the community. The lack of resources for infection control and personal protective equipment are the main reasons for nosocomial transmission. Local strategies to improve infection control, and a greater understanding of local community views on the disease, have helped to bring outbreaks under control. Recommendations from previous outbreaks include improved disease surveillance to enable more rapid health responses, the wider availability of personal protective equipment, and greater international preparedness.

  10. The bushmeat trade: increased opportunities for transmission of zoonotic disease.

    PubMed

    Karesh, William B; Noble, Eric

    2009-10-01

    Bushmeat is a term that refers to the use of wild animals, ranging from cane rats to gorillas, for food. The term typically refers to the practice in forests of Africa. The bushmeat trade is an example of an anthropogenic factor that provides opportunities for the transmission of diseases from wildlife to humans. The expansion of the bushmeat trade over the past 2 decades has provided a venue for the emergence of zoonotic diseases by providing an increased opportunity for the transmission of organisms known to cause disease and organisms with an unknown impact on humans. Because the bushmeat trade is embedded in a complex cultural, political, and economic context, efforts to prevent the emergence of zoonoses require a multidisciplinary approach. Mt Sinai J Med 76:429-434, 2009. (c) 2009 Mount Sinai School of Medicine.

  11. Transmission ecology of rodent-borne diseases: New frontiers.

    PubMed

    Bordes, Frédéric; Blasdell, Kim; Morand, Serge

    2015-09-01

    Rodents are recognized reservoir hosts for many human zoonotic pathogens. The current trends resulting from anthropocene defaunation suggest that in the future they, along with other small mammals, are likely to become the dominant mammals in almost all human-modified environments. Recent intricate studies on bat-borne emerging diseases have highlighted that many gaps exist in our understanding of the zoonotic transmission of rodent-borne pathogens. This has emphasized the need for scientists interested in rodent-borne diseases to integrate rodent ecology into their analysis of rodent-borne pathogen transmission in order to identify in more detail the mechanisms of spillover and chains of transmission. Further studies are required to better understand the true impact of rodent abundance and the importance of pathogen sharing and circulation in multi-host- multi-pathogen communities. We also need to explore in more depth the roles of generalist and abundant species as the potential links between pathogen-sharing, co-infections and disease transmission. PMID:26176684

  12. Routinely vaccinating adolescents against meningococcus: targeting transmission & disease

    PubMed Central

    Vetter, Volker; Baxter, Roger; Denizer, Gülhan; Sáfadi, Marco A. P.; Silfverdal, Sven-Arne; Vyse, Andrew; Borrow, Ray

    2016-01-01

    ABSTRACT Adolescents have the highest rates of meningococcal carriage and transmission. Interrupting the adolescent habitat in order to reduce carriage and transmission within adolescents and to other age groups could help to control meningococcal disease at a population level. Compared to immunization strategies restricted to young children, a strategy focused on adolescents may have more profound and long-lasting indirect impacts, and may be more cost effective. Despite challenges in reaching this age-group, experience with other vaccines show that high vaccine coverage of adolescents is attainable. PMID:26651380

  13. Routinely vaccinating adolescents against meningococcus: targeting transmission & disease.

    PubMed

    Vetter, Volker; Baxter, Roger; Denizer, Gülhan; Sáfadi, Marco A P; Silfverdal, Sven-Arne; Vyse, Andrew; Borrow, Ray

    2016-05-01

    Adolescents have the highest rates of meningococcal carriage and transmission. Interrupting the adolescent habitat in order to reduce carriage and transmission within adolescents and to other age groups could help to control meningococcal disease at a population level. Compared to immunization strategies restricted to young children, a strategy focused on adolescents may have more profound and long-lasting indirect impacts, and may be more cost effective. Despite challenges in reaching this age-group, experience with other vaccines show that high vaccine coverage of adolescents is attainable. PMID:26651380

  14. Aggregation and environmental transmission in Chronic Wasting Disease.

    PubMed

    Vasilyeva, Olga; Oraby, Tamer; Lutscher, Frithjof

    2015-02-01

    Disease transmission depends on the interplay between the infectious agent and the behavior of the host. Some diseases, such as Chronic Wasting Disease, can be transmitted directly between hosts as well as indirectly via the environment. The social behavior of hosts affects both of these pathways, and a successful intervention requires knowledge of the relative influence of the different etiological and behavioral aspects of the disease. We develop a strategic differential equation model for Chronic Wasting Disease and include direct and indirect transmission as well as host aggregation into our model. We calculate the basic reproduction number and perform a sensitivity analysis based on Latin hypercube sampling from published parameter values. We find conditions for the existence of an endemic equilibrium, and show that, under a certain mild assumption on parameters, the model does not exhibit a backward bifurcation or bistability. Hence, the basic reproduction number constitutes the disease elimination threshold. We find that the prevalence of the disease decreases with host aggregation and increases with the lifespan of the infectious agent in the environment.

  15. Aggregation and environmental transmission in Chronic Wasting Disease.

    PubMed

    Vasilyeva, Olga; Oraby, Tamer; Lutscher, Frithjof

    2015-02-01

    Disease transmission depends on the interplay between the infectious agent and the behavior of the host. Some diseases, such as Chronic Wasting Disease, can be transmitted directly between hosts as well as indirectly via the environment. The social behavior of hosts affects both of these pathways, and a successful intervention requires knowledge of the relative influence of the different etiological and behavioral aspects of the disease. We develop a strategic differential equation model for Chronic Wasting Disease and include direct and indirect transmission as well as host aggregation into our model. We calculate the basic reproduction number and perform a sensitivity analysis based on Latin hypercube sampling from published parameter values. We find conditions for the existence of an endemic equilibrium, and show that, under a certain mild assumption on parameters, the model does not exhibit a backward bifurcation or bistability. Hence, the basic reproduction number constitutes the disease elimination threshold. We find that the prevalence of the disease decreases with host aggregation and increases with the lifespan of the infectious agent in the environment. PMID:25811337

  16. Infectious disease transmission and contact networks in wildlife and livestock

    PubMed Central

    Craft, Meggan E.

    2015-01-01

    The use of social and contact networks to answer basic and applied questions about infectious disease transmission in wildlife and livestock is receiving increased attention. Through social network analysis, we understand that wild animal and livestock populations, including farmed fish and poultry, often have a heterogeneous contact structure owing to social structure or trade networks. Network modelling is a flexible tool used to capture the heterogeneous contacts of a population in order to test hypotheses about the mechanisms of disease transmission, simulate and predict disease spread, and test disease control strategies. This review highlights how to use animal contact data, including social networks, for network modelling, and emphasizes that researchers should have a pathogen of interest in mind before collecting or using contact data. This paper describes the rising popularity of network approaches for understanding transmission dynamics in wild animal and livestock populations; discusses the common mismatch between contact networks as measured in animal behaviour and relevant parasites to match those networks; and highlights knowledge gaps in how to collect and analyse contact data. Opportunities for the future include increased attention to experiments, pathogen genetic markers and novel computational tools. PMID:25870393

  17. Research on an Infectious Disease Transmission by Flocking Birds

    PubMed Central

    Mao, Xinjun; Guessoum, Zahia

    2013-01-01

    The swarm intelligence is becoming a hot topic. The flocking of birds is a natural phenomenon, which is formed and organized without central or external controls for some benefits (e.g., reduction of energy consummation). However, the flocking also has some negative effects on the human, as the infectious disease H7N9 will easily be transmited from the denser flocking birds to the human. Zombie-city model has been proposed to help analyzing and modeling the flocking birds and the artificial society. This paper focuses on the H7N9 virus transmission in the flocking birds and from the flocking birds to the human. And some interesting results have been shown: (1) only some simple rules could result in an emergence such as the flocking; (2) the minimum distance between birds could affect H7N9 virus transmission in the flocking birds and even affect the virus transmissions from the flocking birds to the human. PMID:23864820

  18. Research on an infectious disease transmission by flocking birds.

    PubMed

    Tang, Mingsheng; Mao, Xinjun; Guessoum, Zahia

    2013-01-01

    The swarm intelligence is becoming a hot topic. The flocking of birds is a natural phenomenon, which is formed and organized without central or external controls for some benefits (e.g., reduction of energy consummation). However, the flocking also has some negative effects on the human, as the infectious disease H7N9 will easily be transmited from the denser flocking birds to the human. Zombie-city model has been proposed to help analyzing and modeling the flocking birds and the artificial society. This paper focuses on the H7N9 virus transmission in the flocking birds and from the flocking birds to the human. And some interesting results have been shown: (1) only some simple rules could result in an emergence such as the flocking; (2) the minimum distance between birds could affect H7N9 virus transmission in the flocking birds and even affect the virus transmissions from the flocking birds to the human. PMID:23864820

  19. Molecular aspects of disease pathogenesis in the transmissible spongiform encephalopathies.

    PubMed

    Priola, Suzette A; Vorberg, Ina

    2004-01-01

    The transmissible spongiform encephalopathy (TSE) diseases are a group of rare, fatal, and transmissible neurodegenerative diseases that include kuru and Creutzfeldt-Jakob disease (CJD) in humans, scrapie in sheep, transmissible mink encephalopathy (TME), and chronic wasting disease (CWD) in mule deer and elk. Over the last 20 yr, they have gone from a fascinating but relatively obscure group of diseases to one that is a major agricultural and economic problem as well as a threat to human health. The shift in the relative impact of the TSE diseases began in the late 1970s when the United Kingdom altered the process by which animal carcasses were rendered to provide a protein supplement (i.e., meat and bone meal) to sheep, cattle, and other livestock. Several years later a new disease was recognized in the British cattle population. The pathological and immunohistochemical characteristics of the disease clearly placed it among the TSEs. The new disease was named bovine spongiform encephalopathy (BSE) by the scientific community and "mad cow disease" by the less-than-scientific press. At its peak in the UK, several thousand cattle a year were diagnosed with BSE, and millions of cattle were slaughtered. Introduction of the specified offals ban as well as banning the practice of feeding ruminants to other ruminants has led to a drastic decrease in the number of yearly BSE cases in the UK (less than 500 in 2003), and the epidemic is clearly on the wane. However, BSE has now spread throughout the rest of Europe, as well as to Japan, Russia, Canada, and Israel and thus remains a worldwide problem.A primary concern following the identification of BSE in 1985 was that it might cross species barriers to infect humans. Initially, it was thought that transmission of BSE to humans was unlikely, given that humans appeared to be resistant to scrapie, an animal TSE that had been endemic in British sheep for centuries. However, a few years after BSE was first recognized, a

  20. Modeling seasonal behavior changes and disease transmission with application to chronic wasting disease.

    PubMed

    Oraby, Tamer; Vasilyeva, Olga; Krewski, Daniel; Lutscher, Frithjof

    2014-01-01

    Behavior and habitat of wildlife animals change seasonally according to environmental conditions. Mathematical models need to represent this seasonality to be able to make realistic predictions about the future of a population and the effectiveness of human interventions. Managing and modeling disease in wild animal populations requires particular care in that disease transmission dynamics is a critical consideration in the etiology of both human and animal diseases, with different transmission paradigms requiring different disease risk management strategies. Since transmission of infectious diseases among wildlife depends strongly on social behavior, mechanisms of disease transmission could also change seasonally. A specific consideration in this regard confronted by modellers is whether the contact rate between individuals is density-dependent or frequency-dependent. We argue that seasonal behavior changes could lead to a seasonal shift between density and frequency dependence. This hypothesis is explored in the case of chronic wasting disease (CWD), a fatal disease that affects deer, elk and moose in many areas of North America. Specifically, we introduce a strategic CWD risk model based on direct disease transmission that accounts for the seasonal change in the transmission dynamics and habitats occupied, guided by information derived from cervid ecology. The model is composed of summer and winter susceptible-infected (SI) equations, with frequency-dependent and density-dependent transmission dynamics, respectively. The model includes impulsive birth events with density-dependent birth rate. We determine the basic reproduction number as a weighted average of two seasonal reproduction numbers. We parameterize the model from data derived from the scientific literature on CWD and deer ecology, and conduct global and local sensitivity analyses of the basic reproduction number. We explore the effectiveness of different culling strategies for the management of CWD

  1. Modeling seasonal behavior changes and disease transmission with application to chronic wasting disease.

    PubMed

    Oraby, Tamer; Vasilyeva, Olga; Krewski, Daniel; Lutscher, Frithjof

    2014-01-01

    Behavior and habitat of wildlife animals change seasonally according to environmental conditions. Mathematical models need to represent this seasonality to be able to make realistic predictions about the future of a population and the effectiveness of human interventions. Managing and modeling disease in wild animal populations requires particular care in that disease transmission dynamics is a critical consideration in the etiology of both human and animal diseases, with different transmission paradigms requiring different disease risk management strategies. Since transmission of infectious diseases among wildlife depends strongly on social behavior, mechanisms of disease transmission could also change seasonally. A specific consideration in this regard confronted by modellers is whether the contact rate between individuals is density-dependent or frequency-dependent. We argue that seasonal behavior changes could lead to a seasonal shift between density and frequency dependence. This hypothesis is explored in the case of chronic wasting disease (CWD), a fatal disease that affects deer, elk and moose in many areas of North America. Specifically, we introduce a strategic CWD risk model based on direct disease transmission that accounts for the seasonal change in the transmission dynamics and habitats occupied, guided by information derived from cervid ecology. The model is composed of summer and winter susceptible-infected (SI) equations, with frequency-dependent and density-dependent transmission dynamics, respectively. The model includes impulsive birth events with density-dependent birth rate. We determine the basic reproduction number as a weighted average of two seasonal reproduction numbers. We parameterize the model from data derived from the scientific literature on CWD and deer ecology, and conduct global and local sensitivity analyses of the basic reproduction number. We explore the effectiveness of different culling strategies for the management of CWD

  2. Immune responses to airborne fungi and non-invasive airway diseases.

    PubMed

    Vacher, Gaëlle; Niculita-Hirzel, Hélène; Roger, Thierry

    2015-03-01

    Inhalation of fungal particles is a ubiquitous way of exposure to microorganisms during human life; however, this exposure may promote or exacerbate respiratory diseases only in particular exposure conditions and human genetic background. Depending on the fungal species and form, fungal particles can induce symptoms in the lung by acting as irritants, aeroallergens or pathogens causing infection. Some thermophilic species can even act in all these three ways (e.g. Aspergillus, Penicillium), mesophilic species being only involved in allergic and/or non-allergic airway diseases (e.g. Cladosporium, Alternaria, Fusarium). The goal of the present review is to present the current knowledge on the interaction between airborne fungal particles and the host immune system, to illustrate the differences of immune sensing of different fungal species and to emphasise the importance of conducting research on non-conventional mesophilic fungal species. Indeed, the diversity of fungal species we inhale and the complexity of their composition have a direct impact on fungal particle recognition and immune system decision to tolerate or respond to those particles, eventually leading to collateral damages promoting airway pathologies. PMID:25502371

  3. Polymorphism in sexual versus non-sexual disease transmission

    PubMed Central

    Thrall, P. H.; Antonovics, J.

    1997-01-01

    Pathogens causing sexually transmitted diseases (STDs) often consist of related strains that cause non-sexually transmitted, or 'ordinary infectious', diseases (OIDs). We use differential equation models of single populations to derive conditions under which a genetic variant with one (e.g. sexual) transmission mode can invade and successfully displace a genetic variant with a different (e.g. non-sexual) transmission mode. Invasion by an STD is easier if the equilibrium population size in the presence of an OID is smaller; conversely an OID can invade more easily if the equilibrium size of the population with the STD is larger. Invasion of an STD does not depend on the degree of sterility caused by the infection, but does depend on the added mortality caused by a resident OID. In contrast, the ability of an OID to invade a population at equilibrium with an STD decreases as the degree of sterility caused by the STD increases. When equilibrium population sizes for a population infected with an STD are above the point at which non-sexual contacts exceed sexual contacts (the sexual–social crossover point) and when equilibrium population sizes for an OID are below this point, there can be a stable genetic polymorphism for transmission mode. This is most likely when the STD is mildly sterilizing, and the OID causes low or intermediate levels of added mortality. Because we assume the strains are competitively equivalent and there are no heterogeneities associated with the transmission process, the polymorphism is maintained by density-dependent selection brought about by pathogen effects on population size.

  4. Opposing effects of allogrooming on disease transmission in ant societies.

    PubMed

    Theis, Fabian J; Ugelvig, Line V; Marr, Carsten; Cremer, Sylvia

    2015-05-26

    To prevent epidemics, insect societies have evolved collective disease defences that are highly effective at curing exposed individuals and limiting disease transmission to healthy group members. Grooming is an important sanitary behaviour--either performed towards oneself (self-grooming) or towards others (allogrooming)--to remove infectious agents from the body surface of exposed individuals, but at the risk of disease contraction by the groomer. We use garden ants (Lasius neglectus) and the fungal pathogen Metarhizium as a model system to study how pathogen presence affects self-grooming and allogrooming between exposed and healthy individuals. We develop an epidemiological SIS model to explore how experimentally observed grooming patterns affect disease spread within the colony, thereby providing a direct link between the expression and direction of sanitary behaviours, and their effects on colony-level epidemiology. We find that fungus-exposed ants increase self-grooming, while simultaneously decreasing allogrooming. This behavioural modulation seems universally adaptive and is predicted to contain disease spread in a great variety of host-pathogen systems. In contrast, allogrooming directed towards pathogen-exposed individuals might both increase and decrease disease risk. Our model reveals that the effect of allogrooming depends on the balance between pathogen infectiousness and efficiency of social host defences, which are likely to vary across host-pathogen systems.

  5. Opposing effects of allogrooming on disease transmission in ant societies

    PubMed Central

    Theis, Fabian J.; Ugelvig, Line V.; Marr, Carsten; Cremer, Sylvia

    2015-01-01

    To prevent epidemics, insect societies have evolved collective disease defences that are highly effective at curing exposed individuals and limiting disease transmission to healthy group members. Grooming is an important sanitary behaviour—either performed towards oneself (self-grooming) or towards others (allogrooming)—to remove infectious agents from the body surface of exposed individuals, but at the risk of disease contraction by the groomer. We use garden ants (Lasius neglectus) and the fungal pathogen Metarhizium as a model system to study how pathogen presence affects self-grooming and allogrooming between exposed and healthy individuals. We develop an epidemiological SIS model to explore how experimentally observed grooming patterns affect disease spread within the colony, thereby providing a direct link between the expression and direction of sanitary behaviours, and their effects on colony-level epidemiology. We find that fungus-exposed ants increase self-grooming, while simultaneously decreasing allogrooming. This behavioural modulation seems universally adaptive and is predicted to contain disease spread in a great variety of host–pathogen systems. In contrast, allogrooming directed towards pathogen-exposed individuals might both increase and decrease disease risk. Our model reveals that the effect of allogrooming depends on the balance between pathogen infectiousness and efficiency of social host defences, which are likely to vary across host–pathogen systems. PMID:25870394

  6. Transmission and Epidemiology of Zoonotic Protozoal Diseases of Companion Animals

    PubMed Central

    Esch, Kevin J.

    2013-01-01

    Over 77 million dogs and 93 million cats share our households in the United States. Multiple studies have demonstrated the importance of pets in their owners' physical and mental health. Given the large number of companion animals in the United States and the proximity and bond of these animals with their owners, understanding and preventing the diseases that these companions bring with them are of paramount importance. Zoonotic protozoal parasites, including toxoplasmosis, Chagas' disease, babesiosis, giardiasis, and leishmaniasis, can cause insidious infections, with asymptomatic animals being capable of transmitting disease. Giardia and Toxoplasma gondii, endemic to the United States, have high prevalences in companion animals. Leishmania and Trypanosoma cruzi are found regionally within the United States. These diseases have lower prevalences but are significant sources of human disease globally and are expanding their companion animal distribution. Thankfully, healthy individuals in the United States are protected by intact immune systems and bolstered by good nutrition, sanitation, and hygiene. Immunocompromised individuals, including the growing number of obese and/or diabetic people, are at a much higher risk of developing zoonoses. Awareness of these often neglected diseases in all health communities is important for protecting pets and owners. To provide this awareness, this review is focused on zoonotic protozoal mechanisms of virulence, epidemiology, and the transmission of pathogens of consequence to pet owners in the United States. PMID:23297259

  7. Backward bifurcation and control in transmission dynamics of arboviral diseases.

    PubMed

    Abboubakar, Hamadjam; Claude Kamgang, Jean; Tieudjo, Daniel

    2016-08-01

    In this paper, we derive and analyze a compartmental model for the control of arboviral diseases which takes into account an imperfect vaccine combined with individual protection and some vector control strategies already studied in the literature. After the formulation of the model, a qualitative study based on stability analysis and bifurcation theory reveals that the phenomenon of backward bifurcation may occur. The stable disease-free equilibrium of the model coexists with a stable endemic equilibrium when the reproduction number, R0, is less than unity. Using Lyapunov function theory, we prove that the trivial equilibrium is globally asymptotically stable. When the disease-induced death is not considered, or/and, when the standard incidence is replaced by the mass action incidence, the backward bifurcation does not occur. Under a certain condition, we establish the global asymptotic stability of the disease-free equilibrium of the principal model. Through sensitivity analysis, we determine the relative importance of model parameters for disease transmission. Numerical simulations show that the combination of several control mechanisms would significantly reduce the spread of the disease, if we maintain the level of each control high, and this, over a long period. PMID:27321192

  8. Opposing effects of allogrooming on disease transmission in ant societies.

    PubMed

    Theis, Fabian J; Ugelvig, Line V; Marr, Carsten; Cremer, Sylvia

    2015-05-26

    To prevent epidemics, insect societies have evolved collective disease defences that are highly effective at curing exposed individuals and limiting disease transmission to healthy group members. Grooming is an important sanitary behaviour--either performed towards oneself (self-grooming) or towards others (allogrooming)--to remove infectious agents from the body surface of exposed individuals, but at the risk of disease contraction by the groomer. We use garden ants (Lasius neglectus) and the fungal pathogen Metarhizium as a model system to study how pathogen presence affects self-grooming and allogrooming between exposed and healthy individuals. We develop an epidemiological SIS model to explore how experimentally observed grooming patterns affect disease spread within the colony, thereby providing a direct link between the expression and direction of sanitary behaviours, and their effects on colony-level epidemiology. We find that fungus-exposed ants increase self-grooming, while simultaneously decreasing allogrooming. This behavioural modulation seems universally adaptive and is predicted to contain disease spread in a great variety of host-pathogen systems. In contrast, allogrooming directed towards pathogen-exposed individuals might both increase and decrease disease risk. Our model reveals that the effect of allogrooming depends on the balance between pathogen infectiousness and efficiency of social host defences, which are likely to vary across host-pathogen systems. PMID:25870394

  9. Disease transmission promotes evolution of host spatial patterns

    PubMed Central

    Bull, James C.; Keeling, Matthew J.

    2016-01-01

    Ecological dynamics can produce a variety of striking patterns. On ecological time scales, pattern formation has been hypothesized to be due to the interaction between a species and its local environment. On longer time scales, evolutionary factors must be taken into account. To examine the evolutionary robustness of spatial pattern formation, we construct a spatially explicit model of vegetation in the presence of a pathogen. Initially, we compare the dynamics for vegetation parameters that lead to competition induced spatial patterns and those that do not. Over ecological time scales, banded spatial patterns dramatically reduced the ability of the pathogen to spread, lowered its endemic density and hence increased the persistence of the vegetation. To gain an evolutionary understanding, each plant was given a heritable trait defining its resilience to competition; greater competition leads to lower vegetation density but stronger spatial patterns. When a disease is introduced, the selective pressure on the plant's resilience to the competition parameter is determined by the transmission of the disease. For high transmission, vegetation that has low resilience to competition and hence strong spatial patterning is an evolutionarily stable strategy. This demonstrates a novel mechanism by which striking spatial patterns can be maintained by disease-driven selection. PMID:27628172

  10. Disease transmission promotes evolution of host spatial patterns.

    PubMed

    Irvine, Michael A; Bull, James C; Keeling, Matthew J

    2016-09-01

    Ecological dynamics can produce a variety of striking patterns. On ecological time scales, pattern formation has been hypothesized to be due to the interaction between a species and its local environment. On longer time scales, evolutionary factors must be taken into account. To examine the evolutionary robustness of spatial pattern formation, we construct a spatially explicit model of vegetation in the presence of a pathogen. Initially, we compare the dynamics for vegetation parameters that lead to competition induced spatial patterns and those that do not. Over ecological time scales, banded spatial patterns dramatically reduced the ability of the pathogen to spread, lowered its endemic density and hence increased the persistence of the vegetation. To gain an evolutionary understanding, each plant was given a heritable trait defining its resilience to competition; greater competition leads to lower vegetation density but stronger spatial patterns. When a disease is introduced, the selective pressure on the plant's resilience to the competition parameter is determined by the transmission of the disease. For high transmission, vegetation that has low resilience to competition and hence strong spatial patterning is an evolutionarily stable strategy. This demonstrates a novel mechanism by which striking spatial patterns can be maintained by disease-driven selection. PMID:27628172

  11. Biodiversity and disease: a synthesis of ecological perspectives on Lyme disease transmission.

    PubMed

    Wood, Chelsea L; Lafferty, Kevin D

    2013-04-01

    Recent reviews have argued that disease control is among the ecosystem services yielded by biodiversity. Lyme disease (LD) is commonly cited as the best example of the 'diluting' effect of biodiversity on disease transmission, but many studies document the opposite relationship, showing that human LD risk can increase with forestation. Here, we unify these divergent perspectives and find strong evidence for a positive link between biodiversity and LD at broad spatial scales (urban to suburban to rural) and equivocal evidence for a negative link between biodiversity and LD at varying levels of biodiversity within forests. This finding suggests that, across zoonotic disease agents, the biodiversity-disease relationship is scale dependent and complex.

  12. Air pollution and skin diseases: Adverse effects of airborne particulate matter on various skin diseases.

    PubMed

    Kim, Kyung Eun; Cho, Daeho; Park, Hyun Jeong

    2016-05-01

    Environmental air pollution encompasses various particulate matters (PMs). The increased ambient PM from industrialization and urbanization is highly associated with morbidity and mortality worldwide, presenting one of the most severe environmental pollution problems. This article focuses on the correlation between PM and skin diseases, along with related immunological mechanisms. Recent epidemiological studies on the cutaneous impacts of PM showed that PM affects the development and exacerbation of skin diseases. PM induces oxidative stress via production of reactive oxygen species and secretion of pro-inflammatory cytokines such as TNF-α, IL-1α, and IL-8. In addition, the increased production of ROS such as superoxide and hydroxyl radical by PM exposure increases MMPs including MMP-1, MMP-2, and MMP-9, resulting in the degradation of collagen. These processes lead to the increased inflammatory skin diseases and skin aging. In addition, environmental cigarette smoke, which is well known as an oxidizing agent, is closely related with androgenetic alopecia (AGA). Also, ultrafine particles (UFPs) including black carbon and polycyclic aromatic hydrocarbons (PAHs) enhance the incidence of skin cancer. Overall, increased PM levels are highly associated with the development of various skin diseases via the regulation of oxidative stress and inflammatory cytokines. Therefore, anti-oxidant and anti-inflammatory drugs may be useful for treating PM-induced skin diseases. PMID:27018067

  13. Germline transmission in transgenic Huntington’s disease monkeys

    PubMed Central

    Moran, Sean; Chi, Tim; Prucha, Melinda S.; Ahn, Kwang Sung; Connor-Stroud, Fawn; Jean, Sherrie; Gould, Kenneth; Chan, Anthony W. S.

    2015-01-01

    Transgenic nonhuman primate models are increasingly popular model for neurological and neurodegenerative disease because their brain functions and neural anatomies closely resemble those of humans [1–6]. Transgenic Huntington’s disease monkeys (HD monkeys) developed clinical features similar to those seen in HD patients, making the monkeys suitable for preclinical study of HD [6–12]. However, until HD monkey colonies can be readily expanded, their use in preclinical studies will be limited [1, 13, 14]. In the present study, we confirmed germline transmission of the mutant huntingtin (mHTT) transgene in both embryonic stem cells (ESCs) generated from three male HD monkey founders (F0), as well as in second-generation offspring (F1) produced via artificial insemination by using intrauterine insemination (IUI) technique. A total of five offspring were produced from fifteen females that were inseminated by IUI using semen collected from the three HD founders (5/15; 33%). Thus far, sperm collected from HD founder (rHD8) has led to two F1 transgenic HD moenkys with germline transmission rate at 100% (2/2). mHTT expression was confirmed by quantitative real-time PCR (qPCR) using skin fibroblasts from the F1 HD monkeys, as well as induced pluripotent stem cells (iPSCs) established from one of the F1 HD monkeys (rHD8-2). Here we report the stable germline transmission and expression of the mHTT transgene in HD monkeys, which suggest possible expansion of HD monkey colonies for preclinical and biomedical researches. PMID:25917881

  14. [Severe acute respiratory syndrome: the first transmissible disease of the 21st century].

    PubMed

    Nicastri, Emanuele; Petrosillo, Nicola; Macrì, Giulia; Ippolito, Giuseppe

    2003-01-01

    The Severe Acute Respiratory Syndrome (SARS) is the first severe and easily transmissible disease to emerge in the 21st century. It is caused by the infection with a coronavirus, a single strand RNA capsulated virus, recently found in a small mammalian, the masked palm civet. It is likely to represent the source of human infection. The first cases of SARS have been reported in the Chinese province of Guangdong and, since then, probable cases have been reported world wide. The clinical picture is characterized by nonspecific symptoms such as fever, cough or dyspnea in patients affected by air-space opacities (unifocal involvement in the 54.6% of cases) or distress respiratory syndrome and linked to a recent exposure to a SARS case or to a travel/residence in an affected area. The empirical therapy is based on broad-spectrum antibiotics, steroids and ribavirin, but susceptibility testing have failed to demonstrate direct anti-viral activity of ribavirin against SARS-related coronavirus in vitro. The exposure to respiratory droplets and the contact with biologic fluids (respiratory and gastrointestinal secretions) represent the most efficient transmission modality of the SARS-related coronavirus. Hand hygiene is the most simple and cost effective measure of infection control to prevent contagion, and the use of airborne, contact and droplet precaution is strictly recommended to all health care workers taking care of such patients. The spread of SARS, to less developed country with limited resource for public health programs, represent the emerging alarming threat in the new global scenario.

  15. Effect of proximity to a cattle feedlot on Escherichia coli O157:H7 contamination of leafy greens and evaluation of the potential for airborne transmission.

    PubMed

    Berry, Elaine D; Wells, James E; Bono, James L; Woodbury, Bryan L; Kalchayanand, Norasak; Norman, Keri N; Suslow, Trevor V; López-Velasco, Gabriela; Millner, Patricia D

    2015-02-01

    The impact of proximity to a beef cattle feedlot on Escherichia coli O157:H7 contamination of leafy greens was examined. In each of 2 years, leafy greens were planted in nine plots located 60, 120, and 180 m from a cattle feedlot (3 plots at each distance). Leafy greens (270) and feedlot manure samples (100) were collected six different times from June to September in each year. Both E. coli O157:H7 and total E. coli bacteria were recovered from leafy greens at all plot distances. E. coli O157:H7 was recovered from 3.5% of leafy green samples per plot at 60 m, which was higher (P < 0.05) than the 1.8% of positive samples per plot at 180 m, indicating a decrease in contamination as distance from the feedlot was increased. Although E. coli O157:H7 was not recovered from air samples at any distance, total E. coli was recovered from air samples at the feedlot edge and all plot distances, indicating that airborne transport of the pathogen can occur. Results suggest that risk for airborne transport of E. coli O157:H7 from cattle production is increased when cattle pen surfaces are very dry and when this situation is combined with cattle management or cattle behaviors that generate airborne dust. Current leafy green field distance guidelines of 120 m (400 feet) may not be adequate to limit the transmission of E. coli O157:H7 to produce crops planted near concentrated animal feeding operations. Additional research is needed to determine safe set-back distances between cattle feedlots and crop production that will reduce fresh produce contamination.

  16. Effect of Proximity to a Cattle Feedlot on Escherichia coli O157:H7 Contamination of Leafy Greens and Evaluation of the Potential for Airborne Transmission

    PubMed Central

    Wells, James E.; Bono, James L.; Woodbury, Bryan L.; Kalchayanand, Norasak; Norman, Keri N.; Suslow, Trevor V.; López-Velasco, Gabriela; Millner, Patricia D.

    2014-01-01

    The impact of proximity to a beef cattle feedlot on Escherichia coli O157:H7 contamination of leafy greens was examined. In each of 2 years, leafy greens were planted in nine plots located 60, 120, and 180 m from a cattle feedlot (3 plots at each distance). Leafy greens (270) and feedlot manure samples (100) were collected six different times from June to September in each year. Both E. coli O157:H7 and total E. coli bacteria were recovered from leafy greens at all plot distances. E. coli O157:H7 was recovered from 3.5% of leafy green samples per plot at 60 m, which was higher (P < 0.05) than the 1.8% of positive samples per plot at 180 m, indicating a decrease in contamination as distance from the feedlot was increased. Although E. coli O157:H7 was not recovered from air samples at any distance, total E. coli was recovered from air samples at the feedlot edge and all plot distances, indicating that airborne transport of the pathogen can occur. Results suggest that risk for airborne transport of E. coli O157:H7 from cattle production is increased when cattle pen surfaces are very dry and when this situation is combined with cattle management or cattle behaviors that generate airborne dust. Current leafy green field distance guidelines of 120 m (400 feet) may not be adequate to limit the transmission of E. coli O157:H7 to produce crops planted near concentrated animal feeding operations. Additional research is needed to determine safe set-back distances between cattle feedlots and crop production that will reduce fresh produce contamination. PMID:25452286

  17. Seven challenges for modelling indirect transmission: Vector-borne diseases, macroparasites and neglected tropical diseases

    PubMed Central

    Hollingsworth, T. Déirdre; Pulliam, Juliet R.C.; Funk, Sebastian; Truscott, James E.; Isham, Valerie; Lloyd, Alun L.

    2015-01-01

    Many of the challenges which face modellers of directly transmitted pathogens also arise when modelling the epidemiology of pathogens with indirect transmission – whether through environmental stages, vectors, intermediate hosts or multiple hosts. In particular, understanding the roles of different hosts, how to measure contact and infection patterns, heterogeneities in contact rates, and the dynamics close to elimination are all relevant challenges, regardless of the mode of transmission. However, there remain a number of challenges that are specific and unique to modelling vector-borne diseases and macroparasites. Moreover, many of the neglected tropical diseases which are currently targeted for control and elimination are vector-borne, macroparasitic, or both, and so this article includes challenges which will assist in accelerating the control of these high-burden diseases. Here, we discuss the challenges of indirect measures of infection in humans, whether through vectors or transmission life stages and in estimating the contribution of different host groups to transmission. We also discuss the issues of “evolution-proof” interventions against vector-borne disease. PMID:25843376

  18. Transmission of Mitochondrial DNA Diseases and Ways to Prevent Them

    PubMed Central

    Poulton, Joanna; Chiaratti, Marcos R.; Meirelles, Flávio V.; Kennedy, Stephen; Wells, Dagan; Holt, Ian J.

    2010-01-01

    Recent reports of strong selection of mitochondrial DNA (mtDNA) during transmission in animal models of mtDNA disease, and of nuclear transfer in both animal models and humans, have important scientific implications. These are directly applicable to the genetic management of mtDNA disease. The risk that a mitochondrial disorder will be transmitted is difficult to estimate due to heteroplasmy—the existence of normal and mutant mtDNA in the same individual, tissue, or cell. In addition, the mtDNA bottleneck during oogenesis frequently results in dramatic and unpredictable inter-generational fluctuations in the proportions of mutant and wild-type mtDNA. Pre-implantation genetic diagnosis (PGD) for mtDNA disease enables embryos produced by in vitro fertilization (IVF) to be screened for mtDNA mutations. Embryos determined to be at low risk (i.e., those having low mutant mtDNA load) can be preferentially transferred to the uterus with the aim of initiating unaffected pregnancies. New evidence that some types of deleterious mtDNA mutations are eliminated within a few generations suggests that women undergoing PGD have a reasonable chance of generating embryos with a lower mutant load than their own. While nuclear transfer may become an alternative approach in future, there might be more difficulties, ethical as well as technical. This Review outlines the implications of recent advances for genetic management of these potentially devastating disorders. PMID:20711358

  19. On the Identifiability of Transmission Dynamic Models for Infectious Diseases.

    PubMed

    Lintusaari, Jarno; Gutmann, Michael U; Kaski, Samuel; Corander, Jukka

    2016-03-01

    Understanding the transmission dynamics of infectious diseases is important for both biological research and public health applications. It has been widely demonstrated that statistical modeling provides a firm basis for inferring relevant epidemiological quantities from incidence and molecular data. However, the complexity of transmission dynamic models presents two challenges: (1) the likelihood function of the models is generally not computable, and computationally intensive simulation-based inference methods need to be employed, and (2) the model may not be fully identifiable from the available data. While the first difficulty can be tackled by computational and algorithmic advances, the second obstacle is more fundamental. Identifiability issues may lead to inferences that are driven more by prior assumptions than by the data themselves. We consider a popular and relatively simple yet analytically intractable model for the spread of tuberculosis based on classical IS6110 fingerprinting data. We report on the identifiability of the model, also presenting some methodological advances regarding the inference. Using likelihood approximations, we show that the reproductive value cannot be identified from the data available and that the posterior distributions obtained in previous work have likely been substantially dominated by the assumed prior distribution. Further, we show that the inferences are influenced by the assumed infectious population size, which generally has been kept fixed in previous work. We demonstrate that the infectious population size can be inferred if the remaining epidemiological parameters are already known with sufficient precision.

  20. Raccoon social networks and the potential for disease transmission.

    PubMed

    Hirsch, Ben T; Prange, Suzanne; Hauver, Stephanie A; Gehrt, Stanley D

    2013-01-01

    Raccoons are an important vector of rabies and other pathogens. The degree to which these pathogens can spread through a raccoon population should be closely linked to association rates between individual raccoons. Most studies of raccoon sociality have found patterns consistent with low levels of social connectivity within populations, thus the likelihood of direct pathogen transmission between raccoons is theoretically low. We used proximity detecting collars and social network metrics to calculate the degree of social connectivity in an urban raccoon population for purposes of estimating potential pathogen spread. In contrast to previous assumptions, raccoon social association networks were highly connected, and all individuals were connected to one large social network during 15 out of 18 months of study. However, these metrics may overestimate the potential for a pathogen to spread through a population, as many of the social connections were based on relatively short contact periods. To more closely reflect varying probabilities of pathogen spread, we censored the raccoon social networks based on the total amount of time spent in close proximity between two individuals per month. As this time criteria for censoring the social networks increased from one to thirty minutes, corresponding measures of network connectivity declined. These findings demonstrate that raccoon populations are much more tightly connected than would have been predicted based on previous studies, but also point out that additional research is needed to calculate more precise transmission probabilities by infected individuals, and determine how disease infection changes normal social behaviors.

  1. On the Identifiability of Transmission Dynamic Models for Infectious Diseases.

    PubMed

    Lintusaari, Jarno; Gutmann, Michael U; Kaski, Samuel; Corander, Jukka

    2016-03-01

    Understanding the transmission dynamics of infectious diseases is important for both biological research and public health applications. It has been widely demonstrated that statistical modeling provides a firm basis for inferring relevant epidemiological quantities from incidence and molecular data. However, the complexity of transmission dynamic models presents two challenges: (1) the likelihood function of the models is generally not computable, and computationally intensive simulation-based inference methods need to be employed, and (2) the model may not be fully identifiable from the available data. While the first difficulty can be tackled by computational and algorithmic advances, the second obstacle is more fundamental. Identifiability issues may lead to inferences that are driven more by prior assumptions than by the data themselves. We consider a popular and relatively simple yet analytically intractable model for the spread of tuberculosis based on classical IS6110 fingerprinting data. We report on the identifiability of the model, also presenting some methodological advances regarding the inference. Using likelihood approximations, we show that the reproductive value cannot be identified from the data available and that the posterior distributions obtained in previous work have likely been substantially dominated by the assumed prior distribution. Further, we show that the inferences are influenced by the assumed infectious population size, which generally has been kept fixed in previous work. We demonstrate that the infectious population size can be inferred if the remaining epidemiological parameters are already known with sufficient precision. PMID:26739450

  2. Evidence of intrauterine transmission of lumpy skin disease virus.

    PubMed

    Rouby, Sherin; Aboulsoud, Emad

    2016-03-01

    The current study describes the clinical, histopathological, molecular and serological diagnosis of lumpy skin disease (LSD) in a premature 1-day old calf that has been delivered from a cow that exhibited signs of LSD during the seventh month of pregnancy. The calf showed generalized skin lesions accompanied with signs of immaturity and died 36 h after birth. Postmortem and histopathological examinations revealed the involvement of multiple tissues. The presence of Neethling virus DNA in tissues was confirmed by polymerase chain reaction (PCR) and gene sequencing. Results of ELISA and serum neutralization test (SNT) confirmed that the calf had developed precolostral serum antibodies to LSD virus indicating in utero virus transmission. All tested sera collected from animals located in the same area were serologically positive, indicating exposure to LSD virus. PMID:26831170

  3. Modeling the Dynamic Transmission of Dengue Fever: Investigating Disease Persistence

    PubMed Central

    de Castro Medeiros, Líliam César; Castilho, César Augusto Rodrigues; Braga, Cynthia; de Souza, Wayner Vieira; Regis, Leda; Monteiro, Antonio Miguel Vieira

    2011-01-01

    Background Dengue is a disease of great complexity, due to interactions between humans, mosquitoes and various virus serotypes as well as efficient vector survival strategies. Thus, understanding the factors influencing the persistence of the disease has been a challenge for scientists and policy makers. The aim of this study is to investigate the influence of various factors related to humans and vectors in the maintenance of viral transmission during extended periods. Methodology/Principal Findings We developed a stochastic cellular automata model to simulate the spread of dengue fever in a dense community. Each cell can correspond to a built area, and human and mosquito populations are individually monitored during the simulations. Human mobility and renewal, as well as vector infestation, are taken into consideration. To investigate the factors influencing the maintenance of viral circulation, two sets of simulations were performed: (1st) varying human renewal rates and human population sizes and (2nd) varying the house index (fraction of infested buildings) and vector per human ratio. We found that viral transmission is inhibited with the combination of small human populations with low renewal rates. It is also shown that maintenance of viral circulation for extended periods is possible at low values of house index. Based on the results of the model and on a study conducted in the city of Recife, Brazil, which associates vector infestation with Aedes aegytpi egg counts, we question the current methodology used in calculating the house index, based on larval survey. Conclusions/Significance This study contributed to a better understanding of the dynamics of dengue subsistence. Using basic concepts of metapopulations, we concluded that low infestation rates in a few neighborhoods ensure the persistence of dengue in large cities and suggested that better strategies should be implemented to obtain measures of house index values, in order to improve the dengue

  4. Disease transmission from companion parrots to dogs and cats: what is the real risk?

    PubMed

    Bush, Jamie M; Speer, Brian; Opitz, Noel

    2011-11-01

    A number of common misconceptions exist regarding the degree of transmission from companion parrots to dogs and cats. Concern regarding bacterial, viral, fungal, and parasitic transmission is generally unfounded, because disease transmission between companion parrots and dogs and cats is not well-documented. Infections with Mycobacterium spp, Aspergillus spp, Giardia spp, Chlamydophila psittaci, Salmonella spp, Yersinia pseudotuberculosis, Cryptococcus neoformans, Histoplasma capsulatum, Cryptosporidium spp, and avian influenza are often considered possible transmissible diseases, causing pet caregivers unwarranted concerns.

  5. Prions and the Potential Transmissibility of Protein Misfolding Diseases*

    PubMed Central

    Kraus, Allison; Groveman, Bradley R.; Caughey, Byron

    2016-01-01

    Prions, or infectious proteins, represent a major frontier in the study of infectious agents. The prions responsible for mammalian transmissible spongiform encephalopathies (TSEs) are due primarily to infectious self-propagation of misfolded prion proteins. TSE prion structures remain ill-defined, other than being highly structured, self-propagating, and often fibrillar protein multimers with the capacity to seed, or template, the conversion of their normal monomeric precursors into a pathogenic form. Purified TSE prions usually take the form of amyloid fibrils, which are self-seeding ultrastructures common to many serious protein misfolding diseases such as Alzheimer’s, Parkinson’s, Huntington’s and Lou Gehrig’s (amytrophic lateral sclerosis). Indeed, recent reports have now provided evidence of prion-like propagation of several misfolded proteins from cell to cell, if not from tissue to tissue or individual to individual. These findings raise concerns that various protein misfolding diseases might have spreading, prion-like etiologies that contribute to pathogenesis or prevalence. PMID:23808331

  6. VECTRI: A new dynamical disease model for malaria transmission

    NASA Astrophysics Data System (ADS)

    Tompkins, A. M.; Ermert, V.; Lowe, R.

    2012-04-01

    In order to better address the role of population dynamics and surface hydrology in the assessment of malaria risk, a new dynamical disease model been developed at ICTP, known as the VECToR borne disease model of ICTP (VECTRI). The model accounts for the temperature impact on the larvae, parasite and adult vector populations in a similar fashion to previous dynamical models, but additionally explicitly accounts for the local population density, allowing for the incorporation of such impacts as bednet useor migration, as well as including a new simple pond model framework for surface hydrology. These additions allow the model to be reasonably run on resolutions down to O(10km), essentially the resolution of the population and climate input data. Results from the model driven by ERAI reanalysis and FEWS/TRMM rainfall for various regions in Africa will be shown which are focus areas of the Healthy Futures and QWeCI project which demonstrate that the model produces a realistic spatial and temporal variability of malaria transmission

  7. Cholera: Environmental Reservoirs and Impact on Disease Transmission

    PubMed Central

    ALMAGRO-MORENO, SALVADOR; TAYLOR, RONALD K.

    2015-01-01

    Vibrio cholerae is widely known to be the etiological agent of the life-threatening diarrheal disease cholera. Cholera remains a major scourge in many developing countries, infecting hundreds of thousands every year. Remarkably, V. cholerae is a natural inhabitant of brackish riverine, estuarine, and coastal waters, and only a subset of strains are known to be pathogenic to humans. Recent studies have begun to uncover a very complex network of relationships between V. cholerae and other sea dwellers, and the mechanisms associated with the occurrence of seasonal epidemics in regions where cholera is endemic are beginning to be elucidated. Many of the factors required for the organism’s survival and persistence in its natural environment have been revealed, as well as the ubiquitous presence of horizontal gene transfer in the emergence of pathogenic strains of V. cholerae. In this article, we will focus on the environmental stage of pathogenic V. cholerae and the interactions of the microorganism with other inhabitants of aquatic environments. We will discuss the impact that its environmental reservoirs have on disease transmission and the distinction between reservoirs of V. cholerae and the vectors that establish cholera as a zoonosis. PMID:25674360

  8. Biodiversity and disease: a synthesis of ecological perspectives on Lyme disease transmission.

    USGS Publications Warehouse

    Wood, Chelsea L.; Lafferty, Kevin D.

    2013-01-01

    Recent reviews have argued that disease control is among the ecosystem services yielded by biodiversity. Lyme disease (LD) is commonly cited as the best example of the ‘diluting’ effect of biodiversity on disease transmission, but many studies document the opposite relationship, showing that human LD risk can increase with forestation. Here, we unify these divergent perspectives and find strong evidence for a positive link between biodiversity and LD at broad spatial scales (urban to suburban to rural) and equivocal evidence for a negative link between biodiversity and LD at varying levels of biodiversity within forests. This finding suggests that, across zoonotic disease agents, the biodiversity–disease relationship is scale dependent and complex.

  9. Prion Diseases: Update on Mad Cow Disease, Variant Creutzfeldt-Jakob Disease, and the Transmissible Spongiform Encephalopathies.

    PubMed

    Janka, Jacqueline; Maldarelli, Frank

    2004-08-01

    Transmissible spongiform encephalopathies (TSEs) are a group of progressive, fatal neurodegenerative disorders that share a common spongiform histopathology. TSEs may be transmitted in a sporadic, familial, iatrogenic, or zoonotic fashion. The putative infectious agent of TSE, the prion, represents a novel paradigm of infectious disease with disease transmission in the absence of nucleic acid. Several small but spectacular epidemics of TSEs in man have prompted widespread public health and food safety concerns. Although TSEs affect a comparatively small number of individuals, prion research has revealed fascinating insights of direct relevance to common illnesses. This paper reviews recent advances that have shed new light on the nature of prions and TSEs. PMID:15265460

  10. A Generic Model to Simulate Air-Borne Diseases as a Function of Crop Architecture

    PubMed Central

    Casadebaig, Pierre; Quesnel, Gauthier; Langlais, Michel; Faivre, Robert

    2012-01-01

    In a context of pesticide use reduction, alternatives to chemical-based crop protection strategies are needed to control diseases. Crop and plant architectures can be viewed as levers to control disease outbreaks by affecting microclimate within the canopy or pathogen transmission between plants. Modeling and simulation is a key approach to help analyze the behaviour of such systems where direct observations are difficult and tedious. Modeling permits the joining of concepts from ecophysiology and epidemiology to define structures and functions generic enough to describe a wide range of epidemiological dynamics. Additionally, this conception should minimize computing time by both limiting the complexity and setting an efficient software implementation. In this paper, our aim was to present a model that suited these constraints so it could first be used as a research and teaching tool to promote discussions about epidemic management in cropping systems. The system was modelled as a combination of individual hosts (population of plants or organs) and infectious agents (pathogens) whose contacts are restricted through a network of connections. The system dynamics were described at an individual scale. Additional attention was given to the identification of generic properties of host-pathogen systems to widen the model's applicability domain. Two specific pathosystems with contrasted crop architectures were considered: ascochyta blight on pea (homogeneously layered canopy) and potato late blight (lattice of individualized plants). The model behavior was assessed by simulation and sensitivity analysis and these results were discussed against the model ability to discriminate between the defined types of epidemics. Crop traits related to disease avoidance resulting in a low exposure, a slow dispersal or a de-synchronization of plant and pathogen cycles were shown to strongly impact the disease severity at the crop scale. PMID:23226209

  11. A generic model to simulate air-borne diseases as a function of crop architecture.

    PubMed

    Casadebaig, Pierre; Quesnel, Gauthier; Langlais, Michel; Faivre, Robert

    2012-01-01

    In a context of pesticide use reduction, alternatives to chemical-based crop protection strategies are needed to control diseases. Crop and plant architectures can be viewed as levers to control disease outbreaks by affecting microclimate within the canopy or pathogen transmission between plants. Modeling and simulation is a key approach to help analyze the behaviour of such systems where direct observations are difficult and tedious. Modeling permits the joining of concepts from ecophysiology and epidemiology to define structures and functions generic enough to describe a wide range of epidemiological dynamics. Additionally, this conception should minimize computing time by both limiting the complexity and setting an efficient software implementation. In this paper, our aim was to present a model that suited these constraints so it could first be used as a research and teaching tool to promote discussions about epidemic management in cropping systems. The system was modelled as a combination of individual hosts (population of plants or organs) and infectious agents (pathogens) whose contacts are restricted through a network of connections. The system dynamics were described at an individual scale. Additional attention was given to the identification of generic properties of host-pathogen systems to widen the model's applicability domain. Two specific pathosystems with contrasted crop architectures were considered: ascochyta blight on pea (homogeneously layered canopy) and potato late blight (lattice of individualized plants). The model behavior was assessed by simulation and sensitivity analysis and these results were discussed against the model ability to discriminate between the defined types of epidemics. Crop traits related to disease avoidance resulting in a low exposure, a slow dispersal or a de-synchronization of plant and pathogen cycles were shown to strongly impact the disease severity at the crop scale. PMID:23226209

  12. Modeling disease transmission near eradication: An equation free approach

    NASA Astrophysics Data System (ADS)

    Williams, Matthew O.; Proctor, Joshua L.; Kutz, J. Nathan

    2015-01-01

    Although disease transmission in the near eradication regime is inherently stochastic, deterministic quantities such as the probability of eradication are of interest to policy makers and researchers. Rather than running large ensembles of discrete stochastic simulations over long intervals in time to compute these deterministic quantities, we create a data-driven and deterministic "coarse" model for them using the Equation Free (EF) framework. In lieu of deriving an explicit coarse model, the EF framework approximates any needed information, such as coarse time derivatives, by running short computational experiments. However, the choice of the coarse variables (i.e., the state of the coarse system) is critical if the resulting model is to be accurate. In this manuscript, we propose a set of coarse variables that result in an accurate model in the endemic and near eradication regimes, and demonstrate this on a compartmental model representing the spread of Poliomyelitis. When combined with adaptive time-stepping coarse projective integrators, this approach can yield over a factor of two speedup compared to direct simulation, and due to its lower dimensionality, could be beneficial when conducting systems level tasks such as designing eradication or monitoring campaigns.

  13. Re-assessing the likelihood of airborne spread of foot-and-mouth disease at the start of the 1967-1968 UK foot-and-mouth disease epidemic.

    PubMed Central

    Gloster, J.; Freshwater, A.; Sellers, R. F.; Alexandersen, S.

    2005-01-01

    The likelihood of airborne spread of foot-and-mouth disease at the start of the 1967-1968 epidemic is re-assessed in the light of current understanding of airborne disease spread. The findings strongly confirm those made at the time that airborne virus was the most likely cause of the rapid early development of the disease out to 60 km from the source. This conclusion is reached following a detailed epidemiological, meteorological and modelling study using original records and current modelling techniques. The role played by 'lee waves' as the mechanism for the spread is investigated. It is thought that they played little part in influencing the development of the epidemic. A number of lessons learned from the work are drawn, identifying the need for further research on the quantity and characteristics of airborne virus. The results are also used to illustrate what advice would have been available to disease controllers if the outbreak had occurred in 2004. PMID:16181495

  14. Fluid fragmentation shapes rain-induced foliar disease transmission

    PubMed Central

    Gilet, T.; Bourouiba, L.

    2015-01-01

    Plant diseases represent a growing threat to the global food supply. The factors contributing to pathogen transmission from plant to plant remain poorly understood. Statistical correlations between rainfalls and plant disease outbreaks were reported; however, the detailed mechanisms linking the two were relegated to a black box. In this combined experimental and theoretical study, we focus on the impact dynamics of raindrops on infected leaves, one drop at a time. We find that the deposition range of most of the pathogen-bearing droplets is constrained by a hydrodynamical condition and we quantify the effect of leaf size and compliance on such constraint. Moreover, we identify and characterize two dominant fluid fragmentation scenarios as responsible for the dispersal of most pathogen-bearing droplets emitted from infected leaves: (i) the crescent-moon ejection is driven by the direct interaction between the impacting raindrop and the contaminated sessile drop and (ii) the inertial detachment is driven by the motion imparted to the leaf by the raindrop, leading to catapult-like droplet ejections. We find that at first, decreasing leaf size or increasing compliance reduces the range of pathogen-bearing droplets and the subsequent epidemic onset efficiency. However, this conclusion only applies for the crescent moon ejection. Above a certain compliance threshold a more effective mechanism of contaminated fluid ejection, the inertial detachment, emerges. This compliance threshold is determined by the ratio between the leaf velocity and the characteristic velocity of fluid fragmentation. The inertial detachment mechanism enhances the range of deposition of the larger contaminated droplets and suggests a change in epidemic onset pattern and a more efficient potential of infection of neighbouring plants. Dimensionless parameters and scaling laws are provided to rationalize our observations. Our results link for the first time the mechanical properties of foliage with the

  15. Fluid fragmentation shapes rain-induced foliar disease transmission.

    PubMed

    Gilet, T; Bourouiba, L

    2015-03-01

    Plant diseases represent a growing threat to the global food supply. The factors contributing to pathogen transmission from plant to plant remain poorly understood. Statistical correlations between rainfalls and plant disease outbreaks were reported; however, the detailed mechanisms linking the two were relegated to a black box. In this combined experimental and theoretical study, we focus on the impact dynamics of raindrops on infected leaves, one drop at a time. We find that the deposition range of most of the pathogen-bearing droplets is constrained by a hydrodynamical condition and we quantify the effect of leaf size and compliance on such constraint. Moreover, we identify and characterize two dominant fluid fragmentation scenarios as responsible for the dispersal of most pathogen-bearing droplets emitted from infected leaves: (i) the crescent-moon ejection is driven by the direct interaction between the impacting raindrop and the contaminated sessile drop and (ii) the inertial detachment is driven by the motion imparted to the leaf by the raindrop, leading to catapult-like droplet ejections. We find that at first, decreasing leaf size or increasing compliance reduces the range of pathogen-bearing droplets and the subsequent epidemic onset efficiency. However, this conclusion only applies for the crescent moon ejection. Above a certain compliance threshold a more effective mechanism of contaminated fluid ejection, the inertial detachment, emerges. This compliance threshold is determined by the ratio between the leaf velocity and the characteristic velocity of fluid fragmentation. The inertial detachment mechanism enhances the range of deposition of the larger contaminated droplets and suggests a change in epidemic onset pattern and a more efficient potential of infection of neighbouring plants. Dimensionless parameters and scaling laws are provided to rationalize our observations. Our results link for the first time the mechanical properties of foliage with the

  16. Distinction and connection between contact network, social network, and disease transmission network.

    PubMed

    Chen, Shi; Lanzas, Cristina

    2016-09-01

    In this paper we discuss the distinction and connection between three closely related networks in animal ecology and epidemiology studies: the contact, social, and disease transmission networks. We provide a robust theoretical definition and interpretation of these three networks, demonstrate that social and disease transmission networks can be derived as spanning subgraphs of contact network, and show examples based on real-world high-resolution cattle contact structure data. Furthermore, we establish a modeling framework to track potential disease transmission dynamics and construct transmission network based on the observed animal contact network.

  17. Distinction and connection between contact network, social network, and disease transmission network.

    PubMed

    Chen, Shi; Lanzas, Cristina

    2016-09-01

    In this paper we discuss the distinction and connection between three closely related networks in animal ecology and epidemiology studies: the contact, social, and disease transmission networks. We provide a robust theoretical definition and interpretation of these three networks, demonstrate that social and disease transmission networks can be derived as spanning subgraphs of contact network, and show examples based on real-world high-resolution cattle contact structure data. Furthermore, we establish a modeling framework to track potential disease transmission dynamics and construct transmission network based on the observed animal contact network. PMID:27544246

  18. Slow virus disease: deciphering conflicting data on the transmissible spongiform encephalopathies (TSE) also called prion diseases.

    PubMed

    Bastian, Frank O; Fermin, Cesar D

    2005-11-01

    The transmissible spongiform encephalopathies (TSE) that manifest as Creutzfeldt-Jakob disease in humans, as scrapie in sheep and goats, mad cow disease in cattle, or chronic wasting disease in cervids (deer) represent a serious human health crisis and a significant economical problem. Despite much research, the nature of the elusive pathogen directly involved with TSE is currently unresolved. This article reviews current pathogen-cell plasma membrane properties, showing that the primary biochemical marker of the prion disease is used as a receptor by the intracellular bacterium Brucella abortus. Such observation makes plausible the role for the prion in the pathogenesis of TSE, and supports the concept that Spiroplasma, a wall-less bacterium, may be a transmissible agent of TSE. Over the past three decades, we have published convincing evidence that Spiroplasma infection is associated with TSE. The bacterial-prion-receptor concept by other laboratories support a model for TSE wherein a Spiroplasma bacterium can bind to prion receptors (alone or with anchors) on the cell surface lipid raft, allowing entry of the microbe into the cell to initiate infection. The relevance of this new concept is that it offers a new window for future research involving a bacterium in the pathogenesis of TSE. Data from the bacterial-prion-receptor model will aid in the development diagnostic tests and/or treatment protocols for TSE. PMID:16276518

  19. Co-feeding transmission in Lyme disease pathogens.

    PubMed

    Voordouw, Maarten J

    2015-02-01

    This review examines the phenomenon of co-feeding transmission in tick-borne pathogens. This mode of transmission is critical for the epidemiology of several tick-borne viruses but its importance for Borrelia burgdorferi sensu lato, the causative agents of Lyme borreliosis, is still controversial. The molecular mechanisms and ecological factors that facilitate co-feeding transmission are therefore examined with particular emphasis on Borrelia pathogens. Comparison of climate, tick ecology and experimental infection work suggests that co-feeding transmission is more important in European than North American systems of Lyme borreliosis, which potentially explains why this topic has gained more traction in the former continent than the latter. While new theory shows that co-feeding transmission makes a modest contribution to Borrelia fitness, recent experimental work has revealed new ecological contexts where natural selection might favour co-feeding transmission. In particular, co-feeding transmission might confer a fitness advantage in the Darwinian competition among strains in mixed infections. Future studies should investigate the ecological conditions that favour the evolution of this fascinating mode of transmission in tick-borne pathogens.

  20. Impacts of biodiversity on the emergence and transmission of infectious diseases.

    PubMed

    Keesing, Felicia; Belden, Lisa K; Daszak, Peter; Dobson, Andrew; Harvell, C Drew; Holt, Robert D; Hudson, Peter; Jolles, Anna; Jones, Kate E; Mitchell, Charles E; Myers, Samuel S; Bogich, Tiffany; Ostfeld, Richard S

    2010-12-01

    Current unprecedented declines in biodiversity reduce the ability of ecological communities to provide many fundamental ecosystem services. Here we evaluate evidence that reduced biodiversity affects the transmission of infectious diseases of humans, other animals and plants. In principle, loss of biodiversity could either increase or decrease disease transmission. However, mounting evidence indicates that biodiversity loss frequently increases disease transmission. In contrast, areas of naturally high biodiversity may serve as a source pool for new pathogens. Overall, despite many remaining questions, current evidence indicates that preserving intact ecosystems and their endemic biodiversity should generally reduce the prevalence of infectious diseases.

  1. From superspreaders to disease hotspots: linking transmission across hosts and space

    PubMed Central

    Paull, Sara H.; Song, Sejin; McClure, Katherine M.; Sackett, Loren C.; Kilpatrick, A. Marm; Johnson, Pieter T. J.

    2012-01-01

    Since the identification and imprisonment of “Typhoid Mary,” a woman who infected at least 47 people with typhoid in the early 1900s, epidemiologists have recognized that ‘superspreading’ hosts play a key role in disease epidemics. Such variability in transmission also exists among species within a community (amplification hosts) and among habitat patches across a landscape (disease ‘hotspots’), underscoring the need for an integrative framework for studying transmission heterogeneity. Here, we synthesize literature on human, plant, and animal diseases to evaluate the relative contributions of host, pathogen, and environmental factors in driving transmission heterogeneity across hosts and space. We show that host and spatial heterogeneity are closely linked and that quantitatively assessing the contribution of infectious individuals, species, or environmental patches to overall transmission can aid management strategies. We conclude by posing hypotheses regarding how pathogen natural history influences transmission heterogeneity and highlight emerging frontiers in the study of transmission heterogeneity. PMID:23482675

  2. Airborne Fiber Size Characterization in Exposure Estimation: Evaluation of a Modified Transmission Electron Microcopy Protocol for Asbestos and Potential Use for Carbon Nanotubes and Nanofibers

    PubMed Central

    Dement, John M.; Kuempel, Eileen D.; Zumwalde, Ralph D.; Ristich, Anna M.; Fernback, Joseph E.; Smith, Randall J.

    2015-01-01

    Background Airborne fiber size has been shown to be an important factor relative to adverse lung effects of asbestos and suggested in animal studies of carbon nanotubes and nanofibers (CNT/CNF). Materials and Methods The International Standards Organization (ISO) transmission electron microscopy (TEM) method for asbestos was modified to increase the statistical precision of fiber size determinations, improve efficiency, and reduce analysis costs. Comparisons of the fiber size distributions and exposure indices by laboratory and counting method were performed. Results No significant differences in size distributions by the ISO and modified ISO methods were observed. Small but statistically-significant inter-lab differences in the proportion of fibers in some size bins were found, but these differences had little impact on the summary exposure indices. The modified ISO method produced slightly more precise estimates of the long fiber fraction (>15 μm). Conclusions The modified ISO method may be useful for estimating size-specific structure exposures, including CNT/CNF, for risk assessment research. PMID:25675894

  3. A novel neutralizing antibody against diverse clades of H5N1 influenza virus and its mutants capable of airborne transmission.

    PubMed

    Wu, Ruiping; Li, Xingxing; Leung, Ho-Chuen; Cao, Zhiliang; Qiu, Zonglin; Zhou, Yusen; Zheng, Bo-Jian; He, Yuxian

    2014-06-01

    Highly pathogenic avian influenza A virus H5N1 continues to spread among poultry and has frequently broken the species barrier to humans. Recent studies have shown that a laboratory-mutated or reassortant H5N1 virus bearing hemagglutinin (HA) with as few as four or five mutations was capable of transmitting more efficiently via respiratory droplets between ferrets, posing a serious threat to public health and underscoring the priority of effective vaccines and therapeutics. In this study, we identified a novel monoclonal antibody (mAb) named HAb21, that has a broadly neutralizing activity against all tested strains of H5N1 covering clades 0, 1, 2.2, 2.3.4, and 2.3.2.1. Importantly, HAb21 efficiently neutralized diverse H5N1 variants with single or combination forms of mutations capable of airborne transmission. We demonstrated that HAb21 blocked viral entry during the receptor-binding step by targeting a previously uncharacterized epitope at the tip of the HA head. This novel epitope closely neighbors the receptor-binding site (RBS) and the interface of HA trimer and is highly conserved among divergent H5N1 strains. Our studies provide a new tool for use either for therapeutic purposes or as a basis of vaccine development. PMID:24681124

  4. Multiple mechanisms of transmission of the Caribbean coral disease white plague

    NASA Astrophysics Data System (ADS)

    Clemens, E.; Brandt, M. E.

    2015-12-01

    White plague is one of the most devastating coral diseases in the Caribbean, and yet important aspects of its epidemiology, including how the disease transmits, remain unknown. This study tested potential mechanisms and rates of transmission of white plague in a laboratory setting. Transmission mechanisms including the transport of water, contact with macroalgae, and predation via corallivorous worms and snails were tested on the host species Orbicella annularis. Two of the tested mechanisms were shown to transmit disease: water transport and the corallivorous snail Coralliophila abbreviata. Between these transmission mechanisms, transport of water between a diseased coral and a healthy coral resulted in disease incidence significantly more frequently in exposed healthy corals. Transmission via water transport also occurred more quickly and was associated with higher rates of tissue loss (up to 3.5 cm d-1) than with the corallivorous snail treatment. In addition, water that was in contact with diseased corals but was filtered with a 0.22-μm filter prior to being introduced to apparently healthy corals also resulted in the transmission of disease signs, but at a much lower rate than when water was not filtered. This study has provided important information on the transmission potential of Caribbean white plague disease and highlights the need for a greater understanding of how these processes operate in the natural environment.

  5. Tropical diseases: definition, geographic distribution, transmission, and classification.

    PubMed

    Zumla, Alimuddin; Ustianowski, Andrew

    2012-06-01

    The term tropical diseases encompasses all diseases that occur principally in the tropics. This term covers all communicable and noncommunicable diseases, genetic disorders, and disease caused by nutritional deficiencies or environmental conditions (such as heat, humidity, and altitude) that are encountered in areas that lie between, and alongside, the Tropic of Cancer and Tropic of Capricorn belts. In tropical countries, apart from noncommunicable diseases, a severe burden of disease is caused by an array of different microorganisms, parasites, land and sea animals, and arthropods.

  6. Tropical diseases: definition, geographic distribution, transmission, and classification.

    PubMed

    Zumla, Alimuddin; Ustianowski, Andrew

    2012-06-01

    The term tropical diseases encompasses all diseases that occur principally in the tropics. This term covers all communicable and noncommunicable diseases, genetic disorders, and disease caused by nutritional deficiencies or environmental conditions (such as heat, humidity, and altitude) that are encountered in areas that lie between, and alongside, the Tropic of Cancer and Tropic of Capricorn belts. In tropical countries, apart from noncommunicable diseases, a severe burden of disease is caused by an array of different microorganisms, parasites, land and sea animals, and arthropods. PMID:22632634

  7. Relationship Between Pneumocystis carinii Burden and the Degree of Host Immunosuppression in an Airborne Transmission Experimental Model.

    PubMed

    Khalife, Sara; Chabé, Magali; Gantois, Nausicaa; Audebert, Christophe; Pottier, Muriel; Hlais, Sani; Pinçon, Claire; Chassat, Thierry; Pierrot, Christine; Khalife, Jamal; Aliouat-Denis, Cécile-Marie; Aliouat, El Moukhtar

    2016-05-01

    To quantitatively assess the risk of contamination by Pneumocystis depending on the degree of immunosuppression (ID) of the exposed rat hosts, we developed an animal model, where rats went through different doses of dexamethasone. Then, natural and aerial transmission of Pneumocystis carinii occurred during cohousing of the rats undergoing gradual ID levels (receivers) with nude rats developing pneumocystosis (seeders). Following contact between receiver and seeder rats, the P. carinii burden of receiver rats was determined by toluidine blue ortho staining and by qPCR targeting the dhfr monocopy gene of this fungus. In this rat model, the level of circulating CD4(+) and CD8(+) T lymphocytes remained significantly stable and different for each dose of dexamethasone tested, thus reaching the goal of a new stable and gradual ID rat model. In addition, an inverse relationship between the P. carinii burden and the level of circulating CD4(+) or CD8(+) T lymphocytes was evidenced. This rat model may be used to study other opportunistic pathogens or even co-infections in a context of gradual ID.

  8. Relationship Between Pneumocystis carinii Burden and the Degree of Host Immunosuppression in an Airborne Transmission Experimental Model.

    PubMed

    Khalife, Sara; Chabé, Magali; Gantois, Nausicaa; Audebert, Christophe; Pottier, Muriel; Hlais, Sani; Pinçon, Claire; Chassat, Thierry; Pierrot, Christine; Khalife, Jamal; Aliouat-Denis, Cécile-Marie; Aliouat, El Moukhtar

    2016-05-01

    To quantitatively assess the risk of contamination by Pneumocystis depending on the degree of immunosuppression (ID) of the exposed rat hosts, we developed an animal model, where rats went through different doses of dexamethasone. Then, natural and aerial transmission of Pneumocystis carinii occurred during cohousing of the rats undergoing gradual ID levels (receivers) with nude rats developing pneumocystosis (seeders). Following contact between receiver and seeder rats, the P. carinii burden of receiver rats was determined by toluidine blue ortho staining and by qPCR targeting the dhfr monocopy gene of this fungus. In this rat model, the level of circulating CD4(+) and CD8(+) T lymphocytes remained significantly stable and different for each dose of dexamethasone tested, thus reaching the goal of a new stable and gradual ID rat model. In addition, an inverse relationship between the P. carinii burden and the level of circulating CD4(+) or CD8(+) T lymphocytes was evidenced. This rat model may be used to study other opportunistic pathogens or even co-infections in a context of gradual ID. PMID:26509699

  9. Zebra Chip: What is the risk of disease transmission through potato tubers?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Zebra chip disease of potato is an economically devastating disease that causes a reduction in quality and quantity of tubers produced, and has affected growers in the United States, Mexico, Central America, and New Zealand. In an effort to determine if disease transmission can occur through fresh ...

  10. Impacts of wildlife baiting and supplemental feeding on infectious disease transmission risk: a synthesis of knowledge.

    PubMed

    Sorensen, Anja; van Beest, Floris M; Brook, Ryan K

    2014-03-01

    Baiting and supplemental feeding of wildlife are widespread, yet highly controversial management practices, with important implications for ecosystems, livestock production, and potentially human health. An often underappreciated threat of such feeding practices is the potential to facilitate intra- and inter-specific disease transmission. We provide a comprehensive review of the scientific evidence of baiting and supplemental feeding on disease transmission risk in wildlife, with an emphasis on large herbivores in North America. While the objectives of supplemental feeding and baiting typically differ, the effects on disease transmission of these practices are largely the same. Both feeding and baiting provide wildlife with natural or non-natural food at specific locations in the environment, which can result in large congregations of individuals and species in a small area and increased local densities. Feeding can lead to increased potential for disease transmission either directly (via direct animal contact) or indirectly (via feed functioning as a fomite, spreading disease into the adjacent environment and to other animals). We identified numerous diseases that currently pose a significant concern to the health of individuals and species of large wild mammals across North America, the spread of which are either clearly facilitated or most likely facilitated by the application of supplemental feeding or baiting. Wildlife diseases also have important threats to human and livestock health. Although the risk of intra- and inter-species disease transmission likely increases when animals concentrate at feeding stations, only in a few cases was disease prevalence and transmission measured and compared between populations. Mostly these were experimental situations under controlled conditions, limiting direct scientific evidence that feeding practices exacerbates disease occurrence, exposure, transmission, and spread in the environment. Vaccination programs utilizing

  11. Influence of vertical and mechanical transmission on the dynamics of dengue disease.

    PubMed

    Esteva, L; Vargas, C

    2000-09-01

    We formulate a non-linear system of differential equations that models the dynamics of transmission of dengue fever. We consider vertical and mechanical transmission in the vector population, and study the effects that they have on the dynamics of the disease. A qualitative analysis as well as some numerical examples are given for the model.

  12. Transmissible spongiform encephalopathies: a family of etiologically complex diseases--a review.

    PubMed

    Bounias, Michel; Purdey, Mark

    2002-10-01

    The upsurge of 'mad cow disease' with its human implications has raised the problem of the etiological mechanisms and the similarities or differences underlying the family of transmissible spongiform encephalopathies. Structural properties of prions are reviewed in connection with their natural distribution and functions, factors of transmissibility and mechanisms of pathogenicity. Polymorphism is examined in relation to disease phenotype variants. The role of oxidative factors is emphasized, while raising complexity about the role of copper ions. Further investigation directions are suggested. PMID:12389776

  13. Potential for transmission of prion disease by contact lenses: an assessment of risk.

    PubMed

    Hogan, R Nick

    2003-01-01

    Prions are small proteinaceous infectious agents known to cause central nervous system infections in both animals and humans. Interest in the pathogenesis of these diseases has grown since the emergence of bovine spongiform encephalopathy (BSE or "mad cow disease") in the United Kingdom and several other countries in Europe. Ingestion of meat products from animals infected with BSE has resulted in transmission of the disease to humans as a variant form of Creutzfeldt-Jakob Disease (vCJD). CJD has a long asymptomatic incubation period, is untreatable, and universally fatal. Hence concern has arisen over other possible routes of disease transmission. Because it is known that prions are found in low levels in the corneas of animals with experimentally induced prion disease, and that a case of human CJD transmission by corneal transplantation has occurred, the question of possible prion transmission through the reuse of diagnostic fitting of contact lenses has surfaced. This article reviews prion diseases of animals and humans, and the data regarding the presence and location of prions in the eye. Issues inherent in the question of corneal and contact lens transmission are discussed. Although some key information has yet to be derived, it appears that the chance of obtaining prion disease through contact lens use is negligible. PMID:12772730

  14. Observing and quantifying airflows in the infection control of aerosol- and airborne-transmitted diseases: an overview of approaches.

    PubMed

    Tang, J W; Noakes, C J; Nielsen, P V; Eames, I; Nicolle, A; Li, Y; Settles, G S

    2011-03-01

    With concerns about the potential for the aerosol and airborne transmission of infectious agents, particularly influenza, more attention is being focused on the effectiveness of infection control procedures to prevent hospital-acquired infections by this route. More recently a number of different techniques have been applied to examine the temporal-spatial information about the airflow patterns and the movement of related, suspended material within this air in a hospital setting. Closer collaboration with engineers has allowed clinical microbiologists, virologists and infection control teams to assess the effectiveness of hospital isolation and ventilation facilities. The characteristics of human respiratory activities have also been investigated using some familiar engineering techniques. Such studies aim to enhance the effectiveness of such preventive measures and have included experiments with human-like mannequins using various tracer gas/particle techniques, real human volunteers with real-time non-invasive Schlieren imaging, numerical modelling using computational fluid dynamics, and small scale physical analogues with water. This article outlines each of these techniques in a non-technical manner, suitable for a clinical readership without specialist airflow or engineering knowledge.

  15. Clinical evidence for rapid transmission of Lyme disease following a tickbite.

    PubMed

    Hynote, Eleanor D; Mervine, Phyllis C; Stricker, Raphael B

    2012-02-01

    Lyme disease transmission to humans by Ixodes ticks is thought to require at least 36-48 h of tick attachment. We describe 3 cases in which transmission of Borrelia burgdorferi, the spirochetal agent of Lyme disease, appears to have occurred in less than 24 h based on the degree of tick engorgement, clinical signs of acute infection, and immunologic evidence of acute Lyme disease. Health care providers and individuals exposed to ticks should be aware that transmission of Lyme disease may occur more rapidly than animal models suggest. A diagnosis of Lyme disease should not be ruled out based on a short tick attachment time in a subject with clinical evidence of B. burgdorferi infection.

  16. Non-systemic transmission of tick-borne diseases: A network approach

    NASA Astrophysics Data System (ADS)

    Ferreri, Luca; Bajardi, Paolo; Giacobini, Mario

    2016-10-01

    Tick-borne diseases can be transmitted via non-systemic (NS) transmission. This occurs when tick gets the infection by co-feeding with infected ticks on the same host resulting in a direct pathogen transmission between the vectors, without infecting the host. This transmission is peculiar, as it does not require any systemic infection of the host. The NS transmission is the main efficient transmission for the persistence of the tick-borne encephalitis virus in nature. By describing the heterogeneous ticks aggregation on hosts through a bipartite graphs representation, we are able to mathematically define the NS transmission and to depict the epidemiological conditions for the pathogen persistence. Despite the fact that the underlying network is largely fragmented, analytical and computational results show that the larger is the variability of the aggregation, and the easier is for the pathogen to persist in the population.

  17. Animal models of disease shed light on Nipah virus pathogenesis and transmission

    PubMed Central

    de Wit, Emmie; Munster, Vincent J.

    2014-01-01

    Nipah virus is an emerging virus infection that causes yearly disease outbreaks with high case fatality rates in Bangladesh. Nipah virus causes encephalitis and systemic vasculitis, sometimes in combination with respiratory disease. Pteropus species fruit bats are the natural reservoir of Nipah virus and zoonotic transmission can occur directly or via an intermediate host; human-to-human transmission occurs regularly. In this review we discuss the current state of knowledge on the pathogenesis and transmission of Nipah virus, focusing on dissemination of the virus through its host, known determinants of pathogenicity and routes of zoonotic and human-to-human transmission. Since data from human cases are sparse, this knowledge is largely based on the results of studies performed in animal models that recapitulate Nipah virus disease in humans. PMID:25229234

  18. Swine Dysentery: Aetiology, Pathogenicity, Determinants of Transmission and the Fight against the Disease

    PubMed Central

    Alvarez-Ordóñez, Avelino; Martínez-Lobo, Francisco Javier; Arguello, Héctor; Carvajal, Ana; Rubio, Pedro

    2013-01-01

    Swine Dysentery (SD) is a severe mucohaemorhagic enteric disease of pigs caused by Brachyspira hyodysenteriae, which has a large impact on pig production and causes important losses due to mortality and sub-optimal performance. Although B. hyodysenteriae has been traditionally considered a pathogen mainly transmitted by direct contact, through the introduction of subclinically infected animals into a previously uninfected herd, recent findings position B. hyodysenteriae as a potential threat for indirect transmission between farms. This article summarizes the knowledge available on the etiological agent of SD and its virulence traits, and reviews the determinants of SD transmission. The between-herds and within-herd transmission routes are addressed. The factors affecting disease transmission are thoroughly discussed, i.e., environmental survival of the pathogen, husbandry factors (production system, production stage, farm management), role of vectors, diet influence and interaction of the microorganism with gut microbiota. Finally, prophylactic and therapeutic approaches to fight against the disease are briefly described. PMID:23665849

  19. Swine dysentery: aetiology, pathogenicity, determinants of transmission and the fight against the disease.

    PubMed

    Alvarez-Ordóñez, Avelino; Martínez-Lobo, Francisco Javier; Arguello, Héctor; Carvajal, Ana; Rubio, Pedro

    2013-05-10

    Swine Dysentery (SD) is a severe mucohaemorhagic enteric disease of pigs caused by Brachyspira hyodysenteriae, which has a large impact on pig production and causes important losses due to mortality and sub-optimal performance. Although B. hyodysenteriae has been traditionally considered a pathogen mainly transmitted by direct contact, through the introduction of subclinically infected animals into a previously uninfected herd, recent findings position B. hyodysenteriae as a potential threat for indirect transmission between farms. This article summarizes the knowledge available on the etiological agent of SD and its virulence traits, and reviews the determinants of SD transmission. The between-herds and within-herd transmission routes are addressed. The factors affecting disease transmission are thoroughly discussed, i.e., environmental survival of the pathogen, husbandry factors (production system, production stage, farm management), role of vectors, diet influence and interaction of the microorganism with gut microbiota. Finally, prophylactic and therapeutic approaches to fight against the disease are briefly described.

  20. A survey of basic reproductive ratios in vector-borne disease transmission modeling

    NASA Astrophysics Data System (ADS)

    Soewono, E.; Aldila, D.

    2015-03-01

    Vector-borne diseases are commonly known in tropical and subtropical countries. These diseases have contributed to more than 10% of world infectious disease cases. Among the vectors responsible for transmitting the diseases are mosquitoes, ticks, fleas, flies, bugs and worms. Several of the diseases are known to contribute to the increasing threat to human health such as malaria, dengue, filariasis, chikungunya, west nile fever, yellow fever, encephalistis, and anthrax. It is necessary to understand the real process of infection, factors which contribute to the complication of the transmission in order to come up with a good and sound mathematical model. Although it is not easy to simulate the real transmission process of the infection, we could say that almost all models have been developed from the already long known Host-Vector model. It constitutes the main transmission processes i.e. birth, death, infection and recovery. From this simple model, the basic concepts of Disease Free and Endemic Equilibria and Basic Reproductive Ratio can be well explained and understood. Theoretical, modeling, control and treatment aspects of disease transmission problems have then been developed for various related diseases. General construction as well as specific forms of basic reproductive ratios for vector-borne diseases are discusses here.

  1. [Creutzfeldt-Jakob disease and other human transmissible spongiform encephalopathies. Part I].

    PubMed

    Zaborowski, Adam

    2004-01-01

    In the first part of this work the main problems of prion diseases--also called transmissible cerebral amyloidoses (TCA) or subacute (transmissible) encephalopathies (SSE, TSE)--and clinical symptoms of Creutzfeldt-Jakob disease are presented. Some problems of neuropathology of Creutzfeldt-Jakob disease and basic informations about other human prion diseases will be presented in the second part. The growth of the interest in prion diseases during last years is caused by the problem of bovine spongiform encephalopathy (BSE or "mad cow disease") and its transmission into a human. The new variant of Creutzfeldt-Jakob disease (nvCJD) has appeared. Prion diseases: Gerstmann-Sträussler-Scheinker syndrome (GSS), kuru, fatal familial insomnia (FFI) and particularly the most frequent of them--Creutzfeldt-Jakob disease (CJD)--have nonspecific, sometimes variable clinical (psychopathological and neurological) symptoms. The imaging, EEG, cerebrospinal fluid tests and other laboratory tests are not specific either and their diagnostic value is limited. Neuropathological studies are needed but their interpretation is often difficult. The only certain diagnostic marker for TSE is the presence of PrP(Sc), the prion protein, which is presently believed to be a direct cause for all transmissible cerebral amyloidoses (TCA). PMID:15307293

  2. Alternative feeding strategies and potential disease transmission in Wisconsin white-tailed deer

    USGS Publications Warehouse

    Thompson, A.K.; Samuel, M.D.; VanDeelen, T.R.

    2008-01-01

    We conducted experimental feeding using 3 feeding methods (pile, spread, trough) and 2 quantities (rationed, ad libitum) of shelled corn to compare deer activity and behavior with control sites and evaluate potential direct and indirect transmission of infectious disease in white-tailed deer (Odocoileus virginianus) in central Wisconsin, USA. Deer use was higher at 2 of the feeding sites than at natural feeding areas (P ??? 0.02). Deer spent a higher proportion of time (P < 0.01) feeding at pile (49%) and spread (61%) treatments than at natural feeding areas (36%). We found higher deer use for rationed than ad libitum feeding quantities and feeding intensity was greatest at rationed piles and lowest at ad libitum spreads. We also observed closer pairwise distances (???0.3 m) among deer when corn was provided in a trough relative to spread (P=0.03). Supplemental feeding poses risks for both direct and indirect disease transmission due to higher deer concentration and more intensive use relative to control areas. Concentrated feeding and contact among deer at feeding sites can also increase risk for disease transmission. Our results indicated that restrictions on feeding quantity would not mitigate the potential for disease transmission None of the feeding strategies we evaluated substantially reduced the potential risk for disease transmission and banning supplemental feeding to reduce transmission is warranted.

  3. Transmission of chagas disease (American trypanosomiasis) by food.

    PubMed

    Pereira, Karen Signori; Schmidt, Flávio Luis; Barbosa, Rodrigo L; Guaraldo, Ana M A; Franco, Regina M B; Dias, Viviane L; Passos, Luiz A C

    2010-01-01

    In April 2009, the centenary of the discovery of the American trypanosomiasis, or Chagas disease, was celebrated. A hundred years after the discovery, little has been invested in diagnostics and treatment because the disease affects mainly poor people in developing countries. However, some changes in the epidemiology of the disease are of great importance today. Chagas disease transmitted through food is a public health concern in all areas where there is a reservoir of Trypanosoma cruzi in wild animals (e.g., mammals and marsupials) and/or where infected triatomine bugs are in contact with human food source items (especially fruits and vegetables). Recently, several outbreaks of illness related to the ingestion of food contaminated with T. cruzi have been recorded in Brazil, Colombia, and Venezuela.

  4. Ebola (Ebola Virus Disease): Q&As on Transmission

    MedlinePlus

    ... Virus Disease) About Ebola Questions & Answers 2014 West Africa Outbreak What's New Timeline Case Counts Previous Case ... U.S. Q&A: 2014 Ebola Outbreak 2014 West Africa Ebola Outbreak Communication Resources Guinea Guinea-Bissau Liberia ...

  5. Modeling Transmission Dynamics and Control of Vector-Borne Neglected Tropical Diseases

    PubMed Central

    Luz, Paula M.; Struchiner, Claudio J.; Galvani, Alison P.

    2010-01-01

    Neglected tropical diseases affect more than one billion people worldwide. The populations most impacted by such diseases are typically the most resource-limited. Mathematical modeling of disease transmission and cost-effectiveness analyses can play a central role in maximizing the utility of limited resources for neglected tropical diseases. We review the contributions that mathematical modeling has made to optimizing intervention strategies of vector-borne neglected diseases. We propose directions forward in the modeling of these diseases, including integrating new knowledge of vector and pathogen ecology, incorporating evolutionary responses to interventions, and expanding the scope of sensitivity analysis in order to achieve robust results. PMID:21049062

  6. Progress towards the elimination of transmission of Chagas disease in Latin America.

    PubMed

    Moncayo, A

    1997-01-01

    From a global perspective, Chagas disease represents the third largest tropical disease burden after malaria and schistosomiasis. The estimated average annual per-capita gross domestic product in Latin America is US$2,966. The economic loss for the continent due to early mortality and disability by this disease in economically most productive young adults currently amounts to US$8,156 million which is equivalent to 2.5% of the external debt of the whole continent in 1995. In 1991, the Ministers of Health of Argentina, Bolivia, Brazil, Chile, Paraguay and Uruguay, launched the Southern Cone Initiative for elimination of transmission of Chagas disease. The progress towards elimination of vectorial and transfusional transmission of Chagas disease in Uruguay, Chile, Argentina and Brazil has been documented by reports from the national control programmes of the above countries. Current data on disinfestation of houses, coverage of screening in blood banks and serology in children and young adults indicate that the interruption of the vectorial and transfusional transmission of Chagas disease will be achieved in these countries as follows: Uruguay and Chile in 1999, Brazil and Argentina in 2003. By eliminating the transmission of Chagas disease in the above countries, the incidence of the disease in the whole of Latin America will be reduced by more than 70%. PMID:9477549

  7. Criticality of Parasitic Disease Transmission in a Diffusive Population

    NASA Astrophysics Data System (ADS)

    He, Min-Hua; Zhang, Duan-Ming; Pan, Gui-Jun; Yin, Yan-Ping; Chen, Zhi-Yuan

    2008-12-01

    Through using the methods of finite-size effect and short time dynamic scaling, we study the critical behavior of parasitic disease spreading process in a diffusive population mediated by a static vector environment. Through comprehensive analysis of parasitic disease spreading we find that this model presents a dynamical phase transition from disease-free state to endemic state with a finite population density. We determine the critical population density, above which the system reaches an epidemic spreading stationary state. We also perform a scaling analysis to determine the order parameter and critical relaxation exponents. The results show that the model does not belong to the usual directed percolation universality class and is compatible with the class of directed percolation with diffusive and conserved fields.

  8. Molecular Infectious Disease Epidemiology: Survival Analysis and Algorithms Linking Phylogenies to Transmission Trees.

    PubMed

    Kenah, Eben; Britton, Tom; Halloran, M Elizabeth; Longini, Ira M

    2016-04-01

    Recent work has attempted to use whole-genome sequence data from pathogens to reconstruct the transmission trees linking infectors and infectees in outbreaks. However, transmission trees from one outbreak do not generalize to future outbreaks. Reconstruction of transmission trees is most useful to public health if it leads to generalizable scientific insights about disease transmission. In a survival analysis framework, estimation of transmission parameters is based on sums or averages over the possible transmission trees. A phylogeny can increase the precision of these estimates by providing partial information about who infected whom. The leaves of the phylogeny represent sampled pathogens, which have known hosts. The interior nodes represent common ancestors of sampled pathogens, which have unknown hosts. Starting from assumptions about disease biology and epidemiologic study design, we prove that there is a one-to-one correspondence between the possible assignments of interior node hosts and the transmission trees simultaneously consistent with the phylogeny and the epidemiologic data on person, place, and time. We develop algorithms to enumerate these transmission trees and show these can be used to calculate likelihoods that incorporate both epidemiologic data and a phylogeny. A simulation study confirms that this leads to more efficient estimates of hazard ratios for infectiousness and baseline hazards of infectious contact, and we use these methods to analyze data from a foot-and-mouth disease virus outbreak in the United Kingdom in 2001. These results demonstrate the importance of data on individuals who escape infection, which is often overlooked. The combination of survival analysis and algorithms linking phylogenies to transmission trees is a rigorous but flexible statistical foundation for molecular infectious disease epidemiology.

  9. Molecular Infectious Disease Epidemiology: Survival Analysis and Algorithms Linking Phylogenies to Transmission Trees.

    PubMed

    Kenah, Eben; Britton, Tom; Halloran, M Elizabeth; Longini, Ira M

    2016-04-01

    Recent work has attempted to use whole-genome sequence data from pathogens to reconstruct the transmission trees linking infectors and infectees in outbreaks. However, transmission trees from one outbreak do not generalize to future outbreaks. Reconstruction of transmission trees is most useful to public health if it leads to generalizable scientific insights about disease transmission. In a survival analysis framework, estimation of transmission parameters is based on sums or averages over the possible transmission trees. A phylogeny can increase the precision of these estimates by providing partial information about who infected whom. The leaves of the phylogeny represent sampled pathogens, which have known hosts. The interior nodes represent common ancestors of sampled pathogens, which have unknown hosts. Starting from assumptions about disease biology and epidemiologic study design, we prove that there is a one-to-one correspondence between the possible assignments of interior node hosts and the transmission trees simultaneously consistent with the phylogeny and the epidemiologic data on person, place, and time. We develop algorithms to enumerate these transmission trees and show these can be used to calculate likelihoods that incorporate both epidemiologic data and a phylogeny. A simulation study confirms that this leads to more efficient estimates of hazard ratios for infectiousness and baseline hazards of infectious contact, and we use these methods to analyze data from a foot-and-mouth disease virus outbreak in the United Kingdom in 2001. These results demonstrate the importance of data on individuals who escape infection, which is often overlooked. The combination of survival analysis and algorithms linking phylogenies to transmission trees is a rigorous but flexible statistical foundation for molecular infectious disease epidemiology. PMID:27070316

  10. Molecular Infectious Disease Epidemiology: Survival Analysis and Algorithms Linking Phylogenies to Transmission Trees

    PubMed Central

    Kenah, Eben; Britton, Tom; Halloran, M. Elizabeth; Longini, Ira M.

    2016-01-01

    Recent work has attempted to use whole-genome sequence data from pathogens to reconstruct the transmission trees linking infectors and infectees in outbreaks. However, transmission trees from one outbreak do not generalize to future outbreaks. Reconstruction of transmission trees is most useful to public health if it leads to generalizable scientific insights about disease transmission. In a survival analysis framework, estimation of transmission parameters is based on sums or averages over the possible transmission trees. A phylogeny can increase the precision of these estimates by providing partial information about who infected whom. The leaves of the phylogeny represent sampled pathogens, which have known hosts. The interior nodes represent common ancestors of sampled pathogens, which have unknown hosts. Starting from assumptions about disease biology and epidemiologic study design, we prove that there is a one-to-one correspondence between the possible assignments of interior node hosts and the transmission trees simultaneously consistent with the phylogeny and the epidemiologic data on person, place, and time. We develop algorithms to enumerate these transmission trees and show these can be used to calculate likelihoods that incorporate both epidemiologic data and a phylogeny. A simulation study confirms that this leads to more efficient estimates of hazard ratios for infectiousness and baseline hazards of infectious contact, and we use these methods to analyze data from a foot-and-mouth disease virus outbreak in the United Kingdom in 2001. These results demonstrate the importance of data on individuals who escape infection, which is often overlooked. The combination of survival analysis and algorithms linking phylogenies to transmission trees is a rigorous but flexible statistical foundation for molecular infectious disease epidemiology. PMID:27070316

  11. Transmission-Blocking Vaccines: Focus on Anti-Vector Vaccines against Tick-Borne Diseases.

    PubMed

    Neelakanta, Girish; Sultana, Hameeda

    2015-06-01

    Tick-borne diseases are a potential threat that account for significant morbidity and mortality in human population worldwide. Vaccines are not available to treat several of the tick-borne diseases. With the emergence and resurgence of several tick-borne diseases, emphasis on the development of transmission-blocking vaccines remains increasing. In this review, we provide a snap shot on some of the potential candidates for the development of anti-vector vaccines (a form of transmission-blocking vaccines) against wide range of hard and soft ticks that include Ixodes, Haemaphysalis, Dermacentor, Amblyomma, Rhipicephalus and Ornithodoros species.

  12. Spatial model for transmission of mosquito-borne diseases

    NASA Astrophysics Data System (ADS)

    Kon, Cynthia Mui Lian; Labadin, Jane

    2015-05-01

    In this paper, a generic model which takes into account spatial heterogeneity for the dynamics of mosquito-borne diseases is proposed. The dissemination of the disease is described by a system of reaction-diffusion partial differential equations. Host human and vector mosquito populations are divided into susceptible and infectious classes. Diffusion is considered to occur in all classes of both populations. Susceptible humans are infected when bitten by infectious mosquitoes. Susceptible mosquitoes bite infectious humans and become infected. The biting rate of mosquitoes is considered to be density dependent on the total human population in different locations. The system is solved numerically and results are shown.

  13. Integration of Spatial and Social Network Analysis in Disease Transmission Studies

    PubMed Central

    Root, Elisabeth D; Giebultowicz, Sophia; Ali, Mohammad; Perez-Heydrich, Carolina; Yunus, Mohammad

    2013-01-01

    This study presents a case study of how social network and spatial analytical methods can be used simultaneously for disease transmission modeling. The paper first reviews strategies employed in previous studies and then offers the example of transmission of two bacterial diarrheal diseases in rural Bangladesh. The goal is to understand how diseases vary socially above and beyond the effects of the local neighborhood context. Patterns of cholera and shigellosis incidence are analyzed in space and within kinship-based social networks in Matlab, Bangladesh. Data include a spatially referenced longitudinal demographic database which consists of approximately 200,000 people and laboratory-confirmed cholera and shigellosis cases from 1983 to 2003. Matrices are created of kinship ties between households using a complete network design and distance matrices are also created to model spatial relationships. Moran's I statistics are calculated to measure clustering within both social and spatial matrices. Combined spatial effects-spatial disturbance models are built to simultaneously analyze spatial and social effects while controlling for local environmental context. Results indicate that cholera and shigellosis always clusters in space and only sometimes within social networks. This suggests that the local environment is most important for understanding transmission of both diseases however kinship-based social networks also influence their transmission. Simultaneous spatial and social network analysis can help us better understand disease transmission and this study has offered several strategies on how. PMID:24163443

  14. Trade-offs in group living: transmission and disease resistance in leaf-cutting ants.

    PubMed Central

    Hughes, William O H; Eilenberg, Jørgen; Boomsma, Jacobus J

    2002-01-01

    Sociality can be associated with significant costs due to the increased risk of disease transmission. However, in some organisms the costs may be offset by benefits due to improvements in defences against parasites. To examine this possible trade-off between infection risk and disease resistance, we used Acromyrmex leaf-cutting ants and the entomopathogenic fungus Metarhizium anisopliae as the model system. Ants exposed to the parasite were found to have substantially improved survival when they were kept with nest-mates, while the cost of being in a group in terms of increased disease transmission was very low. The efficiency of transmission is described by the transmission parameter, which decreased with increasing host density showing that transmission rates are inversely density dependent. Both grooming and antibiotic secretions appeared to be important in resistance against the parasite, with the defences of small workers being particularly effective. The results indicate that leaf-cutting ant colonies may have much greater resistance to disease than would be predicted from the high densities of host individuals within them. Unlike most organisms, group living in these ants may actually be associated with a net benefit in terms of disease dynamics. PMID:12350269

  15. Impact of environmental stressors on the dynamics of disease transmission.

    PubMed

    Loge, Frank J; Arkoosh, Mary R; Ginn, Timothy R; Johnson, Lyndal L; Collier, Tracy K

    2005-09-15

    Infectious disease within outmigrant juvenile salmon in the Columbia River Basin is modulated, in part, by abiotic stressors that influence host-susceptibility. Through the application of a dose-structured population dynamic model, we show that chemical (both in the river and in the estuary) and in-river (e.g., dams and/or predation) stressors influence host-susceptibility, increasing the mean force of infection (defined as the per capita acquisition rate of infection) by a factor of 2.2 and 1.6, respectively. Using Listonella anguillarum as a model pathogen, nonchemical in-river and chemical stressors contribute equally to a cumulative incidence of delayed disease-induced mortalities in Chinook salmon that range from 3% to 18% for estuary residence times of 30-120 days, respectively. Mitigation of environmental stressors that increase host-susceptibility could represent a significant component in future management strategies to recover listed stocks. PMID:16201666

  16. Evaluation of the transmission risk of foot-and-mouth disease in Japan.

    PubMed

    Hayama, Yoko; Yamamoto, Takehisa; Kobayashi, Sota; Muroga, Norihiko; Tsutsui, Toshiyuki

    2015-09-01

    The transmission risk of foot-and-mouth disease (FMD) in Japan was evaluated using a mathematical FMD transmission model. The distance-based transmission rate between farms, which was parameterized using the FMD epidemic data in 2010 in Japan, was used to calculate the local-level reproduction numbers-expected numbers of secondary infections caused by one infected farm-for all cattle and pig farms in the country, which were then visualized as a risk map. The risk map demonstrated the spatial heterogeneity of transmission risk in the country and identified risk areas with higher possibility of disease spread. This result suggests that, particularly in high-risk areas, it is important to prepare for the smooth and efficient implementation of control measures against FMD outbreaks.

  17. Bat–man disease transmission: zoonotic pathogens from wildlife reservoirs to human populations

    PubMed Central

    Allocati, N; Petrucci, A G; Di Giovanni, P; Masulli, M; Di Ilio, C; De Laurenzi, V

    2016-01-01

    Bats are natural reservoir hosts and sources of infection of several microorganisms, many of which cause severe human diseases. Because of contact between bats and other animals, including humans, the possibility exists for additional interspecies transmissions and resulting disease outbreaks. The purpose of this article is to supply an overview on the main pathogens isolated from bats that have the potential to cause disease in humans. PMID:27551536

  18. Bat-man disease transmission: zoonotic pathogens from wildlife reservoirs to human populations.

    PubMed

    Allocati, N; Petrucci, A G; Di Giovanni, P; Masulli, M; Di Ilio, C; De Laurenzi, V

    2016-01-01

    Bats are natural reservoir hosts and sources of infection of several microorganisms, many of which cause severe human diseases. Because of contact between bats and other animals, including humans, the possibility exists for additional interspecies transmissions and resulting disease outbreaks. The purpose of this article is to supply an overview on the main pathogens isolated from bats that have the potential to cause disease in humans. PMID:27551536

  19. The effect of recruitment rate and other demographic parameters on the transmission of dengue disease

    NASA Astrophysics Data System (ADS)

    Supriatna, A. K.; Anggriani, N.

    2015-03-01

    One of important factors which always appears in most of dengue transmission mathematical model is the number of new susceptible recruited into the susceptible compartment. In this paper we discuss the effect of different rates of recruitment on the transmission of dengue disease. We choose a dengue transmission model with the most realistic form of recruitment rate and analyze the effect of environmental change to the transmission of dengue based on the selected model. We model the effect of environmental change by considering that it can alter the value of mosquito's carrying capacity and mosquito's death rate. We found that the most prevalent effect of the environmental change to the transmission of dengue is when it can alter the death rate of the mosquitoes.

  20. Chronic Wasting Disease: Transmission Mechanisms and the Possibility of Harvest Management

    PubMed Central

    Potapov, Alex; Merrill, Evelyn; Pybus, Margo; Lewis, Mark A.

    2016-01-01

    We develop a model of CWD management by nonselective deer harvest, currently the most feasible approach available for managing CWD in wild populations. We use the model to explore the effects of 6 common harvest strategies on disease prevalence and to identify potential optimal harvest policies for reducing disease prevalence without population collapse. The model includes 4 deer categories (juveniles, adult females, younger adult males, older adult males) that may be harvested at different rates, a food-based carrying capacity, which influences juvenile survival but not adult reproduction or survival, and seasonal force of infection terms for each deer category under differing frequency-dependent transmission dynamics resulting from environmental and direct contact mechanisms. Numerical experiments show that the interval of transmission coefficients β where the disease can be controlled is generally narrow and efficiency of a harvest policy to reduce disease prevalence depends crucially on the details of the disease transmission mechanism, in particular on the intensity of disease transmission to juveniles and the potential differences in the behavior of older and younger males that influence contact rates. Optimal harvest policy to minimize disease prevalence for each of the assumed transmission mechanisms is shown to depend on harvest intensity. Across mechanisms, a harvest that focuses on antlered deer, without distinguishing between age classes reduces disease prevalence most consistently, whereas distinguishing between young and older antlered deer produces higher uncertainty in the harvest effects on disease prevalence. Our results show that, despite uncertainties, a modelling approach can determine classes of harvest strategy that are most likely to be effective in combatting CWD. PMID:26963921

  1. Chronic Wasting Disease: Transmission Mechanisms and the Possibility of Harvest Management.

    PubMed

    Potapov, Alex; Merrill, Evelyn; Pybus, Margo; Lewis, Mark A

    2016-01-01

    We develop a model of CWD management by nonselective deer harvest, currently the most feasible approach available for managing CWD in wild populations. We use the model to explore the effects of 6 common harvest strategies on disease prevalence and to identify potential optimal harvest policies for reducing disease prevalence without population collapse. The model includes 4 deer categories (juveniles, adult females, younger adult males, older adult males) that may be harvested at different rates, a food-based carrying capacity, which influences juvenile survival but not adult reproduction or survival, and seasonal force of infection terms for each deer category under differing frequency-dependent transmission dynamics resulting from environmental and direct contact mechanisms. Numerical experiments show that the interval of transmission coefficients β where the disease can be controlled is generally narrow and efficiency of a harvest policy to reduce disease prevalence depends crucially on the details of the disease transmission mechanism, in particular on the intensity of disease transmission to juveniles and the potential differences in the behavior of older and younger males that influence contact rates. Optimal harvest policy to minimize disease prevalence for each of the assumed transmission mechanisms is shown to depend on harvest intensity. Across mechanisms, a harvest that focuses on antlered deer, without distinguishing between age classes reduces disease prevalence most consistently, whereas distinguishing between young and older antlered deer produces higher uncertainty in the harvest effects on disease prevalence. Our results show that, despite uncertainties, a modelling approach can determine classes of harvest strategy that are most likely to be effective in combatting CWD. PMID:26963921

  2. Chronic Wasting Disease: Transmission Mechanisms and the Possibility of Harvest Management.

    PubMed

    Potapov, Alex; Merrill, Evelyn; Pybus, Margo; Lewis, Mark A

    2016-01-01

    We develop a model of CWD management by nonselective deer harvest, currently the most feasible approach available for managing CWD in wild populations. We use the model to explore the effects of 6 common harvest strategies on disease prevalence and to identify potential optimal harvest policies for reducing disease prevalence without population collapse. The model includes 4 deer categories (juveniles, adult females, younger adult males, older adult males) that may be harvested at different rates, a food-based carrying capacity, which influences juvenile survival but not adult reproduction or survival, and seasonal force of infection terms for each deer category under differing frequency-dependent transmission dynamics resulting from environmental and direct contact mechanisms. Numerical experiments show that the interval of transmission coefficients β where the disease can be controlled is generally narrow and efficiency of a harvest policy to reduce disease prevalence depends crucially on the details of the disease transmission mechanism, in particular on the intensity of disease transmission to juveniles and the potential differences in the behavior of older and younger males that influence contact rates. Optimal harvest policy to minimize disease prevalence for each of the assumed transmission mechanisms is shown to depend on harvest intensity. Across mechanisms, a harvest that focuses on antlered deer, without distinguishing between age classes reduces disease prevalence most consistently, whereas distinguishing between young and older antlered deer produces higher uncertainty in the harvest effects on disease prevalence. Our results show that, despite uncertainties, a modelling approach can determine classes of harvest strategy that are most likely to be effective in combatting CWD.

  3. Vector species richness increases haemorrhagic disease prevalence through functional diversity modulating the duration of seasonal transmission.

    PubMed

    Park, Andrew W; Cleveland, Christopher A; Dallas, Tad A; Corn, Joseph L

    2016-06-01

    Although many parasites are transmitted between hosts by a suite of arthropod vectors, the impact of vector biodiversity on parasite transmission is poorly understood. Positive relationships between host infection prevalence and vector species richness (SR) may operate through multiple mechanisms, including (i) increased vector abundance, (ii) a sampling effect in which species of high vectorial capacity are more likely to occur in species-rich communities, and (iii) functional diversity whereby communities comprised species with distinct phenologies may extend the duration of seasonal transmission. Teasing such mechanisms apart is impeded by a lack of appropriate data, yet could highlight a neglected role for functional diversity in parasite transmission. We used statistical modelling of extensive host, vector and microparasite data to test the hypothesis that functional diversity leading to longer seasonal transmission explained variable levels of disease in a wildlife population. We additionally developed a simple transmission model to guide our expectation of how an increased transmission season translates to infection prevalence. Our study demonstrates that vector SR is associated with increased levels of disease reporting, but not via increases in vector abundance or via a sampling effect. Rather, the relationship operates by extending the length of seasonal transmission, in line with theoretical predictions.

  4. Transmission of sexually transmitted diseases by donor semen.

    PubMed

    Shanis, B S; Check, J H; Baker, A F

    1989-01-01

    Therapeutic insemination by donor (TID) is being used with increasing frequency. Because many diseases, some of which are lethal, can be transmitted through semen, the American Fertility Society established guidelines for use of donor sperm. They limit TID to cases of male infertility or hereditary/genetic disorders. Donor selection requires good health and absence of genetic abnormalities; criteria for semen including normal sperm motility, concentration, and normal morphology, and blood screening for infectious agents. Human immunodeficiency virus (HIV) testing should be performed initially in donors for fresh semen inseminations. If positive, the assay is verified with a Western blot test; if negative, the donor should be screened at 6-month intervals. Frozen samples should not be used until the 180 day reevaluation of the donor. Many studies show higher pregnancy rates using fresh rather than frozen semen samples for insemination. New methods of cryopreservation minimize the deleterious effects of freezing. If these effects, namely decreased sperm motility and impaired penetration ability, are eliminated, pregnancy rates can be expected to rise. Frozen semen is preferable because it allows time for sexually transmitted diseases to manifest themselves and for specimens from those donors to be rejected prior to use. PMID:2619413

  5. Spatio-Temporal Transmission Patterns of Black-Band Disease in a Coral Community

    PubMed Central

    Zvuloni, Assaf; Artzy-Randrup, Yael; Stone, Lewi; Kramarsky-Winter, Esti; Barkan, Roy; Loya, Yossi

    2009-01-01

    Background Transmission mechanisms of black-band disease (BBD) in coral reefs are poorly understood, although this disease is considered to be one of the most widespread and destructive coral infectious diseases. The major objective of this study was to assess transmission mechanisms of BBD in the field based on the spatio-temporal patterns of the disease. Methodology/Principal Findings 3,175 susceptible and infected corals were mapped over an area of 10×10 m in Eilat (northern Gulf of Aqaba, Red Sea) and the distribution of the disease was examined monthly throughout almost two full disease cycles (June 2006–December 2007). Spatial and spatio-temporal analyses were applied to infer the transmission pattern of the disease and to calculate key epidemiological parameters such as (basic reproduction number). We show that the prevalence of the disease is strongly associated with high water temperature. When water temperatures rise and disease prevalence increases, infected corals exhibit aggregated distributions on small spatial scales of up to 1.9 m. Additionally, newly-infected corals clearly appear in proximity to existing infected corals and in a few cases in direct contact with them. We also present and test a model of water-borne infection, indicating that the likelihood of a susceptible coral becoming infected is defined by its spatial location and by the relative spatial distribution of nearby infected corals found in the site. Conclusions/Significance Our results provide evidence that local transmission, but not necessarily by direct contact, is likely to be an important factor in the spread of the disease over the tested spatial scale. In the absence of potential disease vectors with limited mobility (e.g., snails, fireworms) in the studied site, water-borne infection is likely to be a significant transmission mechanism of BBD. Our suggested model of water-borne transmission supports this hypothesis. The spatio-temporal analysis also points out that

  6. Transmission of Chronic Wasting Disease in Wisconsin White-Tailed Deer: Implications for Disease Spread and Management

    PubMed Central

    Jennelle, Christopher S.; Henaux, Viviane; Wasserberg, Gideon; Thiagarajan, Bala; Rolley, Robert E.; Samuel, Michael D.

    2014-01-01

    Few studies have evaluated the rate of infection or mode of transmission for wildlife diseases, and the implications of alternative management strategies. We used hunter harvest data from 2002 to 2013 to investigate chronic wasting disease (CWD) infection rate and transmission modes, and address how alternative management approaches affect disease dynamics in a Wisconsin white-tailed deer population. Uncertainty regarding demographic impacts of CWD on cervid populations, human and domestic animal health concerns, and potential economic consequences underscore the need for strategies to control CWD distribution and prevalence. Using maximum-likelihood methods to evaluate alternative multi-state deterministic models of CWD transmission, harvest data strongly supports a frequency-dependent transmission structure with sex-specific infection rates that are two times higher in males than females. As transmissible spongiform encephalopathies are an important and difficult-to-study class of diseases with major economic and ecological implications, our work supports the hypothesis of frequency-dependent transmission in wild deer at a broad spatial scale and indicates that effective harvest management can be implemented to control CWD prevalence. Specifically, we show that harvest focused on the greater-affected sex (males) can result in stable population dynamics and control of CWD within the next 50 years, given the constraints of the model. We also provide a quantitative estimate of geographic disease spread in southern Wisconsin, validating qualitative assessments that CWD spreads relatively slowly. Given increased discovery and distribution of CWD throughout North America, insights from our study are valuable to management agencies and to the general public concerned about the impacts of CWD on white-tailed deer populations. PMID:24658535

  7. Transmission of chronic wasting disease in Wisconsin white-tailed deer: implications for disease spread and management.

    PubMed

    Jennelle, Christopher S; Henaux, Viviane; Wasserberg, Gideon; Thiagarajan, Bala; Rolley, Robert E; Samuel, Michael D

    2014-01-01

    Few studies have evaluated the rate of infection or mode of transmission for wildlife diseases, and the implications of alternative management strategies. We used hunter harvest data from 2002 to 2013 to investigate chronic wasting disease (CWD) infection rate and transmission modes, and address how alternative management approaches affect disease dynamics in a Wisconsin white-tailed deer population. Uncertainty regarding demographic impacts of CWD on cervid populations, human and domestic animal health concerns, and potential economic consequences underscore the need for strategies to control CWD distribution and prevalence. Using maximum-likelihood methods to evaluate alternative multi-state deterministic models of CWD transmission, harvest data strongly supports a frequency-dependent transmission structure with sex-specific infection rates that are two times higher in males than females. As transmissible spongiform encephalopathies are an important and difficult-to-study class of diseases with major economic and ecological implications, our work supports the hypothesis of frequency-dependent transmission in wild deer at a broad spatial scale and indicates that effective harvest management can be implemented to control CWD prevalence. Specifically, we show that harvest focused on the greater-affected sex (males) can result in stable population dynamics and control of CWD within the next 50 years, given the constraints of the model. We also provide a quantitative estimate of geographic disease spread in southern Wisconsin, validating qualitative assessments that CWD spreads relatively slowly. Given increased discovery and distribution of CWD throughout North America, insights from our study are valuable to management agencies and to the general public concerned about the impacts of CWD on white-tailed deer populations.

  8. The ebb and flow of airborne pathogens: Monitoring and use in disease management decisions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Perhaps the earliest form of monitoring the regional spread of plant disease was a group of growers gathering together at the market and discussing what they see in their crops. This type of reporting continues to this day through regional extension blogs, by crop consultants and more formal scoutin...

  9. Modeling mass drug treatment and resistant filaria disease transmission

    NASA Astrophysics Data System (ADS)

    Fuady, A. M.; Nuraini, N.; Soewono, E.; Tasman, H.; Supriatna, A. K.

    2014-03-01

    It has been indicated that a long term application of combined mass drug treatment may contribute to the development of drug resistance in lymphatic filariasis. This phenomenon is not well understood due to the complexity of filaria life cycle. In this paper we formulate a mathematical model for the spread of mass drug resistant in a filaria endemic region. The model is represented in a 13-dimensional Host-Vector system. The basic reproductive ratio of the system which is obtained from the next generation matrix, and analysis of stability of both the disease free equilibrium and the coexistence equilibria are shown. Numerical simulation for long term dynamics for possible field conditions is also shown.

  10. Somatic Mosaicism: Implications for Disease and Transmission Genetics

    PubMed Central

    Campbell, Ian M.; Shaw, Chad A.; Stankiewicz, Pawel; Lupski, James R.

    2015-01-01

    Nearly all of the genetic material among cells within an organism is identical. However, single nucleotide variants (SNVs), indels, copy number variants (CNVs), and other structural variants (SVs) continually accumulate as cells divide during development. This process results in an organism composed of countless cells, each with its own unique personal genome. Thus, every human is undoubtedly mosaic. Mosaic mutations can go unnoticed, underlie genetic disease or normal human variation, and may be transmitted to the next generation as constitutional variants. Here, we review the influence of the developmental timing of mutations, the mechanisms by which they arise, methods for detecting mosaic variants, and the risk of passing these mutations on to the next generation. PMID:25910407

  11. Oxidative stress-induced telomeric erosion as a mechanism underlying airborne particulate matter-related cardiovascular disease

    PubMed Central

    2012-01-01

    Particulate matter (PM) pollution is responsible for hundreds of thousands of deaths worldwide, the majority due to cardiovascular disease (CVD). While many potential pathophysiological mechanisms have been proposed, there is not yet a consensus as to which are most important in causing pollution-related morbidity/mortality. Nor is there consensus regarding which specific types of PM are most likely to affect public health in this regard. One toxicological mechanism linking exposure to airborne PM with CVD outcomes is oxidative stress, a contributor to the development of CVD risk factors including atherosclerosis. Recent work suggests that accelerated shortening of telomeres and, thus, early senescence of cells may be an important pathway by which oxidative stress may accelerate biological aging and the resultant development of age-related morbidity. This pathway may explain a significant proportion of PM-related adverse health outcomes, since shortened telomeres accelerate the progression of many diseases. There is limited but consistent evidence that vehicular emissions produce oxidative stress in humans. Given that oxidative stress is associated with accelerated erosion of telomeres, and that shortened telomeres are linked with acceleration of biological ageing and greater incidence of various age-related pathology, including CVD, it is hypothesized that associations noted between certain pollution types and sources and oxidative stress may reflect a mechanism by which these pollutants result in CVD-related morbidity and mortality, namely accelerated aging via enhanced erosion of telomeres. This paper reviews the literature providing links among oxidative stress, accelerated erosion of telomeres, CVD, and specific sources and types of air pollutants. If certain PM species/sources might be responsible for adverse health outcomes via the proposed mechanism, perhaps the pathway to reducing mortality/morbidity from PM would become clearer. Not only would pollution

  12. Mother to offspring transmission of chronic wasting disease in reeves' muntjac deer.

    PubMed

    Nalls, Amy V; McNulty, Erin; Powers, Jenny; Seelig, Davis M; Hoover, Clare; Haley, Nicholas J; Hayes-Klug, Jeanette; Anderson, Kelly; Stewart, Paula; Goldmann, Wilfred; Hoover, Edward A; Mathiason, Candace K

    2013-01-01

    The horizontal transmission of prion diseases has been well characterized in bovine spongiform encephalopathy (BSE), chronic wasting disease (CWD) of deer and elk and scrapie of sheep, and has been regarded as the primary mode of transmission. Few studies have monitored the possibility of vertical transmission occurring within an infected mother during pregnancy. To study the potential for and pathway of vertical transmission of CWD in the native cervid species, we used a small cervid model-the polyestrous breeding, indoor maintainable, Reeves' muntjac deer-and determined that the susceptibility and pathogenesis of CWD in these deer reproduce that in native mule and white-tailed deer. Moreover, we demonstrate here that CWD prions are transmitted from doe to fawn. Maternal CWD infection also appears to result in lower percentage of live birth offspring. In addition, evolving evidence from protein misfolding cyclic amplification (PMCA) assays on fetal tissues suggest that covert prion infection occurs in utero. Overall, our findings demonstrate that transmission of prions from mother to offspring can occur, and may be underestimated for all prion diseases.

  13. HIV/AIDS and Other Infectious Diseases Among Correctional Inmates: Transmission, Burden, and an Appropriate Response

    PubMed Central

    Hammett, Theodore M.

    2006-01-01

    Correctional inmates engage in drug-related and sexual risk behaviors, and the transmission of HIV, hepatitis, and sexually transmitted diseases occurs in correctional facilities. However, there is uncertainty about the extent of transmission, and hyperbolic descriptions of its extent may further stigmatize inmates and elicit punitive responses. Whether infection was acquired within or outside correctional facilities, the prevalence of HIV and other infectious diseases is much higher among inmates than among those in the general community, and the burden of disease among inmates and releasees is disproportionately heavy. A comprehensive response is needed, including voluntary counseling and testing on request that is linked to high-quality treatment, disease prevention education, substance abuse treatment, and discharge planning and transitional programs for releasees. PMID:16449578

  14. Determinants of the Transmission Variation of Hand, Foot and Mouth Disease in China

    PubMed Central

    Li, Xinmin

    2016-01-01

    Severe outbreaks of hand, foot and mouth disease (HFMD) have occurred in China for decades. Our understanding of the HFMD transmission process and its determinants is still limited. In this paper, factors that affect the local variation of HFMD transmission process were studied. Three classes of factors, including meteorological, demographic and public health intervention factors, were carefully selected and their effects on HFMD transmission were investigated with Pearson’s correlation coefficient and multiple linear regression models. The determining factors for the variation of HFMD transmission were different for the southeastern and the northwestern regions of China. In the northwest, fadeouts occurred yearly, and the average age at infection and the fadeout were negatively correlated with the population density. In the southeast, HFMD transmission was governed by the combined effects of the birth rate, the relative humidity and the interaction of the Health System Performance and the log of the population density. When the Health System Performance was low, HFMD transmission increased with the population density, but when the Health System Performance was high, the better health performance counteracted the transmission increase due to the higher population density. PMID:27701445

  15. Strain-specific antibodies reduce co-feeding transmission of the Lyme disease pathogen, Borrelia afzelii.

    PubMed

    Jacquet, Maxime; Durand, Jonas; Rais, Olivier; Voordouw, Maarten J

    2016-03-01

    Vector-borne pathogens use a diversity of strategies to evade the vertebrate immune system. Co-feeding transmission is a potential immune evasion strategy because the vector-borne pathogen minimizes the time spent in the vertebrate host. We tested whether the Lyme disease pathogen, Borrelia afzelii, can use co-feeding transmission to escape the acquired immune response in the vertebrate host. We induced a strain-specific, protective antibody response by immunizing mice with one of two variants of OspC (A3 and A10), the highly variable outer surface protein C of Borrelia pathogens. Immunized mice were challenged via tick bite with B. afzelii strains A3 or A10 and infested with larval ticks at days 2 and 34 post-infection to measure co-feeding and systemic transmission respectively. Antibodies against a particular OspC variant significantly reduced co-feeding transmission of the targeted (homologous) strain but not the non-targeted (heterologous) strain. Cross-immunity between OspC antigens had no effect in co-feeding ticks but reduced the spirochaete load twofold in ticks infected via systemic transmission. In summary, OspC-specific antibodies reduced co-feeding transmission of a homologous but not a heterologous strain of B. afzelii. Co-feeding transmission allowed B. afzelii to evade the negative consequences of cross-immunity on the tick spirochaete load.

  16. Modeling routes of chronic wasting disease transmission: Environmental prion persistence promotes deer population decline and extinction

    USGS Publications Warehouse

    Almberg, Emily S.; Cross, Paul C.; Johnson, Christopher J.; Heisey, Dennis M.; Richards, Bryan J.

    2011-01-01

    Chronic wasting disease (CWD) is a fatal disease of deer, elk, and moose transmitted through direct, animal-to-animal contact, and indirectly, via environmental contamination. Considerable attention has been paid to modeling direct transmission, but despite the fact that CWD prions can remain infectious in the environment for years, relatively little information exists about the potential effects of indirect transmission on CWD dynamics. In the present study, we use simulation models to demonstrate how indirect transmission and the duration of environmental prion persistence may affect epidemics of CWD and populations of North American deer. Existing data from Colorado, Wyoming, and Wisconsin's CWD epidemics were used to define plausible short-term outcomes and associated parameter spaces. Resulting long-term outcomes range from relatively low disease prevalence and limited host-population decline to host-population collapse and extinction. Our models suggest that disease prevalence and the severity of population decline is driven by the duration that prions remain infectious in the environment. Despite relatively low epidemic growth rates, the basic reproductive number, R0, may be much larger than expected under the direct-transmission paradigm because the infectious period can vastly exceed the host's life span. High prion persistence is expected to lead to an increasing environmental pool of prions during the early phases (i.e. approximately during the first 50 years) of the epidemic. As a consequence, over this period of time, disease dynamics will become more heavily influenced by indirect transmission, which may explain some of the observed regional differences in age and sex-specific disease patterns. This suggests management interventions, such as culling or vaccination, will become increasingly less effective as CWD epidemics progress.

  17. In the case of transmission of Mycobacterium ulcerans in buruli ulcer disease Acanthamoeba species stand accused.

    PubMed

    Wilson, M D; Boakye, D A; Mosi, L; Asiedu, K

    2011-03-01

    Buruli ulcer disease caused by Mycobacterium ulcerans results in extensive destruction of skin and soft tissue and long-term functional disabilities that ultimately require surgery and rehabilitation. The disease is associated with aquatic and swampy environments with the mycobacterium occurring in biofilms, soil, aquatic insects, fish and wildlife however, the mode of transmission to humans remains an enigma. Current transmission ideas including bites from predatory water bugs and mosquitoes, do not explain satisfactorily the spasmodic disease distribution in human populations. Here we argue that Acanthamoeba species are the natural hosts of M. ulcerans and are mainly responsible for disease transmission because; (i) Acanthamoebae are known natural hosts of several microbial pathogens including M. marinum, M. avium and Legionella pneumophila, (ii) culture of slow-to-grow microbial pathogens hosted in nature by Acanthamoeba spp is enhanced when the media is seeded with the protozoa, (iii) acanthamoebae and M. ulcerans share similar bio-ecological and epidemiological settings, (iv) documented evidence that prior growth of L. pneumophila and M. avium in acanthamoebae influences entry mechanisms, intracellular growth and virulence in human monocytes, (v) Acanthamoeba spp also infect humans and cause diseases via routes of openings including broken skin and sites of trauma similar to M. ulcerans and (vi) M. ulcerans is rather a fastidious intracellular organism as recent analysis of the genome indicate. We argue further that temperature plays a significant role in transmission determining the fate of either the intracellular microbe or the host cells. Also, Acanthamoeba-pathogen association has a long evolutionary history because the same set of bacterial genes and gene products e.g. in L. pneumophila are required for survival in both mammalian and protozoan host cells. We suggest that the involvement of Acanthamoeba in the transmission of M. ulcerans to humans better

  18. Airborne Transparencies.

    ERIC Educational Resources Information Center

    Horne, Lois Thommason

    1984-01-01

    Starting from a science project on flight, art students discussed and investigated various means of moving in space. Then they made acetate illustrations which could be used as transparencies. The projection phenomenon made the illustrations look airborne. (CS)

  19. FIRST REPORT OF ACUTE CHAGAS DISEASE BY VECTOR TRANSMISSION IN RIO DE JANEIRO STATE, BRAZIL

    PubMed Central

    SANGENIS, Luiz Henrique Conde; DE SOUSA, Andréa Silvestre; SPERANDIO DA SILVA, Gilberto Marcelo; XAVIER, Sérgio Salles; MACHADO, Carolina Romero Cardoso; BRASIL, Patrícia; DE CASTRO, Liane; DA SILVA, Sidnei; GEORG, Ingebourg; SARAIVA, Roberto Magalhães; do BRASIL, Pedro Emmanuel Alvarenga Americano; HASSLOCHER-MORENO, Alejandro Marcel

    2015-01-01

    SUMMARY Chagas disease (CD) is an endemic anthropozoonosis from Latin America of which the main means of transmission is the contact of skin lesions or mucosa with the feces of triatomine bugs infected by Trypanosoma cruzi. In this article, we describe the first acute CD case acquired by vector transmission in the Rio de Janeiro State and confirmed by parasitological, serological and PCR tests. The patient presented acute cardiomyopathy and pericardial effusion without cardiac tamponade. Together with fever and malaise, a 3 cm wide erythematous, non-pruritic, papule compatible with a "chagoma" was found on his left wrist. This case report draws attention to the possible transmission of CD by non-domiciled native vectors in non-endemic areas. Therefore, acute CD should be included in the diagnostic workout of febrile diseases and acute myopericarditis in Rio de Janeiro. PMID:26422165

  20. Topological and Historical Considerations for Infectious Disease Transmission among Injecting Drug Users in Bushwick, Brooklyn (USA)

    PubMed Central

    Dombrowski, Kirk; Curtis, Richard; Friedman, Samuel; Khan, Bilal

    2014-01-01

    Recent interest by physicists in social networks and disease transmission factors has prompted debate over the topology of degree distributions in sexual networks. Social network researchers have been critical of “scale-free” Barabasi-Albert approaches, and largely rejected the preferential attachment, “rich-get-richer” assumptions that underlie that model. Instead, research on sexual networks has pointed to the importance of homophily and local sexual norms in dictating degree distributions, and thus disease transmission thresholds. Injecting Drug User (IDU) network topologies may differ from the emerging models of sexual networks, however. Degree distribution analysis of a Brooklyn, NY, IDU network indicates a different topology than the spanning tree configurations discussed for sexual networks, instead featuring comparatively short cycles and high concurrency. Our findings suggest that IDU networks do in some ways conform to a “scale-free” topology, and thus may represent “reservoirs” of potential infection despite seemingly low transmission thresholds. PMID:24672745

  1. Warmer temperatures increase disease transmission and outbreak intensity in a host-pathogen system.

    PubMed

    Elderd, Bret D; Reilly, James R

    2014-07-01

    While rising global temperatures are increasingly affecting both species and their biotic interactions, the debate about whether global warming will increase or decrease disease transmission between individuals remains far from resolved. This may stem from the lack of empirical data. Using a tractable and easily manipulated insect host-pathogen system, we conducted a series of field and laboratory experiments to examine how increased temperatures affect disease transmission using the crop-defoliating pest, the fall armyworm (Spodoptera frugiperda) and its species-specific baculovirus, which causes a fatal infection. To examine the effects of temperature on disease transmission in the field, we manipulated baculovirus density and temperature. As infection occurs when a host consumes leaf tissue on which the pathogen resides, baculovirus density was controlled by placing varying numbers of infected neonate larvae on experimental plants. Temperature was manipulated by using open-top chambers (OTCs). The laboratory experiments examined how increased temperatures affect fall armyworm feeding and development rates, which provide insight into how host feeding behaviour and physiology may affect transmission. Disease transmission and outbreak intensity, measured as the cumulative fraction infected during an epizootic, increased at higher temperatures. However, there was no appreciable change in the mean transmission rate of the disease, which is often the focus of empirical and theoretical research. Instead, the coefficient of variation (CV) associated with the transmission rate shrunk. As the CV decreased, heterogeneity in disease risk across individuals declined, which resulted in an increase in outbreak intensity. In the laboratory, increased temperatures increased feeding rates and decreased developmental times. As the host consumes the virus along with the leaf tissue on which it resides, increased feeding rate is likely to increase the probability of an individual

  2. Warmer temperatures increase disease transmission and outbreak intensity in a host-pathogen system.

    PubMed

    Elderd, Bret D; Reilly, James R

    2014-07-01

    While rising global temperatures are increasingly affecting both species and their biotic interactions, the debate about whether global warming will increase or decrease disease transmission between individuals remains far from resolved. This may stem from the lack of empirical data. Using a tractable and easily manipulated insect host-pathogen system, we conducted a series of field and laboratory experiments to examine how increased temperatures affect disease transmission using the crop-defoliating pest, the fall armyworm (Spodoptera frugiperda) and its species-specific baculovirus, which causes a fatal infection. To examine the effects of temperature on disease transmission in the field, we manipulated baculovirus density and temperature. As infection occurs when a host consumes leaf tissue on which the pathogen resides, baculovirus density was controlled by placing varying numbers of infected neonate larvae on experimental plants. Temperature was manipulated by using open-top chambers (OTCs). The laboratory experiments examined how increased temperatures affect fall armyworm feeding and development rates, which provide insight into how host feeding behaviour and physiology may affect transmission. Disease transmission and outbreak intensity, measured as the cumulative fraction infected during an epizootic, increased at higher temperatures. However, there was no appreciable change in the mean transmission rate of the disease, which is often the focus of empirical and theoretical research. Instead, the coefficient of variation (CV) associated with the transmission rate shrunk. As the CV decreased, heterogeneity in disease risk across individuals declined, which resulted in an increase in outbreak intensity. In the laboratory, increased temperatures increased feeding rates and decreased developmental times. As the host consumes the virus along with the leaf tissue on which it resides, increased feeding rate is likely to increase the probability of an individual

  3. Oral transmission of Chagas disease by consumption of açaí palm fruit, Brazil.

    PubMed

    Nóbrega, Aglaêr A; Garcia, Marcio H; Tatto, Erica; Obara, Marcos T; Costa, Elenild; Sobel, Jeremy; Araujo, Wildo N

    2009-04-01

    In 2006, a total of 178 cases of acute Chagas disease were reported from the Amazonian state of Pará, Brazil. Eleven occurred in Barcarena and were confirmed by visualization of parasites on blood smears. Using cohort and case-control studies, we implicated oral transmission by consumption of açaí palm fruit.

  4. Experimental oral transmission of chronic wasting disease to reindeer (Rangifer tarandus tarandus)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Chronic wasting disease (CWD) is a transmissible spongiform encephalopathy or TSE of wild and farmed cervid ruminants in the North America, including white tailed, black tailed and mule deer, Rocky Mountain elk and Shira's moose. CWD, like the other TSEs, is associated with accumulation of an abnorm...

  5. What Teachers and Coaches MUST Know about Blood To Prevent Transmission of Disease.

    ERIC Educational Resources Information Center

    Colvin, A. Vonnie; Cole, Kathy

    2000-01-01

    Provides teachers and coaches with basic safety information they must know when dealing with blood, focusing on: the likelihood of disease transmission; use of universal precautions when blood is involved (e.g., washing hands and wearing protective equipment); wearing gloves; cleaning up blood spills; and handling special situations (e.g., loss of…

  6. Modelling inter-human transmission dynamics of Chagas disease: analysis and application.

    PubMed

    Fabrizio, M C; Schweigmann, N J; Bartoloni, N J

    2014-05-01

    Transmission of Trypanosoma cruzi, the causal agent of Chagas disease, has expanded from rural endemic to urban areas due to migration. This so-called urban Chagas is an emerging health problem in American, European, Australian and Japanese cities. We present a mathematical model to analyse the dynamics of urban Chagas to better understand its epidemiology. The model considers the three clinical stages of the disease and the main routes of inter-human transmission. To overcome the complexities of the infection dynamics, the next-generation matrix method was developed. We deduced expressions which allowed estimating the number of new infections generated by an infected individual through each transmission route at each disease stage, the basic reproduction number and the number of individuals at each disease stage at the outbreak of the infection. The analysis was applied to Buenos Aires city (Argentina). We estimated that 94% of the new infections are generated by individuals in the chronic indeterminate stage. When migration was not considered, the infection disappeared slowly and R0 = 0.079, whereas when migration was considered, the number of individuals in each stage of the infection tended to stabilize. The expressions can be used to estimate different numbers of infected individuals in any place where only inter-human transmission is possible. PMID:24533945

  7. The corallivorous invertebrate Drupella aids in transmission of brown band disease on the Great Barrier Reef

    NASA Astrophysics Data System (ADS)

    Nicolet, K. J.; Hoogenboom, M. O.; Gardiner, N. M.; Pratchett, M. S.; Willis, B. L.

    2013-06-01

    Brown band disease (BrB) is an increasingly prevalent coral disease in the Indo-Pacific, but although the macroscopic signs of BrB have been associated with the ciliate Philaster guamensis, many aspects of its ecology remain unknown, particularly how the disease is transmitted among coral colonies. The aim of this study was to assess biotic factors affecting BrB transmission, explicitly testing whether corallivorous species contribute to disease spread. Several fish species were observed feeding on diseased tissue in the field, but did not influence either the progression or transmission rates of BrB on coral colonies in situ. In aquarium-based experiments, the butterflyfish Chaetodon aureofasciatus neither aided nor hindered the transmission of BrB from infected to uninfected corals. In contrast, the coral-feeding gastropod Drupella sp. was a highly effective vector of BrB, infecting more than 40 % of experimental colonies. This study also demonstrated the importance of injury in facilitating BrB infection, supporting the hypothesis that the BrB pathogen invades compromised coral tissue. In conclusion, disturbances and corallivorous activities that injure live corals are likely to contribute to increased occurrence of BrB provided that feeding scars create entry wounds sufficiently extensive to facilitate infection. These findings increase the understanding of the ecology of BrB, enabling better predictions of the prevalence and severity of this disease, and informing strategies for managing the impact of BrB on coral reefs.

  8. Human Herpesviruses as Copathogens of HIV Infection, Their Role in HIV Transmission, and Disease Progression

    PubMed Central

    Munawwar, Arshi; Singh, Sarman

    2016-01-01

    Of eight human herpesviruses (HHVs), often, only herpes simplex virus types 1 (HSV-1) and 2 (HSV-2) find mention in medical literature as both of these viruses are commonly associated with genital lesions and oral ulcers, commonly known as cold sores. However, role of human herpesviruses as copathogens and in aggravation and in the transmission of other human diseases, especially the Acquired immunodeficiency syndrome (HIV/AIDS) has only very recently been recognized. Therefore, screening and treating subclinical HHV infections may offer slowing of HIV infection, disease progression, and its transmission. Beside HSV-1 and HSV-2, HHV-3 a causative agent of herpes zoster remained one of the first manifestations of HIV disease before the era of highly active antiretroviral therapy (HAART). HHV-5 also known as human Cytomegalovirus infection remains a significant risk factor for HIV-associated mortality and morbidity even in HAART era. It is proposed that Cytomegalovirus viremia could be a better predictor of HIV disease progression than CD4+ T-lymphocyte count. The role of HHV-4 or Epstein–Burr virus and HHV-6, HHV-7, and HHV-8 is still being investigated in HIV disease progression. This review provides insight into the current understanding about these 8 HHVs, their co-pathogenesis, and role in HIV/AIDS disease progression. The review also covers recent literature in favor and against administering anti-HHV treatment along with HAART for slower AIDS progression and interrupted sexual transmission. PMID:27013807

  9. Retinal function and morphology are altered in cattle infected with the prion disease transmissible mink encephalopathy.

    PubMed

    Smith, J D; Greenlee, J J; Hamir, A N; Richt, J A; Greenlee, M H West

    2009-09-01

    Transmissible spongiform encephalopathies (TSEs) are a group of diseases that result in progressive and invariably fatal neurologic disease in both animals and humans. TSEs are characterized by the accumulation of an abnormal protease-resistant form of the prion protein in the central nervous system. Transmission of infectious TSEs is believed to occur via ingestion of prion protein-contaminated material. This material is also involved in the transmission of bovine spongiform encephalopathy ("mad cow disease") to humans, which resulted in the variant form of Creutzfeldt-Jakob disease. Abnormal prion protein has been reported in the retina of TSE-affected cattle, but despite these observations, the specific effect of abnormal prion protein on retinal morphology and function has not been assessed. The objective of this study was to identify and characterize potential functional and morphologic abnormalities in the retinas of cattle infected with a bovine-adapted isolate of transmissible mink encephalopathy. We used electroretinography and immunohistochemistry to examine retinas from 10 noninoculated and 5 transmissible mink encephalopathy-inoculated adult Holstein steers. Here we show altered retinal function, as evidenced by prolonged implicit time of the electroretinogram b-wave, in transmissible mink encephalopathy-infected cattle before the onset of clinical illness. We also demonstrate disruption of rod bipolar cell synaptic terminals, indicated by decreased immunoreactivity for the alpha isoform of protein kinase C and vesicular glutamate transporter 1, and activation of Müller glia, as evidenced by increased glial fibrillary acidic protein and glutamine synthetase expression, in the retinas of these cattle at the time of euthanasia due to clinical deterioration. This is the first study to identify both functional and morphologic alterations in the retinas of TSE-infected cattle. Our results support future efforts to focus on the retina for the development of

  10. Airborne exposure patterns from a passenger source in aircraft cabins

    PubMed Central

    Bennett, James S.; Jones, Byron W.; Hosni, Mohammad H.; Zhang, Yuanhui; Topmiller, Jennifer L.; Dietrich, Watts L.

    2015-01-01

    Airflow is a critical factor that influences air quality, airborne contaminant distribution, and disease transmission in commercial airliner cabins. The general aircraft-cabin air-contaminant transport effect model seeks to build exposure-spatial relationships between contaminant sources and receptors, quantify the uncertainty, and provide a platform for incorporation of data from a variety of studies. Knowledge of infection risk to flight crews and passengers is needed to form a coherent response to an unfolding epidemic, and infection risk may have an airborne pathogen exposure component. The general aircraf-tcabin air-contaminant transport effect model was applied to datasets from the University of Illinois and Kansas State University and also to case study information from a flight with probable severe acute respiratory syndrome transmission. Data were fit to regression curves, where the dependent variable was contaminant concentration (normalized for source strength and ventilation rate), and the independent variable was distance between source and measurement locations. The data-driven model showed exposure to viable small droplets and post-evaporation nuclei at a source distance of several rows in a mock-up of a twin-aisle airliner with seven seats per row. Similar behavior was observed in tracer gas, particle experiments, and flight infection data for severe acute respiratory syndrome. The study supports the airborne pathway as part of the matrix of possible disease transmission modes in aircraft cabins. PMID:26526769

  11. Airborne exposure patterns from a passenger source in aircraft cabins.

    PubMed

    Bennett, James S; Jones, Byron W; Hosni, Mohammad H; Zhang, Yuanhui; Topmiller, Jennifer L; Dietrich, Watts L

    2013-01-01

    Airflow is a critical factor that influences air quality, airborne contaminant distribution, and disease transmission in commercial airliner cabins. The general aircraft-cabin air-contaminant transport effect model seeks to build exposure-spatial relationships between contaminant sources and receptors, quantify the uncertainty, and provide a platform for incorporation of data from a variety of studies. Knowledge of infection risk to flight crews and passengers is needed to form a coherent response to an unfolding epidemic, and infection risk may have an airborne pathogen exposure component. The general aircraf-tcabin air-contaminant transport effect model was applied to datasets from the University of Illinois and Kansas State University and also to case study information from a flight with probable severe acute respiratory syndrome transmission. Data were fit to regression curves, where the dependent variable was contaminant concentration (normalized for source strength and ventilation rate), and the independent variable was distance between source and measurement locations. The data-driven model showed exposure to viable small droplets and post-evaporation nuclei at a source distance of several rows in a mock-up of a twin-aisle airliner with seven seats per row. Similar behavior was observed in tracer gas, particle experiments, and flight infection data for severe acute respiratory syndrome. The study supports the airborne pathway as part of the matrix of possible disease transmission modes in aircraft cabins. PMID:26526769

  12. Monkeypox disease transmission in an experimental setting: prairie dog animal model.

    PubMed

    Hutson, Christina L; Carroll, Darin S; Gallardo-Romero, Nadia; Weiss, Sonja; Clemmons, Cody; Hughes, Christine M; Salzer, Johanna S; Olson, Victoria A; Abel, Jason; Karem, Kevin L; Damon, Inger K

    2011-01-01

    Monkeypox virus (MPXV) is considered the most significant human public health threat in the genus Orthopoxvirus since the eradication of variola virus (the causative agent of smallpox). MPXV is a zoonotic agent endemic to forested areas of Central and Western Africa. In 2003, MPXV caused an outbreak in the United States due to the importation of infected African rodents, and subsequent sequential infection of North American prairie dogs (Cynomys ludovicianus) and humans. In previous studies, the prairie dog MPXV model has successfully shown to be very useful for understanding MPXV since the model emulates key characteristics of human monkeypox disease. In humans, percutaneous exposure to animals has been documented but the primary method of human-to-human MPXV transmission is postulated to be by respiratory route. Only a few animal model studies of MPXV transmission have been reported. Herein, we show that MPXV infected prairie dogs are able to transmit the virus to naive animals through multiple transmission routes. All secondarily exposed animals were infected with MPXV during the course of the study. Notably, animals secondarily exposed appeared to manifest more severe disease; however, the disease course was very similar to those of experimentally challenged animals including inappetence leading to weight loss, development of lesions, production of orthopoxvirus antibodies and shedding of similar levels or in some instances higher levels of MPXV from the oral cavity. Disease was transmitted via exposure to contaminated bedding, co-housing, or respiratory secretions/nasal mucous (we could not definitively say that transmission occurred via respiratory route exclusively). Future use of the model will allow us to evaluate infection control measures, vaccines and antiviral strategies to decrease disease transmission. PMID:22164263

  13. Reconstructing transmission trees for communicable diseases using densely sampled genetic data

    PubMed Central

    Worby, Colin J.; O'Neill, Philip D.; Kypraios, Theodore; Robotham, Julie V.; De Angelis, Daniela; Cartwright, Edward J. P.; Peacock, Sharon J.; Cooper, Ben S.

    2016-01-01

    Whole genome sequencing of pathogens from multiple hosts in an epidemic offers the potential to investigate who infected whom with unparalleled resolution, potentially yielding important insights into disease dynamics and the impact of control measures. We considered disease outbreaks in a setting with dense genomic sampling, and formulated stochastic epidemic models to investigate person-to-person transmission, based on observed genomic and epidemiological data. We constructed models in which the genetic distance between sampled genotypes depends on the epidemiological relationship between the hosts. A data augmented Markov chain Monte Carlo algorithm was used to sample over the transmission trees, providing a posterior probability for any given transmission route. We investigated the predictive performance of our methodology using simulated data, demonstrating high sensitivity and specificity, particularly for rapidly mutating pathogens with low transmissibility. We then analyzed data collected during an outbreak of methicillin-resistant Staphylococcus aureus in a hospital, identifying probable transmission routes and estimating epidemiological parameters. Our approach overcomes limitations of previous methods, providing a framework with the flexibility to allow for unobserved infection times, multiple independent introductions of the pathogen, and within-host genetic diversity, as well as allowing forward simulation. PMID:27042253

  14. Socialization Strategies and Disease Transmission in Captive Colonies of Nonhuman Primates

    PubMed Central

    Schapiro, Steven J.; Bernacky, Bruce J.

    2011-01-01

    In captive research environments for nonhuman primates (NHP), social housing strategies are often in conflict with protocols designed to minimize disease transmission. This is particularly true in breeding colonies, and is especially relevant when attempting to eliminate specific pathogens from a population of primates. Numerous strategies have been used to establish such specific pathogen free (SPF) breeding colonies (primarily of macaques), ranging from nursery rearing of neonates to single housing of socially-reared yearlings to the rearing of infants in large social groups. All of these strategies attempt to balance the effects of the chosen socialization strategy on parameters related to disease transmission, including the ultimate elimination of the target pathogens. Such strategies may affect the overall disease states of NHP breeding colonies through selective breeding processes. This can occur either by creating subpopulations of animals that do not have target diseases (SPF colonies), but may have other issues; or by creating situations in which the ‘best’ animals are sold and the breeding colony is stocked with animals that may be more disease susceptible than those that were sold. The disease states of NHP research colonies also may be affected by selective utilization programs, in which animals removed from the breeding colony for health/behavior reasons, are preferentially chosen for use in scientific investigations. Such utilization criteria raise the question of whether ideal subjects are being chosen for use in research. Finally, captive primate colonies, where both socialization and disease states are intensely managed, may provide opportunities for those testing predictions from models of the interactions of socialization and disease transmission in the evolution of wild populations of NHP. This would be especially true for some extreme conditions of these disease ecology models, given the exceedingly high social densities and levels of

  15. Airborne asbestos in buildings.

    PubMed

    Lee, R J; Van Orden, D R

    2008-03-01

    The concentration of airborne asbestos in buildings nationwide is reported in this study. A total of 3978 indoor samples from 752 buildings, representing nearly 32 man-years of sampling, have been analyzed by transmission electron microscopy. The buildings that were surveyed were the subject of litigation related to suits alleging the general building occupants were exposed to a potential health hazard as a result the presence of asbestos-containing materials (ACM). The average concentration of all airborne asbestos structures was 0.01structures/ml (s/ml) and the average concentration of airborne asbestos > or = 5microm long was 0.00012fibers/ml (f/ml). For all samples, 99.9% of the samples were <0.01 f/ml for fibers longer than 5microm; no building averaged above 0.004f/ml for fibers longer than 5microm. No asbestos was detected in 27% of the buildings and in 90% of the buildings no asbestos was detected that would have been seen optically (> or = 5microm long and > or = 0.25microm wide). Background outdoor concentrations have been reported at 0.0003f/ml > or = 5microm. These results indicate that in-place ACM does not result in elevated airborne asbestos in building atmospheres approaching regulatory levels and that it does not result in a significantly increased risk to building occupants.

  16. Understanding foot-and-mouth disease virus transmission biology: identification of the indicators of infectiousness

    PubMed Central

    2013-01-01

    The control of foot-and-mouth disease virus (FMDV) outbreaks in non-endemic countries relies on the rapid detection and removal of infected animals. In this paper we use the observed relationship between the onset of clinical signs and direct contact transmission of FMDV to identify predictors for the onset of clinical signs and identify possible approaches to preclinical screening in the field. Threshold levels for various virological and immunological variables were determined using Receiver Operating Characteristic (ROC) curve analysis and then tested using generalized linear mixed models to determine their ability to predict the onset of clinical signs. In addition, concordance statistics between qualitative real time PCR test results and virus isolation results were evaluated. For the majority of animals (71%), the onset of clinical signs occurred 3–4 days post infection. The onset of clinical signs was associated with high levels of virus in the blood, oropharyngeal fluid and nasal fluid. Virus is first detectable in the oropharyngeal fluid, but detection of virus in the blood and nasal fluid may also be good candidates for preclinical indicators. Detection of virus in the air was also significantly associated with transmission. This study is the first to identify statistically significant indicators of infectiousness for FMDV at defined time periods during disease progression in a natural host species. Identifying factors associated with infectiousness will advance our understanding of transmission mechanisms and refine intra-herd and inter-herd disease transmission models. PMID:23822567

  17. Human prion protein sequence elements impede cross-species chronic wasting disease transmission.

    PubMed

    Kurt, Timothy D; Jiang, Lin; Fernández-Borges, Natalia; Bett, Cyrus; Liu, Jun; Yang, Tom; Spraker, Terry R; Castilla, Joaquín; Eisenberg, David; Kong, Qingzhong; Sigurdson, Christina J

    2015-04-01

    Chronic wasting disease (CWD) is a fatal prion disease of North American deer and elk and poses an unclear risk for transmission to humans. Human exposure to CWD occurs through hunting activities and consumption of venison from prion-infected animals. Although the amino acid residues of the prion protein (PrP) that prevent or permit human CWD infection are unknown, NMR-based structural studies suggest that the β2-α2 loop (residues 165-175) may impact species barriers. Here we sought to define PrP sequence determinants that affect CWD transmission to humans. We engineered transgenic mice that express human PrP with four amino acid substitutions that result in expression of PrP with a β2-α2 loop (residues 165-175) that exactly matches that of elk PrP. Compared with transgenic mice expressing unaltered human PrP, mice expressing the human-elk chimeric PrP were highly susceptible to elk and deer CWD prions but were concurrently less susceptible to human Creutzfeldt-Jakob disease prions. A systematic in vitro survey of amino acid differences between humans and cervids identified two additional residues that impacted CWD conversion of human PrP. This work identifies amino acids that constitute a substantial structural barrier for CWD transmission to humans and helps illuminate the molecular requirements for cross-species prion transmission. PMID:25705888

  18. Human prion protein sequence elements impede cross-species chronic wasting disease transmission

    PubMed Central

    Kurt, Timothy D.; Jiang, Lin; Fernández-Borges, Natalia; Bett, Cyrus; Liu, Jun; Yang, Tom; Spraker, Terry R.; Castilla, Joaquín; Eisenberg, David; Kong, Qingzhong; Sigurdson, Christina J.

    2015-01-01

    Chronic wasting disease (CWD) is a fatal prion disease of North American deer and elk and poses an unclear risk for transmission to humans. Human exposure to CWD occurs through hunting activities and consumption of venison from prion-infected animals. Although the amino acid residues of the prion protein (PrP) that prevent or permit human CWD infection are unknown, NMR-based structural studies suggest that the β2-α2 loop (residues 165–175) may impact species barriers. Here we sought to define PrP sequence determinants that affect CWD transmission to humans. We engineered transgenic mice that express human PrP with four amino acid substitutions that result in expression of PrP with a β2-α2 loop (residues 165–175) that exactly matches that of elk PrP. Compared with transgenic mice expressing unaltered human PrP, mice expressing the human-elk chimeric PrP were highly susceptible to elk and deer CWD prions but were concurrently less susceptible to human Creutzfeldt-Jakob disease prions. A systematic in vitro survey of amino acid differences between humans and cervids identified two additional residues that impacted CWD conversion of human PrP. This work identifies amino acids that constitute a substantial structural barrier for CWD transmission to humans and helps illuminate the molecular requirements for cross-species prion transmission. PMID:25705888

  19. Efficient Transmission and Characterization of Creutzfeldt–Jakob Disease Strains in Bank Voles

    PubMed Central

    Nonno, Romolo; Bari, Michele A. Di; Cardone, Franco; Vaccari, Gabriele; Fazzi, Paola; Dell'Omo, Giacomo; Cartoni, Claudia; Ingrosso, Loredana; Boyle, Aileen; Galeno, Roberta; Sbriccoli, Marco; Lipp, Hans-Peter; Bruce, Moira; Pocchiari, Maurizio; Agrimi, Umberto

    2006-01-01

    Transmission of prions between species is limited by the “species barrier,” which hampers a full characterization of human prion strains in the mouse model. We report that the efficiency of primary transmission of prions from Creutzfeldt–Jakob disease patients to a wild rodent species, the bank vole (Clethrionomys glareolus), is comparable to that reported in transgenic mice carrying human prion protein, in spite of a low prion protein–sequence homology between man and vole. Voles infected with sporadic and genetic Creutzfeldt–Jakob disease isolates show strain-specific patterns of spongiform degeneration and pathological prion protein–deposition, and accumulate protease-resistant prion protein with biochemical properties similar to the human counterpart. Adaptation of genetic Creutzfeldt–Jakob disease isolates to voles shows little or no evidence of a transmission barrier, in contrast to the striking barriers observed during transmission of mouse, hamster, and sheep prions to voles. Our results imply that in voles there is no clear relationship between the degree of homology of the prion protein of the donor and recipient species and susceptibility, consistent with the view that the prion strain gives a major contribution to the species barrier. The vole is therefore a valuable model to study human prion diversity and, being susceptible to a range of animal prions, represents a unique tool for comparing isolates from different species. PMID:16518470

  20. Chronic wasting disease prions are not transmissible to transgenic mice overexpressing human prion protein.

    PubMed

    Sandberg, Malin K; Al-Doujaily, Huda; Sigurdson, Christina J; Glatzel, Markus; O'Malley, Catherine; Powell, Caroline; Asante, Emmanuel A; Linehan, Jacqueline M; Brandner, Sebastian; Wadsworth, Jonathan D F; Collinge, John

    2010-10-01

    Chronic wasting disease (CWD) is a prion disease that affects free-ranging and captive cervids, including mule deer, white-tailed deer, Rocky Mountain elk and moose. CWD-infected cervids have been reported in 14 USA states, two Canadian provinces and in South Korea. The possibility of a zoonotic transmission of CWD prions via diet is of particular concern in North America where hunting of cervids is a popular sport. To investigate the potential public health risks posed by CWD prions, we have investigated whether intracerebral inoculation of brain and spinal cord from CWD-infected mule deer transmits prion infection to transgenic mice overexpressing human prion protein with methionine or valine at polymorphic residue 129. These transgenic mice have been utilized in extensive transmission studies of human and animal prion disease and are susceptible to BSE and vCJD prions, allowing comparison with CWD. Here, we show that these mice proved entirely resistant to infection with mule deer CWD prions arguing that the transmission barrier associated with this prion strain/host combination is greater than that observed with classical BSE prions. However, it is possible that CWD may be caused by multiple prion strains. Further studies will be required to evaluate the transmission properties of distinct cervid prion strains as they are characterized.

  1. Efficient transmission and characterization of Creutzfeldt-Jakob disease strains in bank voles.

    PubMed

    Nonno, Romolo; Di Bari, Michele A; Cardone, Franco; Vaccari, Gabriele; Fazzi, Paola; Dell'Omo, Giacomo; Cartoni, Claudia; Ingrosso, Loredana; Boyle, Aileen; Galeno, Roberta; Sbriccoli, Marco; Lipp, Hans-Peter; Bruce, Moira; Pocchiari, Maurizio; Agrimi, Umberto

    2006-02-01

    Transmission of prions between species is limited by the "species barrier," which hampers a full characterization of human prion strains in the mouse model. We report that the efficiency of primary transmission of prions from Creutzfeldt-Jakob disease patients to a wild rodent species, the bank vole (Clethrionomys glareolus), is comparable to that reported in transgenic mice carrying human prion protein, in spite of a low prion protein-sequence homology between man and vole. Voles infected with sporadic and genetic Creutzfeldt-Jakob disease isolates show strain-specific patterns of spongiform degeneration and pathological prion protein-deposition, and accumulate protease-resistant prion protein with biochemical properties similar to the human counterpart. Adaptation of genetic Creutzfeldt-Jakob disease isolates to voles shows little or no evidence of a transmission barrier, in contrast to the striking barriers observed during transmission of mouse, hamster, and sheep prions to voles. Our results imply that in voles there is no clear relationship between the degree of homology of the prion protein of the donor and recipient species and susceptibility, consistent with the view that the prion strain gives a major contribution to the species barrier. The vole is therefore a valuable model to study human prion diversity and, being susceptible to a range of animal prions, represents a unique tool for comparing isolates from different species.

  2. A species barrier limits transmission of chronic wasting disease to mink (Mustela vison)

    PubMed Central

    Harrington, Robert D.; Baszler, Timothy V.; O'Rourke, Katherine I.; Schneider, David A.; Spraker, Terry R.; Liggitt, H. Denny; Knowles, Donald P.

    2008-01-01

    Transmissible mink encephalopathy (TME) occurs as sporadic outbreaks associated with ingestion of feed presumably contaminated with some type of prion disease. Mink lack a species barrier to primary oral challenge with bovine spongiform encephalopathy, whereas they have a barrier to such challenge with scrapie. We investigated whether mink have a species barrier to chronic wasting disease (CWD) by performing primary intracerebral (IC) and primary oral challenge with CWD-positive elk brain. Primary IC challenge resulted in clinical disease in two of eight mink at 31–33 months incubation. Affected mink had spongiform vacuolation and astrocytosis within the central nervous system and immunoreactivity to disease-associated prion protein (PrPd) in brain, retina and lymph node. CWD IC recipients had significantly lower brain vacuolation and PrPd deposition scores, significantly lower cerebrocortical astrocyte counts and significantly higher hippocampal astrocyte counts than TME IC recipients. Primary oral challenge with CWD-positive elk brain (n=22) or with CWD-negative elk brain given IC (n=7) or orally (n=23) did not result in clinical or microscopic abnormalities during 42 months observation. Novel prion gene polymorphisms were identified at codon 27 (arginine/tryptophan) and codon 232 (arginine/lysine). This study shows that, whilst CWD can cause disease when given IC to mink, the lesions are not characteristic of TME, transmission is inefficient compared with TME and oral challenge does not result in disease. The demonstration of a species barrier in cervid-to-mustelid prion transmission indicates that mink are unlikely to be involved in natural CWD transmission. PMID:18343853

  3. Disease transmission models for public health decision-making: designing intervention strategies for Schistosoma japonicum.

    PubMed

    Seto, Edmund Y W; Carlton, Elizabeth J

    2010-01-01

    The purpose of infectious disease transmission modelling is often to understand the factors that are responsible for the persistence of transmission, the dynamics of the infection process and how best to control transmission. As such, there should be great potential to use mathematical models to routinely plan and evaluate disease control programs. In reality, there are many challenges that have precluded the practical use of disease models in this regard. One challenge relates to the mathematical complexity of the models, which has made it difficult for field workers and health officials to understand and use them. Another challenge is that, despite their mathematical complexity, models typically do not have sufficient structural complexity to consider many of the site-specific epidemiologic and disease control details that the practicing health official routinely considers. Moreover, most modelling studies have not been sufficiently explicit or exemplary in explaining how field data may be incorporated into the models to impact public health decision-making. In this chapter, we start with a classic model of schistosomiasis transmission and relate its key properties to the more detailed model of Schistosoma japonicum model presented in chapter by Remais and chapter by Spear and Hubbard. We then discuss how various controls (e.g., chemotherapy, snail control and sanitation) may be evaluated via the detailed model. We then demonstrate in a practical manner, using S. japonicum data from China, how field data may be incorporated to inform the practice of disease control. Finally, we present a new model structure that considers how heterogeneous populations are interconnected, which has particular relevance to understanding disease control and emergence in today's highly mobile world.

  4. Modulation of the glutamatergic transmission by Dopamine: a focus on Parkinson, Huntington and Addiction diseases

    PubMed Central

    Gardoni, Fabrizio; Bellone, Camilla

    2015-01-01

    Dopamine (DA) plays a major role in motor and cognitive functions as well as in reward processing by regulating glutamatergic inputs. In particular in the striatum the release of DA rapidly influences synaptic transmission modulating both AMPA and NMDA receptors. Several neurodegenerative and neuropsychiatric disorders, including Parkinson, Huntington and addiction-related diseases, manifest a dysregulation of glutamate and DA signaling. Here, we will focus our attention on the mechanisms underlying the modulation of the glutamatergic transmission by DA in striatal circuits. PMID:25784855

  5. Amazonian Triatomine Biodiversity and the Transmission of Chagas Disease in French Guiana: In Medio Stat Sanitas.

    PubMed

    Péneau, Julie; Nguyen, Anne; Flores-Ferrer, Alheli; Blanchet, Denis; Gourbière, Sébastien

    2016-02-01

    The effects of biodiversity on the transmission of infectious diseases now stand as a cornerstone of many public health policies. The upper Amazonia and Guyana shield are hot-spots of biodiversity that offer genuine opportunities to explore the relationship between the risk of transmission of Chagas disease and the diversity of its triatomine vectors. Over 730 triatomines were light-trapped in four geomorphological landscapes shaping French-Guiana, and we determined their taxonomic status and infection by Trypanosoma cruzi. We used a model selection approach to unravel the spatial and temporal variations in species abundance, diversity and infection. The vector community in French-Guiana is typically made of one key species (Panstrongylus geniculatus) that is more abundant than three secondary species combined (Rhodnius pictipes, Panstrongylus lignarius and Eratyrus mucronatus), and four other species that complete the assemblage. Although the overall abundance of adult triatomines does not vary across French-Guiana, their diversity increases along a coastal-inland gradient. These variations unravelled a non-monotonic relationship between vector biodiversity and the risk of transmission of Chagas disease, so that intermediate biodiversity levels are associated with the lowest risks. We also observed biannual variations in triatomine abundance, representing the first report of a biannual pattern in the risk of Chagas disease transmission. Those variations were highly and negatively correlated with the average monthly rainfall. We discuss the implications of these patterns for the transmission of T. cruzi by assemblages of triatomine species, and for the dual challenge of controlling Amazonian vector communities that are made of both highly diverse and mostly intrusive species. PMID:26867025

  6. Amazonian Triatomine Biodiversity and the Transmission of Chagas Disease in French Guiana: In Medio Stat Sanitas

    PubMed Central

    Flores-Ferrer, Alheli; Blanchet, Denis; Gourbière, Sébastien

    2016-01-01

    The effects of biodiversity on the transmission of infectious diseases now stand as a cornerstone of many public health policies. The upper Amazonia and Guyana shield are hot-spots of biodiversity that offer genuine opportunities to explore the relationship between the risk of transmission of Chagas disease and the diversity of its triatomine vectors. Over 730 triatomines were light-trapped in four geomorphological landscapes shaping French-Guiana, and we determined their taxonomic status and infection by Trypanosoma cruzi. We used a model selection approach to unravel the spatial and temporal variations in species abundance, diversity and infection. The vector community in French-Guiana is typically made of one key species (Panstrongylus geniculatus) that is more abundant than three secondary species combined (Rhodnius pictipes, Panstrongylus lignarius and Eratyrus mucronatus), and four other species that complete the assemblage. Although the overall abundance of adult triatomines does not vary across French-Guiana, their diversity increases along a coastal-inland gradient. These variations unravelled a non-monotonic relationship between vector biodiversity and the risk of transmission of Chagas disease, so that intermediate biodiversity levels are associated with the lowest risks. We also observed biannual variations in triatomine abundance, representing the first report of a biannual pattern in the risk of Chagas disease transmission. Those variations were highly and negatively correlated with the average monthly rainfall. We discuss the implications of these patterns for the transmission of T. cruzi by assemblages of triatomine species, and for the dual challenge of controlling Amazonian vector communities that are made of both highly diverse and mostly intrusive species. PMID:26867025

  7. Amazonian Triatomine Biodiversity and the Transmission of Chagas Disease in French Guiana: In Medio Stat Sanitas.

    PubMed

    Péneau, Julie; Nguyen, Anne; Flores-Ferrer, Alheli; Blanchet, Denis; Gourbière, Sébastien

    2016-02-01

    The effects of biodiversity on the transmission of infectious diseases now stand as a cornerstone of many public health policies. The upper Amazonia and Guyana shield are hot-spots of biodiversity that offer genuine opportunities to explore the relationship between the risk of transmission of Chagas disease and the diversity of its triatomine vectors. Over 730 triatomines were light-trapped in four geomorphological landscapes shaping French-Guiana, and we determined their taxonomic status and infection by Trypanosoma cruzi. We used a model selection approach to unravel the spatial and temporal variations in species abundance, diversity and infection. The vector community in French-Guiana is typically made of one key species (Panstrongylus geniculatus) that is more abundant than three secondary species combined (Rhodnius pictipes, Panstrongylus lignarius and Eratyrus mucronatus), and four other species that complete the assemblage. Although the overall abundance of adult triatomines does not vary across French-Guiana, their diversity increases along a coastal-inland gradient. These variations unravelled a non-monotonic relationship between vector biodiversity and the risk of transmission of Chagas disease, so that intermediate biodiversity levels are associated with the lowest risks. We also observed biannual variations in triatomine abundance, representing the first report of a biannual pattern in the risk of Chagas disease transmission. Those variations were highly and negatively correlated with the average monthly rainfall. We discuss the implications of these patterns for the transmission of T. cruzi by assemblages of triatomine species, and for the dual challenge of controlling Amazonian vector communities that are made of both highly diverse and mostly intrusive species.

  8. Aerosol transmission of foot-and-mouth disease virus Asia-1 under experimental conditions.

    PubMed

    Colenutt, C; Gonzales, J L; Paton, D J; Gloster, J; Nelson, N; Sanders, C

    2016-06-30

    Foot-and-mouth disease virus (FMDV) control measures rely on understanding of virus transmission mechanisms. Direct contact between naïve and infected animals or spread by contaminated fomites is prevented by quarantines and rigorous decontamination procedures during outbreaks. Transmission of FMDV by aerosol may not be prevented by these control measures and this route of transmission may allow infection of animals at distance from the infection source. Understanding the potential for aerosol spread of specific FMDV strains is important for informing control strategies in an outbreak. Here, the potential for transmission of an FMDV Asia 1 strain between pigs and cattle by indirect aerosol exposure was evaluated in an experimental setting. Four naïve calves were exposed to aerosols emitted from three infected pigs in an adjacent room for a 10h period. Direct contact between pigs and cattle and fomite transfer between rooms was prevented. Viral titres in aerosols emitted by the infected pigs were measured to estimate the dose that calves were exposed to. One of the calves developed clinical signs of FMD, whilst there was serological evidence for spread to cattle by aerosol transmission in the remaining three calves. This highlights the possibility that this FMDV Asia 1 strain could be spread by aerosol transmission given appropriate environmental conditions should an outbreak occur in pigs. Our estimates suggest the exposure dose required for aerosol transmission was higher than has been previously quantified for other serotypes, implying that aerosols are less likely to play a significant role in transmission and spread of this FMDV strain. PMID:27259825

  9. Characteristics of cyprinid herpesvirus 3 in different phases of infection: implications for disease transmission and control.

    PubMed

    Sunarto, Agus; McColl, Kenneth A; Crane, Mark St J; Schat, Karel A; Slobedman, Barry; Barnes, Andrew C; Walker, Peter J

    2014-08-01

    Koi herpesvirus disease (KHVD) is an emerging and highly contagious viral disease of koi and common carp (Cyprinus carpio), causing mass mortalities and huge economic losses to the carp aquaculture industry. The disease has spread rapidly to 28 countries worldwide. However, mechanisms of koi herpesvirus (species Cyprinid herpesvirus 3; CyHV-3) transmission remain unclear. A potential experimental model of CyHV-3 infection in carp was used to characterise CyHV-3 in different phases of infection and to demonstrate that CyHV-3 persists in survivor fish and has the capacity to reactivate and transmit the disease to healthy fish. During acute infection, which occurred when fish were maintained at 22°C, viral genes were abundantly expressed and infectious virus was produced in association with tissue damage, clinical disease and mortality. In fish maintained at a lower temperature (11°C), viral DNA was present but viral gene expression was absent or greatly restricted, infectious virus was not recovered and there was no evidence of disease. Productive replication was re-initiated following an increase in water temperature to 22°C, resulting in 45% mortality. Shedding of reactivated virus killed 75% of cohabitating naïve fish, suggesting a potential risk for disease transmission.

  10. Characteristics of cyprinid herpesvirus 3 in different phases of infection: implications for disease transmission and control.

    PubMed

    Sunarto, Agus; McColl, Kenneth A; Crane, Mark St J; Schat, Karel A; Slobedman, Barry; Barnes, Andrew C; Walker, Peter J

    2014-08-01

    Koi herpesvirus disease (KHVD) is an emerging and highly contagious viral disease of koi and common carp (Cyprinus carpio), causing mass mortalities and huge economic losses to the carp aquaculture industry. The disease has spread rapidly to 28 countries worldwide. However, mechanisms of koi herpesvirus (species Cyprinid herpesvirus 3; CyHV-3) transmission remain unclear. A potential experimental model of CyHV-3 infection in carp was used to characterise CyHV-3 in different phases of infection and to demonstrate that CyHV-3 persists in survivor fish and has the capacity to reactivate and transmit the disease to healthy fish. During acute infection, which occurred when fish were maintained at 22°C, viral genes were abundantly expressed and infectious virus was produced in association with tissue damage, clinical disease and mortality. In fish maintained at a lower temperature (11°C), viral DNA was present but viral gene expression was absent or greatly restricted, infectious virus was not recovered and there was no evidence of disease. Productive replication was re-initiated following an increase in water temperature to 22°C, resulting in 45% mortality. Shedding of reactivated virus killed 75% of cohabitating naïve fish, suggesting a potential risk for disease transmission. PMID:24704574

  11. Computational modeling of interventions and protective thresholds to prevent disease transmission in deploying populations.

    PubMed

    Burgess, Colleen; Peace, Angela; Everett, Rebecca; Allegri, Buena; Garman, Patrick

    2014-01-01

    Military personnel are deployed abroad for missions ranging from humanitarian relief efforts to combat actions; delay or interruption in these activities due to disease transmission can cause operational disruptions, significant economic loss, and stressed or exceeded military medical resources. Deployed troops function in environments favorable to the rapid and efficient transmission of many viruses particularly when levels of protection are suboptimal. When immunity among deployed military populations is low, the risk of vaccine-preventable disease outbreaks increases, impacting troop readiness and achievement of mission objectives. However, targeted vaccination and the optimization of preexisting immunity among deployed populations can decrease the threat of outbreaks among deployed troops. Here we describe methods for the computational modeling of disease transmission to explore how preexisting immunity compares with vaccination at the time of deployment as a means of preventing outbreaks and protecting troops and mission objectives during extended military deployment actions. These methods are illustrated with five modeling case studies for separate diseases common in many parts of the world, to show different approaches required in varying epidemiological settings. PMID:25009579

  12. Computational modeling of interventions and protective thresholds to prevent disease transmission in deploying populations.

    PubMed

    Burgess, Colleen; Peace, Angela; Everett, Rebecca; Allegri, Buena; Garman, Patrick

    2014-01-01

    Military personnel are deployed abroad for missions ranging from humanitarian relief efforts to combat actions; delay or interruption in these activities due to disease transmission can cause operational disruptions, significant economic loss, and stressed or exceeded military medical resources. Deployed troops function in environments favorable to the rapid and efficient transmission of many viruses particularly when levels of protection are suboptimal. When immunity among deployed military populations is low, the risk of vaccine-preventable disease outbreaks increases, impacting troop readiness and achievement of mission objectives. However, targeted vaccination and the optimization of preexisting immunity among deployed populations can decrease the threat of outbreaks among deployed troops. Here we describe methods for the computational modeling of disease transmission to explore how preexisting immunity compares with vaccination at the time of deployment as a means of preventing outbreaks and protecting troops and mission objectives during extended military deployment actions. These methods are illustrated with five modeling case studies for separate diseases common in many parts of the world, to show different approaches required in varying epidemiological settings.

  13. Computational Modeling of Interventions and Protective Thresholds to Prevent Disease Transmission in Deploying Populations

    PubMed Central

    2014-01-01

    Military personnel are deployed abroad for missions ranging from humanitarian relief efforts to combat actions; delay or interruption in these activities due to disease transmission can cause operational disruptions, significant economic loss, and stressed or exceeded military medical resources. Deployed troops function in environments favorable to the rapid and efficient transmission of many viruses particularly when levels of protection are suboptimal. When immunity among deployed military populations is low, the risk of vaccine-preventable disease outbreaks increases, impacting troop readiness and achievement of mission objectives. However, targeted vaccination and the optimization of preexisting immunity among deployed populations can decrease the threat of outbreaks among deployed troops. Here we describe methods for the computational modeling of disease transmission to explore how preexisting immunity compares with vaccination at the time of deployment as a means of preventing outbreaks and protecting troops and mission objectives during extended military deployment actions. These methods are illustrated with five modeling case studies for separate diseases common in many parts of the world, to show different approaches required in varying epidemiological settings. PMID:25009579

  14. Fourth Airborne Geoscience Workshop

    NASA Technical Reports Server (NTRS)

    1991-01-01

    The focus of the workshop was on how the airborne community can assist in achieving the goals of the Global Change Research Program. The many activities that employ airborne platforms and sensors were discussed: platforms and instrument development; airborne oceanography; lidar research; SAR measurements; Doppler radar; laser measurements; cloud physics; airborne experiments; airborne microwave measurements; and airborne data collection.

  15. Airborne biological hazards and urban transport infrastructure: current challenges and future directions.

    PubMed

    Nasir, Zaheer Ahmad; Campos, Luiza Cintra; Christie, Nicola; Colbeck, Ian

    2016-08-01

    Exposure to airborne biological hazards in an ever expanding urban transport infrastructure and highly diverse mobile population is of growing concern, in terms of both public health and biosecurity. The existing policies and practices on design, construction and operation of these infrastructures may have severe implications for airborne disease transmission, particularly, in the event of a pandemic or intentional release of biological of agents. This paper reviews existing knowledge on airborne disease transmission in different modes of transport, highlights the factors enhancing the vulnerability of transport infrastructures to airborne disease transmission, discusses the potential protection measures and identifies the research gaps in order to build a bioresilient transport infrastructure. The unification of security and public health research, inclusion of public health security concepts at the design and planning phase, and a holistic system approach involving all the stakeholders over the life cycle of transport infrastructure hold the key to mitigate the challenges posed by biological hazards in the twenty-first century transport infrastructure.

  16. Airborne biological hazards and urban transport infrastructure: current challenges and future directions.

    PubMed

    Nasir, Zaheer Ahmad; Campos, Luiza Cintra; Christie, Nicola; Colbeck, Ian

    2016-08-01

    Exposure to airborne biological hazards in an ever expanding urban transport infrastructure and highly diverse mobile population is of growing concern, in terms of both public health and biosecurity. The existing policies and practices on design, construction and operation of these infrastructures may have severe implications for airborne disease transmission, particularly, in the event of a pandemic or intentional release of biological of agents. This paper reviews existing knowledge on airborne disease transmission in different modes of transport, highlights the factors enhancing the vulnerability of transport infrastructures to airborne disease transmission, discusses the potential protection measures and identifies the research gaps in order to build a bioresilient transport infrastructure. The unification of security and public health research, inclusion of public health security concepts at the design and planning phase, and a holistic system approach involving all the stakeholders over the life cycle of transport infrastructure hold the key to mitigate the challenges posed by biological hazards in the twenty-first century transport infrastructure. PMID:27318484

  17. A Novel Statistical Model to Estimate Host Genetic Effects Affecting Disease Transmission

    PubMed Central

    Anacleto, Osvaldo; Garcia-Cortés, Luis Alberto; Lipschutz-Powell, Debby; Woolliams, John A.; Doeschl-Wilson, Andrea B.

    2015-01-01

    There is increasing recognition that genetic diversity can affect the spread of diseases, potentially affecting plant and livestock disease control as well as the emergence of human disease outbreaks. Nevertheless, even though computational tools can guide the control of infectious diseases, few epidemiological models can simultaneously accommodate the inherent individual heterogeneity in multiple infectious disease traits influencing disease transmission, such as the frequently modeled propensity to become infected and infectivity, which describes the host ability to transmit the infection to susceptible individuals. Furthermore, current quantitative genetic models fail to fully capture the heritable variation in host infectivity, mainly because they cannot accommodate the nonlinear infection dynamics underlying epidemiological data. We present in this article a novel statistical model and an inference method to estimate genetic parameters associated with both host susceptibility and infectivity. Our methodology combines quantitative genetic models of social interactions with stochastic processes to model the random, nonlinear, and dynamic nature of infections and uses adaptive Bayesian computational techniques to estimate the model parameters. Results using simulated epidemic data show that our model can accurately estimate heritabilities and genetic risks not only of susceptibility but also of infectivity, therefore exploring a trait whose heritable variation is currently ignored in disease genetics and can greatly influence the spread of infectious diseases. Our proposed methodology offers potential impacts in areas such as livestock disease control through selective breeding and also in predicting and controlling the emergence of disease outbreaks in human populations. PMID:26405030

  18. Disease dynamics of Porites bleaching with tissue loss: prevalence, virulence, transmission, and environmental drivers.

    PubMed

    Sudek, M; Williams, G J; Runyon, C; Aeby, G S; Davy, S K

    2015-02-10

    The prevalence, number of species affected, and geographical extent of coral diseases have been increasing worldwide. We present ecological data on the coral disease Porites bleaching with tissue loss (PBTL) from Kaneohe Bay, Oahu (Hawaii, USA), affecting P. compressa. This disease is prevalent throughout the year, although it shows spatio-temporal variability with peak prevalence during the warmer summer months. Temporal variability in disease prevalence showed a strong positive relationship with elevated water temperature. Spatially, PBTL prevalence peaked in clearer waters (lower turbidity) with higher water flow and higher densities of parrotfish, together explaining approximately 26% of the spatial variability in PBTL prevalence. However, the relatively poor performance of the spatial model suggests that other, unmeasured factors may be more important in driving spatial prevalence. PBTL was not transmissible through direct contact or the water column in controlled aquaria experiments, suggesting that this disease may not be caused by a pathogen, is not highly infectious, or perhaps requires a vector for transmission. In general, PBTL results in partial tissue mortality of affected colonies; on average, one-third of the tissue is lost. This disease can affect the same colonies repeatedly, suggesting a potential for progressive damage which could cause increased tissue loss over time. P. compressa is the main framework-building species in Kaneohe Bay; PBTL therefore has the potential to negatively impact the structure of the reefs at this location.

  19. Investigations of the relationship betw een disease and airborne (1→3)-β-D-glucan in buildings

    PubMed Central

    Rylander, Ragnar

    1997-01-01

    Studies on the relationship between symptoms in indoor air and the amount of airborne (1→3)-β-D-glucan were reviewed. Relationships were found for symptoms and objective tests of airways inflammation. The data suggest that (1→3)-β-D-glucan could be a causative agent. PMID:18472858

  20. Malaria Transmission, Infection, and Disease at Three Sites with Varied Transmission Intensity in Uganda: Implications for Malaria Control

    PubMed Central

    Kamya, Moses R.; Arinaitwe, Emmanuel; Wanzira, Humphrey; Katureebe, Agaba; Barusya, Chris; Kigozi, Simon P.; Kilama, Maxwell; Tatem, Andrew J.; Rosenthal, Philip J.; Drakeley, Chris; Lindsay, Steve W.; Staedke, Sarah G.; Smith, David L.; Greenhouse, Bryan; Dorsey, Grant

    2015-01-01

    The intensification of control interventions has led to marked reductions in malaria burden in some settings, but not others. To provide a comprehensive description of malaria epidemiology in Uganda, we conducted surveillance studies over 24 months in 100 houses randomly selected from each of three subcounties: Walukuba (peri-urban), Kihihi (rural), and Nagongera (rural). Annual entomological inoculation rate (aEIR) was estimated from monthly Centers for Disease Control and Prevention (CDC) light trap mosquito collections. Children aged 0.5–10 years were provided long-lasting insecticidal nets (LLINs) and followed for measures of parasite prevalence, anemia and malaria incidence. Estimates of aEIR were 2.8, 32.0, and 310 infectious bites per year, and estimates of parasite prevalence 7.4%, 9.3%, and 28.7% for Walukuba, Kihihi, and Nagongera, respectively. Over the 2-year study, malaria incidence per person-years decreased in Walukuba (0.51 versus 0.31, P = 0.001) and increased in Kihihi (0.97 versus 1.93, P < 0.001) and Nagongera (2.33 versus 3.30, P < 0.001). Of 2,582 episodes of malaria, only 8 (0.3%) met criteria for severe disease. The prevalence of anemia was low and not associated with transmission intensity. In our cohorts, where LLINs and prompt effective treatment were provided, the risk of complicated malaria and anemia was extremely low. However, malaria incidence was high and increased over time at the two rural sites, suggesting improved community-wide coverage of LLIN and additional malaria control interventions are needed in Uganda. PMID:25778501

  1. Malaria transmission, infection, and disease at three sites with varied transmission intensity in Uganda: implications for malaria control.

    PubMed

    Kamya, Moses R; Arinaitwe, Emmanuel; Wanzira, Humphrey; Katureebe, Agaba; Barusya, Chris; Kigozi, Simon P; Kilama, Maxwell; Tatem, Andrew J; Rosenthal, Philip J; Drakeley, Chris; Lindsay, Steve W; Staedke, Sarah G; Smith, David L; Greenhouse, Bryan; Dorsey, Grant

    2015-05-01

    The intensification of control interventions has led to marked reductions in malaria burden in some settings, but not others. To provide a comprehensive description of malaria epidemiology in Uganda, we conducted surveillance studies over 24 months in 100 houses randomly selected from each of three subcounties: Walukuba (peri-urban), Kihihi (rural), and Nagongera (rural). Annual entomological inoculation rate (aEIR) was estimated from monthly Centers for Disease Control and Prevention (CDC) light trap mosquito collections. Children aged 0.5-10 years were provided long-lasting insecticidal nets (LLINs) and followed for measures of parasite prevalence, anemia and malaria incidence. Estimates of aEIR were 2.8, 32.0, and 310 infectious bites per year, and estimates of parasite prevalence 7.4%, 9.3%, and 28.7% for Walukuba, Kihihi, and Nagongera, respectively. Over the 2-year study, malaria incidence per person-years decreased in Walukuba (0.51 versus 0.31, P = 0.001) and increased in Kihihi (0.97 versus 1.93, P < 0.001) and Nagongera (2.33 versus 3.30, P < 0.001). Of 2,582 episodes of malaria, only 8 (0.3%) met criteria for severe disease. The prevalence of anemia was low and not associated with transmission intensity. In our cohorts, where LLINs and prompt effective treatment were provided, the risk of complicated malaria and anemia was extremely low. However, malaria incidence was high and increased over time at the two rural sites, suggesting improved community-wide coverage of LLIN and additional malaria control interventions are needed in Uganda.

  2. Prioritization of Companion Animal Transmissible Diseases for Policy Intervention in Europe.

    PubMed

    Cito, F; Rijks, J; Rantsios, A T; Cunningham, A A; Baneth, G; Guardabassi, L; Kuiken, T; Giovannini, A

    2016-07-01

    A number of papers have been published on the prioritization of transmissible diseases in farm animals and wildlife, based either on semiquantitative or truly quantitative methods, but there is no published literature on the prioritization of transmissible diseases in companion animals. In this study, available epidemiological data for diseases transmissible from companion animals to man were analysed with the aim of developing a procedure suitable for their prioritization within a European framework. A new method and its associated questionnaire and scoring system were designed based on methods described by the World Organisation for Animal Health (OIE). Modifications were applied to allow for the paucity of specific information on companion animal transmissible diseases. The OIE method was also adapted to the subject and to the regional scope of the interprofessional network addressing zoonotic diseases transmitted via companion animals in Europe: the Companion Animals multisectoriaL interprofessionaL Interdisciplinary Strategic Think tank On zoonoses (CALLISTO). Adaptations were made based on information collected from expert groups on viral, bacterial and parasitic diseases using a structured questionnaire, in which all questions were closed-ended. The expert groups were asked to select the most appropriate answer for each question taking into account the relevance and reliability of the data available in the scientific literature. Subsequently, the scoring of the answers obtained for each disease covered by the questionnaire was analysed to obtain two final overall scores, one for human health impact and one for agricultural economic impact. The adapted method was then applied to select the 15 most important pathogens (five for each pathogen group: viral, bacterial and parasitic) on the basis of their overall impact on public health and agriculture. The result of the prioritization exercise was a joint priority list (available at www.callistoproject.eu) of

  3. Foot and mouth disease virus transmission among vaccinated pigs after exposure to virus shedding pigs.

    PubMed

    Orsel, K; de Jong, M C M; Bouma, A; Stegeman, J A; Dekker, A

    2007-08-21

    The aim of this study was to design a transmission experiment that enabled quantification of the effectiveness of vaccination against foot and mouth disease (FMD) virus in groups of pigs. Previous experiments showed that intradermal injection of pigs with FMD virus 14 days after vaccination was not suitable to start an infection chain, as inoculated vaccinated pigs resisted challenge. Therefore, we carried out two experiments in which we used direct contact to a non-vaccinated pig as route of infection. In the first experiment only the vaccine effect on susceptibility was quantified by exposing pigs, either vaccinated 14 days before or not vaccinated, each to a non-vaccinated seeder pig inoculated with FMD virus O/NET/2001. Since no significant differences were observed between contact infections in vaccinated or non-vaccinated pigs, we performed a second experiment in which both susceptibility and infectivity were subject to vaccination. We quantified virus transmission in homogenous groups of vaccinated or non-vaccinated pigs in which the infection chain was started by exposure to a third group of non-vaccinated infected pigs. Transmission occurred to all contact-exposed pigs in the non-vaccinated groups and to 9 out of 10 contact-exposed pigs in the vaccinated groups. The rate of transmission (beta) was significantly reduced in the vaccine group. Yet, the estimated reproduction ratio in both groups was still above 1. In conclusion, by adjusting our transmission study design and challenge method, we were able to quantify transmission of FMDV among vaccinated pigs. According to this study a single vaccination was not sufficient to stop pig to pig virus transmission. With these results major outbreaks may still be expected, even in groups of vaccinated pigs. PMID:17658199

  4. Modeling the trade-off between transmissibility and contact in infectious disease dynamics.

    PubMed

    Lin, Chiu-Ju; Deger, Kristen A; Tien, Joseph H

    2016-07-01

    Symptom severity affects disease transmission both by impacting contact rates, as well as by influencing the probability of transmission given contact. This involves a trade-off between these two factors, as increased symptom severity will tend to decrease contact rates, but increase the probability of transmission given contact (as pathogen shedding rates increase with symptom severity). This paper explores this trade-off between contact and transmission given contact, using a simple compartmental susceptible-infected-recovered type model. Under mild assumptions on how contact and transmission probability vary with symptom severity, we give sufficient, biologically intuitive criteria for when the basic reproduction number varies non-monotonically with symptom severity. Multiple critical points are possible. We give a complete characterization of the region in parameter space where multiple critical points are located in the special case where contact rate decreases exponentially with symptom severity. We consider a multi-strain version of the model with complete cross-immunity and no super-infection. In this model, we prove that the strain with highest basic reproduction number drives the other strains to extinction. This has both evolutionary and epidemiological implications, including the possibility of an intervention paradoxically resulting in increased infection prevalence.

  5. Modeling the trade-off between transmissibility and contact in infectious disease dynamics.

    PubMed

    Lin, Chiu-Ju; Deger, Kristen A; Tien, Joseph H

    2016-07-01

    Symptom severity affects disease transmission both by impacting contact rates, as well as by influencing the probability of transmission given contact. This involves a trade-off between these two factors, as increased symptom severity will tend to decrease contact rates, but increase the probability of transmission given contact (as pathogen shedding rates increase with symptom severity). This paper explores this trade-off between contact and transmission given contact, using a simple compartmental susceptible-infected-recovered type model. Under mild assumptions on how contact and transmission probability vary with symptom severity, we give sufficient, biologically intuitive criteria for when the basic reproduction number varies non-monotonically with symptom severity. Multiple critical points are possible. We give a complete characterization of the region in parameter space where multiple critical points are located in the special case where contact rate decreases exponentially with symptom severity. We consider a multi-strain version of the model with complete cross-immunity and no super-infection. In this model, we prove that the strain with highest basic reproduction number drives the other strains to extinction. This has both evolutionary and epidemiological implications, including the possibility of an intervention paradoxically resulting in increased infection prevalence. PMID:27102055

  6. Spatial Transmission of Swine Vesicular Disease Virus in the 2006–2007 Epidemic in Lombardy

    PubMed Central

    Nassuato, Claudia; Boender, Gert Jan; Eblé, Phaedra L.; Alborali, Loris; Bellini, Silvia; Hagenaars, Thomas J.

    2013-01-01

    In 2006 and 2007 pig farming in the region of Lombardy, in the north of Italy, was struck by an epidemic of Swine Vesicular Disease virus (SVDV). In fact this epidemic could be viewed as consisting of two sub-epidemics, as the reported outbreaks occurred in two separate time periods. These periods differed in terms of the provinces or municipalities that were affected and also in terms of the timing of implementation of movement restrictions. Here we use a simple mathematical model to analyse the epidemic data, quantifying between-farm transmission probability as a function of between-farm distance. The results show that the distance dependence of between-farm transmission differs between the two periods. In the first period transmission over relatively long distances occurred with higher probability than in the second period, reflecting the effect of movement restrictions in the second period. In the second period however, more intensive transmission occurred over relatively short distances. Our model analysis explains this in terms of the relatively high density of pig farms in the area most affected in this period, which exceeds a critical farm density for between-farm transmission. This latter result supports the rationale for the additional control measure taken in 2007 of pre-emptively culling farms in that area. PMID:23667534

  7. Quantifying the disease transmission function: effects of density on Batrachochytrium dendrobatidis transmission in the mountain yellow-legged frog Rana muscosa.

    PubMed

    Rachowicz, Lara J; Briggs, Cheryl J

    2007-07-01

    1. Chytridiomycosis is an emerging infectious disease of amphibians, caused by the fungal pathogen Batrachochytrium dendrobatidis, which has been implicated recently in population declines and possible extinctions throughout the world. 2. The transmission rate of this pathogen was quantified in the mountain yellow-legged frog Rana muscosa through laboratory and field experiments, and a maximum likelihood approach was used to determine the form of the transmission function that was best supported by the experimental data. 3. The proportion of R. muscosa tadpole hosts that became infected increased with the number of previously infected R. muscosa tadpoles to which they were exposed, as would be expected in an infectious disease. 4. The laboratory experiment revealed some support for a transmission function in which the transmission rate levels off as the density of infected individuals increases. However, there was not enough power to distinguish between a frequency-dependent form and several other asymptotic forms of the transmission function. 5. The impacts of crowding and temperature on transmission were also investigated; however, neither of these factors significantly affected the transmission rate.

  8. The dangers of disease transmission by artificial insemination and embryo transfer.

    PubMed

    Philpott, M

    1993-01-01

    This review summarizes the major infectious diseases of the three major agricultural species (cattle, sheep and pigs) and horses, and presents the evidence for and against the possibility of infectious agents being transmitted between animals via the venereal route or by the use of semen or early embryos in commercial artificial insemination (AI) or embryo transfer (ET). Cattle feature most prominently in the widespread distribution of frozen semen, and national and international organizations have set out guidelines to work towards disease-free bull studs with semen free from potential pathogens. With the control of major epizootic diseases, attention has been focused on such diseases as IBR, BVD and blue tongue, where clinical signs are rarely evident but the detection of virus in semen is of great importance. New information on the relevance of bacterial disease such as Mycobacterium paratuberculosis, campylobacteriosis and leptospirosis is reviewed, along with details of the mycoplasma and ureaplasma species of the bull's genital tract. Bovine spongiform encephalopathy (BSE) has attracted much research and semen is not regarded as a source of infection. New work on the pathogenesis of a number of diseases and the use of new biotechnology in diagnosis is included. The International Embryo Transfer Society (IETS) has encouraged a great deal of experimental work--much originating in Canada--on the risk of transmission of disease from donors to recipients via a 7-day-old blastocyst. There has been much success in demonstrating that with an approved protocol of handling the embryos, to date there is very little danger in disease transmission with both viruses and bacteria. The mycoplasma group appear more intractable and the role of BSE is still being evaluated. In sheep, scrapie, Brucella ovis infection and blue tongue feature in current work. In the pig there is a surge in international movement of pig semen, and Aujeszky's disease and the new so-called Blue Ear

  9. Effects of vulture declines on facultative scavengers and potential implications for mammalian disease transmission.

    PubMed

    Ogada, D L; Torchin, M E; Kinnaird, M F; Ezenwa, V O

    2012-06-01

    Vultures (Accipitridae and Cathartidae) are the only known obligate scavengers. They feed on rotting carcasses and are the most threatened avian functional group in the world. Possible effects of vulture declines include longer persistence of carcasses and increasing abundance of and contact between facultative scavengers at these carcasses. These changes could increase rates of transmission of infectious diseases, with carcasses serving as hubs of infection. To evaluate these possibilities, we conducted a series of observations and experimental tests of the effects of vulture extirpation on decomposition rates of livestock carcasses and mammalian scavengers in Kenya. We examined whether the absence of vultures changed carcass decomposition time, number of mammalian scavengers visiting carcasses, time spent by mammals at carcasses, and potential for disease transmission at carcasses (measured by changes in intraspecific contact rates). In the absence of vultures, mean carcass decomposition rates nearly tripled. Furthermore, the mean number of mammals at carcasses increased 3-fold (from 1.5 to 4.4 individuals/carcass), and the average time spent by mammals at carcasses increased almost 3-fold (from 55 min to 143 min). There was a nearly 3-fold increase in the mean number of contacts between mammalian scavengers at carcasses without vultures. These results highlight the role of vultures in carcass decomposition and level of contact among mammalian scavengers. In combination, our findings lead us to hypothesize that changes in vulture abundance may affect patterns of disease transmission among mammalian carnivores.

  10. Transmission of Hand, Foot and Mouth Disease and Its Potential Driving Factors in Hong Kong

    PubMed Central

    Yang, Bingyi; Lau, Eric H. Y.; Wu, Peng; Cowling, Benjamin J.

    2016-01-01

    Hand-foot-and-mouth disease (HFMD) is a common childhood disease with substantial disease burden in Asia. Mixed results were reported on the associations between HFMD incidence and meteorological factors or school holidays, while limited studies focused on their association on transmissibility. We aimed to measure the transmissibility of HFMD and to examine its potential driving factors in Hong Kong. A likelihood-based procedure was used to estimate time-dependent effective reproduction number (Rt) based on weekly number of HFMD-associated hospitalizations from 2010 to 2014. The associations of between-year effects, depletion of susceptibles, absolute humidity and school holidays with Rt were examined using linear regression. Rt usually started increasing between early spring and summer and peaked in April to May at around 1.1–1.2, followed by a slight rebound in autumn. Depletion of susceptibles and between-years effects explained most of the variances (19 and 13% respectively) in Rt. We found a negative association between depletion of susceptibles and Rt (coefficients ranged from −0.14 to −0.03 for different years), but the estimated effects of absolute humidity and school holidays were insignificant. Overall, HFMD transmission was moderate in Hong Kong and was mainly associated with depletion of susceptibles. Limited impact was suggested from meteorological factors and school holidays. PMID:27271966

  11. Anti-triatomine saliva immunoassays for the evaluation of impregnated netting trials against Chagas disease transmission

    PubMed Central

    Schwarz, Alexandra; Juarez, Jenny Ancca; Richards, Jean; Rath, Bruno; Machaca, Victor Quispe; Castro, Yagahira E.; Málaga, Edith S.; Levy, Katelyn; Gilman, Robert H.; Bern, Caryn; Verastegui, Manuela; Levy, Michael Z.

    2011-01-01

    Insecticide-impregnated nets can kill triatomine bugs, but it remains unclear whether they can protect against Chagas disease transmission. In a field trial in Quequeña, Peru, sentinel guinea pigs placed in intervention enclosures covered by deltamethrin-treated nets showed significantly lower antibody responses to saliva of Triatoma infestans compared with animals placed in pre-existing control enclosures. Our results strongly suggest that insecticide-treated nets prevent triatomine bites and can thereby protect against infection with Trypanosoma cruzi. Anti-salivary immunoassays are powerful new tools to evaluate intervention strategies against Chagas disease. PMID:21426907

  12. Anti-triatomine saliva immunoassays for the evaluation of impregnated netting trials against Chagas disease transmission.

    PubMed

    Schwarz, Alexandra; Juarez, Jenny Ancca; Richards, Jean; Rath, Bruno; Machaca, Victor Quispe; Castro, Yagahira E; Málaga, Edith S; Levy, Katelyn; Gilman, Robert H; Bern, Caryn; Verastegui, Manuela; Levy, Michael Z

    2011-05-01

    Insecticide-impregnated nets can kill triatomine bugs, but it remains unclear whether they can protect against Chagas disease transmission. In a field trial in Quequeña, Peru, sentinel guinea pigs placed in intervention enclosures covered by deltamethrin-treated nets showed significantly lower antibody responses to saliva of Triatoma infestans compared with animals placed in pre-existing control enclosures. Our results strongly suggest that insecticide-treated nets prevent triatomine bites and can thereby protect against infection with Trypanosoma cruzi. Anti-salivary immunoassays are powerful new tools to evaluate intervention strategies against Chagas disease.

  13. Airborne Imagery

    NASA Technical Reports Server (NTRS)

    1983-01-01

    ATM (Airborne Thematic Mapper) was developed for NSTL (National Space Technology Companies) by Daedalus Company. It offers expanded capabilities for timely, accurate and cost effective identification of areas with prospecting potential. A related system is TIMS, Thermal Infrared Multispectral Scanner. Originating from Landsat 4, it is also used for agricultural studies, etc.

  14. Cell-to-cell transmission of pathogenic proteins in neurodegenerative diseases

    PubMed Central

    Guo, Jing L; Lee, Virginia M Y

    2014-01-01

    A common feature of many neurodegenerative diseases is the deposition of β-sheet-rich amyloid aggregates formed by proteins specific to these diseases. These protein aggregates are thought to cause neuronal dysfunction, directly or indirectly. Recent studies have strongly implicated cell-to-cell transmission of misfolded proteins as a common mechanism for the onset and progression of various neurodegenerative disorders. Emerging evidence also suggests the presence of conformationally diverse ‘strains’ of each type of disease protein, which may be another shared feature of amyloid aggregates, accounting for the tremendous heterogeneity within each type of neurodegenerative disease. Although there are many more questions to be answered, these studies have opened up new avenues for therapeutic interventions in neurodegenerative disorders. PMID:24504409

  15. Disease transmission in territorial populations: the small-world network of Serengeti lions.

    PubMed

    Craft, Meggan E; Volz, Erik; Packer, Craig; Meyers, Lauren Ancel

    2011-06-01

    Territoriality in animal populations creates spatial structure that is thought to naturally buffer disease invasion. Often, however, territorial populations also include highly mobile, non-residential individuals that potentially serve as disease superspreaders. Using long-term data from the Serengeti Lion Project, we characterize the contact network structure of a territorial wildlife population and address the epidemiological impact of nomadic individuals. As expected, pride contacts are dominated by interactions with neighbouring prides and interspersed by encounters with nomads as they wander throughout the ecosystem. Yet the pride-pride network also includes occasional long-range contacts between prides, making it surprisingly small world and vulnerable to epidemics, even without nomads. While nomads increase both the local and global connectivity of the network, their epidemiological impact is marginal, particularly for diseases with short infectious periods like canine distemper virus. Thus, territoriality in Serengeti lions may be less protective and non-residents less important for disease transmission than previously considered.

  16. High-frequency electroacupuncture evidently reinforces hippocampal synaptic transmission in Alzheimer's disease rats

    PubMed Central

    Li, Wei; Kong, Li-hong; Wang, Hui; Shen, Feng; Wang, Ya-wen; Zhou, Hua; Sun, Guo-jie

    2016-01-01

    The frequency range of electroacupuncture in treatment of Alzheimer's disease in rats is commonly 2–5 Hz (low frequency) and 50–100 Hz (high frequency). We established a rat model of Alzheimer's disease by injecting β-amyloid 1–42 (Aβ1–42) into the bilateral hippocampal dentate gyrus to verify which frequency may be better suited in treatment. Electroacupuncture at 2 Hz or 50 Hz was used to stimulate Baihui (DU20) and Shenshu (BL23) acupoints. The water maze test and electrophysiological studies demonstrated that spatial memory ability was apparently improved, and the ranges of long-term potentiation and long-term depression were increased in Alzheimer's disease rats after electroacupuncture treatment. Moreover, the effects of electroacupuncture at 50 Hz were better than that at 2 Hz. These findings suggest that high-frequency electroacupuncture may enhance hippocampal synaptic transmission and potentially improve memory disorders in Alzheimer's disease rats. PMID:27335565

  17. Transmission dynamics of Ebola virus disease and intervention effectiveness in Sierra Leone.

    PubMed

    Fang, Li-Qun; Yang, Yang; Jiang, Jia-Fu; Yao, Hong-Wu; Kargbo, David; Li, Xin-Lou; Jiang, Bao-Gui; Kargbo, Brima; Tong, Yi-Gang; Wang, Ya-Wei; Liu, Kun; Kamara, Abdul; Dafae, Foday; Kanu, Alex; Jiang, Rui-Ruo; Sun, Ye; Sun, Ruo-Xi; Chen, Wan-Jun; Ma, Mai-Juan; Dean, Natalie E; Thomas, Harold; Longini, Ira M; Halloran, M Elizabeth; Cao, Wu-Chun

    2016-04-19

    Sierra Leone is the most severely affected country by an unprecedented outbreak of Ebola virus disease (EVD) in West Africa. Although successfully contained, the transmission dynamics of EVD and the impact of interventions in the country remain unclear. We established a database of confirmed and suspected EVD cases from May 2014 to September 2015 in Sierra Leone and mapped the spatiotemporal distribution of cases at the chiefdom level. A Poisson transmission model revealed that the transmissibility at the chiefdom level, estimated as the average number of secondary infections caused by a patient per week, was reduced by 43% [95% confidence interval (CI): 30%, 52%] after October 2014, when the strategic plan of the United Nations Mission for Emergency Ebola Response was initiated, and by 65% (95% CI: 57%, 71%) after the end of December 2014, when 100% case isolation and safe burials were essentially achieved, both compared with before October 2014. Population density, proximity to Ebola treatment centers, cropland coverage, and atmospheric temperature were associated with EVD transmission. The household secondary attack rate (SAR) was estimated to be 0.059 (95% CI: 0.050, 0.070) for the overall outbreak. The household SAR was reduced by 82%, from 0.093 to 0.017, after the nationwide campaign to achieve 100% case isolation and safe burials had been conducted. This study provides a complete overview of the transmission dynamics of the 2014-2015 EVD outbreak in Sierra Leone at both chiefdom and household levels. The interventions implemented in Sierra Leone seem effective in containing the epidemic, particularly in interrupting household transmission.

  18. Transmission dynamics of Ebola virus disease and intervention effectiveness in Sierra Leone

    PubMed Central

    Fang, Li-Qun; Yang, Yang; Jiang, Jia-Fu; Yao, Hong-Wu; Kargbo, David; Li, Xin-Lou; Jiang, Bao-Gui; Kargbo, Brima; Tong, Yi-Gang; Wang, Ya-Wei; Liu, Kun; Kamara, Abdul; Dafae, Foday; Kanu, Alex; Jiang, Rui-Ruo; Sun, Ye; Sun, Ruo-Xi; Chen, Wan-Jun; Ma, Mai-Juan; Dean, Natalie E.; Thomas, Harold; Longini, Ira M.; Halloran, M. Elizabeth; Cao, Wu-Chun

    2016-01-01

    Sierra Leone is the most severely affected country by an unprecedented outbreak of Ebola virus disease (EVD) in West Africa. Although successfully contained, the transmission dynamics of EVD and the impact of interventions in the country remain unclear. We established a database of confirmed and suspected EVD cases from May 2014 to September 2015 in Sierra Leone and mapped the spatiotemporal distribution of cases at the chiefdom level. A Poisson transmission model revealed that the transmissibility at the chiefdom level, estimated as the average number of secondary infections caused by a patient per week, was reduced by 43% [95% confidence interval (CI): 30%, 52%] after October 2014, when the strategic plan of the United Nations Mission for Emergency Ebola Response was initiated, and by 65% (95% CI: 57%, 71%) after the end of December 2014, when 100% case isolation and safe burials were essentially achieved, both compared with before October 2014. Population density, proximity to Ebola treatment centers, cropland coverage, and atmospheric temperature were associated with EVD transmission. The household secondary attack rate (SAR) was estimated to be 0.059 (95% CI: 0.050, 0.070) for the overall outbreak. The household SAR was reduced by 82%, from 0.093 to 0.017, after the nationwide campaign to achieve 100% case isolation and safe burials had been conducted. This study provides a complete overview of the transmission dynamics of the 2014−2015 EVD outbreak in Sierra Leone at both chiefdom and household levels. The interventions implemented in Sierra Leone seem effective in containing the epidemic, particularly in interrupting household transmission. PMID:27035948

  19. Cross-reactive acquired immunity influences transmission success of the Lyme disease pathogen, Borrelia afzelii.

    PubMed

    Jacquet, Maxime; Durand, Jonas; Rais, Olivier; Voordouw, Maarten J

    2015-12-01

    Cross-reactive acquired immunity in the vertebrate host induces indirect competition between strains of a given pathogen species and is critical for understanding the ecology of mixed infections. In vector-borne diseases, cross-reactive antibodies can reduce pathogen transmission at the vector-to-host and the host-to-vector lifecycle transition. The highly polymorphic, immunodominant, outer surface protein C (OspC) of the tick-borne spirochete bacterium Borrelia afzelii induces a strong antibody response in the vertebrate host. To test how cross-immunity in the vertebrate host influences tick-to-host and host-to-tick transmission, mice were immunized with one of two strain-specific recombinant OspC proteins (A3, A10), challenged via tick bite with one of the two B. afzelii ospC strains (A3, A10), and infested with xenodiagnostic ticks. Immunization with a given rOspC antigen protected mice against homologous strains carrying the same major ospC group allele but provided little or no cross-protection against heterologous strains carrying a different major ospC group allele. There were cross-immunity effects on the tick spirochete load but not on the probability of host-to-tick transmission. The spirochete load in ticks that had fed on mice with cross-immune experience was reduced by a factor of two compared to ticks that had fed on naive control mice. In addition, strain-specific differences in mouse spirochete load, host-to-tick transmission, tick spirochete load, and the OspC-specific IgG response revealed the mechanisms that determine variation in transmission success between strains of B. afzelii. This study shows that cross-immunity in infected vertebrate hosts can reduce pathogen load in the arthropod vector with potential consequences for vector-to-host pathogen transmission.

  20. Cross-reactive acquired immunity influences transmission success of the Lyme disease pathogen, Borrelia afzelii.

    PubMed

    Jacquet, Maxime; Durand, Jonas; Rais, Olivier; Voordouw, Maarten J

    2015-12-01

    Cross-reactive acquired immunity in the vertebrate host induces indirect competition between strains of a given pathogen species and is critical for understanding the ecology of mixed infections. In vector-borne diseases, cross-reactive antibodies can reduce pathogen transmission at the vector-to-host and the host-to-vector lifecycle transition. The highly polymorphic, immunodominant, outer surface protein C (OspC) of the tick-borne spirochete bacterium Borrelia afzelii induces a strong antibody response in the vertebrate host. To test how cross-immunity in the vertebrate host influences tick-to-host and host-to-tick transmission, mice were immunized with one of two strain-specific recombinant OspC proteins (A3, A10), challenged via tick bite with one of the two B. afzelii ospC strains (A3, A10), and infested with xenodiagnostic ticks. Immunization with a given rOspC antigen protected mice against homologous strains carrying the same major ospC group allele but provided little or no cross-protection against heterologous strains carrying a different major ospC group allele. There were cross-immunity effects on the tick spirochete load but not on the probability of host-to-tick transmission. The spirochete load in ticks that had fed on mice with cross-immune experience was reduced by a factor of two compared to ticks that had fed on naive control mice. In addition, strain-specific differences in mouse spirochete load, host-to-tick transmission, tick spirochete load, and the OspC-specific IgG response revealed the mechanisms that determine variation in transmission success between strains of B. afzelii. This study shows that cross-immunity in infected vertebrate hosts can reduce pathogen load in the arthropod vector with potential consequences for vector-to-host pathogen transmission. PMID:26384476

  1. Application of Radar Altimetry Methods to Monitoring of Parasitic Disease Transmission: Schistosomiasis in Poyang Lake, China

    NASA Astrophysics Data System (ADS)

    McCandless, M.; Ibaraki, M.; Shum, C.; Lee, H.; Liang, S.

    2008-12-01

    Schistosomiasis is the second-most prevalent tropical disease after malaria affecting two-hundred million people annually world-wide; it shortens lifespan on average by ten years in endemic areas and no vaccine exists. The current control methods of human host chemotherapy and application of molluscicides to the environment do not break the disease transmission cycle. Schistosomiasis transmission in southern China involves an amphibious intermediate host snail for which hydrology is a key factor because the adults need moist vegetation while the juveniles are fully aquatic. Thus, hydrology is a key factor in schistosomiasis transmission and understanding its role can inform control measures. Our objective is to integrate hydrologic, ecologic, and other environmental factors to determine the changes in available snail habitat through space and time. We use radar altimetry measurements to determine water level every 35 days when the Envisat (Environmental Satellite) passes over the lake. The radar altimetry readings have been calibrated to levels from in-situ gauging stations and will support remote analysis of disease transmission potential without the need for gauging station data. A geographic information system was used to combine key factors including water level, topography, and air temperature data to identify areas of available snail habitat. In order to accomplish this, we conducted three steps including: delineating the watershed, specifying potential snail habitat areas through topography and air temperature classification, and calculating the intersection between potential snail habitat and non-flooded areas in the watershed. Statistical analyses of total available habitat area are also conducted. These maps and statistics analyses can be used by public health agencies to monitor snail habitat trends over time. Coupling remote sensing of water levels with a geographic information system model will continue to be important as the hydrology of the lake

  2. A transmissible Creutzfeldt-Jakob disease-like agent is prevalent in the human population.

    PubMed Central

    Manuelidis, E E; Manuelidis, L

    1993-01-01

    The etiology of most human dementias is unknown. Creutzfeldt-Jakob disease (CJD), a relatively uncommon human dementia, is caused by a transmissible virus-like agent. Molecular markers that are specific for the agent have not yet been defined. However, the infectious disease can be transmitted to rodents from both brain and infected buffy coat (blood) samples. To determine whether human CJD infections are more widespread than is apparent from the low incidence of neurological disease, we attempted to transmit CJD from buffy coat samples of 30 healthy volunteers who had no family history of dementing illness. Primary transmissions from 26 of 30 individuals produced CJD-like spongiform changes in the brains of recipient hamsters at 200-500 days postinoculation. This positive evidence of viremia was found for individuals in all age groups (20-30, 40-50, and 61-71 years old), whereas 12 negatively scored brain samples failed to produce similar changes in hamsters observed for > 900 days in the same setting. We suggest that a CJD agent endemically infects humans but only infrequently produces an infectious dementia. Disease expression is likely to be influenced by several host factors in combination with viral variants that have altered neurovirulence. Images Fig. 1 PMID:8356076

  3. Simulating the spread of malaria using a generic transmission model for mosquito-borne infectious diseases

    NASA Astrophysics Data System (ADS)

    Kon, Cynthia Mui Lian; Labadin, Jane

    2016-06-01

    Malaria is a critical infection caused by parasites which are spread to humans through mosquito bites. Approximately half of the world's population is in peril of getting infected by malaria. Mosquito-borne diseases have a standard behavior where they are transmitted in the same manner, only through vector mosquito. Taking this into account, a generic spatial-temporal model for transmission of multiple mosquito-borne diseases had been formulated. Our interest is to reproduce the actual cases of different mosquito-borne diseases using the generic model and then predict future cases so as to improve control and target measures competently. In this paper, we utilize notified weekly malaria cases in four districts in Sarawak, Malaysia, namely Kapit, Song, Belaga and Marudi. The actual cases for 36 weeks, which is from week 39 in 2012 to week 22 in 2013, are compared with simulations of the generic spatial-temporal transmission mosquito-borne diseases model. We observe that the simulation results display corresponding result to the actual malaria cases in the four districts.

  4. Ross River Virus Transmission, Infection, and Disease: a Cross-Disciplinary Review

    PubMed Central

    Harley, David; Sleigh, Adrian; Ritchie, Scott

    2001-01-01

    Ross River virus (RRV) is a fascinating, important arbovirus that is endemic and enzootic in Australia and Papua New Guinea and was epidemic in the South Pacific in 1979 and 1980. Infection with RRV may cause disease in humans, typically presenting as peripheral polyarthralgia or arthritis, sometimes with fever and rash. RRV disease notifications in Australia average 5,000 per year. The first well-described outbreak occurred in 1928. During World War II there were more outbreaks, and the name epidemic polyarthritis was applied. During a 1956 outbreak, epidemic polyarthritis was linked serologically to a group A arbovirus (Alphavirus). The virus was subsequently isolated from Aedes vigilax mosquitoes in 1963 and then from epidemic polyarthritis patients. We review the literature on the evolutionary biology of RRV, immune response to infection, pathogenesis, serologic diagnosis, disease manifestations, the extraordinary variety of vertebrate hosts, mosquito vectors, and transmission cycles, antibody prevalence, epidemiology of asymptomatic and symptomatic human infection, infection risks, and public health impact. RRV arthritis is due to joint infection, and treatment is currently based on empirical anti-inflammatory regimens. Further research on pathogenesis may improve understanding of the natural history of this disease and lead to new treatment strategies. The burden of morbidity is considerable, and the virus could spread to other countries. To justify and design preventive programs, we need accurate data on economic costs and better understanding of transmission and behavioral and environmental risks. PMID:11585790

  5. Vertical transmission of Tetracapsuloides bryosalmonae (Myxozoa), the causative agent of salmonid proliferative kidney disease.

    PubMed

    Abd-Elfattah, Ahmed; Fontes, Inês; Kumar, Gokhlesh; Soliman, Hatem; Hartikainen, Hanna; Okamura, Beth; El-Matbouli, Mansour

    2014-04-01

    The freshwater bryozoan, Fredericella sultana, is the main primary host of the myxozoan endoparasite, Tetracapsuloides bryosalmonae which causes proliferative kidney disease (PKD) of salmonid fish. Because spores that develop in bryozoan colonies are infectious to fish, bryozoans represent the ultimate source of PKD. Bryozoans produce numerous seed-like dormant stages called statoblasts that enable persistence during unfavourable conditions and achieve long-distance dispersal. The possibility that T. bryosalmonae may undergo vertical transmission via infection of statoblasts has been the subject of much speculation since this is observed in close relatives. This study provides the first evidence that such vertical transmission of T. bryosalmonae is extensive by examining the proportions of infected statoblasts in populations of F. sultana on two different rivers systems and confirms its effectiveness by demonstrating transmission from material derived from infected statoblasts to fish hosts. Vertical transmission in statoblasts is likely to play an important role in the infection dynamics of both bryozoan and fish hosts and may substantially contribute to the widespread distribution of PKD.

  6. Inhibition of infectious bursal disease virus transmission using bioceramic derived from chicken feces.

    PubMed

    Thammakarn, Chanathip; Ishida, Yuki; Suguro, Atsushi; Hakim, Hakimullah; Nakajima, Katsuhiro; Kitazawa, Minori; Takehara, Kazuaki

    2015-06-01

    Bioceramic powder (BCX), at pH 13.0, derived from chicken feces, was evaluated for its efficacy to inactivate virus and inhibit virus horizontal transmission by fecal-oral route, using infectious bursal disease virus (IBDV) vaccine strain D78 as a challenge virus. Three 1-week-old SPF chicks were vaccinated per os and used as seeder birds. Six hours later, 3 sentinel 1-week-old SPF chicks were introduced into the same cage. Results revealed that BCX had excellent efficacy to inactivate IBDV within 3 min. Treating IBDV contaminated litter in the cage with BCX could prevent transmission of IBDV to new sensitive chicks completely. Further, transmission of IBDV to the sentinel chicks was significantly inhibited by adding BCX to litter and chicken feed. These data suggest that BCX at pH 13, derived from chicken feces, has excellent efficacy to inactivate IBDV, which can be applied in bedding materials for preventing viral transmission during production round. It is a good material that can effectively be used for enhancing biosecurity system in poultry farms. PMID:25892716

  7. Vertical transmission of Tetracapsuloides bryosalmonae (Myxozoa), the causative agent of salmonid proliferative kidney disease.

    PubMed

    Abd-Elfattah, Ahmed; Fontes, Inês; Kumar, Gokhlesh; Soliman, Hatem; Hartikainen, Hanna; Okamura, Beth; El-Matbouli, Mansour

    2014-04-01

    The freshwater bryozoan, Fredericella sultana, is the main primary host of the myxozoan endoparasite, Tetracapsuloides bryosalmonae which causes proliferative kidney disease (PKD) of salmonid fish. Because spores that develop in bryozoan colonies are infectious to fish, bryozoans represent the ultimate source of PKD. Bryozoans produce numerous seed-like dormant stages called statoblasts that enable persistence during unfavourable conditions and achieve long-distance dispersal. The possibility that T. bryosalmonae may undergo vertical transmission via infection of statoblasts has been the subject of much speculation since this is observed in close relatives. This study provides the first evidence that such vertical transmission of T. bryosalmonae is extensive by examining the proportions of infected statoblasts in populations of F. sultana on two different rivers systems and confirms its effectiveness by demonstrating transmission from material derived from infected statoblasts to fish hosts. Vertical transmission in statoblasts is likely to play an important role in the infection dynamics of both bryozoan and fish hosts and may substantially contribute to the widespread distribution of PKD. PMID:24229733

  8. On The Use Of Models To Assess Foot-And-Mouth Disease Transmission And Control

    SciTech Connect

    Kostova-Vassilevska, T

    2004-07-12

    The 2001 outbreaks of foot-and-mouth disease (FMD) in Europe (Ferguson et al. 2001a, 2001b; Bouma et al. 2003) and concern about the possibility of an intentional introduction of a devastating foreign animal disease triggered renewed interest in both theoretical and experimental research related to FMD. Theoretical models of disease transmission, which influenced the tactical decisions of the United Kingdom (UK) government during the epidemic (Taylor 2003), resulted in large numbers of uninfected animals being slaughtered. After the epidemic, the adopted control policies were sharply criticized (Kitching 2004;, Taylor 2003). Still, the role of computationaL modeling for analyzing the scope of the epidemic and devising control strategies was recognized as substantial and necessary.

  9. Transmission of enteric disease associated with wastewater irrigation: A prospective epidemiological study

    SciTech Connect

    Shuval, H.I.; Wax, Y.; Yekutiel, P.; Fattal, B.

    1989-01-01

    A prospective epidemiological study of possible enteric disease transmission by aerosolized pathogens from sprinkler irrigation of partially treated waste water in 20 kibbutzim (collective agricultural settlements) in Israel between March 1981 and February 1982 was conducted. Medical data were collected from the patients' files and daily logs of physicians and nurses at each kibbutzim clinic (total population 10,231). Episodes of enteric disease were similar in the kibbutzim most exposed to wastewater aerosols (11.6 per 100 person-year) and the kibbutzim not exposed to wastewater in any form (11.0 per 100 person-year). No excess of enteric disease was seen among waste water contract workers or their families as compared with the unexposed. No negative health effects were detected in the study which involved a large population, including many young children exposed to treated waste water aerosols generated at distances of 300-600 miles.

  10. Genomics reveals historic and contemporary transmission dynamics of a bacterial disease among wildlife and livestock.

    PubMed

    Kamath, Pauline L; Foster, Jeffrey T; Drees, Kevin P; Luikart, Gordon; Quance, Christine; Anderson, Neil J; Clarke, P Ryan; Cole, Eric K; Drew, Mark L; Edwards, William H; Rhyan, Jack C; Treanor, John J; Wallen, Rick L; White, Patrick J; Robbe-Austerman, Suelee; Cross, Paul C

    2016-05-11

    Whole-genome sequencing has provided fundamental insights into infectious disease epidemiology, but has rarely been used for examining transmission dynamics of a bacterial pathogen in wildlife. In the Greater Yellowstone Ecosystem (GYE), outbreaks of brucellosis have increased in cattle along with rising seroprevalence in elk. Here we use a genomic approach to examine Brucella abortus evolution, cross-species transmission and spatial spread in the GYE. We find that brucellosis was introduced into wildlife in this region at least five times. The diffusion rate varies among Brucella lineages (∼3 to 8 km per year) and over time. We also estimate 12 host transitions from bison to elk, and 5 from elk to bison. Our results support the notion that free-ranging elk are currently a self-sustaining brucellosis reservoir and the source of livestock infections, and that control measures in bison are unlikely to affect the dynamics of unrelated strains circulating in nearby elk populations.

  11. Genomics reveals historic and contemporary transmission dynamics of a bacterial disease among wildlife and livestock.

    PubMed

    Kamath, Pauline L; Foster, Jeffrey T; Drees, Kevin P; Luikart, Gordon; Quance, Christine; Anderson, Neil J; Clarke, P Ryan; Cole, Eric K; Drew, Mark L; Edwards, William H; Rhyan, Jack C; Treanor, John J; Wallen, Rick L; White, Patrick J; Robbe-Austerman, Suelee; Cross, Paul C

    2016-01-01

    Whole-genome sequencing has provided fundamental insights into infectious disease epidemiology, but has rarely been used for examining transmission dynamics of a bacterial pathogen in wildlife. In the Greater Yellowstone Ecosystem (GYE), outbreaks of brucellosis have increased in cattle along with rising seroprevalence in elk. Here we use a genomic approach to examine Brucella abortus evolution, cross-species transmission and spatial spread in the GYE. We find that brucellosis was introduced into wildlife in this region at least five times. The diffusion rate varies among Brucella lineages (∼3 to 8 km per year) and over time. We also estimate 12 host transitions from bison to elk, and 5 from elk to bison. Our results support the notion that free-ranging elk are currently a self-sustaining brucellosis reservoir and the source of livestock infections, and that control measures in bison are unlikely to affect the dynamics of unrelated strains circulating in nearby elk populations. PMID:27165544

  12. Horizontal Transmissible Protection against Myxomatosis and Rabbit Hemorrhagic Disease by Using a Recombinant Myxoma Virus

    PubMed Central

    Bárcena, Juan; Morales, Mónica; Vázquez, Belén; Boga, José A.; Parra, Francisco; Lucientes, Javier; Pagès-Manté, Albert; Sánchez-Vizcaíno, José M.; Blasco, Rafael; Torres, Juan M.

    2000-01-01

    We have developed a new strategy for immunization of wild rabbit populations against myxomatosis and rabbit hemorrhagic disease (RHD) that uses recombinant viruses based on a naturally attenuated field strain of myxoma virus (MV). The recombinant viruses expressed the RHDV major capsid protein (VP60) including a linear epitope tag from the transmissible gastroenteritis virus (TGEV) nucleoprotein. Following inoculation, the recombinant viruses induced specific antibody responses against MV, RHDV, and the TGEV tag. Immunization of wild rabbits by the subcutaneous and oral routes conferred protection against virulent RHDV and MV challenges. The recombinant viruses showed a limited horizontal transmission capacity, either by direct contact or in a flea-mediated process, promoting immunization of contact uninoculated animals. PMID:10627521

  13. Genomics reveals historic and contemporary transmission dynamics of a bacterial disease among wildlife and livestock

    PubMed Central

    Kamath, Pauline L.; Foster, Jeffrey T.; Drees, Kevin P.; Luikart, Gordon; Quance, Christine; Anderson, Neil J.; Clarke, P. Ryan; Cole, Eric K.; Drew, Mark L.; Edwards, William H.; Rhyan, Jack C.; Treanor, John J.; Wallen, Rick L.; White, Patrick J.; Robbe-Austerman, Suelee; Cross, Paul C.

    2016-01-01

    Whole-genome sequencing has provided fundamental insights into infectious disease epidemiology, but has rarely been used for examining transmission dynamics of a bacterial pathogen in wildlife. In the Greater Yellowstone Ecosystem (GYE), outbreaks of brucellosis have increased in cattle along with rising seroprevalence in elk. Here we use a genomic approach to examine Brucella abortus evolution, cross-species transmission and spatial spread in the GYE. We find that brucellosis was introduced into wildlife in this region at least five times. The diffusion rate varies among Brucella lineages (∼3 to 8 km per year) and over time. We also estimate 12 host transitions from bison to elk, and 5 from elk to bison. Our results support the notion that free-ranging elk are currently a self-sustaining brucellosis reservoir and the source of livestock infections, and that control measures in bison are unlikely to affect the dynamics of unrelated strains circulating in nearby elk populations. PMID:27165544

  14. Genomics reveals historic and contemporary transmission dynamics of a bacterial disease among wildlife and livestock

    USGS Publications Warehouse

    Kamath, Pauline L.; Foster, Jeffrey T.; Drees, Kevin P.; Luikart, Gordon; Quance, Christine; Anderson, Neil J.; Clarke, P. Ryan; Cole, Eric K.; Drew, Mark L.; Edwards, William H.; Rhyan, Jack C.; Treanor, John J.; Wallen, Rick L.; White, Patrick J.; Robbe-Austerman, Suelee; Cross, Paul C.

    2016-01-01

    Whole-genome sequencing has provided fundamental insights into infectious disease epidemiology, but has rarely been used for examining transmission dynamics of a bacterial pathogen in wildlife. In the Greater Yellowstone Ecosystem (GYE), outbreaks of brucellosis have increased in cattle along with rising seroprevalence in elk. Here we use a genomic approach to examine Brucella abortus evolution, cross-species transmission and spatial spread in the GYE. We find that brucellosis was introduced into wildlife in this region at least five times. The diffusion rate varies among Brucella lineages (B3 to 8 km per year) and over time. We also estimate 12 host transitions from bison to elk, and 5 from elk to bison. Our results support the notion that free-ranging elk are currently a self-sustaining brucellosis reservoir and the source of livestock infections, and that control measures in bison are unlikely to affect the dynamics of unrelated strains circulating in nearby elk populations.

  15. Epidemiological consequences of a pathogen having both virulent and avirulent modes of transmission: the case of rabbit haemorrhagic disease virus.

    PubMed Central

    White, P. J.; Norman, R. A.; Hudson, P. J.

    2002-01-01

    A number of pathogens cause chronic infection in survivors of acute disease and this is believed to be a common means of persistence, including for highly virulent agents. We present a model in which transmission from chronically infected hosts causes chronic infection in naive individuals, without causing acute disease--indeed 'protecting' against it. Thus the pathogen obtains the benefit of virulence (high transmission rate), but mitigates against the cost (high host mortality). Recent findings suggest that rabbit haemorrhagic disease virus (RHDV), a highly contagious and virulent pathogen, may also utilize this alternative, 'avirulent', mode of transmission. The model may resolve the paradox of how RHDV can be highly prevalent in some populations, in the absence of mortality. Differences in host demography determine whether avirulent transmission prevents large-scale mortality (as in most UK populations) or not. Other pathogens may exhibit similar behaviour and the implications for emerging diseases in general are discussed. PMID:12558352

  16. Surveillance for Neisseria meningitidis Disease Activity and Transmission Using Information Technology

    PubMed Central

    Ahmed, S. Sohail; Oviedo-Orta, Ernesto; Mekaru, Sumiko R.; Freifeld, Clark C.; Tougas, Gervais; Brownstein, John S.

    2015-01-01

    Background While formal reporting, surveillance, and response structures remain essential to protecting public health, a new generation of freely accessible, online, and real-time informatics tools for disease tracking are expanding the ability to raise earlier public awareness of emerging disease threats. The rationale for this study is to test the hypothesis that the HealthMap informatics tools can complement epidemiological data captured by traditional surveillance monitoring systems for meningitis due to Neisseria meningitides (N. meningitides) by highlighting severe transmissible disease activity and outbreaks in the United States. Methods Annual analyses of N. meningitides disease alerts captured by HealthMap were compared to epidemiological data captured by the Centers for Disease Control’s Active Bacterial Core surveillance (ABCs) for N. meningitides. Morbidity and mortality case reports were measured annually from 2010 to 2013 (HealthMap) and 2005 to 2012 (ABCs). Findings HealthMap N. meningitides monitoring captured 80-90% of alerts as diagnosed N. meningitides, 5-20% of alerts as suspected cases, and 5-10% of alerts as related news articles. HealthMap disease alert activity for emerging disease threats related to N. meningitides were in agreement with patterns identified historically using traditional surveillance systems. HealthMap’s strength lies in its ability to provide a cumulative “snapshot” of weak signals that allows for rapid dissemination of knowledge and earlier public awareness of potential outbreak status while formal testing and confirmation for specific serotypes is ongoing by public health authorities. Conclusions The underreporting of disease cases in internet-based data streaming makes inadequate any comparison to epidemiological trends illustrated by the more comprehensive ABCs network published by the Centers for Disease Control. However, the expected delays in compiling confirmatory reports by traditional surveillance systems

  17. Programming of maternal and offspring disease: impact of growth restriction, fetal sex and transmission across generations.

    PubMed

    Cheong, Jean N; Wlodek, Mary E; Moritz, Karen M; Cuffe, James S M

    2016-09-01

    Babies born small are at an increased risk of developing myriad adult diseases. While growth restriction increases disease risk in all individuals, often a second hit is required to unmask 'programmed' impairments in physiology. Programmed disease outcomes are demonstrated more commonly in male offspring compared with females, with these sex-specific outcomes partly attributed to different placenta-regulated growth strategies of the male and female fetus. Pregnancy is known to be a major risk factor for unmasking a number of conditions and can be considered a 'second hit' for women who were born small. As such, female offspring often develop impairments of physiology for the first time during pregnancy that present as pregnancy complications. Numerous maternal stressors can further increase the risk of developing a maternal complication during pregnancy. Importantly, these maternal complications can have long-term consequences for both the mother after pregnancy and the developing fetus. Conditions such as preeclampsia, gestational diabetes and hypertension as well as thyroid, liver and kidney diseases are all conditions that can complicate pregnancy and have long-term consequences for maternal and offspring health. Babies born to mothers who develop these conditions are often at a greater risk of developing disease in adulthood. This has implications as a mechanism for transmission of disease across generations. In this review, we discuss the evidence surrounding long-term intergenerational implications of being born small and/or experiencing stress during pregnancy on programming outcomes.

  18. Prospective cohort studies of dengue viral transmission and severity of disease.

    PubMed

    Endy, Timothy P; Yoon, In-Kyu; Mammen, Mammen P

    2010-01-01

    As the four serotypes of dengue virus (DENV) systematically spread throughout the tropical and subtropical regions globally, dengue is increasingly contributing to the overall morbidity and mortality sustained by populations and thereby challenging the health infrastructures of most endemic countries. DENV-human host-mosquito vector interactions are complex and cause in humans either asymptomatic or subclinical DENV infection, mild to severe dengue fever (DF), severe dengue hemorrhagic fever (DHF), or dengue shock syndrome (DSS). Over the past decade, we have seen an increase in research funding and public health efforts to offset the effects of this pandemic. Though multiple vaccine development efforts are underway, the need remains to further characterize the determinants of varying severities of clinical outcomes. Several long-term prospective studies on DENV transmission and dengue severity have sought to define the epidemiology and pathogenesis of this disease. Yet, more studies are required to quantify the disease burden on different populations, explore the impact of DENV serotype-specific transmission on host-responses and dengue severity and measure the economic impact of dengue on a population. In this section, we will review the critical past and recent findings of dengue prospective studies on our understanding of the disease and the potential role of future prospective cohort studies in advancing issues required for vaccine field evaluations.

  19. Transmission of chronic wasting disease identifies a prion strain causing cachexia and heart infection in hamsters.

    PubMed

    Bessen, Richard A; Robinson, Cameron J; Seelig, Davis M; Watschke, Christopher P; Lowe, Diana; Shearin, Harold; Martinka, Scott; Babcock, Alex M

    2011-01-01

    Chronic wasting disease (CWD) is an emerging prion disease of free-ranging and captive cervids in North America. In this study we established a rodent model for CWD in Syrian golden hamsters that resemble key features of the disease in cervids including cachexia and infection of cardiac muscle. Following one to three serial passages of CWD from white-tailed deer into transgenic mice expressing the hamster prion protein gene, CWD was subsequently passaged into Syrian golden hamsters. In one passage line there were preclinical changes in locomotor activity and a loss of body mass prior to onset of subtle neurological symptoms around 340 days. The clinical symptoms included a prominent wasting disease, similar to cachexia, with a prolonged duration. Other features of CWD in hamsters that were similar to cervid CWD included the brain distribution of the disease-specific isoform of the prion protein, PrP(Sc), prion infection of the central and peripheral neuroendocrine system, and PrP(Sc) deposition in cardiac muscle. There was also prominent PrP(Sc) deposition in the nasal mucosa on the edge of the olfactory sensory epithelium with the lumen of the nasal airway that could have implications for CWD shedding into nasal secretions and disease transmission. Since the mechanism of wasting disease in prion diseases is unknown this hamster CWD model could provide a means to investigate the physiological basis of cachexia, which we propose is due to a prion-induced endocrinopathy. This prion disease phenotype has not been described in hamsters and we designate it as the 'wasting' or WST strain of hamster CWD.

  20. Three pathogens in sympatric populations of pumas, bobcats, and domestic cats: implications for infectious disease transmission.

    PubMed

    Bevins, Sarah N; Carver, Scott; Boydston, Erin E; Lyren, Lisa M; Alldredge, Mat; Logan, Kenneth A; Riley, Seth P D; Fisher, Robert N; Vickers, T Winston; Boyce, Walter; Salman, Mo; Lappin, Michael R; Crooks, Kevin R; VandeWoude, Sue

    2012-01-01

    Anthropogenic landscape change can lead to increased opportunities for pathogen transmission between domestic and non-domestic animals. Pumas, bobcats, and domestic cats are sympatric in many areas of North America and share many of the same pathogens, some of which are zoonotic. We analyzed bobcat, puma, and feral domestic cat samples collected from targeted geographic areas. We examined exposure to three pathogens that are taxonomically diverse (bacterial, protozoal, viral), that incorporate multiple transmission strategies (vector-borne, environmental exposure/ingestion, and direct contact), and that vary in species-specificity. Bartonella spp., Feline Immunodeficiency Virus (FIV), and Toxoplasma gondii IgG were detected in all three species with mean respective prevalence as follows: puma 16%, 41% and 75%; bobcat 31%, 22% and 43%; domestic cat 45%, 10% and 1%. Bartonella spp. were highly prevalent among domestic cats in Southern California compared to other cohort groups. Feline Immunodeficiency Virus exposure was primarily associated with species and age, and was not influenced by geographic location. Pumas were more likely to be infected with FIV than bobcats, with domestic cats having the lowest infection rate. Toxoplasma gondii seroprevalence was high in both pumas and bobcats across all sites; in contrast, few domestic cats were seropositive, despite the fact that feral, free ranging domestic cats were targeted in this study. Interestingly, a directly transmitted species-specific disease (FIV) was not associated with geographic location, while exposure to indirectly transmitted diseases--vector-borne for Bartonella spp. and ingestion of oocysts via infected prey or environmental exposure for T. gondii--varied significantly by site. Pathogens transmitted by direct contact may be more dependent upon individual behaviors and intra-specific encounters. Future studies will integrate host density, as well as landscape features, to better understand the

  1. Three pathogens in sympatric populations of pumas, bobcats, and domestic cats: implications for infections disease transmission

    USGS Publications Warehouse

    Bevins, Sarah N.; Carver, Scott; Boydston, Erin E.; Lyren, Lisa M.; Alldredge, Mat; Logan, Kenneth A.; Riley, Seth P.D.; Fisher, Robert N.; Vickers, T. Winston; Boyce, Walter; Salman, Mo; Lappin, Michael R.; Crooks, Kevin R.; VandeWoude, Sue

    2012-01-01

    Anthropogenic landscape change can lead to increased opportunities for pathogen transmission between domestic and non-domestic animals. Pumas, bobcats, and domestic cats are sympatric in many areas of North America and share many of the same pathogens, some of which are zoonotic. We analyzed bobcat, puma, and feral domestic cat samples collected from targeted geographic areas. We examined exposure to three pathogens that are taxonomically diverse (bacterial, protozoal, viral), that incorporate multiple transmission strategies (vector-borne, environmental exposure/ingestion, and direct contact), and that vary in species-specificity. Bartonella spp., Feline Immunodeficiency Virus (FIV), and Toxoplasma gondii IgG were detected in all three species with mean respective prevalence as follows: puma 16%, 41% and 75%; bobcat 31%, 22% and 43%; domestic cat 45%, 10% and 1%. Bartonella spp. were highly prevalent among domestic cats in Southern California compared to other cohort groups. Feline Immunodeficiency Virus exposure was primarily associated with species and age, and was not influenced by geographic location. Pumas were more likely to be infected with FIV than bobcats, with domestic cats having the lowest infection rate. Toxoplasma gondii seroprevalence was high in both pumas and bobcats across all sites; in contrast, few domestic cats were seropositive, despite the fact that feral, free ranging domestic cats were targeted in this study. Interestingly, a directly transmitted species-specific disease (FIV) was not associated with geographic location, while exposure to indirectly transmitted diseases - vectorborne for Bartonella spp. and ingestion of oocysts via infected prey or environmental exposure for T. gondii - varied significantly by site. Pathogens transmitted by direct contact may be more dependent upon individual behaviors and intra-specific encounters. Future studies will integrate host density, as well as landscape features, to better understand the

  2. Three pathogens in sympatric populations of pumas, bobcats, and domestic cats: Implications for infectious disease transmission

    USGS Publications Warehouse

    Bevins, S.N.; Carver, S.; Boydston, E.E.; Lyren, L.M.; Alldredge, M.; Logan, K.A.; Riley, S.P.D.; Fisher, R.N.; Vickers, T.W.; Boyce, W.; Salman, M.; Lappin, M.R.; Crooks, K.R.; VandeWoude, S.

    2012-01-01

    Anthropogenic landscape change can lead to increased opportunities for pathogen transmission between domestic and non-domestic animals. Pumas, bobcats, and domestic cats are sympatric in many areas of North America and share many of the same pathogens, some of which are zoonotic. We analyzed bobcat, puma, and feral domestic cat samples collected from targeted geographic areas. We examined exposure to three pathogens that are taxonomically diverse (bacterial, protozoal, viral), that incorporate multiple transmission strategies (vector-borne, environmental exposure/ingestion, and direct contact), and that vary in species-specificity. Bartonella spp., Feline Immunodeficiency Virus (FIV), and Toxoplasma gondii IgG were detected in all three species with mean respective prevalence as follows: puma 16%, 41% and 75%; bobcat 31%, 22% and 43%; domestic cat 45%, 10% and 1%. Bartonella spp. were highly prevalent among domestic cats in Southern California compared to other cohort groups. Feline Immunodeficiency Virus exposure was primarily associated with species and age, and was not influenced by geographic location. Pumas were more likely to be infected with FIV than bobcats, with domestic cats having the lowest infection rate. Toxoplasma gondii seroprevalence was high in both pumas and bobcats across all sites; in contrast, few domestic cats were seropositive, despite the fact that feral, free ranging domestic cats were targeted in this study. Interestingly, a directly transmitted species-specific disease (FIV) was not associated with geographic location, while exposure to indirectly transmitted diseases - vector-borne for Bartonella spp. and ingestion of oocysts via infected prey or environmental exposure for T. gondii - varied significantly by site. Pathogens transmitted by direct contact may be more dependent upon individual behaviors and intra-specific encounters. Future studies will integrate host density, as well as landscape features, to better understand the

  3. Modulating mitochondrial quality in disease transmission: towards enabling mitochondrial DNA disease carriers to have healthy children.

    PubMed

    Diot, Alan; Dombi, Eszter; Lodge, Tiffany; Liao, Chunyan; Morten, Karl; Carver, Janet; Wells, Dagan; Child, Tim; Johnston, Iain G; Williams, Suzannah; Poulton, Joanna

    2016-08-15

    One in 400 people has a maternally inherited mutation in mtDNA potentially causing incurable disease. In so-called heteroplasmic disease, mutant and normal mtDNA co-exist in the cells of carrier women. Disease severity depends on the proportion of inherited abnormal mtDNA molecules. Families who have had a child die of severe, maternally inherited mtDNA disease need reliable information on the risk of recurrence in future pregnancies. However, prenatal diagnosis and even estimates of risk are fraught with uncertainty because of the complex and stochastic dynamics of heteroplasmy. These complications include an mtDNA bottleneck, whereby hard-to-predict fluctuations in the proportions of mutant and normal mtDNA may arise between generations. In 'mitochondrial replacement therapy' (MRT), damaged mitochondria are replaced with healthy ones in early human development, using nuclear transfer. We are developing non-invasive alternatives, notably activating autophagy, a cellular quality control mechanism, in which damaged cellular components are engulfed by autophagosomes. This approach could be used in combination with MRT or with the regular management, pre-implantation genetic diagnosis (PGD). Mathematical theory, supported by recent experiments, suggests that this strategy may be fruitful in controlling heteroplasmy. Using mice that are transgenic for fluorescent LC3 (the hallmark of autophagy) we quantified autophagosomes in cleavage stage embryos. We confirmed that the autophagosome count peaks in four-cell embryos and this correlates with a drop in the mtDNA content of the whole embryo. This suggests removal by mitophagy (mitochondria-specific autophagy). We suggest that modulating heteroplasmy by activating mitophagy may be a useful complement to mitochondrial replacement therapy. PMID:27528757

  4. Modulating mitochondrial quality in disease transmission: towards enabling mitochondrial DNA disease carriers to have healthy children

    PubMed Central

    Diot, Alan; Dombi, Eszter; Lodge, Tiffany; Liao, Chunyan; Morten, Karl; Carver, Janet; Wells, Dagan; Child, Tim; Johnston, Iain G.; Williams, Suzannah; Poulton, Joanna

    2016-01-01

    One in 400 people has a maternally inherited mutation in mtDNA potentially causing incurable disease. In so-called heteroplasmic disease, mutant and normal mtDNA co-exist in the cells of carrier women. Disease severity depends on the proportion of inherited abnormal mtDNA molecules. Families who have had a child die of severe, maternally inherited mtDNA disease need reliable information on the risk of recurrence in future pregnancies. However, prenatal diagnosis and even estimates of risk are fraught with uncertainty because of the complex and stochastic dynamics of heteroplasmy. These complications include an mtDNA bottleneck, whereby hard-to-predict fluctuations in the proportions of mutant and normal mtDNA may arise between generations. In ‘mitochondrial replacement therapy’ (MRT), damaged mitochondria are replaced with healthy ones in early human development, using nuclear transfer. We are developing non-invasive alternatives, notably activating autophagy, a cellular quality control mechanism, in which damaged cellular components are engulfed by autophagosomes. This approach could be used in combination with MRT or with the regular management, pre-implantation genetic diagnosis (PGD). Mathematical theory, supported by recent experiments, suggests that this strategy may be fruitful in controlling heteroplasmy. Using mice that are transgenic for fluorescent LC3 (the hallmark of autophagy) we quantified autophagosomes in cleavage stage embryos. We confirmed that the autophagosome count peaks in four-cell embryos and this correlates with a drop in the mtDNA content of the whole embryo. This suggests removal by mitophagy (mitochondria-specific autophagy). We suggest that modulating heteroplasmy by activating mitophagy may be a useful complement to mitochondrial replacement therapy. PMID:27528757

  5. Efficient transmission of Cassava brown streak disease viral pathogens by chip bud grafting

    PubMed Central

    2013-01-01

    Background Techniques to study plant viral diseases under controlled growth conditions are required to fully understand their biology and investigate host resistance. Cassava brown streak disease (CBSD) presents a major threat to cassava production in East Africa. No infectious clones of the causal viruses, Cassava brown streak virus (CBSV) or Ugandan cassava brown streak virus (UCBSV) are available, and mechanical transmission to cassava is not effective. An improved method for transmission of the viruses, both singly and as co-infections has been developed using bud grafts. Findings Axillary buds from CBSD symptomatic plants infected with virulent isolates of CBSV and UCBSV were excised and grafted onto 6–8 week old greenhouse-grown, disease-free cassava plants of cultivars Ebwanateraka, TME204 and 60444. Plants were assessed visually for development of CBSD symptoms and by RT-PCR for presence of the viruses in leaf and storage root tissues. Across replicated experiments, 70-100% of plants inoculated with CBSV developed CBSD leaf and stem symptoms 2–6 weeks after bud grafting. Infected plants showed typical, severe necrotic lesions in storage roots at harvest 12–14 weeks after graft inoculation. Sequential grafting of buds from plants infected with UCBSV followed 10–14 days later by buds carrying CBSV, onto the same test plant, resulted in 100% of the rootstocks becoming co-infected with both pathogens. This dual transmission rate was greater than that achieved by simultaneous grafting with UCBSV and CBSV (67%), or when grafting first with CBSV followed by UCBSV (17%). Conclusions The bud grafting method described presents an improved tool for screening cassava germplasm for resistance to CBSD causal viruses, and for studying pathogenicity of this important disease. Bud grafting provides new opportunities compared to previously reported top and side grafting systems. Test plants can be inoculated as young, uniform plants of a size easily handled in a

  6. Hand, Foot and Mouth Disease in China: Patterns of Spread and Transmissibility during 2008-2009

    PubMed Central

    Wang, Yu; Feng, Zijian; Yang, Yang; Self, Steve; Gao, Yongjun; Longini, Ira M.; Wakefield, Jon; Zhang, Jing; Wang, Liping; Chen, Xi; Yao, Lena; Stanaway, Jeffrey D.; Wang, Zijun; Yang, Weizhong

    2011-01-01

    Background Large outbreaks of hand, foot and mouth disease (HFMD) were observed in both 2008 and 2009 in China. Methods Using the national surveillance data since May 2, 2008, epidemiological characteristics of the outbreaks are summarized, and the transmissibility of the disease and the effects of potential risk factors were evaluated via a susceptible-infectious-recovered transmission model. Results Children of 1.0–2.9 years were the most susceptible group to HFMD (odds ratios [OR] > 2.3 as compared to other age groups). Infant cases had the highest incidences of severe disease (ORs > 1.4) and death (ORs > 2.4), as well as the longest delay from symptom onset to diagnosis (2.3 days). Males were more susceptible to HFMD than females (OR=1.56 [95% confidence interval=1.56, 1.57]). An one day delay in diagnosis was associated with increases in the odds of severe disease by 40.3% [38.7%, 41.9%] and in the odds of death by 53.7% [43.6%, 64.5%]. Compared to Coxsackie A16, enterovirus (EV) 71 is more strongly associated with severe disease (OR=15.6 [13.4, 18.1]) and death (OR=40.7 [13.0, 127.3]). The estimated local effective reproductive numbers among prefectures ranged from 1.4 to 1.6 (median=1.4) in spring and stayed below 1.2 in other seasons. A higher risk of transmission was associated with temperatures in the range of 70-80F, higher relative humidity, wind speed, precipitation, population density, and the periods in which schools were open. Conclusion HFMD is a moderately transmittable infectious disease, mainly among pre-school children. EV71 was responsible for most severe cases and fatalities. Mixing of asymptomatically infected children in schools might have contributed to the spread of HFMD. Timely diagnosis may be a key to reducing the high mortality rate in infants. PMID:21968769

  7. Noradrenaline transmission reducing drugs may protect against a broad range of diseases.

    PubMed

    Fitzgerald, P J

    2015-04-01

    1 A growing body of evidence suggests that the signalling molecule, noradrenaline (NA), plays a pathophysiological role in a broad range of psychiatric, neurological and peripheral disorders. Both preclinical and clinical data suggest that elevated NA signalling may be involved in the aetiology of major diseases such as depression, Alzheimer's disease and diabetes mellitus. 2 The molecular pathways by which NA may cause the manifestation of disease remain poorly understood, although they may include G protein-coupled receptor modulation of the Ras/MAP kinase, Stat3 and PI3K pathways, among others. In both individual animals and humans, NA tone may be elevated largely due to genetics, but also because of the exposure to marked psychological stress or trauma, or other environmental factors. 3 As NA is involved in the 'fight or flight' response by the sympathetic nervous system, this transmitter may be elevated in a large number of organisms due to evolutionary selection of enhancing responses to immediate environmental dangers. Likewise, acetylcholine signalling by the parasympathetic ('rest and digest') nervous system may be relatively diminished. This putative autonomic imbalance may result in diminished engagement in homeostatic processes, resulting in the emergence and progression of a number of diseases throughout the body. 4 In this scenario, a large number of individuals may benefit from chronic use of pharmacological agents - such as clonidine, guanfacine, propranolol or prazosin - that diminish NA signalling throughout the body. If so, NA transmission lowering drugs may protect against a wide range of diseases.

  8. Histochemical approaches to assess cell-to-cell transmission of misfolded proteins in neurodegenerative diseases

    PubMed Central

    Natale, G.; Pompili, E.; Biagioni, F.; Paparelli, S.; Lenzi, P.; Fornai, F.

    2013-01-01

    Formation, aggregation and transmission of abnormal proteins are common features in neurodegenerative disorders including Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis, and Huntington's disease. The mechanisms underlying protein alterations in neurodegenerative diseases remain controversial. Novel findings highlighted altered protein clearing systems as common biochemical pathways which generate protein misfolding, which in turn causes protein aggregation and protein spreading. In fact, proteinaceous aggregates are prone to cell-tocell propagation. This is reminiscent of what happens in prion disorders, where the prion protein misfolds thus forming aggregates which spread to neighbouring cells. For this reason, the term prionoids is currently used to emphasize how several misfolded proteins are transmitted in neurodegenerative diseases following this prion-like pattern. Histochemical techniques including the use of specific antibodies covering both light and electron microscopy offer a powerful tool to describe these phenomena and investigate specific molecular steps. These include: prion like protein alterations; glycation of prion-like altered proteins to form advanced glycation end-products (AGEs); mechanisms of extracellular secretion; interaction of AGEs with specific receptors placed on neighbouring cells (RAGEs). The present manuscript comments on these phenomena aimed to provide a consistent scenario of the available histochemical approaches to dissect each specific step. PMID:23549464

  9. Clozapine and GABA transmission in schizophrenia disease models: establishing principles to guide treatments.

    PubMed

    O'Connor, William T; O'Shea, Sean D

    2015-06-01

    Schizophrenia disease models are necessary to elucidate underlying changes and to establish new therapeutic strategies towards a stage where drug efficacy in schizophrenia (against all classes of symptoms) can be predicted. Here we summarise the evidence for a GABA dysfunction in schizophrenia and review the functional neuroanatomy of five pathways implicated in schizophrenia, namely the mesocortical, mesolimbic, ventral striopallidal, dorsal striopallidal and perforant pathways including the role of local GABA transmission and we describe the effect of clozapine on local neurotransmitter release. This review also evaluates psychotropic drug-induced, neurodevelopmental and environmental disease models including their compatibility with brain microdialysis. The validity of disease models including face, construct, etiological and predictive validity and how these models constitute theories about this illness is also addressed. A disease model based on the effect of the abrupt withdrawal of clozapine on GABA release is also described. The review concludes that while no single animal model is entirely successful in reproducing schizophreniform symptomatology, a disease model based on an ability to prevent and/or reverse the abrupt clozapine discontinuation-induced changes in GABA release in brain regions implicated in schizophrenia may be useful for hypothesis testing and for in vivo screening of novel ligands not limited to a single pharmacological class. PMID:25585121

  10. The effects of demographic change on disease transmission and vaccine impact in a household structured population.

    PubMed

    Geard, Nicholas; Glass, Kathryn; McCaw, James M; McBryde, Emma S; Korb, Kevin B; Keeling, Matt J; McVernon, Jodie

    2015-12-01

    The demographic structure of populations in both more developed and less developed countries is changing: increases in life expectancy and declining fertility have led to older populations and smaller households. The implications of these demographic changes for the spread and control of infectious diseases are not fully understood. Here we use an individual based model with realistic and dynamic age and household structure to demonstrate the marked effect that demographic change has on disease transmission at the population and household level. The decline in fertility is associated with a decrease in disease incidence and an increase in the age of first infection, even in the absence of vaccination or other control measures. Although large households become rarer as fertility decreases, we show that there is a proportionate increase in incidence of disease in these households as the accumulation of susceptible clusters increases the potential for explosive outbreaks. By modelling vaccination, we provide a direct comparison of the relative importance of demographic change and vaccination on incidence of disease. We highlight the increased risks associated with unvaccinated households in a low fertility setting if vaccine behaviour is correlated with household membership. We suggest that models that do not account for future demographic change, and especially its effect on household structure, may potentially overestimate the impact of vaccination. PMID:26616042

  11. Contribution of seasonality in transmission of Mycobacterium tuberculosis to seasonality in tuberculosis disease: a simulation study.

    PubMed

    Soetens, Lucia C; Boshuizen, Hendriek C; Korthals Altes, Hester

    2013-10-15

    A seasonal rise in tuberculosis (TB) notifications has been confirmed in several studies. Here, we examined one hypothesis for its cause: increased transmission of TB during wintertime due to crowding. Seasonality analysis was performed on actual and simulated notifications of clustered TB cases, which are considered to be representative of recent transmission, diagnosed from 1993 to 2004 in the Netherlands (n = 4,746). To test the hypothesis of winter crowding, notifications were simulated by adding patient delay and incubation period to an infection date randomly taken to be in winter in 80% of cases. The incubation periods were derived from frequency distributions for different TB disease localizations drawn from the literature. Seasonality analysis was performed using autocorrelation function plots and spectral analysis. Actual notifications showed strong seasonality in clustered TB and clustered extrapulmonary TB cases but not in clustered pulmonary TB cases. Analysis of simulated notifications revealed barely significant seasonality only in extrapulmonary TB cases. Our results suggest that increased transmission of TB during wintertime is unlikely to be the only cause of the seasonal peak in TB notifications. A factor closer to the notification date probably contributes to the seasonality observed in TB notifications.

  12. Modeling the Epidemiology of Cholera to Prevent Disease Transmission in Developing Countries.

    PubMed

    Mukandavire, Zindoga; Morris, J Glenn

    2015-06-01

    Cholera remains an important global cause of morbidity and mortality, which is capable of causing periodic epidemic disease. A number of mathematical models have been developed to help in understanding the dynamics of cholera outbreaks and for use as a tool in planning interventions, including vaccination campaigns. We have explored the utility of models in assessing the spread of cholera in the recent epidemics in Zimbabwe and Haiti. In both instances, a mathematical model was formulated and fitted to cumulative cholera cases to estimate the basic reproductive number ℛ0, and the partial reproductive numbers reflecting potential differences in environmental-to-human versus human-to-human transmission were quantified. In Zimbabwe, estimated ℛ0 for the epidemic using aggregated data at the national level was 1.15; in Haiti, it was 1.55. However, when calculated at a provincial/departmental level, estimated basic reproductive numbers were highly heterogeneous, with a range of 1.11 to 2.72 in Zimbabwe and 1.06 to 2.63 in Haiti. Our models suggest that the underlying patterns of cholera transmission varied widely from region to region, with a corresponding variation in the amenability of outbreaks to control measures such as immunization. These data underscore the heterogeneity of transmission dynamics, potentially linked to differences in environment, socio-economic conditions, and cultural practices. They also highlight the potential utility of these types of models in guiding development of public health intervention strategies.

  13. Modeling Heterogeneity in Direct Infectious Disease Transmission in a Compartmental Model

    PubMed Central

    Kong, Lingcai; Wang, Jinfeng; Han, Weiguo; Cao, Zhidong

    2016-01-01

    Mathematical models have been used to understand the transmission dynamics of infectious diseases and to assess the impact of intervention strategies. Traditional mathematical models usually assume a homogeneous mixing in the population, which is rarely the case in reality. Here, we construct a new transmission function by using as the probability density function a negative binomial distribution, and we develop a compartmental model using it to model the heterogeneity of contact rates in the population. We explore the transmission dynamics of the developed model using numerical simulations with different parameter settings, which characterize different levels of heterogeneity. The results show that when the reproductive number, R0, is larger than one, a low level of heterogeneity results in dynamics similar to those predicted by the homogeneous mixing model. As the level of heterogeneity increases, the dynamics become more different. As a test case, we calibrated the model with the case incidence data for severe acute respiratory syndrome (SARS) in Beijing in 2003, and the estimated parameters demonstrated the effectiveness of the control measures taken during that period. PMID:26927140

  14. Juxtaposition between host population structures: implications for disease transmission in a sympatric cervid community

    PubMed Central

    Vander Wal, Eric; Edye, Iain; Paquet, Paul C; Coltman, David W; Bayne, Erin; Brook, Ryan K; Andrés, José A

    2013-01-01

    Sympatric populations of phylogenetically related species are often vulnerable to similar communicable diseases. Although some host populations may exhibit spatial structure, other hosts within the community may have unstructured populations. Thus, individuals from unstructured host populations may act as interspecific vectors among discrete subpopulations of sympatric alternate hosts. We used a cervid-bovine tuberculosis (Mycobacterium bovis) system to investigate the landscape-scale potential for bovine tuberculosis transmission within a nonmigratory white-tailed deer (Odocoileus virginianus) and elk (Cervus canadensis) community. Using landscape population genetics, we tested for genetic and spatial structure in white-tailed deer. We then compared these findings with the sympatric elk population that is structured and which has structure that correlates spatially and genetically to physiognomic landscape features. Despite genetic structure that indicates the white-tailed deer population forms three sympatric clusters, the absence of spatial structure suggested that intraspecific pathogen transmission is not likely to be limited by physiognomic landscape features. The potential for intraspecific transmission among subpopulations of elk is low due to spatial population structure. Given that white-tailed deer are abundant, widely distributed, and exhibit a distinct lack of spatial population structure, white-tailed deer likely pose a greater threat as bovine tuberculosis vectors among elk subpopulations than elk. PMID:24187583

  15. Modeling Heterogeneity in Direct Infectious Disease Transmission in a Compartmental Model.

    PubMed

    Kong, Lingcai; Wang, Jinfeng; Han, Weiguo; Cao, Zhidong

    2016-03-01

    Mathematical models have been used to understand the transmission dynamics of infectious diseases and to assess the impact of intervention strategies. Traditional mathematical models usually assume a homogeneous mixing in the population, which is rarely the case in reality. Here, we construct a new transmission function by using as the probability density function a negative binomial distribution, and we develop a compartmental model using it to model the heterogeneity of contact rates in the population. We explore the transmission dynamics of the developed model using numerical simulations with different parameter settings, which characterize different levels of heterogeneity. The results show that when the reproductive number, R₀, is larger than one, a low level of heterogeneity results in dynamics similar to those predicted by the homogeneous mixing model. As the level of heterogeneity increases, the dynamics become more different. As a test case, we calibrated the model with the case incidence data for severe acute respiratory syndrome (SARS) in Beijing in 2003, and the estimated parameters demonstrated the effectiveness of the control measures taken during that period. PMID:26927140

  16. Reservoir Targeted Vaccine Against Borrelia burgdorferi: A New Strategy to Prevent Lyme Disease Transmission

    PubMed Central

    Richer, Luciana Meirelles; Brisson, Dustin; Melo, Rita; Ostfeld, Richard S.; Zeidner, Nordin; Gomes-Solecki, Maria

    2014-01-01

    A high prevalence of infection with Borrelia burgdorferi in ixodid ticks is correlated with a high incidence of Lyme disease. The transmission of B. burgdorferi to humans can be disrupted by targeting 2 key elements in its enzootic cycle: the reservoir host and the tick vector. In a prospective 5-year field trial, we show that oral vaccination of wild white-footed mice resulted in outer surface protein A–specific seropositivity that led to reductions of 23% and 76% in the nymphal infection prevalence in a cumulative, time-dependent manner (2 and 5 years, respectively), whereas the proportion of infected ticks recovered from control plots varied randomly over time. Significant decreases in tick infection prevalence were observed within 3 years of vaccine deployment. Implementation of such a long-term public health measure could substantially reduce the risk of human exposure to Lyme disease. PMID:24523510

  17. Reservoir targeted vaccine against Borrelia burgdorferi: a new strategy to prevent Lyme disease transmission.

    PubMed

    Richer, Luciana Meirelles; Brisson, Dustin; Melo, Rita; Ostfeld, Richard S; Zeidner, Nordin; Gomes-Solecki, Maria

    2014-06-15

    A high prevalence of infection with Borrelia burgdorferi in ixodid ticks is correlated with a high incidence of Lyme disease. The transmission of B. burgdorferi to humans can be disrupted by targeting 2 key elements in its enzootic cycle: the reservoir host and the tick vector. In a prospective 5-year field trial, we show that oral vaccination of wild white-footed mice resulted in outer surface protein A-specific seropositivity that led to reductions of 23% and 76% in the nymphal infection prevalence in a cumulative, time-dependent manner (2 and 5 years, respectively), whereas the proportion of infected ticks recovered from control plots varied randomly over time. Significant decreases in tick infection prevalence were observed within 3 years of vaccine deployment. Implementation of such a long-term public health measure could substantially reduce the risk of human exposure to Lyme disease.

  18. Baculovirus-Induced Climbing Behavior Favors Intraspecific Necrophagy and Efficient Disease Transmission in Spodoptera exigua

    PubMed Central

    Rebolledo, Dulce; Guevara, Roger; Murillo, Rosa

    2015-01-01

    Shortly prior to death, many species of Lepidoptera infected with nucleopolyhedrovirus climb upwards on the host plant. This results in improved dissemination of viral occlusion bodies over plant foliage and an increased probability of transmission to healthy conspecific larvae. Following applications of Spodoptera exigua multiple nucleopolyhedrovirus for control of Spodoptera exigua on greenhouse-grown sweet pepper crops, necrophagy was observed by healthy S. exigua larvae that fed on virus-killed conspecifics. We examined whether this risky behavior was induced by olfactory or phagostimulant compounds associated with infected cadavers. Laboratory choice tests and olfactometer studies, involving infected and non-infected cadavers placed on spinach leaf discs, revealed no evidence for greater attraction of healthy larvae to virus-killed over non-infected cadavers. Physical contact or feeding on infected cadavers resulted in a very high incidence of transmission (82–93% lethal disease). Observations on the behavior of S. exigua larvae on pepper plants revealed that infected insects died on the uppermost 10% of foliage and closer to the plant stem than healthy conspecifics of the same stage, which we considered clear evidence of baculovirus-induced climbing behavior. Healthy larvae that subsequently foraged on the plant were more frequently observed closer to the infected than the non-infected cadaver. Healthy larvae also encountered and fed on infected cadavers significantly more frequently and more rapidly than larvae that fed on non-infected cadavers. Intraspecific necrophagy on infected cadavers invariably resulted in virus transmission and death of the necrophagous insect. We conclude that, in addition to improving the dissemination of virus particles over plant foliage, baculovirus-induced climbing behavior increases the incidence of intraspecific necrophagy in S. exigua, which is the most efficient mechanism of transmission of this lethal pathogen. PMID

  19. Linking community and disease ecology: the impact of biodiversity on pathogen transmission.

    PubMed

    Roche, Benjamin; Dobson, Andrew P; Guégan, Jean-François; Rohani, Pejman

    2012-10-19

    The increasing number of zoonotic diseases spilling over from a range of wild animal species represents a particular concern for public health, especially in light of the current dramatic trend of biodiversity loss. To understand the ecology of these multi-host pathogens and their response to environmental degradation and species extinctions, it is necessary to develop a theoretical framework that takes into account realistic community assemblages. Here, we present a multi-host species epidemiological model that includes empirically determined patterns of diversity and composition derived from community ecology studies. We use this framework to study the interaction between wildlife diversity and directly transmitted pathogen dynamics. First, we demonstrate that variability in community composition does not affect significantly the intensity of pathogen transmission. We also show that the consequences of community diversity can differentially impact the prevalence of pathogens and the number of infectious individuals. Finally, we show that ecological interactions among host species have a weaker influence on pathogen circulation than inter-species transmission rates. We conclude that integration of a community perspective to study wildlife pathogens is crucial, especially in the context of understanding and predicting infectious disease emergence events.

  20. Transmission of sexually transmitted disease in complex network of the Penna model

    NASA Astrophysics Data System (ADS)

    Chen, Feng; Li, Chunguang

    2007-04-01

    The Penna model is a computational model which can encompass the inheritance, mutation, evolution and ageing phenomena of population successfully. Some researchers considered social interactions in an asexual Penna model, got a complex network and found some interesting properties. We consider a sexual Penna model to study the transmission of sexually transmitted diseases (STD). Our model can also generate a complex network and we observed some properties in real networks, such as small-world and assortative mixing. In the real world, the fatality of STD is changing with the advancing of medicine and it can affect our life. In this paper, we uncover the effect induced by the fatality of STD. We found that fatality plays an important role in the transmission of STD because whether the STD will disappear or continue to exist depends on the fatality of STD. Also, the fatality of STD can affect the evolution of inherited diseases and average life span. Some properties found in the model should be useful for the prevention and control of STD.

  1. Experimental oral transmission of chronic wasting disease to reindeer (Rangifer tarandus tarandus).

    PubMed

    Mitchell, Gordon B; Sigurdson, Christina J; O'Rourke, Katherine I; Algire, James; Harrington, Noel P; Walther, Ines; Spraker, Terry R; Balachandran, Aru

    2012-01-01

    Chronic wasting disease (CWD), a transmissible spongiform encephalopathy of cervids, remains prevalent in North American elk, white-tailed deer and mule deer. A natural case of CWD in reindeer (Rangifer tarandus tarandus) has not been reported despite potential habitat overlap with CWD-infected deer or elk herds. This study investigates the experimental transmission of CWD from elk or white-tailed deer to reindeer by the oral route of inoculation. Ante-mortem testing of the three reindeer exposed to CWD from white-tailed deer identified the accumulation of pathological PrP (PrP(CWD)) in the recto-anal mucosa associated lymphoid tissue (RAMALT) of two reindeer at 13.4 months post-inoculation. Terminal CWD occurred in the two RAMALT-positive reindeer at 18.5 and 20 months post-inoculation while one other reindeer in the white-tailed deer CWD inoculum group and none of the 3 reindeer exposed to elk CWD developed disease. Tissue distribution analysis of PrP(CWD) in CWD-affected reindeer revealed widespread deposition in central and peripheral nervous systems, lymphoreticular tissues, the gastrointestinal tract, neuroendocrine tissues and cardiac muscle. Analysis of prion protein gene (PRNP) sequences in the 6 reindeer identified polymorphisms at residues 2 (V/M), 129 (G/S), 138 (S/N) and 169 (V/M). These findings demonstrate that (i) a sub-population of reindeer are susceptible to CWD by oral inoculation implicating the potential for transmission to other Rangifer species, and (ii) certain reindeer PRNP polymorphisms may be protective against CWD infection.

  2. Models to capture the potential for disease transmission in domestic sheep flocks.

    PubMed

    Schley, David; Whittle, Sophie; Taylor, Michael; Kiss, Istvan Zoltan

    2012-09-15

    Successful control of livestock diseases requires an understanding of how they spread amongst animals and between premises. Mathematical models can offer important insight into the dynamics of disease, especially when built upon experimental and/or field data. Here the dynamics of a range of epidemiological models are explored in order to determine which models perform best in capturing real-world heterogeneities at sufficient resolution. Individual based network models are considered together with one- and two-class compartmental models, for which the final epidemic size is calculated as a function of the probability of disease transmission occurring during a given physical contact between two individuals. For numerical results the special cases of a viral disease with a fast recovery rate (foot-and-mouth disease) and a bacterial disease with a slow recovery rate (brucellosis) amongst sheep are considered. Quantitative results from observational studies of physical contact amongst domestic sheep are applied and results from the differently structured flocks (ewes with newborn lambs, ewes with nearly weaned lambs and ewes only) compared. These indicate that the breeding cycle leads to significant changes in the expected basic reproduction ratio of diseases. The observed heterogeneity of contacts amongst animals is best captured by full network simulations, although simple compartmental models describe the key features of an outbreak but, as expected, often overestimate the speed of an outbreak. Here the weights of contacts are heterogeneous, with many low weight links. However, due to the well-connected nature of the networks, this has little effect and differences between models remain small. These results indicate that simple compartmental models can be a useful tool for modelling real-world flocks; their applicability will be greater still for more homogeneously mixed livestock, which could be promoted by higher intensity farming practices.

  3. Mycobacterium avium complex--the role of potable water in disease transmission.

    PubMed

    Whiley, H; Keegan, A; Giglio, S; Bentham, R

    2012-08-01

    Mycobacterium avium complex (MAC) is a group of opportunistic pathogens of major public health concern. It is responsible for a wide spectrum of disease dependent on subspecies, route of infection and patients pre-existing conditions. Presently, there is limited research on the incidence of MAC infection that considers both pulmonary and other clinical manifestations. MAC has been isolated from various terrestrial and aquatic environments including natural waters, engineered water systems and soils. Identifying the specific environmental sources responsible for human infection is essential in minimizing disease prevalence. This paper reviews current literature and case studies regarding the wide spectrum of disease caused by MAC and the role of potable water in disease transmission. Potable water was recognized as a putative pathway for MAC infection. Contaminated potable water sources associated with human infection included warm water distribution systems, showers, faucets, household drinking water, swimming pools and hot tub spas. MAC can maintain long-term contamination of potable water sources through its high resistance to disinfectants, association with biofilms and intracellular parasitism of free-living protozoa. Further research is required to investigate the efficiency of water treatment processes against MAC and into construction and maintenance of warm water distribution systems and the role they play in MAC proliferation.

  4. Do mites phoretic on elm bark beetles contribute to the transmission of Dutch elm disease?

    NASA Astrophysics Data System (ADS)

    Moser, John C.; Konrad, Heino; Blomquist, Stacy R.; Kirisits, Thomas

    2010-02-01

    Dutch elm disease (DED) is a destructive vascular wilt disease of elm ( Ulmus) trees caused by the introduced Ascomycete fungus Ophiostoma novo-ulmi. In Europe, this DED pathogen is transmitted by elm bark beetles in the genus Scolytus. These insects carry phoretic mites to new, suitable habitats. The aim of this study was to record and quantify conidia and ascospores of O. novo-ulmi on phoretic mites on the three elm bark beetle species Scolytus multistriatus, Scolytus pygmaeus, and Scolytus scolytus. Spores of O. novo-ulmi were found on four of the ten mite species phoretic on Scolytus spp. These included Elattoma fraxini, Proctolaelaps scolyti, Pseudotarsonemoides eccoptogasteri, and Tarsonemus crassus. All four species had spores attached externally to their body surfaces. However, T. crassus carried most spores within its sporothecae, two paired pocket-like structures adapted for fungal transmission. Individuals of Pr. scolyti also had O. novo-ulmi conidia and ascospores frequently in their digestive system, where they may remain viable. While E. fraxini and P. eccoptogasteri rarely had spores attached to their bodies, large portions of Pr. scolyti and T. crassus carried significant numbers of conidia and/or ascospores of O. novo-ulmi. P. scolyti and T. crassus, which likely are fungivores, may thus contribute to the transmission of O. novo-ulmi, by increasing the spore loads of individual Scolytus beetles during their maturation feeding on twigs of healthy elm trees, enhancing the chance for successful infection with the pathogen. Only S. scolytus, which is the most efficient vector of O. novo-ulmi in Europe, carried high numbers of Pr. scolyti and T. crassus, in contrast to S. multistriatus and S. pygmaeus, which are known as less efficient vectors. The high efficiency of S. scolytus in spreading Dutch elm disease may be partly due to its association with these two mites and the hyperphoretic spores of O. novo-ulmi they carry.

  5. A survey of the transmission of infectious diseases/infections between wild and domestic ungulates in Europe

    PubMed Central

    2011-01-01

    The domestic animals/wildlife interface is becoming a global issue of growing interest. However, despite studies on wildlife diseases being in expansion, the epidemiological role of wild animals in the transmission of infectious diseases remains unclear most of the time. Multiple diseases affecting livestock have already been identified in wildlife, especially in wild ungulates. The first objective of this paper was to establish a list of infections already reported in European wild ungulates. For each disease/infection, three additional materials develop examples already published, specifying the epidemiological role of the species as assigned by the authors. Furthermore, risk factors associated with interactions between wild and domestic animals and regarding emerging infectious diseases are summarized. Finally, the wildlife surveillance measures implemented in different European countries are presented. New research areas are proposed in order to provide efficient tools to prevent the transmission of diseases between wild ungulates and livestock. PMID:21635726

  6. Lesions and transmission of experimental adenovirus hemorrhagic disease in black-tailed deer fawns.

    PubMed

    Woods, L W; Hanley, R S; Chiu, P H; Lehmkuhl, H D; Nordhausen, R W; Stillian, M H; Swift, P K

    1999-03-01

    Adenovirus infection was the cause of an epizootic of hemorrhagic disease that is believed to have killed thousands of mule deer (Odocoileus hemionus) in California during the latter half of 1993. A systemic vasculitis with pulmonary edema and hemorrhagic enteropathy or a localized vasculitis associated with necrotizing stomatitis/pharyngitis/glossitis or osteomyelitis of the jaw were common necropsy findings in animals that died during this epizootic. To study transmission of adenovirus infection in deer and susceptibility of black-tailed deer (Odocoileus hemionus columbianus) fawns to adenovirus infection, six 3-6-month-old black-tailed fawns were divided into two treatment groups. One group was inoculated intravenously and the other group was inoculated through the mucous membranes of the eyes, nose and mouth with purified adenovirus. Each treatment group also included two additional fawns (four total) that were not inoculated but were exposed to inoculated animals (contact animals). One fawn served as a negative control. Between 4 and 16 days postinoculation, 8/10 fawns developed systemic or localized infection with lesions identical to lesions seen in animals with natural disease that died during the epizootic. Transmission was by direct contact, and the route of inoculation did not affect the incubation period or the distribution of the virus (systemic or the localized infection). Immunohistochemical analysis using polyclonal antiserum against bovine adenovirus type 5 demonstrated staining in endothelial cells of vessels in numerous tissues in animals with systemic infection and endothelial staining only in vessels subtending necrotic foci in the upper alimentary tract in animals with the localized form of the disease. All inoculated or exposed animals had staining in the tonsillar epithelium. Transmission electron microscopic examination of lung and ileum from two fawns with pulmonary edema and hemorrhagic enteropathy demonstrated endothelial necrosis and

  7. Meat and bone meal and mineral feed additives may increase the risk of oral prion disease transmission

    USGS Publications Warehouse

    Johnson, Christopher J.; McKenzie, Debbie; Pedersen, Joel A.; Aiken, Judd M.

    2011-01-01

    Ingestion of prion-contaminated materials is postulated to be a primary route of prion disease transmission. Binding of prions to soil (micro)particles dramatically enhances peroral disease transmission relative to unbound prions, and it was hypothesized that micrometer-sized particles present in other consumed materials may affect prion disease transmission via the oral route of exposure. Small, insoluble particles are present in many substances, including soil, human foods, pharmaceuticals, and animal feeds. It is known that meat and bone meal (MBM), a feed additive believed responsible for the spread of bovine spongiform encephalopathy (BSE), contains particles smaller than 20 μm and that the pathogenic prion protein binds to MBM. The potentiation of disease transmission via the oral route by exposure to MBM or three micrometer-sized mineral feed additives was determined. Data showed that when the disease agent was bound to any of the tested materials, the penetrance of disease was increased compared to unbound prions. Our data suggest that in feed or other prion-contaminated substances consumed by animals or, potentially, humans, the addition of MBM or the presence of microparticles could heighten risks of prion disease acquisition.

  8. Meat and bone meal and mineral feed additives may increase the risk of oral prion disease transmission

    USGS Publications Warehouse

    Johnson, C.J.; McKenzie, D.; Pedersen, J.A.; Aiken, Judd M.

    2011-01-01

    Ingestion of prion-contaminated materials is postulated to be a primary route of prion disease transmission. Binding of prions to soil (micro)particles dramatically enhances peroral disease transmission relative to unbound prions, and it was hypothesized that micrometer-sized particles present in other consumed materials may affect prion disease transmission via the oral route of exposure. Small, insoluble particles are present in many substances, including soil, human foods, pharmaceuticals, and animal feeds. It is known that meat and bone meal (MBM), a feed additive believed responsible for the spread of bovine spongiform encephalopathy (BSE), contains particles smaller than 20 ??m and that the pathogenic prion protein binds to MBM. The potentiation of disease transmission via the oral route by exposure to MBM or three micrometer-sized mineral feed additives was determined. Data showed that when the disease agent was bound to any of the tested materials, the penetrance of disease was increased compared to unbound prions. Our data suggest that in feed or other prion-contaminated substances consumed by animals or, potentially, humans, the addition of MBM or the presence of microparticles could heighten risks of prion disease acquisition. Copyright ?? 2011 Taylor & Francis Group, LLC.

  9. MEAT AND BONE MEAL AND MINERAL FEED ADDITIVES MAY INCREASE THE RISK OF ORAL PRION DISEASE TRANSMISSION

    PubMed Central

    Johnson, Christopher J.; McKenzie, Debbie; Pedersen, Joel A.; Aiken, Judd M.

    2011-01-01

    Ingestion of prion-contaminated materials is postulated to be a primary route of prion disease transmission. Binding of prions to soil (micro)particles dramatically enhances peroral disease transmission relative to unbound prions, and it was hypothesized that micrometer–sized particles present in other consumed materials may affect prion disease transmission via the oral route of exposure. Small, insoluble particles are present in many substances, including soil, human foods, pharmaceuticals, and animal feeds. It is known that meat and bone meal (MBM), a feed additive believed responsible for the spread of bovine spongiform encephalopathy (BSE), contains particles smaller than 20 μm and that the pathogenic prion protein binds to MBM. The potentiation of disease transmission via the oral route by exposure to MBM or three micrometer-sized mineral feed additives was determined. Data showed that when the disease agent was bound to any of the tested materials, the penetrance of disease was increased compared to unbound prions. Our data suggest that in feed or other prion–contaminated substances consumed by animals or, potentially, humans, the addition of MBM or the presence of microparticles could heighten risks of prion disease acquisition. PMID:21218345

  10. Pathogens and diseases of freshwater mussels in the United States: Studies on bacterial transmission and depuration

    USGS Publications Warehouse

    Starliper, Clifford E.; Cipriano, R.C.; Bruckner, A.W.; Shchelkunov, I.S.

    2011-01-01

    Unionid mussels are recognized as important contributors to healthy aquatic ecosystems, as well as bioindicators of environmental perturbations. Because they are sedentary, filter feeding animals and require hosts (i.e., fishes) to transform embryonic glochidia, mussels are susceptible to direct adverse environmental parameters, and indirect parameters that restrict the timely presence of the host(s). Their numbers have declined in recent decades to a point that this fauna is regarded as one of the most imperiled in North America. The most significant threat to populations of native unionids in recent years has been the introduction and spread of zebra mussels Dreissena polymorpha. Many federal and state agencies, and private interests are now engaged in mussel conservation efforts, including collecting selected imperiled species from impacted rivers and lakes and propagating them at refuges for future population augmentations. One essential consideration with mussel propagation and their intensive culture at refugia is the prevention of pathogen introductions and control of diseases. Currently, there are few reports of etiological agents causing diseases among freshwater mussels; however, because of increased observations of mussel die-offs in conjunction with transfers of live animals between natural waters and refugia, disease problems can be anticipated to emerge. This review summarizes research to develop bacterial isolation techniques, study pathogen transmission between fish and mussels, identify causes of seasonal mussel die-offs, and develop non-destructive methods for pathogen detection. These efforts were done to develop disease preventative techniques for use by resource managers to avoid potential large-scale disease problems in restoration and population augmentation efforts among imperiled populations.

  11. Transmission Pathways of Foot-and-Mouth Disease Virus in the United Kingdom in 2007

    PubMed Central

    Cottam, Eleanor M.; Wadsworth, Jemma; Shaw, Andrew E.; Rowlands, Rebecca J.; Goatley, Lynnette; Maan, Sushila; Maan, Narender S.; Mertens, Peter P. C.; Ebert, Katja; Li, Yanmin; Ryan, Eoin D.; Juleff, Nicholas; Ferris, Nigel P.; Wilesmith, John W.; Haydon, Daniel T.; King, Donald P.; Paton, David J.; Knowles, Nick J.

    2008-01-01

    Foot-and-mouth disease (FMD) virus causes an acute vesicular disease of domesticated and wild ruminants and pigs. Identifying sources of FMD outbreaks is often confounded by incomplete epidemiological evidence and the numerous routes by which virus can spread (movements of infected animals or their products, contaminated persons, objects, and aerosols). Here, we show that the outbreaks of FMD in the United Kingdom in August 2007 were caused by a derivative of FMDV O1 BFS 1860, a virus strain handled at two FMD laboratories located on a single site at Pirbright in Surrey. Genetic analysis of complete viral genomes generated in real-time reveals a probable chain of transmission events, predicting undisclosed infected premises, and connecting the second cluster of outbreaks in September to those in August. Complete genome sequence analysis of FMD viruses conducted in real-time have identified the initial and intermediate sources of these outbreaks and demonstrate the value of such techniques in providing information useful to contemporary disease control programmes. PMID:18421380

  12. Feral swine contact with domestic swine: a serologic survey and assessment of potential for disease transmission.

    PubMed

    Wyckoff, A Christy; Henke, Scott E; Campbell, Tyler A; Hewitt, David G; VerCauteren, Kurt C

    2009-04-01

    Feral swine (Sus scrofa) are present in 38 of the 50 United States, and their populations continue to expand. Domestic swine are widely regarded as vulnerable to diseases harbored by feral swine. Our objectives were to determine antibody prevalence for selected pathogens in Texas feral swine populations and identify contact events between feral and domestic swine. Overall prevalence of antibodies against brucellosis and pseudorabies virus was 11% and 30%, respectively. Antibodies to porcine reproductive and respiratory disease virus were detected in 3% of feral swine from southern Texas. All samples tested negative for antibodies to classical swine fever virus. To determine the frequency of contact events between feral swine and domestic swine in neighboring facilities, we analyzed movement data from 37 adult feral swine that were trapped < or =10 km from domestic swine facilities and equipped with geographic positioning system collars. Seven of the 37 feral swine had contact (relocated within 100 m) with domestic swine. We found that contact between feral swine and domestic swine occurred predominantly at night. Additionally, we analyzed 60 consecutive days of experimental track plots around pens that contained domestic swine and empty control pens, and found greater visitation by feral swine to the domestic swine pens. Our data demonstrate that feral swine have direct contact with domestic swine, which presents opportunity for disease transmission.

  13. Effect of vaccination on transmission characteristics of highly virulent Newcastle disease virus in experimentally infected chickens.

    PubMed

    Fentie, Tsegaw; Dadi, Kara; Kassa, Tesfu; Sahle, Mesfin; Cattoli, Giovanni

    2014-01-01

    An experimental study was conducted to evaluate the effect of vaccines produced in Ethiopia from vaccine strains used worldwide on the transmission characteristics of velogenic Newcastle disease virus field strain after different vaccination schemes. Chickens were vaccinated with Hitchner B1, La Sota or I-2 via the intraocular and intranasal routes. Vaccine and challenge viruses induced high antibody levels, both in inoculated and contact birds. Prime-boost vaccination protected birds against morbidity and mortality and significantly reduced the incidence of viral shedding from chickens compared with single vaccinated and unvaccinated birds. Protection from disease and mortality was correlated with the presence of positive antibody titres (>4 log2) at day of challenge. Most of the unvaccinated and in-contact birds excreted the virus and showed a high level of antibody titres, indicating the high infectivity of the challenge virus. The detection of the challenge virus in most of vaccinated birds demonstrated that the tested vaccination protocols cannot fully protect birds from viral infection, replication and shedding, and vaccinated-infected birds can act as a source of infection for susceptible flocks. The high mortality observed in unvaccinated birds and their contacts confirmed the virulence of the challenge virus and indicated that this field virus strain can easily spread in an unvaccinated poultry population and cause major outbreaks. Progressive vaccinations supported by biosecurity measures should therefore be implemented to control the disease and introduction of the virus to the poultry farms.

  14. Investigation of the swimming mechanics of Schistosoma cercariae and its role in disease transmission

    NASA Astrophysics Data System (ADS)

    Krishnamurthy, Deepak; Bhargava, Arjun; Katsikis, Georgios; Prakash, Manu

    2015-11-01

    Schistosomiasis is a Neglected Tropical Disease responsible for the deaths of an estimated 200,000 people annually. Human infection occurs when the infectious forms of the worm known as cercariae swim through freshwater, detect humans and penetrate the skin. Cercarial swimming is a bottleneck in disease transmission since cercariae have finite energy reserves, hence motivating studies of their swimming mechanics. Here we build on earlier studies which revealed the existence of two swimming modes: the tail-first and head-first modes. Of these the former was shown to display a novel symmetry breaking mechanism enabling locomotion at low Reynolds numbers. Here we propose simple models for the two swimming modes based on a three-link swimmer geometry. Using local slender-body-theory, we calculate the swimming gait for these model swimmers and compare with experiments, both on live cercariae and on scaled-up robotic swimmers. We use data from these experiments and the models to calculate the energy expended while swimming in the two modes. This along with long-time tracking of swimming cercariae in a lab setting allows estimation of the decrease in activity of the swimmer as a function of time which is an important factor in cercarial infectivity. Finally, we consider, through experiments and theoretical models, the effects of gravity since cercariae are negatively buoyant and sink in the water column while not swimming. This sinking affects cercarial spatial distribution which is important from a disease perspective.

  15. El Niño and the dynamics of vectorborne disease transmission.

    PubMed

    Hales, S; Weinstein, P; Souares, Y; Woodward, A

    1999-02-01

    The objective of the study was to investigate the relationship between reported incidence of dengue fever and El Niño southern oscillation (ENSO) in 14 island nations of the South Pacific. Using a mixed ecological study design, we calculated correlations between annual averages of the southern oscillation index (SOI), local temperature and rainfall, and dengue fever. We also calculated temporal correlations between monthly reports of dengue fever cases on different islands. There were positive correlations between SOI and dengue in 10 countries. In five of these (including all of the larger islands) there were also positive correlations between SOI and estimates of local temperature and/or rainfall. There were temporal correlations between monthly reports of dengue cases within two groups of countries. Climate changes associated with ENSO may trigger an increase in dengue fever transmission in larger, more populated islands where the disease is endemic. There was also evidence of propagation of infection from larger islands to smaller neighbors. Unlike the initiation of epidemics, this transfer between islands appears to be independent of interannual climate variations, pointing to the importance of modulating factors in dengue transmission such as population density and travel. In the future, models of the impact of climate change must attempt to account for these factors.

  16. The Impact of Economic Crises on Communicable Disease Transmission and Control: A Systematic Review of the Evidence

    PubMed Central

    Suhrcke, Marc; Stuckler, David; Suk, Jonathan E.; Desai, Monica; Senek, Michaela; McKee, Martin; Tsolova, Svetla; Basu, Sanjay; Abubakar, Ibrahim; Hunter, Paul; Rechel, Boika; Semenza, Jan C.

    2011-01-01

    There is concern among public health professionals that the current economic downturn, initiated by the financial crisis that started in 2007, could precipitate the transmission of infectious diseases while also limiting capacity for control. Although studies have reviewed the potential effects of economic downturns on overall health, to our knowledge such an analysis has yet to be done focusing on infectious diseases. We performed a systematic literature review of studies examining changes in infectious disease burden subsequent to periods of crisis. The review identified 230 studies of which 37 met our inclusion criteria. Of these, 30 found evidence of worse infectious disease outcomes during recession, often resulting from higher rates of infectious contact under poorer living circumstances, worsened access to therapy, or poorer retention in treatment. The remaining studies found either reductions in infectious disease or no significant effect. Using the paradigm of the “SIR” (susceptible-infected-recovered) model of infectious disease transmission, we examined the implications of these findings for infectious disease transmission and control. Key susceptible groups include infants and the elderly. We identified certain high-risk groups, including migrants, homeless persons, and prison populations, as particularly vulnerable conduits of epidemics during situations of economic duress. We also observed that the long-term impacts of crises on infectious disease are not inevitable: considerable evidence suggests that the magnitude of effect depends critically on budgetary responses by governments. Like other emergencies and natural disasters, preparedness for financial crises should include consideration of consequences for communicable disease control. PMID:21695209

  17. Stochastic eco-epidemiological model of dengue disease transmission by Aedes aegypti mosquito.

    PubMed

    Otero, M; Solari, H G

    2010-01-01

    We present a stochastic dynamical model for the transmission of dengue that takes into account seasonal and spatial dynamics of the vector Aedes aegypti. It describes disease dynamics triggered by the arrival of infected people in a city. We show that the probability of an epidemic outbreak depends on seasonal variation in temperature and on the availability of breeding sites. We also show that the arrival date of an infected human in a susceptible population dramatically affects the distribution of the final size of epidemics and that early outbreaks have a low probability. However, early outbreaks are likely to produce large epidemics because they have a longer time to evolve before the winter extinction of vectors. Our model could be used to estimate the risk and final size of epidemic outbreaks in regions with seasonal climatic variations.

  18. Transmission of seasonal outbreak of childhood enteroviral aseptic meningitis and hand-foot-mouth disease.

    PubMed

    Park, Sue K; Park, Boyoung; Ki, Moran; Kim, Ho; Lee, Kwan; Jung, Cheoll; Sohn, Young Mo; Choi, Sung-Min; Kim, Doo-Kwun; Lee, Dong Seok; Ko, Joon Tae; Kim, Moon Kyu; Cheong, Hae-Kwan

    2010-05-01

    This study was conducted to evaluate the modes of transmission of aseptic meningitis (AM) and hand-foot-mouth disease (HFMD) using a case-control and a case-crossover design. We recruited 205 childhood AM and 116 HFMD cases and 170 non-enteroviral disease controls from three general hospitals in Gyeongju, Pohang, and Seoul between May and August in both 2002 and 2003. For the case-crossover design, we established the hazard and non-hazard periods as week one and week four before admission, respectively. In the case-control design, drinking water that had not been boiled, not using a water purifier, changes in water quality, and contact with AM patients were significantly associated with the risk of AM (odds ratio [OR]=2.8, 2.9, 4.6, and 10.9, respectively), while drinking water that had not been boiled, having a non-water closet toilet, changes in water quality, and contact with HFMD patients were associated with risk of HFMD (OR=3.3, 2.8, 6.9, and 5.0, respectively). In the case-crossover design, many life-style variables such as contact with AM or HFMD patients, visiting a hospital, changes in water quality, presence of a skin wound, eating out, and going shopping were significantly associated with the risk of AM (OR=18.0, 7.0, 8.0, 2.2, 22.3, and 3.0, respectively) and HFMD (OR=9.0, 37.0, 11.0, 12.0, 37.0, and 5.0, respectively). Our findings suggest that person-to-person contact and contaminated water could be the principal modes of transmission of AM and HFMD. PMID:20436701

  19. Foot-and-mouth Disease Transmission in Africa: Implications for Control, a Review.

    PubMed

    Tekleghiorghis, T; Moormann, R J M; Weerdmeester, K; Dekker, A

    2016-04-01

    In Africa, for the control of foot-and-mouth disease (FMD), more information is needed on the spread of the disease at local, regional and inter-regional level. The aim of this review is to identify the role that animal husbandry, trade and wildlife have on the transmission of FMD and to provide a scientific basis for different FMD control measures in Africa. Review of literature, published reports and databases shows that there is more long distance spread of FMD virus serotypes within North, West, Central and East Africa than in southern Africa. In North, West, Central and East Africa migratory animal husbandry systems often related with search for grazing and water as well as trade are practiced to a greater extent than in southern Africa. In southern Africa, the role of African buffalo (Syncerus caffer) is more extensively studied than in the other parts of Africa, but based on the densities of African buffalo in Central and East Africa, one would assume that buffalo should also play a role in the epidemiology of FMD in this part of Africa. More sampling of buffalo is necessary in West, Central and East Africa. The genetic analysis of virus strains has proven to be valuable to increase our understanding in the spread of FMD in Africa. This review shows that there is a difference in FMD occurrence between southern Africa and the rest of the continent; this distinction is most likely based on differences in animal husbandry and trade systems. Insufficient data on FMD in wildlife outside southern Africa is limiting our understanding on the role wildlife plays in the transmission of FMD in the other buffalo inhabited areas of Africa.

  20. The Improbable Transmission of Trypanosoma cruzi to Human: The Missing Link in the Dynamics and Control of Chagas Disease

    PubMed Central

    Nouvellet, Pierre; Dumonteil, Eric; Gourbière, Sébastien

    2013-01-01

    Chagas disease has a major impact on human health in Latin America and is becoming of global concern due to international migrations. Trypanosoma cruzi, the etiological agent of the disease, is one of the rare human parasites transmitted by the feces of its vector, as it is unable to reach the salivary gland of the insect. This stercorarian transmission is notoriously poorly understood, despite its crucial role in the ecology and evolution of the pathogen and the disease. The objective of this study was to quantify the probability of T. cruzi vectorial transmission to humans, and to use such an estimate to predict human prevalence from entomological data. We developed several models of T. cruzi transmission to estimate the probability of transmission from vector to host. Using datasets from the literature, we estimated the probability of transmission per contact with an infected triatomine to be 5.8×10−4 (95%CI: [2.6 ; 11.0]×10−4). This estimate was consistent across triatomine species, robust to variations in other parameters, and corresponded to 900–4,000 contacts per case. Our models subsequently allowed predicting human prevalence from vector abundance and infection rate in 7/10 independent datasets covering various triatomine species and epidemiological situations. This low probability of T. cruzi transmission reflected well the complex and unlikely mechanism of transmission via insect feces, and allowed predicting human prevalence from basic entomological data. Although a proof of principle study would now be valuable to validate our models' predictive ability in an even broader range of entomological and ecological settings, our quantitative estimate could allow switching the evaluation of disease risk and vector control program from purely entomological indexes to parasitological measures, as commonly done for other major vector borne diseases. This might lead to different quantitative perspectives as these indexes are well known not to be

  1. Risk factors for transmission of Ebola or Marburg virus disease: a systematic review and meta-analysis

    PubMed Central

    Brainard, Julii; Hooper, Lee; Pond, Katherine; Edmunds, Kelly; Hunter, Paul R

    2016-01-01

    Background: The Ebola virus disease outbreak that started in Western Africa in 2013 was unprecedented because it spread within densely populated urban environments and affected many thousands of people. As a result, previous advice and guidelines need to be critically reviewed, especially with regard to transmission risks in different contexts. Methods: Scientific and grey literature were searched for articles about any African filovirus. Articles were screened for information about transmission (prevalence or odds ratios especially). Data were extracted from eligible articles and summarized narratively with partial meta-analysis. Study quality was also evaluated. Results: A total of 31 reports were selected from 6552 found in the initial search. Eight papers gave numerical odds for contracting filovirus illness; 23 further articles provided supporting anecdotal observations about how transmission probably occurred for individuals. Many forms of contact (conversation, sharing a meal, sharing a bed, direct or indirect touching) were unlikely to result in disease transmission during incubation or early illness. Among household contacts who reported directly touching a case, the attack rate was 32% [95% confidence interval (CI) 26–38%]. Risk of disease transmission between household members without direct contact was low (1%; 95% CI 0–5%). Caring for a case in the community, especially until death, and participation in traditional funeral rites were strongly associated with acquiring disease, probably due to a high degree of direct physical contact with case or cadaver. Conclusions: Transmission of filovirus is unlikely except through close contact, especially during the most severe stages of acute illness. More data are needed about the context, intimacy and timing of contact required to raise the odds of disease transmission. Risk factors specific to urban settings may need to be determined. PMID:26589246

  2. Foot-and-mouth disease in feral swine: susceptibility and transmission.

    PubMed

    Mohamed, F; Swafford, S; Petrowski, H; Bracht, A; Schmit, B; Fabian, A; Pacheco, J M; Hartwig, E; Berninger, M; Carrillo, C; Mayr, G; Moran, K; Kavanaugh, D; Leibrecht, H; White, W; Metwally, S

    2011-08-01

    Experimental studies of foot-and-mouth disease (FMD) in feral swine are limited, and data for clinical manifestations and disease transmissibility are lacking. In this report, feral and domestic swine were experimentally infected with FMDV (A24-Cruzeiro), and susceptibility and virus transmission were studied. Feral swine were proved to be highly susceptible to A-24 Cruzeiro FMD virus by intradermal inoculation and by contact with infected domestic and feral swine. Typical clinical signs in feral swine included transient fever, lameness and vesicular lesions in the coronary bands, heel bulbs, tip of the tongue and snout. Domestic swine exhibited clinical signs of the disease within 24 h after contact with feral swine, whereas feral swine did not show clinical signs of FMD until 48 h after contact with infected domestic and feral swine. Clinical scores of feral and domestic swine were comparable. However, feral swine exhibited a higher tolerance for the disease, and their thicker, darker skin made vesicular lesions difficult to detect. Virus titration of oral swabs showed that both feral and domestic swine shed similar amounts of virus, with levels peaking between 2 to 4 dpi/dpc (days post-inoculation/days post-contact). FMDV RNA was intermittently detectable in the oral swabs by real-time RT-PCR of both feral and domestic swine between 1 and 8 dpi/dpc and in some instances until 14 dpi/12 dpc. Both feral and domestic swine seroconverted 6-8 dpi/dpc as measured by 3ABC antibody ELISA and VIAA assays. FMDV RNA levels in animal room air filters were similar in feral and domestic swine animal rooms, and were last detected at 22 dpi, while none were detectable at 28 or 35 dpi. The FMDV RNA persisted in domestic and feral swine tonsils up to 33-36 dpi/dpc, whereas virus isolation was negative. Results from this study will help understand the role feral swine may play in sustaining an FMD outbreak, and may be utilized in guiding surveillance, epidemiologic and economic

  3. Influence of landscape factors and management decisions on spatial and temporal patterns of the transmission of chronic wasting disease transmission in white-tailed deer.

    PubMed

    O'Hara Ruiz, Marilyn; Kelly, Amy C; Brown, William M; Novakofski, Jan E; Mateus-Pinilla, Nohra E

    2013-11-01

    Chronic wasting disease (CWD) has been reported in white-tailed deer at the border of the US states of Illinois and Wisconsin since 2002. Transmission of infectious prions between animals and from the environment has resulted in spatial and temporal structure observable in the spatio-temporal patterns of reported cases. Case locations of 382 positive cases from 28,954 deer tested between 2002 and 2009 provided insight into the potential risk factors and landscape features associated with transmission using a combination of clustering, generalised linear modelling and descriptive evaluations of a risk map of predicted cases of CWD. A species distribution map of white-tailed deer developed using MaxEnt provided an estimate of deer locations. We found that deer probability increased in areas with larger forests and less urban and agricultural lands. Spatial clustering analysis revealed a core area of persistent CWD transmission in the northern part of the region. The regression model indicated that larger and more compact forests were associated with higher risk for CWD. High risk areas also had soils with less clay and more sand than other parts of the region. The transmission potential was higher where landscape features indicated the potential for higher deer concentrations. The inclusion of spatial lag variables improved the model. Of the 102 cases reported in the study area in the two years following the study period, 89 (87%) of those were in the 32% of the study area with the highest 50% of predicted risk of cases. PMID:24258897

  4. Influence of landscape factors and management decisions on spatial and temporal patterns of the transmission of chronic wasting disease transmission in white-tailed deer.

    PubMed

    O'Hara Ruiz, Marilyn; Kelly, Amy C; Brown, William M; Novakofski, Jan E; Mateus-Pinilla, Nohra E

    2013-11-01

    Chronic wasting disease (CWD) has been reported in white-tailed deer at the border of the US states of Illinois and Wisconsin since 2002. Transmission of infectious prions between animals and from the environment has resulted in spatial and temporal structure observable in the spatio-temporal patterns of reported cases. Case locations of 382 positive cases from 28,954 deer tested between 2002 and 2009 provided insight into the potential risk factors and landscape features associated with transmission using a combination of clustering, generalised linear modelling and descriptive evaluations of a risk map of predicted cases of CWD. A species distribution map of white-tailed deer developed using MaxEnt provided an estimate of deer locations. We found that deer probability increased in areas with larger forests and less urban and agricultural lands. Spatial clustering analysis revealed a core area of persistent CWD transmission in the northern part of the region. The regression model indicated that larger and more compact forests were associated with higher risk for CWD. High risk areas also had soils with less clay and more sand than other parts of the region. The transmission potential was higher where landscape features indicated the potential for higher deer concentrations. The inclusion of spatial lag variables improved the model. Of the 102 cases reported in the study area in the two years following the study period, 89 (87%) of those were in the 32% of the study area with the highest 50% of predicted risk of cases.

  5. A generic model of contagious disease and its application to human-to-human transmission of avian influenza.

    SciTech Connect

    Hirsch, Gary B.

    2007-03-01

    Modeling contagious diseases has taken on greater importance over the past several years as diseases such as SARS and avian influenza have raised concern about worldwide pandemics. Most models developed to consider projected outbreaks have been specific to a single disease. This paper describes a generic System Dynamics contagious disease model and its application to human-to-human transmission of a mutant version of avian influenza. The model offers the option of calculating rates of new infections over time based either on a fixed ''reproductive number'' that is traditional in contagious disease models or on contact rates for different sub-populations and likelihood of transmission per contact. The paper reports on results with various types of interventions. These results suggest the potential importance of contact tracing, limited quarantine, and targeted vaccination strategies as methods for controlling outbreaks, especially when vaccine supplies may initially be limited and the efficacy of anti-viral drugs uncertain.

  6. Quantification of airborne African swine fever virus after experimental infection.

    PubMed

    de Carvalho Ferreira, H C; Weesendorp, E; Quak, S; Stegeman, J A; Loeffen, W L A

    2013-08-30

    Knowledge on African Swine Fever (ASF) transmission routes can be useful when designing control measures against the spread of ASF virus (ASFV). Few studies have focused on the airborne transmission route, and until now no data has been available on quantities of ASF virus (ASFV) in the air. Our aim was to validate an air sampling technique for ASF virus (ASFV) that could be used to detect and quantify virus excreted in the air after experimental infection of pigs. In an animal experiment with the Brazil'78, the Malta'78 and Netherlands'86 isolates, air samples were collected at several time points. For validation of the air sampling technique, ASFV was aerosolised in an isolator, and air samples were obtained using the MD8 air scan device, which was shown to be suitable to detect ASFV. The half-life of ASFV in the air was on average 19 min when analysed by PCR, and on average 14 min when analysed by virus titration. In rooms with infected pigs, viral DNA with titres up to 10(3.2) median tissue culture infective dose equivalents (TCID50eq.)/m(3) could be detected in air samples from day 4 post-inoculation (dpi 4) until the end of the experiments, at dpi 70. In conclusion, this study shows that pigs infected with ASFV will excrete virus in the air, particularly during acute disease. This study provides the first available parameters to model airborne transmission of ASFV.

  7. Atlas of Mexican Triatominae (Reduviidae: Hemiptera) and vector transmission of Chagas disease.

    PubMed

    Ramsey, Janine M; Peterson, A Townsend; Carmona-Castro, Oscar; Moo-Llanes, David A; Nakazawa, Yoshinori; Butrick, Morgan; Tun-Ku, Ezequiel; la Cruz-Félix, Keynes de; Ibarra-Cerdeña, Carlos N

    2015-05-01

    Chagas disease is one of the most important yet neglected parasitic diseases in Mexico and is transmitted by Triatominae. Nineteen of the 31 Mexican triatomine species have been consistently found to invade human houses and all have been found to be naturally infected with Trypanosoma cruzi. The present paper aims to produce a state-of-knowledge atlas of Mexican triatomines and analyse their geographic associations with T. cruzi, human demographics and landscape modification. Ecological niche models (ENMs) were constructed for the 19 species with more than 10 records in North America, as well as for T. cruzi. The 2010 Mexican national census and the 2007 National Forestry Inventory were used to analyse overlap patterns with ENMs. Niche breadth was greatest in species from the semiarid Nearctic Region, whereas species richness was associated with topographic heterogeneity in the Neotropical Region, particularly along the Pacific Coast. Three species, Triatoma longipennis, Triatoma mexicana and Triatoma barberi, overlapped with the greatest numbers of human communities, but these communities had the lowest rural/urban population ratios. Triatomine vectors have urbanised in most regions, demonstrating a high tolerance to human-modified habitats and broadened historical ranges, exposing more than 88% of the Mexican population and leaving few areas in Mexico without the potential for T. cruzi transmission. PMID:25993505

  8. Feeding of ticks on animals for transmission and xenodiagnosis in Lyme disease research.

    PubMed

    Embers, Monica E; Grasperge, Britton J; Jacobs, Mary B; Philipp, Mario T

    2013-01-01

    Transmission of the etiologic agent of Lyme disease, Borrelia burgdorferi, occurs by the attachment and blood feeding of Ixodes species ticks on mammalian hosts. In nature, this zoonotic bacterial pathogen may use a variety of reservoir hosts, but the white-footed mouse (Peromyscus leucopus) is the primary reservoir for larval and nymphal ticks in North America. Humans are incidental hosts most frequently infected with B. burgdorferi by the bite of ticks in the nymphal stage. B. burgdorferi adapts to its hosts throughout the enzootic cycle, so the ability to explore the functions of these spirochetes and their effects on mammalian hosts requires the use of tick feeding. In addition, the technique of xenodiagnosis (using the natural vector for detection and recovery of an infectious agent) has been useful in studies of cryptic infection. In order to obtain nymphal ticks that harbor B. burgdorferi, ticks are fed live spirochetes in culture through capillary tubes. Two animal models, mice and nonhuman primates, are most commonly used for Lyme disease studies involving tick feeding. We demonstrate the methods by which these ticks can be fed upon, and recovered from animals for either infection or xenodiagnosis. PMID:24022694

  9. Revealing the Micro-scale Signature of Endemic Zoonotic Disease Transmission in an African Urban Setting.

    PubMed

    Bourhy, Hervé; Nakouné, Emmanuel; Hall, Matthew; Nouvellet, Pierre; Lepelletier, Anthony; Talbi, Chiraz; Watier, Laurence; Holmes, Edward C; Cauchemez, Simon; Lemey, Philippe; Donnelly, Christl A; Rambaut, Andrew

    2016-04-01

    The development of novel approaches that combine epidemiological and genomic data provides new opportunities to reveal the spatiotemporal dynamics of infectious diseases and determine the processes responsible for their spread and maintenance. Taking advantage of detailed epidemiological time series and viral sequence data from more than 20 years reported by the National Reference Centre for Rabies of Bangui, the capital city of Central African Republic, we used a combination of mathematical modeling and phylogenetic analysis to determine the spatiotemporal dynamics of rabies in domestic dogs as well as the frequency of extinction and introduction events in an African city. We show that although dog rabies virus (RABV) appears to be endemic in Bangui, its epidemiology is in fact shaped by the regular extinction of local chains of transmission coupled with the introduction of new lineages, generating successive waves of spread. Notably, the effective reproduction number during each wave was rarely above the critical value of 1, such that rabies is not self-sustaining in Bangui. In turn, this suggests that rabies at local geographic scales is driven by human-mediated dispersal of RABV among sparsely connected peri-urban and rural areas as opposed to dispersion in a relatively large homogenous urban dog population. This combined epidemiological and genomic approach enables development of a comprehensive framework for understanding disease persistence and informing control measures, indicating that control measures are probably best targeted towards areas neighbouring the city that appear as the source of frequent incursions seeding outbreaks in Bangui. PMID:27058957

  10. Sociality and health: impacts of sociality on disease susceptibility and transmission in animal and human societies

    PubMed Central

    Kappeler, Peter M.; Cremer, Sylvia; Nunn, Charles L.

    2015-01-01

    This paper introduces a theme issue presenting the latest developments in research on the impacts of sociality on health and fitness. The articles that follow cover research on societies ranging from insects to humans. Variation in measures of fitness (i.e. survival and reproduction) has been linked to various aspects of sociality in humans and animals alike, and variability in individual health and condition has been recognized as a key mediator of these relationships. Viewed from a broad evolutionary perspective, the evolutionary transitions from a solitary lifestyle to group living have resulted in several new health-related costs and benefits of sociality. Social transmission of parasites within groups represents a major cost of group living, but some behavioural mechanisms, such as grooming, have evolved repeatedly to reduce this cost. Group living also has created novel costs in terms of altered susceptibility to infectious and non-infectious disease as a result of the unavoidable physiological consequences of social competition and integration, which are partly alleviated by social buffering in some vertebrates. Here, we define the relevant aspects of sociality, summarize their health-related costs and benefits, and discuss possible fitness measures in different study systems. Given the pervasive effects of social factors on health and fitness, we propose a synthesis of existing conceptual approaches in disease ecology, ecological immunology and behavioural neurosciences by adding sociality as a key factor, with the goal to generate a broader framework for organismal integration of health-related research. PMID:25870402

  11. Revealing the Micro-scale Signature of Endemic Zoonotic Disease Transmission in an African Urban Setting

    PubMed Central

    Bourhy, Hervé; Nakouné, Emmanuel; Hall, Matthew; Nouvellet, Pierre; Lepelletier, Anthony; Talbi, Chiraz; Watier, Laurence; Holmes, Edward C.; Cauchemez, Simon; Lemey, Philippe; Donnelly, Christl A.; Rambaut, Andrew

    2016-01-01

    The development of novel approaches that combine epidemiological and genomic data provides new opportunities to reveal the spatiotemporal dynamics of infectious diseases and determine the processes responsible for their spread and maintenance. Taking advantage of detailed epidemiological time series and viral sequence data from more than 20 years reported by the National Reference Centre for Rabies of Bangui, the capital city of Central African Republic, we used a combination of mathematical modeling and phylogenetic analysis to determine the spatiotemporal dynamics of rabies in domestic dogs as well as the frequency of extinction and introduction events in an African city. We show that although dog rabies virus (RABV) appears to be endemic in Bangui, its epidemiology is in fact shaped by the regular extinction of local chains of transmission coupled with the introduction of new lineages, generating successive waves of spread. Notably, the effective reproduction number during each wave was rarely above the critical value of 1, such that rabies is not self-sustaining in Bangui. In turn, this suggests that rabies at local geographic scales is driven by human-mediated dispersal of RABV among sparsely connected peri-urban and rural areas as opposed to dispersion in a relatively large homogenous urban dog population. This combined epidemiological and genomic approach enables development of a comprehensive framework for understanding disease persistence and informing control measures, indicating that control measures are probably best targeted towards areas neighbouring the city that appear as the source of frequent incursions seeding outbreaks in Bangui. PMID:27058957

  12. Atlas of Mexican Triatominae (Reduviidae: Hemiptera) and vector transmission of Chagas disease.

    PubMed

    Ramsey, Janine M; Peterson, A Townsend; Carmona-Castro, Oscar; Moo-Llanes, David A; Nakazawa, Yoshinori; Butrick, Morgan; Tun-Ku, Ezequiel; la Cruz-Félix, Keynes de; Ibarra-Cerdeña, Carlos N

    2015-05-01

    Chagas disease is one of the most important yet neglected parasitic diseases in Mexico and is transmitted by Triatominae. Nineteen of the 31 Mexican triatomine species have been consistently found to invade human houses and all have been found to be naturally infected with Trypanosoma cruzi. The present paper aims to produce a state-of-knowledge atlas of Mexican triatomines and analyse their geographic associations with T. cruzi, human demographics and landscape modification. Ecological niche models (ENMs) were constructed for the 19 species with more than 10 records in North America, as well as for T. cruzi. The 2010 Mexican national census and the 2007 National Forestry Inventory were used to analyse overlap patterns with ENMs. Niche breadth was greatest in species from the semiarid Nearctic Region, whereas species richness was associated with topographic heterogeneity in the Neotropical Region, particularly along the Pacific Coast. Three species, Triatoma longipennis, Triatoma mexicana and Triatoma barberi, overlapped with the greatest numbers of human communities, but these communities had the lowest rural/urban population ratios. Triatomine vectors have urbanised in most regions, demonstrating a high tolerance to human-modified habitats and broadened historical ranges, exposing more than 88% of the Mexican population and leaving few areas in Mexico without the potential for T. cruzi transmission.

  13. Feeding of ticks on animals for transmission and xenodiagnosis in Lyme disease research.

    PubMed

    Embers, Monica E; Grasperge, Britton J; Jacobs, Mary B; Philipp, Mario T

    2013-08-31

    Transmission of the etiologic agent of Lyme disease, Borrelia burgdorferi, occurs by the attachment and blood feeding of Ixodes species ticks on mammalian hosts. In nature, this zoonotic bacterial pathogen may use a variety of reservoir hosts, but the white-footed mouse (Peromyscus leucopus) is the primary reservoir for larval and nymphal ticks in North America. Humans are incidental hosts most frequently infected with B. burgdorferi by the bite of ticks in the nymphal stage. B. burgdorferi adapts to its hosts throughout the enzootic cycle, so the ability to explore the functions of these spirochetes and their effects on mammalian hosts requires the use of tick feeding. In addition, the technique of xenodiagnosis (using the natural vector for detection and recovery of an infectious agent) has been useful in studies of cryptic infection. In order to obtain nymphal ticks that harbor B. burgdorferi, ticks are fed live spirochetes in culture through capillary tubes. Two animal models, mice and nonhuman primates, are most commonly used for Lyme disease studies involving tick feeding. We demonstrate the methods by which these ticks can be fed upon, and recovered from animals for either infection or xenodiagnosis.

  14. Atlas of Mexican Triatominae (Reduviidae: Hemiptera) and vector transmission of Chagas disease

    PubMed Central

    Ramsey, Janine M; Peterson, A Townsend; Carmona-Castro, Oscar; Moo-Llanes, David A; Nakazawa, Yoshinori; Butrick, Morgan; Tun-Ku, Ezequiel; de la Cruz-Félix, Keynes; Ibarra-Cerdeña, Carlos N

    2015-01-01

    Chagas disease is one of the most important yet neglected parasitic diseases in Mexico and is transmitted by Triatominae. Nineteen of the 31 Mexican triatomine species have been consistently found to invade human houses and all have been found to be naturally infected with Trypanosoma cruzi. The present paper aims to produce a state-of-knowledge atlas of Mexican triatomines and analyse their geographic associations with T. cruzi, human demographics and landscape modification. Ecological niche models (ENMs) were constructed for the 19 species with more than 10 records in North America, as well as for T. cruzi. The 2010 Mexican national census and the 2007 National Forestry Inventory were used to analyse overlap patterns with ENMs. Niche breadth was greatest in species from the semiarid Nearctic Region, whereas species richness was associated with topographic heterogeneity in the Neotropical Region, particularly along the Pacific Coast. Three species, Triatoma longipennis, Triatoma mexicana and Triatoma barberi, overlapped with the greatest numbers of human communities, but these communities had the lowest rural/urban population ratios. Triatomine vectors have urbanised in most regions, demonstrating a high tolerance to human-modified habitats and broadened historical ranges, exposing more than 88% of the Mexican population and leaving few areas in Mexico without the potential for T. cruzi transmission. PMID:25993505

  15. A potential role for ixodid (hard) tick vectors in the transmission of lumpy skin disease virus in cattle.

    PubMed

    Tuppurainen, E S M; Stoltsz, W H; Troskie, M; Wallace, D B; Oura, C A L; Mellor, P S; Coetzer, J A W; Venter, E H

    2011-04-01

    Lumpy skin disease (LSD) is an economically important cattle disease. The disease is endemic in many African countries, but outbreaks have also been reported in Madagascar and the Middle East. The aim of this study was to investigate the potential role of ixodid (hard) ticks in the transmission of the disease. Cattle were infected with a virulent, South African field isolate of lumpy skin disease virus (LSDV). Three common African tick species (genera Rhipicephalus, Amblyomma and Rhipicephalus (Boophilus)) in different life cycle stages were fed on the infected animals during the viraemic stage and on skin lesions. Post-feeding, the partially fed male ticks were transferred to the skin of non-infected 'recipient' animals, while females were allowed to lay eggs that were then tested using the polymerase chain reaction (PCR) method and virus isolation. Nymphs were allowed to develop for 2-3 weeks after which time they were tested. The non-infected 'recipient' cattle were closely monitored, both skin and blood samples were tested using PCR and virus isolation, and serum samples were tested by the serum neutralization test. This is the first report showing molecular evidence of potential transmission of LSDV by ixodid ticks. The study showed evidence of transstadial and transovarial transmission of LSDV by R. (B.) decoloratus ticks and mechanical or intrastadial transmission by R. appendiculatus and A. hebraeum ticks.

  16. Transmission and Progression to Disease of Mycobacterium tuberculosis Phylogenetic Lineages in The Netherlands.

    PubMed

    Nebenzahl-Guimaraes, Hanna; Verhagen, Lilly M; Borgdorff, Martien W; van Soolingen, Dick

    2015-10-01

    The aim of this study was to determine if mycobacterial lineages affect infection risk, clustering, and disease progression among Mycobacterium tuberculosis cases in The Netherlands. Multivariate negative binomial regression models adjusted for patient-related factors and stratified by patient ethnicity were used to determine the association between phylogenetic lineages and infectivity (mean number of positive contacts around each patient) and clustering (as defined by number of secondary cases within 2 years after diagnosis of an index case sharing the same fingerprint) indices. An estimate of progression to disease by each risk factor was calculated as a bootstrapped risk ratio of the clustering index by the infectivity index. Compared to the Euro-American reference, Mycobacterium africanum showed significantly lower infectivity and clustering indices in the foreign-born population, while Mycobacterium bovis showed significantly lower infectivity and clustering indices in the native population. Significantly lower infectivity was also observed for the East African Indian lineage in the foreign-born population. Smear positivity was a significant risk factor for increased infectivity and increased clustering. Estimates of progression to disease were significantly associated with age, sputum-smear status, and behavioral risk factors, such as alcohol and intravenous drug abuse, but not with phylogenetic lineages. In conclusion, we found evidence of a bacteriological factor influencing indicators of a strain's transmissibility, namely, a decreased ability to infect and a lower clustering index in ancient phylogenetic lineages compared to their modern counterparts. Confirmation of these findings via follow-up studies using tuberculin skin test conversion data should have important implications on M. tuberculosis control efforts.

  17. Alzheimer's disease Braak Stage progressions: reexamined and redefined as Borrelia infection transmission through neural circuits.

    PubMed

    MacDonald, Alan B

    2007-01-01

    Brain structure in health is a dynamic energized equation incorporating chemistry, neuronal structure, and circuitry components. The chemistry "piece" is represented by multiple neurotransmitters such as Acetylcholine, Serotonin, and Dopamine. The neuronal structure "piece" incorporates synapses and their connections. And finally circuits of neurons establish "architectural blueprints" of anatomic wiring diagrams of the higher order of brain neuron organizations. In Alzheimer's disease, there are progressive losses in all of these components. Brain structure crumbles. The deterioration in Alzheimer's is ordered, reproducible, and stepwise. Drs. Braak and Braak have described stages in the Alzheimer disease continuum. "Progressions" through Braak Stages benchmark "Regressions" in Cognitive function. Under the microscope, the Stages of Braak commence in brain regions near to the hippocampus, and over time, like a tsunami wave of destruction, overturn healthy brain regions, with neurofibrillary tangle damaged neurons "marching" through the temporal lobe, neocortex and occipital cortex. In effect the destruction ascends from the limbic regions to progressively destroy the higher brain centers. Rabies infection also "begins low and finishes high" in its wave of destruction of brain tissue. Herpes Zoster infections offer the paradigm of clinical latency of infection inside of nerves before the "marching commences". Varicella Zoster virus enters neurons in the pediatric years. Dormant virus remains inside the neurons for 50-80 years, tissue damage late in life (shingles) demonstrates the "march of the infection" down neural pathways (dermatomes) as linear areas of painful blisters loaded with virus from a childhood infection. Amalgamation of Zoster with Rabies models produces a hybrid model to explain all of the Braak Stages of Alzheimer's disease under a new paradigm, namely "Alzheimer's neuroborreliosis" in which latent Borrelia infections ascend neural circuits through

  18. The Sociospatial Network: Risk and the Role of Place in the Transmission of Infectious Diseases.

    PubMed

    Logan, James J; Jolly, Ann M; Blanford, Justine I

    2016-01-01

    Control of sexually transmitted infections and blood-borne pathogens is challenging due to their presence in groups exhibiting complex social interactions. In particular, sharing injection drug use equipment and selling sex (prostitution) puts people at high risk. Previous work examining the involvement of risk behaviours in social networks has suggested that social and geographic distance of persons within a group contributes to these pathogens' endemicity. In this study, we examine the role of place in the connectedness of street people, selected by respondent driven sampling, in the transmission of blood-borne and sexually transmitted pathogens. A sample of 600 injection drug users, men who have sex with men, street youth and homeless people were recruited in Winnipeg, Canada from January to December, 2009. The residences of participants and those of their social connections were linked to each other and to locations where they engaged in risk activity. Survey responses identified 101 unique sites where respondents participated in injection drug use or sex transactions. Risk sites and respondents' residences were geocoded, with residence representing the individuals. The sociospatial network and estimations of geographic areas most likely to be frequented were mapped with network graphs and spatially using a Geographic Information System (GIS). The network with the most nodes connected 7.7% of respondents; consideration of the sociospatial network increased this to 49.7%. The mean distance between any two locations in the network was within 3.5 kilometres. Kernel density estimation revealed key activity spaces where the five largest networks overlapped. Here, the combination of spatial and social entities in network analysis defines the overlap of vulnerable populations in risk space, over and above the person to person links. Implications of this work are far reaching, not just for understanding transmission dynamics of sexually transmitted infections by

  19. Avian influenza shedding patterns in waterfowl: implications for surveillance, environmental transmission, and disease spread

    USGS Publications Warehouse

    Viviane Henaux,; Samuel, Michael D.

    2011-01-01

    Despite the recognized importance of fecal/oral transmission of low pathogenic avian influenza (LPAI) via contaminated wetlands, little is known about the length, quantity, or route of AI virus shed by wild waterfowl. We used published laboratory challenge studies to evaluate the length and quantity of low pathogenic (LP) and highly pathogenic (HP) virus shed via oral and cloacal routes by AI-infected ducks and geese, and how these factors might influence AI epidemiology and virus detection. We used survival analysis to estimate the duration of infection (from virus inoculation to the last day virus was shed) and nonlinear models to evaluate temporal patterns in virus shedding. We found higher mean virus titer and longer median infectious period for LPAI-infected ducks (10–11.5 days in oral and cloacal swabs) than HPAI-infected ducks (5 days) and geese (7.5 days). Based on the median bird infectious dose, we found that environmental contamination is two times higher for LPAI- than HPAI-infectious ducks, which implies that susceptible birds may have a higher probability of infection during LPAI than HPAI outbreaks. Less environmental contamination during the course of infection and previously documented shorter environmental persistence for HPAI than LPAI suggest that the environment is a less favorable reservoir for HPAI. The longer infectious period, higher virus titers, and subclinical infections with LPAI viruses favor the spread of these viruses by migratory birds in comparison to HPAI. Given the lack of detection of HPAI viruses through worldwide surveillance, we suggest monitoring for AI should aim at improving our understanding of AI dynamics (in particular, the role of the environment and immunity) using long-term comprehensive live bird, serologic, and environmental sampling at targeted areas. Our findings on LPAI and HPAI shedding patterns over time provide essential information to parameterize environmental transmission and virus spread in predictive

  20. The Sociospatial Network: Risk and the Role of Place in the Transmission of Infectious Diseases.

    PubMed

    Logan, James J; Jolly, Ann M; Blanford, Justine I

    2016-01-01

    Control of sexually transmitted infections and blood-borne pathogens is challenging due to their presence in groups exhibiting complex social interactions. In particular, sharing injection drug use equipment and selling sex (prostitution) puts people at high risk. Previous work examining the involvement of risk behaviours in social networks has suggested that social and geographic distance of persons within a group contributes to these pathogens' endemicity. In this study, we examine the role of place in the connectedness of street people, selected by respondent driven sampling, in the transmission of blood-borne and sexually transmitted pathogens. A sample of 600 injection drug users, men who have sex with men, street youth and homeless people were recruited in Winnipeg, Canada from January to December, 2009. The residences of participants and those of their social connections were linked to each other and to locations where they engaged in risk activity. Survey responses identified 101 unique sites where respondents participated in injection drug use or sex transactions. Risk sites and respondents' residences were geocoded, with residence representing the individuals. The sociospatial network and estimations of geographic areas most likely to be frequented were mapped with network graphs and spatially using a Geographic Information System (GIS). The network with the most nodes connected 7.7% of respondents; consideration of the sociospatial network increased this to 49.7%. The mean distance between any two locations in the network was within 3.5 kilometres. Kernel density estimation revealed key activity spaces where the five largest networks overlapped. Here, the combination of spatial and social entities in network analysis defines the overlap of vulnerable populations in risk space, over and above the person to person links. Implications of this work are far reaching, not just for understanding transmission dynamics of sexually transmitted infections by

  1. Vertically acquired hepatitis C virus infection: Correlates of transmission and disease progression

    PubMed Central

    Tovo, Pier-Angelo; Calitri, Carmelina; Scolfaro, Carlo; Gabiano, Clara; Garazzino, Silvia

    2016-01-01

    The worldwide prevalence of hepatitis C virus (HCV) infection in children is 0.05%-0.4% in developed countries and 2%-5% in resource-limited settings, where inadequately tested blood products or un-sterile medical injections still remain important routes of infection. After the screening of blood donors, mother-to-child transmission (MTCT) of HCV has become the leading cause of pediatric infection, at a rate of 5%. Maternal HIV co-infection is a significant risk factor for MTCT and anti-HIV therapy during pregnancy seemingly can reduce the transmission rate of both viruses. Conversely, a high maternal viral load is an important, but not preventable risk factor, because at present no anti-HCV treatment can be administered to pregnant women to block viral replication. Caution is needed in adopting obstetric procedures, such as amniocentesis or internal fetal monitoring, that can favor fetal exposure to HCV contaminated maternal blood, though evidence is lacking on the real risk of single obstetric practices. Mode of delivery and type of feeding do not represent significant risk factors for MTCT. Therefore, there is no reason to offer elective caesarean section or discourage breast-feeding to HCV infected parturients. Information on the natural history of vertical HCV infection is limited. The primary infection is asymptomatic in infants. At least one quarter of infected children shows a spontaneous viral clearance (SVC) that usually occurs within 6 years of life. IL-28B polymorphims and genotype 3 infection have been associated with greater chances of SVC. In general, HCV progression is mild or moderate in children with chronic infection who grow regularly, though cases with marked liver fibrosis or hepatic failure have been described. Non-organ specific autoantibodies and cryoglobulins are frequently found in children with chronic infection, but autoimmune diseases or HCV associated extrahepatic manifestations are rare. PMID:26819507

  2. The Sociospatial Network: Risk and the Role of Place in the Transmission of Infectious Diseases

    PubMed Central

    2016-01-01

    Control of sexually transmitted infections and blood-borne pathogens is challenging due to their presence in groups exhibiting complex social interactions. In particular, sharing injection drug use equipment and selling sex (prostitution) puts people at high risk. Previous work examining the involvement of risk behaviours in social networks has suggested that social and geographic distance of persons within a group contributes to these pathogens’ endemicity. In this study, we examine the role of place in the connectedness of street people, selected by respondent driven sampling, in the transmission of blood-borne and sexually transmitted pathogens. A sample of 600 injection drug users, men who have sex with men, street youth and homeless people were recruited in Winnipeg, Canada from January to December, 2009. The residences of participants and those of their social connections were linked to each other and to locations where they engaged in risk activity. Survey responses identified 101 unique sites where respondents participated in injection drug use or sex transactions. Risk sites and respondents’ residences were geocoded, with residence representing the individuals. The sociospatial network and estimations of geographic areas most likely to be frequented were mapped with network graphs and spatially using a Geographic Information System (GIS). The network with the most nodes connected 7.7% of respondents; consideration of the sociospatial network increased this to 49.7%. The mean distance between any two locations in the network was within 3.5 kilometres. Kernel density estimation revealed key activity spaces where the five largest networks overlapped. Here, the combination of spatial and social entities in network analysis defines the overlap of vulnerable populations in risk space, over and above the person to person links. Implications of this work are far reaching, not just for understanding transmission dynamics of sexually transmitted infections by

  3. Investigation of the pathogenesis of transplacental transmission of Aleutian mink disease parvovirus in experimentally infected mink.

    PubMed Central

    Broll, S; Alexandersen, S

    1996-01-01

    The transplacental transmission of Aleutian mink disease parvovirus (ADV) was studied in experimental infection of 1-year-old female non-Aleutian mink. The ADV-seronegative female mink were inoculated with ADV prior to mating or after the expected implantation of the embryos during pregnancy. A group of uninfected females served as a control group. Animals from each group were killed prior to or shortly after parturition. The in situ hybridization technique with radiolabeled strand-specific RNA probes was used to determine target cells of virus infection and virus replication. In both infected groups, ADV crossed the endotheliochorial placental barrier, although animals infected before mating already had high antibody titers against ADV at the time of implantation. The percentage of dead and resorbed fetuses was much higher in dams infected before mating. In the placentae of these mink, virus DNA and viral mRNA were detected in cells in the mesenchymal stroma of the placental labyrinth and hematoma but only occasionally in the cytotrophoblast of the placental hematoma. Placentae of animals infected during pregnancy showed in addition very high levels of virus and also viral replication in a large number of cytotrophoblast cells in the placental hematoma, which exhibited distinct inclusion bodies. In both groups, neither virus nor virus replication could be detected in maternal endothelial cells or fetal syncytiotrophoblast of the placental labyrinth. Fetuses were positive for virus and viral replication at high levels in a wide range of tissues. Possible routes of transplacental transmission of ADV and the role of trophoblast cells as targets for viral replication are discussed. PMID:8627663

  4. Airborne asbestos in public buildings

    SciTech Connect

    Chesson, J.; Hatfield, J.; Schultz, B.; Dutrow, E.; Blake, J. )

    1990-02-01

    The U.S. Environmental Protection Agency sampled air in 49 government-owned buildings (six buildings with no asbestos-containing material, six buildings with asbestos-containing material in generally good condition, and 37 buildings with damaged asbestos-containing material). This is the most comprehensive study to date of airborne asbestos levels in U.S. public buildings during normal building activities. The air outside each building was also sampled. Air samples were analyzed by transmission electron microscopy using a direct transfer preparation technique. The results show an increasing trend in average airborne asbestos levels; outdoor levels are lowest and levels in buildings with damaged asbestos-containing material are highest. However, the measured levels and the differences between indoors and outdoors and between building categories are small in absolute magnitude. Comparable studies from Canada and the UK, although differing in their estimated concentrations, also conclude that while airborne asbestos levels may be elevated in buildings that contain asbestos, levels are generally low. This conclusion does not eliminate the possibility of higher airborne asbestos levels during maintenance or renovation that disturbs the asbestos-containing material.

  5. A review of the effects of artemether-lumefantrine on gametocyte carriage and disease transmission

    PubMed Central

    2014-01-01

    While significant advances have been made in the prevention and treatment of malaria in recent years, these successes continue to fall short of the World Health Organization (WHO) goals for malaria control and elimination. For elimination strategies to be effective, limited disease transmission, achieved through rapid reduction in the infectious parasite reservoir and decreased gametocyte carriage, will be critical. Artemisinin-based combination therapy (ACT) forms the cornerstone of WHO-recommended treatment for uncomplicated Plasmodium falciparum malaria, and in combination with other effective interventions will undoubtedly play a vital role in elimination programmes. The gametocytocidal properties of artemisinins are a bonus attribute; there is epidemiological evidence of reductions in malaria incidence and transmission in African regions since the introduction of these agents. Many studies and analyses have specifically investigated the effects of the ACT, artemether-lumefantrine (AL) on gametocyte carriage. In this systematic review of 62 articles published between 1998 and January 2014, the effects of AL on gametocyte carriage and malaria transmission are compared with other artemisinin-based anti-malarials and non-ACT. The impact of AL treatment of asymptomatic carriers on population gametocyte carriage, and the potential future role of AL in malaria elimination initiatives are also considered. Despite the inherent difficulties in comparing data from a range of different studies that also utilized different diagnostic approaches to assess baseline gametocyte counts, the gametocytocidal effect of AL was proportionately consistent across the studies reviewed, suggesting that AL will continue to play a vital role in the treatment of malaria and contribute to clearing the path towards malaria elimination. However, the specific place of AL is the subject of much ongoing research and will undoubtedly be dependent on different demographic and geographical

  6. A review of the effects of artemether-lumefantrine on gametocyte carriage and disease transmission.

    PubMed

    Makanga, Michael

    2014-07-28

    While significant advances have been made in the prevention and treatment of malaria in recent years, these successes continue to fall short of the World Health Organization (WHO) goals for malaria control and elimination. For elimination strategies to be effective, limited disease transmission, achieved through rapid reduction in the infectious parasite reservoir and decreased gametocyte carriage, will be critical. Artemisinin-based combination therapy (ACT) forms the cornerstone of WHO-recommended treatment for uncomplicated Plasmodium falciparum malaria, and in combination with other effective interventions will undoubtedly play a vital role in elimination programmes. The gametocytocidal properties of artemisinins are a bonus attribute; there is epidemiological evidence of reductions in malaria incidence and transmission in African regions since the introduction of these agents. Many studies and analyses have specifically investigated the effects of the ACT, artemether-lumefantrine (AL) on gametocyte carriage. In this systematic review of 62 articles published between 1998 and January 2014, the effects of AL on gametocyte carriage and malaria transmission are compared with other artemisinin-based anti-malarials and non-ACT. The impact of AL treatment of asymptomatic carriers on population gametocyte carriage, and the potential future role of AL in malaria elimination initiatives are also considered. Despite the inherent difficulties in comparing data from a range of different studies that also utilized different diagnostic approaches to assess baseline gametocyte counts, the gametocytocidal effect of AL was proportionately consistent across the studies reviewed, suggesting that AL will continue to play a vital role in the treatment of malaria and contribute to clearing the path towards malaria elimination. However, the specific place of AL is the subject of much ongoing research and will undoubtedly be dependent on different demographic and geographical

  7. Mosquito vectors developing in atypical anthropogenic habitats: Global overview of recent observations, mechanisms and impact on disease transmission.

    PubMed

    Ramasamy, Ranjan; Surendran, Sinnathamby N

    2016-01-01

    The major mosquito vectors of human diseases have co-evolved with humans over a long period of time. However, the rapid growth in human population and the associated expansion in agricultural activity and greater urbanisation have created ecological changes that have had a marked impact on biology of mosquito vectors. Adaptation of the vectors of malaria and important arbovial diseases over a much shorter time scale to the new types of preimaginal habitats recently created by human population growth and activity is highlighted here in the context of its potential for increasing disease transmission rates. Possible measures that can reduce the effects on the transmission of mosquito-borne diseases are also outlined. PMID:27353577

  8. Population- and individual-based approaches to the design and analysis of epidemiologic studies of sexually transmitted disease transmission.

    PubMed

    Shiboski, S; Padian, N S

    1996-10-01

    Epidemiologic studies of sexually transmitted disease (STD) transmission present a number of unique challenges in design and analysis. These arise both from the social nature of STD transmission and from inherent difficulties in collecting accurate and informative data on exposure and infection. Risk of acquiring an STD depends on both individual-level factors and the behavior and infectiousness of others. Consequently, study designs and analysis methods developed for studying chronic disease risk in individuals or groups may not apply directly. Simple models of STD transmission were used to investigate these issues, focusing on how the interplay between individual- and population-level factors influences design and interpretation of epidemiologic studies, with particular attention to interpretation of common measures of association and to common sources of bias in epidemiologic data. Existing methods for investigating risk factors can be modified such that these issues may be addressed directly. PMID:8843249

  9. THE ROLE OF REEF FISH IN THE TRANSMISSION DYNAMICS OF BLACK-BAND DISEASE IN THE FLORIDA KEYS

    EPA Science Inventory

    Aeby, Greta S. and Deborah L. Santavy. In press. Role of Reef Fish in the Transmission Dynamics of Black-Band Disease in the Florida Keys (Abstract). To be presented at the 10th International Coral Reef Symposium, 28 June-2 July 2004, Okinawa, Japan. 1 p. (ERL,GB R998).

    T...

  10. Distantiae Transmission of Trypanosoma cruzi: A New Epidemiological Feature of Acute Chagas Disease in Brazil

    PubMed Central

    Xavier, Samanta Cristina das Chagas; Roque, André Luiz Rodrigues; Bilac, Daniele; de Araújo, Vitor Antônio Louzada; Neto, Sócrates Fraga da Costa; Lorosa, Elias Seixas; da Silva, Luiz Felipe Coutinho Ferreira; Jansen, Ana Maria

    2014-01-01

    Background The new epidemiological scenario of orally transmitted Chagas disease that has emerged in Brazil, and mainly in the Amazon region, needs to be addressed with a new and systematic focus. Belém, the capital of Pará state, reports the highest number of acute Chagas disease (ACD) cases associated with the consumption of açaí juice. Methodology/Principal Findings The wild and domestic enzootic transmission cycles of Trypanosoma cruzi were evaluated in the two locations (Jurunas and Val-de Cães) that report the majority of the autochthonous cases of ACD in Belém city. Moreover, we evaluated the enzootic cycle on the three islands that provide most of the açaí fruit that is consumed in these localities. We employed parasitological and serological tests throughout to evaluate infectivity competence and exposure to T. cruzi. In Val-de-Cães, no wild mammal presented positive parasitological tests, and 56% seroprevalence was observed, with low serological titers. Three of 14 triatomines were found to be infected (TcI). This unexpected epidemiological picture does not explain the high number of autochthonous ACD cases. In Jurunas, the cases of ACD could not be autochthonous because of the absence of any enzootic cycle of T. cruzi. In contrast, in the 3 island areas from which the açaí fruit originates, 66.7% of wild mammals and two dogs displayed positive hemocultures, and 15.6% of triatomines were found to be infected by T. cruzi. Genotyping by mini-exon gene and PCR-RFLP (1f8/Akw21I) targeting revealed that the mammals and triatomines from the islands harbored TcI and Trypanosoma rangeli in single and mixed infections. Conclusion/Significance These findings show that cases of Chagas disease in the urban area of Belém may be derived from infected triatomines coming together with the açaí fruits from distant islands. We term this new epidemiological feature of Chagas disease as “Distantiae transmission”. PMID:24854494

  11. Genetic determinants of pediatric HIV-1 infection: vertical transmission and disease progression among children.

    PubMed Central

    Matt, C.; Roger, M.

    2001-01-01

    It is very likely that perinatal human immunodeficiency virus type 1 (HIV-1) infection is influenced by a combination of virologic and host factors. A greater understanding of the role played by various risk factors for HIV-1 infection is crucial for the design of new preventive and therapeutic strategies. In recent years, a number of studies have suggested that host genetic factors are important determinants of both the susceptibility to perinatal HIV-1 infection and the subsequent pathogenesis of acquired immunodeficiency syndrome (AIDS). Control of HIV-1 infection involves the processing of specific viral peptides and their presentation to cells of the immune system by highly polymorphic human leukocyte antigen (HLA) alleles. The contribution of multiple HLA class I and II alleles in modulating pediatric HIV/AIDS outcomes has now been confirmed by several independent groups. Penetration of HIV-1 into cells is mediated by interaction between CD4 and chemokine receptors that serve as entry coreceptors. Genetic polymorphisms in chemokine ligand and chemokine receptor genes have recently been associated both with mother-to-child HIV-1 transmission and disease progression in children. These observations suggest a key role for genetic factors in pediatric HIV-1 infection. This article describes the current state of knowledge regarding host genetic influences on pediatric HIV-1 infection and discusses the role of these genes in HIV/AIDS pathogenesis. PMID:11778647

  12. Hepatitis C virus molecular evolution: transmission, disease progression and antiviral therapy.

    PubMed

    Preciado, Maria Victoria; Valva, Pamela; Escobar-Gutierrez, Alejandro; Rahal, Paula; Ruiz-Tovar, Karina; Yamasaki, Lilian; Vazquez-Chacon, Carlos; Martinez-Guarneros, Armando; Carpio-Pedroza, Juan Carlos; Fonseca-Coronado, Salvador; Cruz-Rivera, Mayra

    2014-11-21

    Hepatitis C virus (HCV) infection represents an important public health problem worldwide. Reduction of HCV morbidity and mortality is a current challenge owned to several viral and host factors. Virus molecular evolution plays an important role in HCV transmission, disease progression and therapy outcome. The high degree of genetic heterogeneity characteristic of HCV is a key element for the rapid adaptation of the intrahost viral population to different selection pressures (e.g., host immune responses and antiviral therapy). HCV molecular evolution is shaped by different mechanisms including a high mutation rate, genetic bottlenecks, genetic drift, recombination, temporal variations and compartmentalization. These evolutionary processes constantly rearrange the composition of the HCV intrahost population in a staging manner. Remarkable advances in the understanding of the molecular mechanism controlling HCV replication have facilitated the development of a plethora of direct-acting antiviral agents against HCV. As a result, superior sustained viral responses have been attained. The rapidly evolving field of anti-HCV therapy is expected to broad its landscape even further with newer, more potent antivirals, bringing us one step closer to the interferon-free era.

  13. Transmission and adaptation of chronic wasting disease to hamsters and transgenic mice: evidence for strains.

    PubMed

    Raymond, Gregory J; Raymond, Lynne D; Meade-White, Kimberly D; Hughson, Andrew G; Favara, Cynthia; Gardner, Donald; Williams, Elizabeth S; Miller, Michael W; Race, Richard E; Caughey, Byron

    2007-04-01

    In vitro screening using the cell-free prion protein conversion system indicated that certain rodents may be susceptible to chronic wasting disease (CWD). Therefore, CWD isolates from mule deer, white-tailed deer, and elk were inoculated intracerebrally into various rodent species to assess the rodents' susceptibility and to develop new rodent models of CWD. The species inoculated were Syrian golden, Djungarian, Chinese, Siberian, and Armenian hamsters, transgenic mice expressing the Syrian golden hamster prion protein, and RML Swiss and C57BL10 wild-type mice. The transgenic mice and the Syrian golden, Chinese, Siberian, and Armenian hamsters had limited susceptibility to certain of the CWD inocula, as evidenced by incomplete attack rates and long incubation periods. For serial passages of CWD isolates in Syrian golden hamsters, incubation periods rapidly stabilized, with isolates having either short (85 to 89 days) or long (408 to 544 days) mean incubation periods and distinct neuropathological patterns. In contrast, wild-type mouse strains and Djungarian hamsters were not susceptible to CWD. These results show that CWD can be transmitted and adapted to some species of rodents and suggest that the cervid-derived CWD inocula may have contained or diverged into at least two distinct transmissible spongiform encephalopathy strains.

  14. Subcellular distribution of the transmissible agent in Creutzfeldt-Jakob disease mouse brain.

    PubMed

    Tamai, Y; Kojima, H; Ohtani, Y; Uchida, K; Taguchi, F; Kawaguchi, T; Miura, S; Tateishi, J

    1989-01-01

    To determine the intracellular localization of the Creutzfeldt-Jakob disease (CJD) agent in mouse brain, cerebrum tissue of the mouse brain affected with the Fukuoka-1 strain was separated into six subcellular fractions (microsome, nerve ending, myelin, mitochondria, nucleus, and soluble fractions) by differential sucrose density gradient, and then the CJD infectivity of these fractions was examined. Serially diluted samples of each subfraction were inoculated intracerebrally into groups of BALB/c mice, and the infectivity was determined as to end point titration value, incubation period, and number of affected mice. On the basis of the protein content, the highest CJD infectivity was observed in the microsomal fraction. The nerve ending (synaptic plasma membrane) and myelin fractions were also infective. The mitochondria and nucleus fractions showed the lower infectivity. The infectivity of the soluble fraction was the lowest among the six subcellular fractions. From the findings obtained in this study two possibilities as to the intracellular localization of CJD agent were suggested: 1) the transmissible agent of CJD is closely associated with surface membranes of neuronal and/or glial cells, including their processes; 2) the CJD agent is diffusely present intracellularly, including in the surface membranes, but for manifestation of infectivity the agent needs membrane components as prerequisite factors.

  15. [Ecology of Aedes aegypti and Aedes albopictus in the Americas and disease transmission].

    PubMed

    Rey, Jorge R; Lounibos, Philip

    2015-01-01

    The recent range expansion of the mosquito Aedes albopictus has been associated in some areas by declines in abundance or local elimination of Aedes aegypti, but the two species still coexist in large regions of the Americas. We offer a summary of the possible mechanisms responsible for the abundance and displacement pattern observed and of their significance in terms of disease transmission. Among these mechanisms we may mention the competition for limiting resources, the differences in the ability to withstand starvation, the apparent competition through differential effects of the parasite Ascogregarina taiwanensis, and the inhibition of Ae. aegypti egg development by Ae. albopictus larvae. Habitat segregation has been proposed as a mechanism promoting the coexistence of the two species through avoidance of direct competition. Aedes aegypti predominates in urban areas, Ae. albopictus in rural ones, and both species coexist in the suburbs. There is also evidence that in certain areas, habitat segregation in terms of distance from the coast can influence the distribution of both species. Another possible cause of the rapid disappearance of Ae. aegypti is reproductive interference between the species. According to this hypothesis, asymmetric effects of interspecific mating favor Ae. albopictus. This type of reproductive interference can result in the elimination of sympatric populations of the affected species and can be one of the major causes for the swiftness with which Ae. aegypti disappeared from some places in the Americas following invasions by Ae. albopictus.

  16. Factors determining the potential for onward transmission of variant Creutzfeldt-Jakob disease via surgical instruments.

    PubMed

    Garske, Tini; Ward, Hester J T; Clarke, Paul; Will, Robert G; Ghani, Azra C

    2006-12-22

    While the number of variant Creutzfeldt-Jakob disease (vCJD) cases continues to decline, concern has been raised that transmission could occur directly from one person to another through routes including the transfer of blood and shared use of surgical instruments. Here we firstly present data on the surgical procedures undertaken on vCJD patients prior to onset of clinical symptoms, which supports the hypothesis that cases via this route are possible. We then apply a mathematical framework to assess the potential for self-sustaining epidemics via surgical procedures. Data from hospital episode statistics on the rates of high- and medium-risk procedures in the UK were used to estimate model parameters, and sensitivity to other unknown parameters about surgically transmitted vCJD was assessed. Our results demonstrate that a key uncertainty determining the scale of an epidemic and whether it is self-sustaining is the number of times a single instrument is re-used, alongside the infectivity of contaminated instruments and the effectiveness of cleaning. A survey into the frequency of re-use of surgical instruments would help reduce these uncertainties.

  17. Hepatitis C virus molecular evolution: Transmission, disease progression and antiviral therapy

    PubMed Central

    Preciado, Maria Victoria; Valva, Pamela; Escobar-Gutierrez, Alejandro; Rahal, Paula; Ruiz-Tovar, Karina; Yamasaki, Lilian; Vazquez-Chacon, Carlos; Martinez-Guarneros, Armando; Carpio-Pedroza, Juan Carlos; Fonseca-Coronado, Salvador; Cruz-Rivera, Mayra

    2014-01-01

    Hepatitis C virus (HCV) infection represents an important public health problem worldwide. Reduction of HCV morbidity and mortality is a current challenge owned to several viral and host factors. Virus molecular evolution plays an important role in HCV transmission, disease progression and therapy outcome. The high degree of genetic heterogeneity characteristic of HCV is a key element for the rapid adaptation of the intrahost viral population to different selection pressures (e.g., host immune responses and antiviral therapy). HCV molecular evolution is shaped by different mechanisms including a high mutation rate, genetic bottlenecks, genetic drift, recombination, temporal variations and compartmentalization. These evolutionary processes constantly rearrange the composition of the HCV intrahost population in a staging manner. Remarkable advances in the understanding of the molecular mechanism controlling HCV replication have facilitated the development of a plethora of direct-acting antiviral agents against HCV. As a result, superior sustained viral responses have been attained. The rapidly evolving field of anti-HCV therapy is expected to broad its landscape even further with newer, more potent antivirals, bringing us one step closer to the interferon-free era. PMID:25473152

  18. Inferring host-parasite relationships using stable isotopes: implications for disease transmission and host specificity.

    PubMed

    Stapp, Paul; Salkeld, Daniel J

    2009-11-01

    Identifying the roles of different hosts and vectors is a major challenge in the study of the ecology of diseases caused by multi-host pathogens. Intensive field studies suggested that grasshopper mice (Onychomys leucogaster) help spread the bacterium that causes plague (Yersinia pestis) in prairie dog colonies by sharing fleas with prairie dogs (Cynomys ludovicianus); yet conclusive evidence that prairie dog fleas (Oropsylla hirsuta) feed on grasshopper mice is lacking. Using stable nitrogen isotope analysis, we determined that many blood-engorged O. hirsuta collected from wild grasshopper mice apparently contained blood meals of prairie dogs. These results suggest that grasshopper mice may be infected with Y. pestis via mechanisms other than flea feeding, e.g., early phase or mechanical transmission or scavenging carcasses, and raise questions about the ability of grasshopper mice to maintain Y. pestis in prairie dog colonies during years between plague outbreaks. They also indicate that caution may be warranted when inferring feeding relationships based purely on the occurrence of fleas or other haematophagous ectoparasites on hosts. Stable-isotope analysis may complement or provide a useful alternative to immunological or molecular techniques for identifying hosts of cryptically feeding ectoparasites, and for clarifying feeding relationships in studies of host-parasite interactions. PMID:19967881

  19. Experimental oral transmission of chronic wasting disease to red deer (Cervus elaphus elaphus): Early detection and late stage distribution of protease-resistant prion protein

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Chronic wasting disease CWD is the transmissible spongiform encephalopathy or prion disease of wild and farmed cervid ruminants, including Rocky Mountain elk (Cervus elaphus nelsoni), white tailed deer (Odocoileus virginianus), mule deer (Odocoileus hemionus), or moose (Alces alces). Reliable data ...

  20. The Bordetella bronchiseptica type III secretion system is required for persistence and disease severity but not transmission in swine.

    PubMed

    Nicholson, Tracy L; Brockmeier, Susan L; Loving, Crystal L; Register, Karen B; Kehrli, Marcus E; Shore, Sarah M

    2014-03-01

    Bordetella bronchiseptica is pervasive in swine populations and plays multiple roles in respiratory disease. Most studies addressing virulence factors of B. bronchiseptica utilize isolates derived from hosts other than pigs in conjunction with rodent infection models. Based on previous in vivo mouse studies, we hypothesized that the B. bronchiseptica type III secretion system (T3SS) would be required for maximal disease severity and persistence in the swine lower respiratory tract. To examine the contribution of the T3SS to the pathogenesis of B. bronchiseptica in swine, we compared the abilities of a virulent swine isolate and an isogenic T3SS mutant to colonize, cause disease, and be transmitted from host to host. We found that the T3SS is required for maximal persistence throughout the lower swine respiratory tract and contributed significantly to the development of nasal lesions and pneumonia. However, the T3SS mutant and the wild-type parent are equally capable of transmission among swine by both direct and indirect routes, demonstrating that transmission can occur even with attenuated disease. Our data further suggest that the T3SS skews the adaptive immune response in swine by hindering the development of serum anti-Bordetella antibody levels and inducing an interleukin-10 (IL-10) cell-mediated response, likely contributing to the persistence of B. bronchiseptica in the respiratory tract. Overall, our results demonstrate that the Bordetella T3SS is required for maximal persistence and disease severity in pigs, but not for transmission.

  1. A Rare Case of Transfusion Transmission of Hepatitis A Virus to Two Patients with Haematological Disease

    PubMed Central

    da Silva, Suely Gonçalves Cordeiro; Leon, Luciane Almeida Amado; Alves, Gilda; Brito, Selma Magalhães; Sandes, Valcieny de Souza; Lima, Magda Maria Adorno Ferreira; Nogueira, Marta Colares; Tavares, Rita de Cássia Barbosa da Silva; Dobbin, Jane; Apa, Alexandre; de Paula, Vanessa Salete; Oliveira, Jaqueline Mendes de Oliveira; Pinto, Marcelo Alves; Ferreira Jr, Orlando da Costa; Motta, Iara de Jesus Ferreira

    2016-01-01

    Summary Background This paper describes the transmission of hepatitis A virus (HAV) to two blood recipients from a healthy donor that later presented to the blood bank with jaundice. Methods The RNA of HAV was detected by qualitative nested reverse transcription polymerase chain reaction (nested RT-PCR) and quantified by real-time RT-PCR. HAV RNA samples were genotyped by direct sequencing of PCR products. A sequence from a fragment of 168 bp from the VP1/2A HAV region was used to construct a phylogenetic tree. Case Report A 31-year-old male donor accepted for donation of a whole blood unit returned to the blood bank with clinical jaundice 20 days after donation. His serological and NAT tests were negative for HBV and HCV. Serological tests for HAV IgM and IgG were negative on donation sample but positive on follow-up sample, confirming donor's HAV acute infection. Both recipients of red blood cells (R1) and platelet concentrate (R2) from the same implicated donation were HAV IgM-negative and IgG-positive. Qualitative PCR was positive on samples from all three individuals and phylogenetic analysis of viruses proved HAV transmission to the two recipients of blood products. HAV viral load on donor follow-up sample and the platelet recipient was 1.3 and 1.5 × 103 IU/ml, respectively. The RBC recipient, also infected by HCV, was undergoing bone marrow transplantation and died from fulminant hepatitis, 26 days after the implicated HAV transfusion. Conclusion The blood donor, a garbage collector, spontaneously returned to the blood bank when developing jaundice. This highlights the importance of donor education to immediately report to blood banks of any signs and symptoms related to infectious disease developed after blood donation. The fact that one immunocompromised patient with HCV infection died from fulminant hepatitis after receiving a HAV-contaminated platelet transfusion underpins the importance of a HAV vaccination program for these group of patients. PMID

  2. Puffy Skin Disease Is an Emerging Transmissible Condition in Rainbow Trout Oncorhynchus mykiss Walbaum

    PubMed Central

    Cano, Irene; Verner-Jeffreys, David W.; van Aerle, Ronny; Paley, Richard K.; Peeler, Edmund J.; Green, Matthew; Rimmer, Georgina S. E.; Savage, Jacqueline; Joiner, Claire L.; Bayley, Amanda E.; Mewett, Jason; Hulland, Jonathan; Feist, Stephen W.

    2016-01-01

    The transmission of puffy skin disease (PSD) to rainbow trout Oncorhynchus mykiss Walbaum was tested in the laboratory by conducting co-habitation challenges with puffy skin (PS)-affected fish (Trojans) collected from the field. Two separate challenges were conducted using Trojans sourced from two different sites and diploid (first trial) or triploid (second trial) naïve fish. PSD-specific clinical signs were observed in both groups of naïve fish, with 66% of the fish sampled during the challenges showing signs of varying severity. The first clinical features of PSD were presented as white oval skin patches on one or both flanks 15–21 days post-challenge (dpc). The extent of the lesions ranged from 10 to 90% of the body surface, depending on the severity of the lesion. Both the severity and number of affected fish increased during the challenge. Macroscopically, oedema of the skin and multifocal petechial haemorrhaging were observed towards the end of the trials. Abnormal fish behaviour consisting of “flashing” and excessive mucous production was noted from 15 dpc onwards. Fish with severe PSD lesions also displayed inappetence and associated emaciation. Rodlet cells were observed in 41% of the fresh skin scrapes analysed from the second trial. Histologically epidermal oedema was observed in 31% of the naive fish showing gross pathology, with additional 12% displaying epidermal hyperplasia, mostly observed at the end of the challenge. Other concomitant features of the PSD lesions in challenged fish were epithelial erosion and sloughing, and occasionally mild or focal inflammation. No consistent pathology of internal organs was observed. The parasites Ichthyophthirius multifiliis and Ichthyobodo necator were observed in skin samples of a proportion of naïve challenged fish and in Trojans but not in control fish. The presence of these and other known fish pathogens in the skin of PSD-fish was confirmed by high-throughput sequencing analysis. In summary, we

  3. Puffy Skin Disease Is an Emerging Transmissible Condition in Rainbow Trout Oncorhynchus mykiss Walbaum.

    PubMed

    Cano, Irene; Verner-Jeffreys, David W; van Aerle, Ronny; Paley, Richard K; Peeler, Edmund J; Green, Matthew; Rimmer, Georgina S E; Savage, Jacqueline; Joiner, Claire L; Bayley, Amanda E; Mewett, Jason; Hulland, Jonathan; Feist, Stephen W

    2016-01-01

    The transmission of puffy skin disease (PSD) to rainbow trout Oncorhynchus mykiss Walbaum was tested in the laboratory by conducting co-habitation challenges with puffy skin (PS)-affected fish (Trojans) collected from the field. Two separate challenges were conducted using Trojans sourced from two different sites and diploid (first trial) or triploid (second trial) naïve fish. PSD-specific clinical signs were observed in both groups of naïve fish, with 66% of the fish sampled during the challenges showing signs of varying severity. The first clinical features of PSD were presented as white oval skin patches on one or both flanks 15-21 days post-challenge (dpc). The extent of the lesions ranged from 10 to 90% of the body surface, depending on the severity of the lesion. Both the severity and number of affected fish increased during the challenge. Macroscopically, oedema of the skin and multifocal petechial haemorrhaging were observed towards the end of the trials. Abnormal fish behaviour consisting of "flashing" and excessive mucous production was noted from 15 dpc onwards. Fish with severe PSD lesions also displayed inappetence and associated emaciation. Rodlet cells were observed in 41% of the fresh skin scrapes analysed from the second trial. Histologically epidermal oedema was observed in 31% of the naive fish showing gross pathology, with additional 12% displaying epidermal hyperplasia, mostly observed at the end of the challenge. Other concomitant features of the PSD lesions in challenged fish were epithelial erosion and sloughing, and occasionally mild or focal inflammation. No consistent pathology of internal organs was observed. The parasites Ichthyophthirius multifiliis and Ichthyobodo necator were observed in skin samples of a proportion of naïve challenged fish and in Trojans but not in control fish. The presence of these and other known fish pathogens in the skin of PSD-fish was confirmed by high-throughput sequencing analysis. In summary, we have

  4. Airborne thermography or infrared remote sensing.

    PubMed

    Goillot, C C

    1975-01-01

    Airborne thermography is part of the more general remote sensing activity. The instruments suitable for image display are infrared line scanners. A great deal of interest has developed during the past 10 years in airborne thermal remote sensing and many applications are in progress. Infrared scanners on board a satellite are used for observation of cloud cover; airborne infrared scanners are used for forest fire detection, heat budget of soils, detecting insect attack, diseases, air pollution damage, water stress, salinity stress on vegetation, only to cite some main applications relevant to agronomy. Using this system it has become possible to get a 'picture' of our thermal environment.

  5. Transmissible amyloid.

    PubMed

    Tjernberg, L O; Rising, A; Johansson, J; Jaudzems, K; Westermark, P

    2016-08-01

    There are around 30 human diseases associated with protein misfolding and amyloid formation, each one caused by a certain protein or peptide. Many of these diseases are lethal and together they pose an enormous burden to society. The prion protein has attracted particular interest as being shown to be the pathogenic agent in transmissible diseases such as kuru, Creutzfeldt-Jakob disease and bovine spongiform encephalopathy. Whether similar transmission could occur also in other amyloidoses such as Alzheimer's disease, Parkinson's disease and serum amyloid A amyloidosis is a matter of intense research and debate. Furthermore, it has been suggested that novel biomaterials such as artificial spider silk are potentially amyloidogenic. Here, we provide a brief introduction to amyloid, prions and other proteins involved in amyloid disease and review recent evidence for their potential transmission. We discuss the similarities and differences between amyloid and silk, as well as the potential hazards associated with protein-based biomaterials. PMID:27002185

  6. Dynamic Transmission Economic Evaluation of Infectious Disease Interventions in Low- and Middle-Income Countries: A Systematic Literature Review.

    PubMed

    Drake, Tom L; Devine, Angela; Yeung, Shunmay; Day, Nicholas P J; White, Lisa J; Lubell, Yoel

    2016-02-01

    Economic evaluation using dynamic transmission models is important for capturing the indirect effects of infectious disease interventions. We examine the use of these methods in low- and middle-income countries, where infectious diseases constitute a major burden. This review is comprised of two parts: (1) a summary of dynamic transmission economic evaluations across all disease areas published between 2011 and mid-2014 and (2) an in-depth review of mosquito-borne disease studies focusing on health economic methods and reporting. Studies were identified through a systematic search of the MEDLINE database and supplemented by reference list screening. Fifty-seven studies were eligible for inclusion in the all-disease review. The most common subject disease was HIV/AIDS, followed by malaria. A diverse range of modelling methods, outcome metrics and sensitivity analyses were used, indicating little standardisation. Seventeen studies were included in the mosquito-borne disease review. With notable exceptions, most studies did not employ economic evaluation methods beyond calculating a cost-effectiveness ratio or net benefit. Many did not adhere to health care economic evaluations reporting guidelines, particularly with respect to full model reporting and uncertainty analysis. We present a summary of the state-of-the-art and offer recommendations for improved implementation and reporting of health economic methods in this crossover discipline.

  7. The Role of the Home Environment in the Transmission of Infectious Diseases.

    ERIC Educational Resources Information Center

    Kagan, Lori J.; Aiello, Allison E.; Larson, Elaine

    2002-01-01

    Examines current health care literature on the microbiology of the home environment, summarizing evidence of transmission within the home and assessing the effectiveness of cleaning practices and products. The article focuses on the kitchen, bathroom, and laundry room, then looks at routes of transmission of infection within the home and discusses…

  8. Population-level differences in disease transmission: A Bayesian analysis of multiple smallpox epidemics

    PubMed Central

    Elderd, Bret D.; Dwyer, Greg; Dukic, Vanja

    2013-01-01

    Estimates of a disease’s basic reproductive rate R0 play a central role in understanding outbreaks and planning intervention strategies. In many calculations of R0, a simplifying assumption is that different host populations have effectively identical transmission rates. This assumption can lead to an underestimate of the overall uncertainty associated with R0, which, due to the non-linearity of epidemic processes, may result in a mis-estimate of epidemic intensity and miscalculated expenditures associated with public-health interventions. In this paper, we utilize a Bayesian method for quantifying the overall uncertainty arising from differences in population-specific basic reproductive rates. Using this method, we fit spatial and non-spatial susceptible-exposed-infected-recovered (SEIR) models to a series of 13 smallpox outbreaks. Five outbreaks occurred in populations that had been previously exposed to smallpox, while the remaining eight occurred in Native-American populations that were naïve to the disease at the time. The Native-American outbreaks were close in a spatial and temporal sense. Using Bayesian Information Criterion (BIC), we show that the best model includes population-specific R0 values. These differences in R0 values may, in part, be due to differences in genetic background, social structure, or food and water availability. As a result of these inter-population differences, the overall uncertainty associated with the “population average” value of smallpox R0 is larger, a finding that can have important consequences for controlling epidemics. In general, Bayesian hierarchical models are able to properly account for the uncertainty associated with multiple epidemics, provide a clearer understanding of variability in epidemic dynamics, and yield a better assessment of the range of potential risks and consequences that decision makers face. PMID:24021521

  9. Transmission dynamics of rabies virus in Thailand: Implications for disease control

    PubMed Central

    Denduangboripant, Jessada; Wacharapluesadee, Supaporn; Lumlertdacha, Boonlert; Ruankaew, Nipada; Hoonsuwan, Wirongrong; Puanghat , Apirom; Hemachudha, Thiravat

    2005-01-01

    Background In Thailand, rabies remains a neglected disease with authorities continuing to rely on human death statistics while ignoring the financial burden resulting from an enormous increase in post-exposure prophylaxis. Past attempts to conduct a mass dog vaccination and sterilization program have been limited to Bangkok city and have not been successful. We have used molecular epidemiology to define geographic localization of rabies virus phylogroups and their pattern of spread in Thailand. Methods We analyzed 239 nucleoprotein gene sequences from animal and human brain samples collected from all over Thailand between 1998 and 2002. We then reconstructed a phylogenetic tree correlating these data with geographical information. Results All sequences formed a monophyletic tree of 2 distinct phylogroups, TH1 and TH2. Three subgroups were identified in the TH1 subgroup and were distributed in the middle region of the country. Eight subgroups of TH2 viruses were identified widely distributed throughout the country overlapping the TH1 territory. There was a correlation between human-dependent transportation routes and the distribution of virus. Conclusion Inter-regional migration paths of the viruses might be correlated with translocation of dogs associated with humans. Interconnecting factors between human socioeconomic and population density might determine the transmission dynamics of virus in a rural-to-urban polarity. The presence of 2 or more rabies virus groups in a location might be indicative of a gene flow, reflecting a translocation of dogs within such region and adjacent areas. Different approaches may be required for rabies control based on the homo- or heterogeneity of the virus. Areas containing homogeneous virus populations should be targeted first. Control of dog movement associated with humans is essential. PMID:15985183

  10. A History of Chagas Disease Transmission, Control, and Re-Emergence in Peri-Rural La Joya, Peru

    PubMed Central

    Delgado, Stephen; Castillo Neyra, Ricardo; Quispe Machaca, Víctor R.; Ancca Juárez, Jenny; Chou Chu, Lily; Verastegui, Manuela Renee; Moscoso Apaza, Giovanna M.; Bocángel, César D.; Tustin, Aaron W.; Sterling, Charles R.; Comrie, Andrew C.; Náquira, César; Cornejo del Carpio, Juan G.; Gilman, Robert H.; Bern, Caryn; Levy, Michael Z.

    2011-01-01

    Background The history of Chagas disease control in Peru and many other nations is marked by scattered and poorly documented vector control campaigns. The complexities of human migration and sporadic control campaigns complicate evaluation of the burden of Chagas disease and dynamics of Trypanosoma cruzi transmission. Methodology/Principal Findings We conducted a cross-sectional serological and entomological study to evaluate temporal and spatial patterns of T. cruzi transmission in a peri-rural region of La Joya, Peru. We use a multivariate catalytic model and Bayesian methods to estimate incidence of infection over time and thereby elucidate the complex history of transmission in the area. Of 1,333 study participants, 101 (7.6%; 95% CI: 6.2–9.0%) were confirmed T. cruzi seropositive. Spatial clustering of parasitic infection was found in vector insects, but not in human cases. Expanded catalytic models suggest that transmission was interrupted in the study area in 1996 (95% credible interval: 1991–2000), with a resultant decline in the average annual incidence of infection from 0.9% (95% credible interval: 0.6–1.3%) to 0.1% (95% credible interval: 0.005–0.3%). Through a search of archival newspaper reports, we uncovered documentation of a 1995 vector control campaign, and thereby independently validated the model estimates. Conclusions/Significance High levels of T. cruzi transmission had been ongoing in peri-rural La Joya prior to interruption of parasite transmission through a little-documented vector control campaign in 1995. Despite the efficacy of the 1995 control campaign, T. cruzi was rapidly reemerging in vector populations in La Joya, emphasizing the need for continuing surveillance and control at the rural-urban interface. PMID:21364970

  11. Global Climate Change and Its Potential Impact on Disease Transmission by Salinity-Tolerant Mosquito Vectors in Coastal Zones

    PubMed Central

    Ramasamy, Ranjan; Surendran, Sinnathamby Noble

    2012-01-01

    Global climate change can potentially increase the transmission of mosquito vector-borne diseases such as malaria, lymphatic filariasis, and dengue in many parts of the world. These predictions are based on the effects of changing temperature, rainfall, and humidity on mosquito breeding and survival, the more rapid development of ingested pathogens in mosquitoes and the more frequent blood feeds at moderately higher ambient temperatures. An expansion of saline and brackish water bodies (water with <0.5 ppt or parts per thousand, 0.5–30 ppt and >30 ppt salt are termed fresh, brackish, and saline respectively) will also take place as a result of global warming causing a rise in sea levels in coastal zones. Its possible impact on the transmission of mosquito-borne diseases has, however, not been adequately appreciated. The relevant impacts of global climate change on the transmission of mosquito-borne diseases in coastal zones are discussed with reference to the Ross–McDonald equation and modeling studies. Evidence is presented to show that an expansion of brackish water bodies in coastal zones can increase the densities of salinity-tolerant mosquitoes like Anopheles sundaicus and Culex sitiens, and lead to the adaptation of fresh water mosquito vectors like Anopheles culicifacies, Anopheles stephensi, Aedes aegypti, and Aedes albopictus to salinity. Rising sea levels may therefore act synergistically with global climate change to increase the transmission of mosquito-borne diseases in coastal zones. Greater attention therefore needs to be devoted to monitoring disease incidence and preimaginal development of vector mosquitoes in artificial and natural coastal brackish/saline habitats. It is important that national and international health agencies are aware of the increased risk of mosquito-borne diseases in coastal zones and develop preventive and mitigating strategies. Application of appropriate counter measures can greatly reduce the potential for

  12. Global climate change and its potential impact on disease transmission by salinity-tolerant mosquito vectors in coastal zones.

    PubMed

    Ramasamy, Ranjan; Surendran, Sinnathamby Noble

    2012-01-01

    Global climate change can potentially increase the transmission of mosquito vector-borne diseases such as malaria, lymphatic filariasis, and dengue in many parts of the world. These predictions are based on the effects of changing temperature, rainfall, and humidity on mosquito breeding and survival, the more rapid development of ingested pathogens in mosquitoes and the more frequent blood feeds at moderately higher ambient temperatures. An expansion of saline and brackish water bodies (water with <0.5 ppt or parts per thousand, 0.5-30 ppt and >30 ppt salt are termed fresh, brackish, and saline respectively) will also take place as a result of global warming causing a rise in sea levels in coastal zones. Its possible impact on the transmission of mosquito-borne diseases has, however, not been adequately appreciated. The relevant impacts of global climate change on the transmission of mosquito-borne diseases in coastal zones are discussed with reference to the Ross-McDonald equation and modeling studies. Evidence is presented to show that an expansion of brackish water bodies in coastal zones can increase the densities of salinity-tolerant mosquitoes like Anopheles sundaicus and Culex sitiens, and lead to the adaptation of fresh water mosquito vectors like Anopheles culicifacies, Anopheles stephensi, Aedes aegypti, and Aedes albopictus to salinity. Rising sea levels may therefore act synergistically with global climate change to increase the transmission of mosquito-borne diseases in coastal zones. Greater attention therefore needs to be devoted to monitoring disease incidence and preimaginal development of vector mosquitoes in artificial and natural coastal brackish/saline habitats. It is important that national and international health agencies are aware of the increased risk of mosquito-borne diseases in coastal zones and develop preventive and mitigating strategies. Application of appropriate counter measures can greatly reduce the potential for increased

  13. Climate, environmental and socio-economic change: weighing up the balance in vector-borne disease transmission.

    PubMed

    Parham, Paul E; Waldock, Joanna; Christophides, George K; Hemming, Deborah; Agusto, Folashade; Evans, Katherine J; Fefferman, Nina; Gaff, Holly; Gumel, Abba; LaDeau, Shannon; Lenhart, Suzanne; Mickens, Ronald E; Naumova, Elena N; Ostfeld, Richard S; Ready, Paul D; Thomas, Matthew B; Velasco-Hernandez, Jorge; Michael, Edwin

    2015-04-01

    Arguably one of the most important effects of climate change is the potential impact on human health. While this is likely to take many forms, the implications for future transmission of vector-borne diseases (VBDs), given their ongoing contribution to global disease burden, are both extremely important and highly uncertain. In part, this is owing not only to data limitations and methodological challenges when integrating climate-driven VBD models and climate change projections, but also, perhaps most crucially, to the multitude of epidemiological, ecological and socio-economic factors that drive VBD transmission, and this complexity has generated considerable debate over the past 10-15 years. In this review, we seek to elucidate current knowledge around this topic, identify key themes and uncertainties, evaluate ongoing challenges and open research questions and, crucially, offer some solutions for the field. Although many of these challenges are ubiquitous across multiple VBDs, more specific issues also arise in different vector-pathogen systems.

  14. 21 CFR 1271.145 - Prevention of the introduction, transmission, or spread of communicable diseases.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... spread of communicable diseases. 1271.145 Section 1271.145 Food and Drugs FOOD AND DRUG ADMINISTRATION... diseases. You must recover, process, store, label, package, and distribute HCT/Ps, and screen and test cell... diseases....

  15. 21 CFR 1271.145 - Prevention of the introduction, transmission, or spread of communicable diseases.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... spread of communicable diseases. 1271.145 Section 1271.145 Food and Drugs FOOD AND DRUG ADMINISTRATION... diseases. You must recover, process, store, label, package, and distribute HCT/Ps, and screen and test cell... diseases....

  16. 21 CFR 1271.145 - Prevention of the introduction, transmission, or spread of communicable diseases.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... spread of communicable diseases. 1271.145 Section 1271.145 Food and Drugs FOOD AND DRUG ADMINISTRATION... diseases. You must recover, process, store, label, package, and distribute HCT/Ps, and screen and test cell... diseases....

  17. 21 CFR 1271.145 - Prevention of the introduction, transmission, or spread of communicable diseases.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... spread of communicable diseases. 1271.145 Section 1271.145 Food and Drugs FOOD AND DRUG ADMINISTRATION... diseases. You must recover, process, store, label, package, and distribute HCT/Ps, and screen and test cell... diseases....

  18. The impact of climate change on infectious disease transmission: perceptions of CDC health professionals in Shanxi Province, China.

    PubMed

    Wei, Junni; Hansen, Alana; Zhang, Ying; Li, Hong; Liu, Qiyong; Sun, Yehuan; Xue, Shulian; Zhao, Shufang; Bi, Peng

    2014-01-01

    There have been increasing concerns about the challenge of emerging and re-emerging infectious diseases due to climate change, especially in developing countries including China. Health professionals play a significant role in the battle to control and prevent infectious diseases. This study therefore aims to investigate the perceptions and attitudes of health professionals at the Centers for Disease Control and Prevention (CDC) in different levels in China, and to consider adaptation measures to deal with the challenge of climate change. In 2013, a cross-sectional questionnaire survey was undertaken among 314 staff in CDCs in Shanxi Province, China, whose routine work involves disease control and prevention. Data were analyzed using descriptive methods and logistic regression. A majority of the CDC staff were aware of the health risks from climate change, especially its impacts on infectious disease transmission in their jurisdictions, and believed climate change might bring about both temporal and spatial change in transmission patterns. It was thought that adaptation measures should be established including: strengthening/improving currently existing disease surveillance systems and vector monitoring; building CDC capacity in terms of infrastructure and in-house health professional training; development and refinement of relevant legislation, policies and guidelines; better coordination among various government departments; the involvement of the community in infectious disease interventions; and collaborative research with other institutions. This study provides a snapshot of the understanding of CDC staff regarding climate change risks relevant to infectious diseases and adaptation in China. Results may help inform future efforts to develop adaptation measures to minimize infectious disease risks due to climate change. PMID:25285440

  19. The impact of climate change on infectious disease transmission: perceptions of CDC health professionals in Shanxi Province, China.

    PubMed

    Wei, Junni; Hansen, Alana; Zhang, Ying; Li, Hong; Liu, Qiyong; Sun, Yehuan; Xue, Shulian; Zhao, Shufang; Bi, Peng

    2014-01-01

    There have been increasing concerns about the challenge of emerging and re-emerging infectious diseases due to climate change, especially in developing countries including China. Health professionals play a significant role in the battle to control and prevent infectious diseases. This study therefore aims to investigate the perceptions and attitudes of health professionals at the Centers for Disease Control and Prevention (CDC) in different levels in China, and to consider adaptation measures to deal with the challenge of climate change. In 2013, a cross-sectional questionnaire survey was undertaken among 314 staff in CDCs in Shanxi Province, China, whose routine work involves disease control and prevention. Data were analyzed using descriptive methods and logistic regression. A majority of the CDC staff were aware of the health risks from climate change, especially its impacts on infectious disease transmission in their jurisdictions, and believed climate change might bring about both temporal and spatial change in transmission patterns. It was thought that adaptation measures should be established including: strengthening/improving currently existing disease surveillance systems and vector monitoring; building CDC capacity in terms of infrastructure and in-house health professional training; development and refinement of relevant legislation, policies and guidelines; better coordination among various government departments; the involvement of the community in infectious disease interventions; and collaborative research with other institutions. This study provides a snapshot of the understanding of CDC staff regarding climate change risks relevant to infectious diseases and adaptation in China. Results may help inform future efforts to develop adaptation measures to minimize infectious disease risks due to climate change.

  20. The role of remote sensing and GIS for spatial prediction of vector-borne diseases transmission: a systematic review.

    PubMed

    Palaniyandi, M

    2012-12-01

    There have been several attempts made to the appreciation of remote sensing and GIS for the study of vectors, biodiversity, vector presence, vector abundance and the vector-borne diseases with respect to space and time. This study was made for reviewing and appraising the potential use of remote sensing and GIS applications for spatial prediction of vector-borne diseases transmission. The nature of the presence and the abundance of vectors and vector-borne diseases, disease infection and the disease transmission are not ubiquitous and are confined with geographical, environmental and climatic factors, and are localized. The presence of vectors and vector-borne diseases is most complex in nature, however, it is confined and fueled by the geographical, climatic and environmental factors including man-made factors. The usefulness of the present day availability of the information derived from the satellite data including vegetation indices of canopy cover and its density, soil types, soil moisture, soil texture, soil depth, etc. is integrating the information in the expert GIS engine for the spatial analysis of other geoclimatic and geoenvironmental variables. The present study gives the detailed information on the classical studies of the past and present, and the future role of remote sensing and GIS for the vector-borne diseases control. The ecological modeling directly gives us the relevant information to understand the spatial variation of the vector biodiversity, vector presence, vector abundance and the vector-borne diseases in association with geoclimatic and the environmental variables. The probability map of the geographical distribution and seasonal variations of horizontal and vertical distribution of vector abundance and its association with vector -borne diseases can be obtained with low cost remote sensing and GIS tool with reliable data and speed.

  1. Object-based assessment of burn severity in diseased forests using high-spatial and high-spectral resolution MASTER airborne imagery

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Metz, Margaret R.; Rizzo, David M.; Dillon, Whalen W.; Meentemeyer, Ross K.

    2015-04-01

    Forest ecosystems are subject to a variety of disturbances with increasing intensities and frequencies, which may permanently change the trajectories of forest recovery and disrupt the ecosystem services provided by trees. Fire and invasive species, especially exotic disease-causing pathogens and insects, are examples of disturbances that together could pose major threats to forest health. This study examines the impacts of fire and exotic disease (sudden oak death) on forests, with an emphasis on the assessment of post-fire burn severity in a forest where trees have experienced three stages of disease progression pre-fire: early-stage (trees retaining dried foliage and fine twigs), middle-stage (trees losing fine crown fuels), and late-stage (trees falling down). The research was conducted by applying Geographic Object-Based Image Analysis (GEOBIA) to MASTER airborne images that were acquired immediately following the fire for rapid assessment and contained both high-spatial (4 m) and high-spectral (50 bands) resolutions. Although GEOBIA has gradually become a standard tool for analyzing high-spatial resolution imagery, high-spectral resolution data (dozens to hundreds of bands) can dramatically reduce computation efficiency in the process of segmentation and object-based variable extraction, leading to complicated variable selection for succeeding modeling. Hence, we also assessed two widely used band reduction algorithms, PCA (principal component analysis) and MNF (minimum noise fraction), for the delineation of image objects and the subsequent performance of burn severity models using either PCA or MNF derived variables. To increase computation efficiency, only the top 5 PCA and MNF and top 10 PCA and MNF components were evaluated, which accounted for 10% and 20% of the total number of the original 50 spectral bands, respectively. Results show that if no band reduction was applied the models developed for the three stages of disease progression had relatively

  2. Role of social networks in shaping disease transmission during a community outbreak of 2009 H1N1 pandemic influenza.

    PubMed

    Cauchemez, Simon; Bhattarai, Achuyt; Marchbanks, Tiffany L; Fagan, Ryan P; Ostroff, Stephen; Ferguson, Neil M; Swerdlow, David

    2011-02-15

    Evaluating the impact of different social networks on the spread of respiratory diseases has been limited by a lack of detailed data on transmission outside the household setting as well as appropriate statistical methods. Here, from data collected during a H1N1 pandemic (pdm) influenza outbreak that started in an elementary school and spread in a semirural community in Pennsylvania, we quantify how transmission of influenza is affected by social networks. We set up a transmission model for which parameters are estimated from the data via Markov chain Monte Carlo sampling. Sitting next to a case or being the playmate of a case did not significantly increase the risk of infection; but the structuring of the school into classes and grades strongly affected spread. There was evidence that boys were more likely to transmit influenza to other boys than to girls (and vice versa), which mimicked the observed assortative mixing among playmates. We also investigated the presence of abnormally high transmission occurring on specific days of the outbreak. Late closure of the school (i.e., when 27% of students already had symptoms) had no significant impact on spread. School-aged individuals (6-18 y) facilitated the introduction and spread of influenza in households, but only about one in five cases aged >18 y was infected by a school-aged household member. This analysis shows the extent to which clearly defined social networks affect influenza transmission, revealing strong between-place interactions with back-and-forth waves of transmission between the school, the community, and the household. PMID:21282645

  3. [Oral transmission of Trypanosoma cruzi : a new epidemiological scenario for Chagas' disease in Colombia and other South American countries].

    PubMed

    Rueda, Karina; Trujillo, Jorge Eduardo; Carranza, Julio César; Vallejo, Gustavo Adolfo

    2014-01-01

    Many cases of infection caused by the oral transmission of Trypanosoma cruzi have been reported during the last decade. These have been due to the contamination of food by faeces from sylvatic triatomines or by leakage from reservoirs in areas where domiciliated vectors have been controlled or where there has been no prior background of domiciliation. The United Nations Food and Agriculture Organization (FAO) and the World Health Organization (WHO) have used epidemiological, clinical and socioeconomic criteria for ranking parasites transmitted by the contamination of food in different areas of the world; T. cruzi was placed tenth in importance amongst a group of 24 parasites in such ranking. Environmental changes such as deforestation and global warming have affected ecotopes and the behaviour of T. cruzi vectors and reservoirs so that these have become displaced to new areas, thereby leading to such new transmission scenario caused by the contamination of food, which requires evaluation in Colombia. The current review deals with the oral transmission of Chagas' disease, emphasising studies aimed at identifying the pertinent risk factors, the triatomine species involved, the physiopathology of oral infection, the parasite's genotypes implicated in this type of transmission in Colombia and other Latin American regions, as well as the need for ongoing epidemiological surveillance and control policies.

  4. [Oral transmission of Trypanosoma cruzi : a new epidemiological scenario for Chagas' disease in Colombia and other South American countries].

    PubMed

    Rueda, Karina; Trujillo, Jorge Eduardo; Carranza, Julio César; Vallejo, Gustavo Adolfo

    2014-01-01

    Many cases of infection caused by the oral transmission of Trypanosoma cruzi have been reported during the last decade. These have been due to the contamination of food by faeces from sylvatic triatomines or by leakage from reservoirs in areas where domiciliated vectors have been controlled or where there has been no prior background of domiciliation. The United Nations Food and Agriculture Organization (FAO) and the World Health Organization (WHO) have used epidemiological, clinical and socioeconomic criteria for ranking parasites transmitted by the contamination of food in different areas of the world; T. cruzi was placed tenth in importance amongst a group of 24 parasites in such ranking. Environmental changes such as deforestation and global warming have affected ecotopes and the behaviour of T. cruzi vectors and reservoirs so that these have become displaced to new areas, thereby leading to such new transmission scenario caused by the contamination of food, which requires evaluation in Colombia. The current review deals with the oral transmission of Chagas' disease, emphasising studies aimed at identifying the pertinent risk factors, the triatomine species involved, the physiopathology of oral infection, the parasite's genotypes implicated in this type of transmission in Colombia and other Latin American regions, as well as the need for ongoing epidemiological surveillance and control policies. PMID:25504253

  5. Intra-epidemic evolutionary dynamics of a Dengue virus type 1 population reveal mutant spectra that correlate with disease transmission.

    PubMed

    Hapuarachchi, Hapuarachchige Chanditha; Koo, Carmen; Kek, Relus; Xu, Helen; Lai, Yee Ling; Liu, Lilac; Kok, Suet Yheng; Shi, Yuan; Chuen, Raphael Lee Tze; Lee, Kim-Sung; Maurer-Stroh, Sebastian; Ng, Lee Ching

    2016-01-01

    Dengue virus (DENV) is currently the most prevalent mosquito-borne viral pathogen. DENVs naturally exist as highly heterogeneous populations. Even though the descriptions on DENV diversity are plentiful, only a few studies have narrated the dynamics of intra-epidemic virus diversity at a fine scale. Such accounts are important to decipher the reciprocal relationship between viral evolutionary dynamics and disease transmission that shape dengue epidemiology. In the current study, we present a micro-scale genetic analysis of a monophyletic lineage of DENV-1 genotype III (epidemic lineage) detected from November 2012 to May 2014. The lineage was involved in an unprecedented dengue epidemic in Singapore during 2013-2014. Our findings showed that the epidemic lineage was an ensemble of mutants (variants) originated from an initial mixed viral population. The composition of mutant spectrum was dynamic and positively correlated with case load. The close interaction between viral evolution and transmission intensity indicated that tracking genetic diversity through time is potentially a useful tool to infer DENV transmission dynamics and thereby, to assess the epidemic risk in a disease control perspective. Moreover, such information is salient to understand the viral basis of clinical outcome and immune response variations that is imperative to effective vaccine design. PMID:26940650

  6. Disease transmission models for public health decision making: toward an approach for designing intervention strategies for Schistosomiasis japonica.

    PubMed Central

    Spear, Robert C; Hubbard, Alan; Liang, Song; Seto, Edmund

    2002-01-01

    Mathematical models of disease transmission processes can serve as platforms for integration of diverse data, including site-specific information, for the purpose of designing strategies for minimizing transmission. A model describing the transmission of schistosomiasis is adapted to incorporate field data typically developed in disease control efforts in the mountainous regions of Sichuan Province in China, with the object of exploring the feasibility of model-based control strategies. The model is studied using computer simulation methods. Mechanistically based models of this sort typically have a large number of parameters that pose challenges in reducing parametric uncertainty to levels that will produce predictions sufficiently precise to discriminate among competing control options. We describe here an approach to parameter estimation that uses a recently developed statistical procedure called Bayesian melding to sequentially reduce parametric uncertainty as field data are accumulated over several seasons. Preliminary results of applying the approach to a historical data set in southwestern Sichuan are promising. Moreover, technologic advances using the global positioning system, remote sensing, and geographic information systems promise cost-effective improvements in the nature and quality of field data. This, in turn, suggests that the utility of the modeling approach will increase over time. PMID:12204826

  7. Intra-epidemic evolutionary dynamics of a Dengue virus type 1 population reveal mutant spectra that correlate with disease transmission.

    PubMed

    Hapuarachchi, Hapuarachchige Chanditha; Koo, Carmen; Kek, Relus; Xu, Helen; Lai, Yee Ling; Liu, Lilac; Kok, Suet Yheng; Shi, Yuan; Chuen, Raphael Lee Tze; Lee, Kim-Sung; Maurer-Stroh, Sebastian; Ng, Lee Ching

    2016-01-01

    Dengue virus (DENV) is currently the most prevalent mosquito-borne viral pathogen. DENVs naturally exist as highly heterogeneous populations. Even though the descriptions on DENV diversity are plentiful, only a few studies have narrated the dynamics of intra-epidemic virus diversity at a fine scale. Such accounts are important to decipher the reciprocal relationship between viral evolutionary dynamics and disease transmission that shape dengue epidemiology. In the current study, we present a micro-scale genetic analysis of a monophyletic lineage of DENV-1 genotype III (epidemic lineage) detected from November 2012 to May 2014. The lineage was involved in an unprecedented dengue epidemic in Singapore during 2013-2014. Our findings showed that the epidemic lineage was an ensemble of mutants (variants) originated from an initial mixed viral population. The composition of mutant spectrum was dynamic and positively correlated with case load. The close interaction between viral evolution and transmission intensity indicated that tracking genetic diversity through time is potentially a useful tool to infer DENV transmission dynamics and thereby, to assess the epidemic risk in a disease control perspective. Moreover, such information is salient to understand the viral basis of clinical outcome and immune response variations that is imperative to effective vaccine design.

  8. Estimating transmission of avian influenza in wild birds from incomplete epizootic data: implications for surveillance and disease spreac

    USGS Publications Warehouse

    Viviane Henaux,; Jane Parmley,; Catherine Soos,; Samuel, Michael D.

    2013-01-01

    Synthesis and applications. Our study highlights the potential of integrating incomplete surveillance data with epizootic models to quantify disease transmission and immunity. This modelling approach provides an important tool to understand spatial and temporal epizootic dynamics and inform disease surveillance. Our findings suggest focusing highly pathogenic avian influenza virus (HPAIv) surveillance on postbreeding areas where mortality of immunologically naïve hatch-year birds is most likely to occur, and collecting serology to enhance HPAIv detection. Our modelling approach can integrate various types of disease data facilitating its use with data from other surveillance programs (as illustrated by the estimation of infection rate during an HPAIv outbreak in mute swansCygnus olor in Europe).

  9. Disease transmission in an extreme environment: nematode parasites infect reindeer during the Arctic winter.

    PubMed

    Carlsson, Anja M; Justin Irvine, R; Wilson, Kenneth; Piertney, Stuart B; Halvorsen, Odd; Coulson, Stephen J; Stien, Audun; Albon, Steve D

    2012-07-01

    Parasitic nematodes are found in almost all wild vertebrate populations but few studies have investigated these host-parasite relationships in the wild. For parasites with free-living stages, the external environment has a major influence on life-history traits, and development and survival is generally low at sub-zero temperatures. For reindeer that inhabit the high Arctic archipelago of Svalbard, parasite transmission is expected to occur in the summer, due to the extreme environmental conditions and the reduced food intake by the host in winter. Here we show experimentally that, contrary to most parasitic nematodes, Marshallagia marshalli of Svalbard reindeer is transmitted during the Arctic winter. Winter transmission was demonstrated by removing parasites in the autumn, using a novel delayed-release anthelmintic bolus, and estimating re-infection rates in reindeer sampled in October, February and April. Larval stages of nematodes were identified using molecular tools, whereas adult stages were identified using microscopy. The abundance of M. marshalli adult worms and L4s increased significantly from October to April, indicating that reindeer were being infected with L3s from the pasture throughout the winter. To our knowledge, this study is the first to experimentally demonstrate over-winter transmission of a gastro-intestinal nematode parasite in a wild animal. Potential mechanisms associated with this unusual transmission strategy are discussed in light of our knowledge of the life-history traits of this parasite.

  10. Contact rates and exposure to inter-species disease transmission in mountain ungulates.

    PubMed

    Richomme, C; Gauthier, D; Fromont, E

    2006-02-01

    The risk for a pathogen to cross the species barrier depends on the rate of efficient contacts between the species. However, contact rates between species have rarely been estimated from observations. Here we estimate contact rates and exposure of chamois Rupicapra rupicapra and Alpine ibex Capra ibex exposed to domestic pasteurellosis and brucellosis carried by sheep or cattle herds summering in mountain pastures. We use field observation data on animal positions treated in a geographic information system (GIS). Comparing 10 pastures, we show that the management of domestic herds influences the risk of inter-species transmission. Exposure to direct transmission of pasteurellosis is high when herds are not guarded nor enclosed, whereas exposure to indirect transmission of brucellosis is increased on epidemiological dangerous points such as salt deposits. Our preliminary results need further investigation, but they underline the importance of both herd management and pathogen transmission mode when the aim is to reduce the risk of contamination of wild populations by a pathogen associated with domestic pathogens.

  11. In utero transmission and tissue distribution of chronic wasting disease-associated prions in free-ranging Rocky Mountain elk.

    PubMed

    Selariu, Anca; Powers, Jenny G; Nalls, Amy; Brandhuber, Monica; Mayfield, Amber; Fullaway, Stephenie; Wyckoff, Christy A; Goldmann, Wilfred; Zabel, Mark M; Wild, Margaret A; Hoover, Edward A; Mathiason, Candace K

    2015-11-01

    The presence of disease-associated prions in tissues and bodily fluids of chronic wasting disease (CWD)-infected cervids has received much investigation, yet little is known about mother-to-offspring transmission of CWD. Our previous work demonstrated that mother-to-offspring transmission is efficient in an experimental setting. To address the question of relevance in a naturally exposed free-ranging population, we assessed maternal and fetal tissues derived from 19 elk dam-calf pairs collected from free-ranging Rocky Mountain elk from north-central Colorado, a known CWD endemic region. Conventional immunohistochemistry identified three of 19 CWD-positive dams, whereas a more sensitive assay [serial protein misfolding cyclic amplification (sPMCA)] detected CWD prion seeding activity (PrPCWD) in 15 of 19 dams. PrPCWD distribution in tissues was widespread, and included the central nervous system (CNS), lymphoreticular system, and reproductive, secretory, excretory and adipose tissues. Interestingly, five of 15 sPMCA-positive dams showed no evidence of PrPCWD in either CNS or lymphoreticular system, sites typically assessed in diagnosing CWD. Analysis of fetal tissues harvested from the 15 sPMCA-positive dams revealed PrPCWD in 80 % of fetuses (12 of 15), regardless of gestational stage. These findings demonstrated that PrPCWD is more abundant in peripheral tissues of CWD-exposed elk than current diagnostic methods suggest, and that transmission of prions from mother to offspring may contribute to the efficient transmission of CWD in naturally exposed cervid populations. PMID:26358706

  12. In utero transmission and tissue distribution of chronic wasting disease-associated prions in free-ranging Rocky Mountain elk

    PubMed Central

    Selariu, Anca; Powers, Jenny G.; Nalls, Amy; Brandhuber, Monica; Mayfield, Amber; Fullaway, Stephenie; Wyckoff, Christy A.; Goldmann, Wilfred; Zabel, Mark M.; Wild, Margaret A.; Hoover, Edward A.

    2015-01-01

    The presence of disease-associated prions in tissues and bodily fluids of chronic wasting disease (CWD)-infected cervids has received much investigation, yet little is known about mother-to-offspring transmission of CWD. Our previous work demonstrated that mother-to-offspring transmission is efficient in an experimental setting. To address the question of relevance in a naturally exposed free-ranging population, we assessed maternal and fetal tissues derived from 19 elk dam–calf pairs collected from free-ranging Rocky Mountain elk from north-central Colorado, a known CWD endemic region. Conventional immunohistochemistry identified three of 19 CWD-positive dams, whereas a more sensitive assay [serial protein misfolding cyclic amplification (sPMCA)] detected CWD prion seeding activity (PrPCWD) in 15 of 19 dams. PrPCWD distribution in tissues was widespread, and included the central nervous system (CNS), lymphoreticular system, and reproductive, secretory, excretory and adipose tissues. Interestingly, five of 15 sPMCA-positive dams showed no evidence of PrPCWD in either CNS or lymphoreticular system, sites typically assessed in diagnosing CWD. Analysis of fetal tissues harvested from the 15 sPMCA-positive dams revealed PrPCWD in 80 % of fetuses (12 of 15), regardless of gestational stage. These findings demonstrated that PrPCWD is more abundant in peripheral tissues of CWD-exposed elk than current diagnostic methods suggest, and that transmission of prions from mother to offspring may contribute to the efficient transmission of CWD in naturally exposed cervid populations. PMID:26358706

  13. In utero transmission and tissue distribution of chronic wasting disease-associated prions in free-ranging Rocky Mountain elk.

    PubMed

    Selariu, Anca; Powers, Jenny G; Nalls, Amy; Brandhuber, Monica; Mayfield, Amber; Fullaway, Stephenie; Wyckoff, Christy A; Goldmann, Wilfred; Zabel, Mark M; Wild, Margaret A; Hoover, Edward A; Mathiason, Candace K

    2015-11-01

    The presence of disease-associated prions in tissues and bodily fluids of chronic wasting disease (CWD)-infected cervids has received much investigation, yet little is known about mother-to-offspring transmission of CWD. Our previous work demonstrated that mother-to-offspring transmission is efficient in an experimental setting. To address the question of relevance in a naturally exposed free-ranging population, we assessed maternal and fetal tissues derived from 19 elk dam-calf pairs collected from free-ranging Rocky Mountain elk from north-central Colorado, a known CWD endemic region. Conventional immunohistochemistry identified three of 19 CWD-positive dams, whereas a more sensitive assay [serial protein misfolding cyclic amplification (sPMCA)] detected CWD prion seeding activity (PrPCWD) in 15 of 19 dams. PrPCWD distribution in tissues was widespread, and included the central nervous system (CNS), lymphoreticular system, and reproductive, secretory, excretory and adipose tissues. Interestingly, five of 15 sPMCA-positive dams showed no evidence of PrPCWD in either CNS or lymphoreticular system, sites typically assessed in diagnosing CWD. Analysis of fetal tissues harvested from the 15 sPMCA-positive dams revealed PrPCWD in 80 % of fetuses (12 of 15), regardless of gestational stage. These findings demonstrated that PrPCWD is more abundant in peripheral tissues of CWD-exposed elk than current diagnostic methods suggest, and that transmission of prions from mother to offspring may contribute to the efficient transmission of CWD in naturally exposed cervid populations.

  14. Social affiliation and contact patterns among white-tailed deer in disparate landscapes: implications for disease transmission

    PubMed Central

    Schauber, Eric M.; Nielsen, Clayton K.; Kjær, Lene J.; Anderson, Charles W.; Storm, Daniel J.

    2015-01-01

    In social species, individuals contact members of the same group much more often than those of other groups, particularly for contacts that could directly transmit disease agents. This disparity in contact rates violates the assumptions of simple disease models, hinders disease spread between groups, and could decouple disease transmission from population density. Social behavior of white-tailed deer has important implications for the long-term dynamics and impact of diseases such as bovine tuberculosis and chronic wasting disease (CWD), so expanding our understanding of their social system is important. White-tailed deer form matrilineal groups, which inhabit stable home ranges that overlap somewhat with others—a pattern intermediate between mass-action and strict territoriality. To quantify how group membership affects their contact rates and document the spectrum of social affiliation, we analyzed location data from global positioning system (GPS) collars on female and juvenile white-tailed deer in 2 study areas: near Carbondale in forest-dominated southern Illinois (2002–2006) and near Lake Shelbyville in agriculture-dominated central Illinois (2006–2009). For each deer dyad (i.e., 2 individual deer with sufficient overlapping GPS data), we measured space-use overlap, correlation of movements, direct contact rate (simultaneous GPS locations < 10 m apart), and indirect contact rate (GPS locations < 10 m apart when offset by 1 or 3 days). Direct contact rates were substantially higher for within-group dyads than between-group dyads, but group membership had little apparent effect on indirect contact rates. The group membership effect on direct contact rates was strongest in winter and weakest in summer, with no apparent difference between study areas. Social affiliations were not dichotomous, with some deer dyads showing loose but positive affiliation. Even for obvious within-group dyads, their strength of affiliation fluctuated between years, seasons, and

  15. Phylogenetic and Pathotypic Characterization of Newcastle Disease Viruses Circulating in South China and Transmission in Different Birds.

    PubMed

    Kang, Yinfeng; Xiang, Bin; Yuan, Runyu; Zhao, Xiaqiong; Feng, Minsha; Gao, Pei; Li, Yanling; Li, Yulian; Ning, Zhangyong; Ren, Tao

    2016-01-01

    Although Newcastle disease virus (NDV) with high pathogenicity has frequently been isolated in poultry in China since 1948, the mode of its transmission among avian species remains largely unknown. Given that various wild bird species have been implicated as sources of transmission, in this study we genotypically and pathotypically characterized 23 NDV isolates collected from chickens, ducks, and pigeons in live bird markets (LBMs) in South China as part of an H7N9 surveillance program during December 2013-February 2014. To simulate the natural transmission of different kinds of animals in LBMs, we selected three representative NDVs-namely, GM, YF18, and GZ289-isolated from different birds to evaluate the pathogenicity and transmission of the indicated viruses in chickens, ducks, and pigeons. Furthermore, to investigate the replication and shedding of NDV in poultry, we inoculated the chickens, ducks, and pigeons with 10(6) EID50 of each virus via intraocular and intranasal routes. Eight hour after infection, the naïve contact groups were housed with those inoculated with each of the viruses as a means to monitor contact transmission. Our results indicated that genetically diverse viruses circulate in LBMs in South China's Guangdong Province and that NDV from different birds have different tissue tropisms and host ranges when transmitted in different birds. We therefore propose the continuous epidemiological surveillance of LBMs to support the prevention of the spread of these viruses in different birds, especially chickens, and highlight the need for studies of the virus-host relationship. PMID:26903997

  16. Phylogenetic and Pathotypic Characterization of Newcastle Disease Viruses Circulating in South China and Transmission in Different Birds

    PubMed Central

    Kang, Yinfeng; Xiang, Bin; Yuan, Runyu; Zhao, Xiaqiong; Feng, Minsha; Gao, Pei; Li, Yanling; Li, Yulian; Ning, Zhangyong; Ren, Tao

    2016-01-01

    Although Newcastle disease virus (NDV) with high pathogenicity has frequently been isolated in poultry in China since 1948, the mode of its transmission among avian species remains largely unknown. Given that various wild bird species have been implicated as sources of transmission, in this study we genotypically and pathotypically characterized 23 NDV isolates collected from chickens, ducks, and pigeons in live bird markets (LBMs) in South China as part of an H7N9 surveillance program during December 2013–February 2014. To simulate the natural transmission of different kinds of animals in LBMs, we selected three representative NDVs—namely, GM, YF18, and GZ289—isolated from different birds to evaluate the pathogenicity and transmission of the indicated viruses in chickens, ducks, and pigeons. Furthermore, to investigate the replication and shedding of NDV in poultry, we inoculated the chickens, ducks, and pigeons with 106 EID50 of each virus via intraocular and intranasal routes. Eight hour after infection, the naïve contact groups were housed with those inoculated with each of the viruses as a means to monitor contact transmission. Our results indicated that genetically diverse viruses circulate in LBMs in South China's Guangdong Province and that NDV from different birds have different tissue tropisms and host ranges when transmitted in different birds. We therefore propose the continuous epidemiological surveillance of LBMs to support the prevention of the spread of these viruses in different birds, especially chickens, and highlight the need for studies of the virus–host relationship. PMID:26903997

  17. The impact of within-herd genetic variation upon inferred transmission trees for foot-and-mouth disease virus.

    PubMed

    Valdazo-González, Begoña; Kim, Jan T; Soubeyrand, Samuel; Wadsworth, Jemma; Knowles, Nick J; Haydon, Daniel T; King, Donald P

    2015-06-01

    Full-genome sequences have been used to monitor the fine-scale dynamics of epidemics caused by RNA viruses. However, the ability of this approach to confidently reconstruct transmission trees is limited by the knowledge of the genetic diversity of viruses that exist within different epidemiological units. In order to address this question, this study investigated the variability of 45 foot-and-mouth disease virus (FMDV) genome sequences (from 33 animals) that were collected during 2007 from eight premises (10 different herds) in the United Kingdom. Bayesian and statistical parsimony analysis demonstrated that these sequences exhibited clustering which was consistent with a transmission scenario describing herd-to-herd spread of the virus. As an alternative to analysing all of the available samples in future epidemics, the impact of randomly selecting one sequence from each of these herds was used to assess cost-effective methods that might be used to infer transmission trees during FMD outbreaks. Using these approaches, 85% and 91% of the resulting topologies were either identical or differed by only one edge from a reference tree comprising all of the sequences generated within the outbreak. The sequence distances that accrued during sequential transmission events between epidemiological units was estimated to be 4.6 nucleotides, although the genetic variability between viruses recovered from chronic carrier animals was higher than between viruses from animals with acute-stage infection: an observation which poses challenges for the use of simple approaches to infer transmission trees. This study helps to develop strategies for sampling during FMD outbreaks, and provides data that will guide the development of further models to support control policies in the event of virus incursions into FMD free countries.

  18. Modeling long distance dispersal of airborne foot-and-mouth disease virus as a polydisperse aerosol - Application to the emergence of a new strain from Egypt to Israel

    NASA Astrophysics Data System (ADS)

    Klausner, Ziv; Klement, Eyal; Fattal, Eyal

    2015-12-01

    Long distance dispersal (LDD) of airborne aerosol of foot-and-mouth disease (FMD) virus was extensively modeled in the literature. Most studies modeled this aerosol in simplistic approach as a passive tracer, neglecting physical and biological mechanisms that affect bio-aerosols such as the FMD aerosol. This approach was justified either because under persistent wind these mechanisms lower the extant of downwind hazard or on the grounds that the effect of some of the physical mechanisms on particles as small as the FMD particles (0.015-20 μm) is supposed to be negligible compared to the effect of atmospheric turbulence. Even when the FMD aerosol was treated as aerosol, it was assumed that it is monodisperse, i.e., all its particles are of the same size. The aim of the study is to examine whether these simplistic approaches are indeed justified when dealing with LDD of a bio-aerosol under actual atmospheric conditions. In order to do so, the influence of a more realistic modeling of the FMD aerosol as a polydisperse aerosol was compared to passive tracer and to monodisperse aerosol. The comparison refers to a case of a widespread FMD outbreak that occurred in 2012 in Egypt. This outbreak involved the emergence of a new serotype in Egypt, SAT2 and concern was raised that this serotype will advance further to Asia and Europe. Israel is located on the land bridge between Africa, Asia and Europe, and shares a long desert border with Egypt as well as a long Mediterranean shore adjacent to Egypt's shore. This unique location as well as the fact that Israel does not have any cattle trade with its neighboring countries make Israel an interesting test case for the examination of the necessary conditions for the long distance dispersal (LDD) of a new FMD strains from Africa to Europe. The analysis in this study shows that under quasi-stationary wind conditions modeling FMD dispersal as a passive tracer results in a significantly longer hazard distance. Under non

  19. A nonlinear programming approach for estimation of transmission parameters in childhood infectious disease using a continuous time model.

    PubMed

    Word, Daniel P; Cummings, Derek A T; Burke, Donald S; Iamsirithaworn, Sopon; Laird, Carl D

    2012-08-01

    Mathematical models can enhance our understanding of childhood infectious disease dynamics, but these models depend on appropriate parameter values that are often unknown and must be estimated from disease case data. In this paper, we develop a framework for efficient estimation of childhood infectious disease models with seasonal transmission parameters using continuous differential equations containing model and measurement noise. The problem is formulated using the simultaneous approach where all state variables are discretized, and the discretized differential equations are included as constraints, giving a large-scale algebraic nonlinear programming problem that is solved using a nonlinear primal-dual interior-point solver. The technique is demonstrated using measles case data from three different locations having different school holiday schedules, and our estimates of the seasonality of the transmission parameter show strong correlation to school term holidays. Our approach gives dramatic efficiency gains, showing a 40-400-fold reduction in solution time over other published methods. While our approach has an increased susceptibility to bias over techniques that integrate over the entire unknown state-space, a detailed simulation study shows no evidence of bias. Furthermore, the computational efficiency of our approach allows for investigation of a large model space compared with more computationally intensive approaches.

  20. A nonlinear programming approach for estimation of transmission parameters in childhood infectious disease using a continuous time model

    PubMed Central

    Word, Daniel P.; Cummings, Derek A. T.; Burke, Donald S.; Iamsirithaworn, Sopon; Laird, Carl D.

    2012-01-01

    Mathematical models can enhance our understanding of childhood infectious disease dynamics, but these models depend on appropriate parameter values that are often unknown and must be estimated from disease case data. In this paper, we develop a framework for efficient estimation of childhood infectious disease models with seasonal transmission parameters using continuous differential equations containing model and measurement noise. The problem is formulated using the simultaneous approach where all state variables are discretized, and the discretized differential equations are included as constraints, giving a large-scale algebraic nonlinear programming problem that is solved using a nonlinear primal–dual interior-point solver. The technique is demonstrated using measles case data from three different locations having different school holiday schedules, and our estimates of the seasonality of the transmission parameter show strong correlation to school term holidays. Our approach gives dramatic efficiency gains, showing a 40–400-fold reduction in solution time over other published methods. While our approach has an increased susceptibility to bias over techniques that integrate over the entire unknown state-space, a detailed simulation study shows no evidence of bias. Furthermore, the computational efficiency of our approach allows for investigation of a large model space compared with more computationally intensive approaches. PMID:22337634

  1. Airborne laser communication technology and flight test

    NASA Astrophysics Data System (ADS)

    Meng, Li-xin; Zhang, Li-zhong; Li, Xiao-ming; Li, Ying-chao; Jiang, Hui-lin

    2015-11-01

    Reconnaissance aircraft is an important node of the space-air-ground integrated information network, on which equipped with a large number of high-resolution surveillance equipment, and need high speed communications equipment to transmit detected information in real time. Currently RF communication methods cannot meet the needs of communication bandwidth. Wireless laser communication has outstanding advantages high speed, high capacity, security, etc., is an important means to solve the high-speed information transmission of airborne platforms. In this paper, detailed analysis of how the system works, the system components, work processes, link power and the key technologies of airborne laser communication were discussed. On this basis, a prototype airborne laser communications was developed, and high-speed, long-distance communications tests were carried out between the two fixed-wing aircraft, and the airborne precision aiming, atmospheric laser communication impacts on laser communication were tested. The experiments ultimately realize that, the communication distance is 144km, the communication rate is 2.5Gbps. The Airborne laser communication experiments provide technical basis for the application of the conversion equipment.

  2. Reverse Zoonotic Disease Transmission (Zooanthroponosis): A Systematic Review of Seldom-Documented Human Biological Threats to Animals

    PubMed Central

    Messenger, Ali M.; Barnes, Amber N.; Gray, Gregory C.

    2014-01-01

    Background Research regarding zoonotic diseases often focuses on infectious diseases animals have given to humans. However, an increasing number of reports indicate that humans are transmitting pathogens to animals. Recent examples include methicillin-resistant Staphylococcus aureus, influenza A virus, Cryptosporidium parvum, and Ascaris lumbricoides. The aim of this review was to provide an overview of published literature regarding reverse zoonoses and highlight the need for future work in this area. Methods An initial broad literature review yielded 4763 titles, of which 4704 were excluded as not meeting inclusion criteria. After careful screening, 56 articles (from 56 countries over three decades) with documented human-to-animal disease transmission were included in this report. Findings In these publications, 21 (38%) pathogens studied were bacterial, 16 (29%) were viral, 12 (21%) were parasitic, and 7 (13%) were fungal, other, or involved multiple pathogens. Effected animals included wildlife (n = 28, 50%), livestock (n = 24, 43%), companion animals (n = 13, 23%), and various other animals or animals not explicitly mentioned (n = 2, 4%). Published reports of reverse zoonoses transmission occurred in every continent except Antarctica therefore indicating a worldwide disease threat. Interpretation As we see a global increase in industrial animal production, the rapid movement of humans and animals, and the habitats of humans and wild animals intertwining with great complexity, the future promises more opportunities for humans to cause reverse zoonoses. Scientific research must be conducted in this area to provide a richer understanding of emerging and reemerging disease threats. As a result, multidisciplinary approaches such as One Health will be needed to mitigate these problems. PMID:24586500

  3. Chagas disease: current epidemiological trends after the interruption of vectorial and transfusional transmission in the Southern Cone countries.

    PubMed

    Moncayo, Alvaro

    2003-07-01

    Chagas disease, named after Carlos Chagas who first described it in 1909, exists only on the American Continent. It is caused by a parasite, Trypanosoma cruzi, transmitted to humans by blood-sucking triatomine bugs and by blood transfusion. Chagas disease has two successive phases, acute and chronic. The acute phase lasts 6 to 8 weeks. After several years of starting the chronic phase, 20% to 35% of the infected individuals, depending on the geographical area will develop irreversible lesions of the autonomous nervous system in the heart, esophagus, colon and the peripheral nervous system. Data on the prevalence and distribution of Chagas disease improved in quality during the 1980's as a result of the demographically representative cross-sectional studies carried out in countries where accurate information was not available. A group of experts met in Bras lia in 1979 and devised standard protocols to carry out countrywide prevalence studies on human T. cruzi infection and triatomine house infestation. Thanks to a coordinated multi-country program in the Southern Cone countries the transmission of Chagas disease by vectors and by blood transfusion has been interrupted in Uruguay in1997, in Chile in 1999, and in 8 of the 12 endemic states of Brazil in 2000 and so the incidence of new infections by T. cruzi in the whole continent has decreased by 70%. Similar control multi-country initiatives have been launched in the Andean countries and in Central America and rapid progress has been recorded to ensure the interruption of the transmission of Chagas disease by 2005 as requested by a Resolution of the World Health Assembly approved in 1998. The cost-benefit analysis of the investments of the vector control program in Brazil indicate that there are savings of US$17 in medical care and disabilities for each dollar spent on prevention, showing that the program is a health investment with good return. Since the inception in 1979 of the Steering Committee on Chagas Disease

  4. Object-based assessment of burn severity in diseased forests using high-spatial and high-spectral resolution MASTER airborne imagery

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Metz, Margaret R.; Rizzo, David M.; Dillon, Whalen W.; Meentemeyer, Ross K.

    2015-04-01

    Forest ecosystems are subject to a variety of disturbances with increasing intensities and frequencies, which may permanently change the trajectories of forest recovery and disrupt the ecosystem services provided by trees. Fire and invasive species, especially exotic disease-causing pathogens and insects, are examples of disturbances that together could pose major threats to forest health. This study examines the impacts of fire and exotic disease (sudden oak death) on forests, with an emphasis on the assessment of post-fire burn severity in a forest where trees have experienced three stages of disease progression pre-fire: early-stage (trees retaining dried foliage and fine twigs), middle-stage (trees losing fine crown fuels), and late-stage (trees falling down). The research was conducted by applying Geographic Object-Based Image Analysis (GEOBIA) to MASTER airborne images that were acquired immediately following the fire for rapid assessment and contained both high-spatial (4 m) and high-spectral (50 bands) resolutions. Although GEOBIA has gradually become a standard tool for analyzing high-spatial resolution imagery, high-spectral resolution data (dozens to hundreds of bands) can dramatically reduce computation efficiency in the process of segmentation and object-based variable extraction, leading to complicated variable selection for succeeding modeling. Hence, we also assessed two widely used band reduction algorithms, PCA (principal component analysis) and MNF (minimum noise fraction), for the delineation of image objects and the subsequent performance of burn severity models using either PCA or MNF derived variables. To increase computation efficiency, only the top 5 PCA and MNF and top 10 PCA and MNF components were evaluated, which accounted for 10% and 20% of the total number of the original 50 spectral bands, respectively. Results show that if no band reduction was applied the models developed for the three stages of disease progression had relatively

  5. Mother-to-Child Transmission of Chagas Disease in El Salvador.

    PubMed

    Sasagawa, Emi; Aiga, Hirotsugu; Corado Soriano, Edith Yanira; Cuyuch Marroquín, Blanca Leticia; Hernández Ramírez, Marta Alicia; Guevara de Aguilar, Ana Vilma; Romero Chévez, José Eduardo; Ramos Hernández, Hector Manuel; Cedillos, Rafael Antonio; Misago, Chizuru; Kita, Kiyoshi

    2015-08-01

    To estimate the incidence (any mother to child) and rate (from seropositive mother to child) of mother-to-child transmission of Trypanosoma cruzi, a serological census was conducted, targeting pregnant women and infants born to seropositive mothers, in four municipalities of El Salvador. Of 943 pregnant women, 36 (3.8%) were seropositive for T. cruzi. Of 36, 32 proceeded to serological tests of their infants when they became 6-8 months of age. Six infants seropositive at the age of 6-8 months further proceeded to second-stage serological test at the age of 9-16 months. As the result, one infant was congenitally infected. Thus, serological tests at the age of 6-8 months produced five false positives. To ensure earlier effective medication only for true positives, identification of seropositive infants at the age of 9-16 months is crucial. Incidence and rate of mother-to-child transmission were 0.14 (per 100 person-years) and 4.0%, respectively. Estimated number of children infected through mother-to-child transmission in El Salvador (170 per year) was much higher than that of human immunodeficiency virus (HIV; seven per year). It is recommended that serological testing for T. cruzi be integrated into those for HIV and syphilis as part of antenatal care package.

  6. Evaluating empirical contact networks as potential transmission pathways for infectious diseases.

    PubMed

    VanderWaal, Kimberly; Enns, Eva A; Picasso, Catalina; Packer, Craig; Craft, Meggan E

    2016-08-01

    Networks are often used to incorporate heterogeneity in contact patterns in mathematical models of pathogen spread. However, few tools exist to evaluate whether potential transmission pathways in a population are adequately represented by an observed contact network. Here, we describe a novel permutation-based approach, the network k-test, to determine whether the pattern of cases within the observed contact network are likely to have resulted from transmission processes in the network, indicating that the network represents potential transmission pathways between nodes. Using simulated data of pathogen spread, we compare the power of this approach to other commonly used analytical methods. We test the robustness of this technique across common sampling constraints, including undetected cases, unobserved individuals and missing interaction data. We also demonstrate the application of this technique in two case studies of livestock and wildlife networks. We show that the power of the k-test to correctly identify the epidemiologic relevance of contact networks is substantially greater than other methods, even when 50% of contact or case data are missing. We further demonstrate that the impact of missing data on network analysis depends on the structure of the network and the type of missing data. PMID:27488249

  7. Mother-to-Child Transmission of Chagas Disease in El Salvador

    PubMed Central

    Sasagawa, Emi; Aiga, Hirotsugu; Soriano, Edith Yanira Corado; Marroquín, Blanca Leticia Cuyuch; Ramírez, Marta Alicia Hernández; de Aguilar, Ana Vilma Guevara; Chévez, José Eduardo Romero; Hernández, Hector Manuel Ramos; Cedillos, Rafael Antonio; Misago, Chizuru; Kita, Kiyoshi

    2015-01-01

    To estimate the incidence (any mother to child) and rate (from seropositive mother to child) of mother-to-child transmission of Trypanosoma cruzi, a serological census was conducted, targeting pregnant women and infants born to seropositive mothers, in four municipalities of El Salvador. Of 943 pregnant women, 36 (3.8%) were seropositive for T. cruzi. Of 36, 32 proceeded to serological tests of their infants when they became 6–8 months of age. Six infants seropositive at the age of 6–8 months further proceeded to second-stage serological test at the age of 9–16 months. As the result, one infant was congenitally infected. Thus, serological tests at the age of 6–8 months produced five false positives. To ensure earlier effective medication only for true positives, identification of seropositive infants at the age of 9–16 months is crucial. Incidence and rate of mother-to-child transmission were 0.14 (per 100 person-years) and 4.0%, respectively. Estimated number of children infected through mother-to-child transmission in El Salvador (170 per year) was much higher than that of human immunodeficiency virus (HIV; seven per year). It is recommended that serological testing for T. cruzi be integrated into those for HIV and syphilis as part of antenatal care package. PMID:26123959

  8. Transmission of chronic wasting disease to sentinel reindeer (Rangifer tarandus tarandus)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Chronic wasting disease (CWD) is a naturally-occurring, fatal neurodegenerative disease of North American cervids. Reindeer (Rangifer tarandus tarandus) are susceptible to CWD following oral challenge, but CWD has not been reported in free-ranging caribou (Rangifer tarandus caribou) or farmed reinde...

  9. Pathological features of chronic wasting disease in reindeer and demonstration of horizontal transmission

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Chronic wasting disease (CWD) is a naturally-occurring, fatal prion disease of cervids. Reindeer (Rangifer tarandus tarandus) are susceptible to CWD following oral challenge, and CWD was recently reported in a free-ranging reindeer of Norway. Potential contact between CWD-affected cervids and Rangif...

  10. Direct contact transmission of three different foot-and-mouth disease virus strains in swine demonstrates important strain-specific differences.

    PubMed

    Pacheco, Juan M; Tucker, Meghan; Hartwig, Ethan; Bishop, Elizabeth; Arzt, Jonathan; Rodriguez, Luis L

    2012-08-01

    A novel direct contact transmission model for the study of foot-and-mouth disease virus (FMDV) infection of swine was utilized to investigate transmission characteristics of three FMDV strains belonging to serotypes A, O and Asia1. Each strain demonstrated distinct transmission characteristics and required different exposure times to achieve successful contact transmission. While a 4h exposure was sufficient for strain A24 Cruzeiro (A24Cru), both O1 Manisa and Asia1 Shamir transmission required 18 h or more. Viral excretion levels from donors (for all three strains) and virus present in room air (for A24Cru and O1 Manisa) were evaluated and associated with clinical signs and observed transmission pattern. Although all directly inoculated donor animals showed acute FMD, A24Cru had the highest levels of viral shedding in saliva and nasal swabs followed by O1 Manisa and Asia1 Shamir. Virus levels in room air were higher and were detected longer for A24Cru than for O1 Manisa. These results provide direct evidence for important strain-specific variation in transmission characteristics and emphasize the need for thorough evaluation of different FMDV viral strains using a well defined contact transmission methodology. This information is critical for vaccine and biotherapeutic efficacy testing, pathogenesis and disease modeling of FMDV transmission.

  11. Health problems associated with consumption of fish and the role of aquatic environments in the transmission of human diseases.

    PubMed

    Aloo, P A

    2000-01-01

    The majority of the numerous fish parasites are harmless to man and many domestic animals because when eaten with their fish hosts, they are digested. However, some of the fish parasites with larval stages in freshwater or marine teleosts have zoonotic potential if eaten raw or partially cooked. These are usually parasites, which have a piscivorous mammalian carnivore as their normal final host and are able to infect man because of the low host specificity of the adult stage. The major groups of fish parasite that are known as potentially dangerous pathogens of man belong to the helminth groups cestoda, trematoda, nematoda and rarely acanthocephala. However, bacterial and viral disease of man transmitted through fish are not uncommon. Toxic substances, metals and insecticides used to control human diseases in aquatic environments may accumulate in fish in po1lluted waters at such levels as to constitute a health risk to the consumer. Other health problems associated with fish arise from its perishable nature for example, in adequate handling, processing and storage, which may lead to the accumulation of microbes enhancing the risk of food poisoning. The aquatic environment in Africa constitutes a breeding habitat to several vectors of human diseases such as mosquitoes, snails and black flies. This paper reviews the role played by fish in transmitting diseases to humans as well as the importance of the aquatic environments in the transmission of human diseases such as Malaria, Schistosomiasis and onchocerciasis.

  12. Hepatitis B virus prevalence and transmission risk factors in inflammatory bowel disease patients at Clementino Fraga Filho university hospital

    PubMed Central

    Tolentino, Yolanda Faia Manhães; Fogaça, Homero Soares; Zaltman, Cyrla; Ximenes, Lia Laura Lewis; Coelho, Henrique Sérgio Moraes

    2008-01-01

    AIM: To evaluate the prevalence of hepatitis B virus (HBV) infection in inflammatory bowel disease (IBD) patients that followed up in our hospital and try to identify the possible risk factors involved in this infection transmission. METHODS: This was a cross-sectional study for which 176 patients were selected according to their arrival for the medical interview. All these patients had already IBD diagnosis. The patient was interviewed and a questionnaire was filled out. RESULTS: In the group of 176 patients whom we examined, we found that 17% (30) were anti-HBc positive. Out of 30 patients with positive anti-HBc, 2.3% (4) had positive HBsAg and negative HBV-DNA. In an attempt to identify the possible HBV infection transmission risk factors in IBD patients, it was observed that 117 patients had been submitted to some kind of surgical procedure, but only 24 patients had positive anti-HBc (P = 0.085). It was also observed that surgery to treat IBD complications was not a risk factor for HBV infection transmission, since we did not get a statically significant P value. However, IBD patients that have been submitted to surgery to treat IBD complications received more blood transfusions then patients submitted to other surgical interventions (P = 0.015). CONCLUSION: There was a high incidence of positive anti-HBc (17%) and positive HBsAg (2.3%) in IBD patient when compared with the overall population (7.9%). PMID:18506926

  13. Influence of apolipoprotein E genotype on the transmission of Alzheimer disease in a community-based sample

    SciTech Connect

    Jarvik, G.P.; Larson, E.B.; Goddard, K.

    1996-01-01

    The {epsilon}4 allele of the apolipoprotein E locus (APOE) has been found to be an important predictor of Alzheimer disease (AD). However, linkage analysis has not clarified the role of APOE in the transmission of AD. The results of the current study provide evidence that the pattern of transmission of memory disorders differs in nuclear families in which the AD-affected proband did carry an {epsilon}4 allele versus those families in which the AD-affected proband did not carry an {epsilon}4 allele. Further, risk of AD due to APOE genotype in the probands is modified by family history of memory disorders, suggesting gene-by-gene interactions. Family history remained a significant predictor of AD for affected probands with some, but not all, APOE genotypes in a logistic regression analysis. Though nonadditive in the prediction of AD, APOE genotype and family history acted additively in the prediction of age at AD onset. The results of complex segregation analysis were inconsistent with Mendelian segregation of memory disorders both in families of affected probands who did or did not carry an {epsilon}4 allele, yet these two groups had significantly different parameter estimates for their transmission models. These results are consistent with gene-by-gene interactions, but also could result from common elements in the familial environment. 41 refs., 1 fig., 7 tabs.

  14. Sporadic Creutzfeldt-Jakob Disease MM1+2C and MM1 are Identical in Transmission Properties.

    PubMed

    Kobayashi, Atsushi; Matsuura, Yuichi; Iwaki, Toru; Iwasaki, Yasushi; Yoshida, Mari; Takahashi, Hitoshi; Murayama, Shigeo; Takao, Masaki; Kato, Shinsuke; Yamada, Masahito; Mohri, Shirou; Kitamoto, Tetsuyuki

    2016-01-01

    The genotype (methionine, M or valine, V) at polymorphic codon 129 of the PRNP gene and the type (1 or 2) of abnormal prion protein in the brain are the major determinants of the clinicopathological features of sporadic Creutzfeldt-Jakob disease (CJD), thus providing molecular basis for classification of sporadic CJD, that is, MM1, MM2, MV1, MV2, VV1 or VV2. In addition to these "pure" cases, "mixed" cases presenting mixed neuropathological and biochemical features have also been recognized. The most frequently observed mixed form is the co-occurrence of MM1 and MM2, namely MM1+2. However, it has remained elusive whether MM1+2 could be a causative origin of dura mater graft-associated CJD (dCJD), one of the largest subgroups of iatrogenic CJD. To test this possibility, we performed transmission experiments of MM1+2 prions and a systematic neuropathological examination of dCJD patients in the present study. The transmission properties of the MM1+2 prions were identical to those of MM1 prions because MM2 prions lacked transmissibility. In addition, the neuropathological characteristics of MM2 were totally absent in dCJD patients examined. These results suggest that MM1+2 can be a causative origin of dCJD and causes neuropathological phenotype similar to that of MM1.

  15. The bba64 gene of Borrelia burgdorferi, the Lyme disease agent, is critical for mammalian infection via tick bite transmission.

    PubMed

    Gilmore, Robert D; Howison, Rebekah R; Dietrich, Gabrielle; Patton, Toni G; Clifton, Dawn R; Carroll, James A

    2010-04-20

    The spirochetal agent of Lyme disease, Borrelia burgdorferi, is transmitted by bites of Ixodes ticks to mammalian reservoir hosts and humans. The mechanism(s) by which the organism is trafficked from vector to host is poorly understood. In this study, we demonstrate that a B. burgdorferi mutant strain deficient in the synthesis of the bba64 gene product was incapable of infecting mice via tick bite even though the mutant was (i) infectious in mice when introduced by needle inoculation, (ii) acquired by larval ticks feeding on infected mice, and (iii) able to persist through tick molting stages. This finding of a B. burgdorferi gene required for pathogen transfer and/or survival from the tick to the susceptible host represents an important breakthrough toward understanding transmission mechanisms involved for the Lyme disease agent.

  16. Managing the risks of disease transmission through trade: a commodities-based approach?

    PubMed

    Brückner, G K

    2011-04-01

    Since its founding in 1924, the World Organisation for Animal Health (OIE) has facilitated safe trade in animals and animal products by developing effective standards to prevent the spread of animal diseases across the globe. A protocol for recognising the disease-free status of countries is an integral part of this process and has been adopted and advanced through the years to assist OIE Member Countries in placing disease-free animals and their products on the international market. Options such as trade from disease-free zones and disease-free compartments are now available to Members and have proven to be a positive mechanism for facilitating trade. A further option is trading in safe commodities, i.e. animals and animal products that have been identified as safe to trade even in the presence of disease, either with or without applying risk mitigation measures before export. Although most Members have incorporated the acceptance of disease-free countries or zones into their animal health policies and sanitary measures, there still appears to be a reluctance to trade in commodities from infected countries, despite clear, scientifically based risk management standards that can be applied if needed. This paper offers some examples reflecting the apparent reluctance to trade in commodities and discusses how the standards in the OIE's Terrestrial Animal Health Code could be used to apply scientifically based risk management practices to review outdated policies. PMID:21809771

  17. Managing the risks of disease transmission through trade: a commodities-based approach?

    PubMed

    Brückner, G K

    2011-04-01

    Since its founding in 1924, the World Organisation for Animal Health (OIE) has facilitated safe trade in animals and animal products by developing effective standards to prevent the spread of animal diseases across the globe. A protocol for recognising the disease-free status of countries is an integral part of this process and has been adopted and advanced through the years to assist OIE Member Countries in placing disease-free animals and their products on the international market. Options such as trade from disease-free zones and disease-free compartments are now available to Members and have proven to be a positive mechanism for facilitating trade. A further option is trading in safe commodities, i.e. animals and animal products that have been identified as safe to trade even in the presence of disease, either with or without applying risk mitigation measures before export. Although most Members have incorporated the acceptance of disease-free countries or zones into their animal health policies and sanitary measures, there still appears to be a reluctance to trade in commodities from infected countries, despite clear, scientifically based risk management standards that can be applied if needed. This paper offers some examples reflecting the apparent reluctance to trade in commodities and discusses how the standards in the OIE's Terrestrial Animal Health Code could be used to apply scientifically based risk management practices to review outdated policies.

  18. On the transmission pattern of Kyasanur Forest disease (KFD) in India.

    PubMed

    Murhekar, Manoj V; Kasabi, Gudadappa S; Mehendale, Sanjay M; Mourya, Devendra T; Yadav, Pragya D; Tandale, Babasaheb V

    2015-01-01

    Kyasanur Forest disease (KFD), a tick-borne viral hemorrhagic fever, is endemic in five districts of Karnataka state, India. Recent reports of the spread of disease to neighboring districts of the Western Ghats, namely Chamarajanagar district in Karnataka, Nilgiri district in Tamil Nadu, Wayanad and Malappuram districts in Kerala, and Pali village in Goa are a cause for concern. Besides vaccination of the affected population, establishing an event-based surveillance system for monkey deaths in the national parks, wildlife sanctuaries and reserve forests of the Western Ghats would help detect the disease early and thereby help implement appropriate control measures.

  19. A VSEIR model for transmission of tuberculosis (TB) disease in North Sumatera, Indonesia

    NASA Astrophysics Data System (ADS)

    Rangkuti, Yulita M.; Sinaga, Marlina S.; Marpaung, F.; Side, Syafruddin

    2014-12-01

    In this work, Vaccination (V), Susceptible (S) Infected (I), and Recovered (R) (VSIR) model for transmission of Tuberculosis in North Sumatera is modified. An exposed class is adopted to VSIR model so called VSEIR to determine the probability of people who infectious before infected. This model is written in ordinary differential equation (ODEs) in five classes. Determination the equilibrium point and stability analysis of the model is discussed to determine the dynamic behaviour of systems. A simulation is also discussed to see the suitable model to North Sumatera data. The simulation of VSEIR model indicates Tuberculosis has not endemic in North Sumatera.

  20. 21 CFR 1271.145 - Prevention of the introduction, transmission, or spread of communicable diseases.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... FOOD AND DRUG ADMINISTRATION HUMAN CELLS, TISSUES, AND CELLULAR AND TISSUE-BASED PRODUCTS Current Good... diseases. You must recover, process, store, label, package, and distribute HCT/Ps, and screen and test...

  1. Transmission of the virus of foot and mouth disease between animals and man*

    PubMed Central

    Hyslop, N. St. G.

    1973-01-01

    The virus of foot and mouth disease causes severe epizootics in animals and infrequently evokes painful, but transient, clinical signs in man. Adults in certain occupational groups and young children are particularly exposed to risk. Infected persons may disseminate virus for up to about 14 days. The virus can be transmitted from animals to animals, from animals to man, from man to animals and, probably, from man to man. Evidence for transfer of the disease between human and animal populations is reviewed in detail and modern methods of diagnosis are described. Predisposing factors play an important role in the development of overt foot and mouth disease in man. Subclinical infection occurs. The possibility of aerial transfer of the virus between man and domestic livestock constitutes a hazard, especially to the latter. Attention is directed to the need for sophisticated diagnostic techniques, to requirements for adequate precautions in the handling and disposal of affected animals, and to hygienic measures for disease control. PMID:4374322

  2. Climate, environmental and socio-economic change: weighing up the balance in vector-borne disease transmission.

    PubMed

    Parham, Paul E; Waldock, Joanna; Christophides, George K; Hemming, Deborah; Agusto, Folashade; Evans, Katherine J; Fefferman, Nina; Gaff, Holly; Gumel, Abba; LaDeau, Shannon; Lenhart, Suzanne; Mickens, Ronald E; Naumova, Elena N; Ostfeld, Richard S; Ready, Paul D; Thomas, Matthew B; Velasco-Hernandez, Jorge; Michael, Edwin

    2015-04-01

    Arguably one of the most important effects of climate change is the potential impact on human health. While this is likely to take many forms, the implications for future transmission of vector-borne diseases (VBDs), given their ongoing contribution to global disease burden, are both extremely important and highly uncertain. In part, this is owing not only to data limitations and methodological challenges when integrating climate-driven VBD models and climate change projections, but also, perhaps most crucially, to the multitude of epidemiological, ecological and socio-economic factors that drive VBD transmission, and this complexity has generated considerable debate over the past 10-15 years. In this review, we seek to elucidate current knowledge around this topic, identify key themes and uncertainties, evaluate ongoing challenges and open research questions and, crucially, offer some solutions for the field. Although many of these challenges are ubiquitous across multiple VBDs, more specific issues also arise in different vector-pathogen systems. PMID:25688012

  3. Climate, environmental and socio-economic change: weighing up the balance in vector-borne disease transmission

    PubMed Central

    Parham, Paul E.; Waldock, Joanna; Christophides, George K.; Hemming, Deborah; Agusto, Folashade; Evans, Katherine J.; Fefferman, Nina; Gaff, Holly; Gumel, Abba; LaDeau, Shannon; Lenhart, Suzanne; Mickens, Ronald E.; Naumova, Elena N.; Ostfeld, Richard S.; Ready, Paul D.; Thomas, Matthew B.; Velasco-Hernandez, Jorge; Michael, Edwin

    2015-01-01

    Arguably one of the most important effects of climate change is the potential impact on human health. While this is likely to take many forms, the implications for future transmission of vector-borne diseases (VBDs), given their ongoing contribution to global disease burden, are both extremely important and highly uncertain. In part, this is owing not only to data limitations and methodological challenges when integrating climate-driven VBD models and climate change projections, but also, perhaps most crucially, to the multitude of epidemiological, ecological and socio-economic factors that drive VBD transmission, and this complexity has generated considerable debate over the past 10–15 years. In this review, we seek to elucidate current knowledge around this topic, identify key themes and uncertainties, evaluate ongoing challenges and open research questions and, crucially, offer some solutions for the field. Although many of these challenges are ubiquitous across multiple VBDs, more specific issues also arise in different vector–pathogen systems. PMID:25688012

  4. [Transmission of agents of the porcine respiratory disease complex (PRDC) between swine herds: a review. Part 2--Pathogen transmission via semen, air and living/nonliving vectors].

    PubMed

    Woeste, K; Grosse Beilage, E

    2007-10-01

    The transmission of PRDC-pathogens (PRRSV, influenza virus A, PCV2, M. hyopneumoniae, A. pleuropneumoniae) between swine herds, which was summarized in the first part of the review, mainly occurs via pig movement. The risk of pathogen transmission by insemination with contaminated semen plays only a relevant role in the infection with PRRSV and PCV2. A risk of the aerogen transmission of pathogens between herds within a distance of 2 to 3 km is described for M. hyopneumoniae and PRRSV. Evidence for the other pathogens is not investigated. The PRDC-pathogens are frequently detected in wild boar populations. Therefore, the transmission between wild boars and domestic pigs seems possible by close contacts. PRRSV and M. hyopneumoniae can be transmitted by contaminated clothes and boots, but the use of sanitation protocols appears to limit their spread. Live vectors like rodents or birds seemed to have no special importance for the transmission of PRDC-pathogens. PMID:17970334

  5. One Health and Food-Borne Disease: Salmonella Transmission between Humans, Animals, and Plants.

    PubMed

    Silva, Claudia; Calva, Edmundo; Maloy, Stanley

    2014-02-01

    There are >2,600 recognized serovars of Salmonella enterica. Many of these Salmonella serovars have a broad host range and can infect a wide variety of animals, including mammals, birds, reptiles, amphibians, fish, and insects. In addition, Salmonella can grow in plants and can survive in protozoa, soil, and water. Hence, broad-host-range Salmonella can be transmitted via feces from wild animals, farm animals, and pets or by consumption of a wide variety of common foods: poultry, beef, pork, eggs, milk, fruit, vegetables, spices, and nuts. Broad-host-range Salmonella pathogens typically cause gastroenteritis in humans. Some Salmonella serovars have a more restricted host range that is associated with changes in the virulence plasmid pSV, accumulation of pseudogenes, and chromosome rearrangements. These changes in host-restricted Salmonella alter pathogen-host interactions such that host-restricted Salmonella organisms commonly cause systemic infections and are transmitted between host populations by asymptomatic carriers. The secondary consequences of efforts to eliminate host-restricted Salmonella serovars demonstrate that basic ecological principles govern the environmental niches occupied by these pathogens, making it impossible to thwart Salmonella infections without a clear understanding of the human, animal, and environmental reservoirs of these pathogens. Thus, transmission of S. enterica provides a compelling example of the One Health paradigm because reducing human infections will require the reduction of Salmonella in animals and limitation of transmission from the environment.

  6. Borrelia burgdorferi BBA52 is a potential target for transmission blocking Lyme disease vaccine.

    PubMed

    Kumar, Manish; Kaur, Simarjot; Kariu, Toru; Yang, Xiuli; Bossis, Ioannis; Anderson, John F; Pal, Utpal

    2011-11-01

    The surface-exposed antigens of Borrelia burgdorferi represent important targets for induction of protective host immune responses. BBA52 is preferentially expressed by B. burgdorferi in the feeding tick, and a targeted deletion of bba52 interferes with vector-host transitions in vivo. In this study, we demonstrate that BBA52 is an outer membrane surface-exposed protein and that disulfide bridges take part in the homo-oligomeric assembly of native protein. BBA52 antibodies lack detectable borreliacidal activities in vitro. However, active immunization studies demonstrated that BBA52 vaccinated mice were significantly less susceptible to subsequent tick-borne challenge infection. Similarly, passive transfer of BBA52 antibodies in ticks completely blocked B. burgdorferi transmission from feeding ticks to naïve mice. Taken together, these studies highlight the role of BBA52 in spirochete dissemination from ticks to mice and demonstrate the potential of BBA52 antibody-mediated strategy to complement the ongoing efforts to develop vaccines for blocking the transmission of B. burgdorferi.

  7. Disease dynamics during wildlife translocations: disruptions to the host population and potential consequences for transmission in desert tortoise contact networks

    USGS Publications Warehouse

    Aiello, Christina M.; Nussear, Kenneth E.; Walde, Andrew D.; Esque, Todd C.; Emblidge, Patrick G.; Sah, Pratha; Bansal, S.; Hudson, Peter J.

    2014-01-01

    Wildlife managers consider animal translocation a means of increasing the viability of a local population. However, augmentation may disrupt existing resident disease dynamics and initiate an outbreak that would effectively offset any advantages the translocation may have achieved. This paper examines fundamental concepts of disease ecology and identifies the conditions that will increase the likelihood of a disease outbreak following translocation. We highlight the importance of susceptibility to infection, population size and population connectivity – a characteristic likely affected by translocation but not often considered in risk assessments – in estimating outbreak risk due to translocation. We then explore these features in a species of conservation concern often translocated in the presence of infectious disease, the Mojave Desert tortoise, and use data from experimental tortoise translocations to detect changes in population connectivity that may influence pathogen transmission. Preliminary analyses comparing contact networks inferred from spatial data at control and translocation plots and infection simulation results through these networks suggest increased outbreak risk following translocation due to dispersal-driven changes in contact frequency and network structure. We outline future research goals to test these concepts and aid managers in designing effective risk assessment and intervention strategies that will improve translocation success.

  8. A review of mutual transmission of important infectious diseases between livestock and wildlife in Europe.

    PubMed

    Frölich, K; Thiede, S; Kozikowski, T; Jakob, W

    2002-10-01

    Oral vaccination of red foxes against rabies has been practiced in Europe since 1978 and has succeeded in greatly reducing the occurrence of this disease in foxes: this is an example of coordinated activity against a disease that affects both wild and domestic animals as well as humans. Some examples of diseases that affect both domestic and wild animals in Europe are: classical swine fever (hog cholera) in wild boars and domestic swine; myxomatosis and rabbit hemorrhagic disease in domestic and wild rabbits; bovine viral diarrhea (BVD) in cattle and roe deer; contagious ecthyma in domestic sheep and goats and also in, e.g., chamois, muskox, and reindeer; Mycobacterium bovis in cattle, wild boars, badgers, and deer; and brucellosis in a broad range of livestock and wildlife in all European countries. In addition, serological surveys performed in different free-ranging ungulate species revealed the presence of alphaherpesviruses related to bovine herpesvirus-1 in 7 European countries; and a study of malignant catarrhal fever in deer in Germany might indicate that in this case sheep are the main reservoir species. Although many data on infectious diseases are available in various European countries, there is more need for systematic surveillance and coordinated research. PMID:12381556

  9. Primary transmission of chronic wasting disease versus scrapie prions from small ruminants to transgenic mice expressing ovine and cervid prion protein

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Identifying transmissible spongiform encephalopathy (TSE) reservoirs that could lead to disease re-emergence is imperative to U.S. scrapie eradication efforts. Transgenic mice expressing the cervid (TgElk) or ovine (Tg338) prion protein have aided characterization of chronic wasting disease (CWD) an...

  10. Insights into the transmission of respiratory infectious diseases through empirical human contact networks.

    PubMed

    Huang, Chunlin; Liu, Xingwu; Sun, Shiwei; Li, Shuai Cheng; Deng, Minghua; He, Guangxue; Zhang, Haicang; Wang, Chao; Zhou, Yang; Zhao, Yanlin; Bu, Dongbo

    2016-01-01

    In this study, we present representative human contact networks among Chinese college students. Unlike schools in the US, human contacts within Chinese colleges are extremely clustered, partly due to the highly organized lifestyle of Chinese college students. Simulations of influenza spreading across real contact networks are in good accordance with real influenza records; however, epidemic simulations across idealized scale-free or small-world networks show considerable overestimation of disease prevalence, thus challenging the widely-applied idealized human contact models in epidemiology. Furthermore, the special contact pattern within Chinese colleges results in disease spreading patterns distinct from those of the US schools. Remarkably, class cancelation, though simple, shows a mitigating power equal to quarantine/vaccination applied on ~25% of college students, which quantitatively explains its success in Chinese colleges during the SARS period. Our findings greatly facilitate reliable prediction of epidemic prevalence, and thus should help establishing effective strategies for respiratory infectious diseases control. PMID:27526868

  11. Insights into the transmission of respiratory infectious diseases through empirical human contact networks

    PubMed Central

    Huang, Chunlin; Liu, Xingwu; Sun, Shiwei; Li, Shuai Cheng; Deng, Minghua; He, Guangxue; Zhang, Haicang; Wang, Chao; Zhou, Yang; Zhao, Yanlin; Bu, Dongbo

    2016-01-01

    In this study, we present representative human contact networks among Chinese college students. Unlike schools in the US, human contacts within Chinese colleges are extremely clustered, partly due to the highly organized lifestyle of Chinese college students. Simulations of influenza spreading across real contact networks are in good accordance with real influenza records; however, epidemic simulations across idealized scale-free or small-world networks show considerable overestimation of disease prevalence, thus challenging the widely-applied idealized human contact models in epidemiology. Furthermore, the special contact pattern within Chinese colleges results in disease spreading patterns distinct from those of the US schools. Remarkably, class cancelation, though simple, shows a mitigating power equal to quarantine/vaccination applied on ~25% of college students, which quantitatively explains its success in Chinese colleges during the SARS period. Our findings greatly facilitate reliable prediction of epidemic prevalence, and thus should help establishing effective strategies for respiratory infectious diseases control. PMID:27526868

  12. Genital ulcers, other sexually transmitted diseases, and the sexual transmission of HIV.

    PubMed

    Piot, P; Laga, M

    1989-03-11

    There is increasing evidence that genital ulceration, including syphilis, chancroid, and herpes simplex type 2, increases susceptibility to HIV infection. It may be that the HIV penetrates more easily through ulcerated membranes or that the lymphocytes associated with the inflammatory response present target cells for HIV infection. There is also evidence that HIV-infected women with genital ulcers are themselves more infective due to shedding of the virus in the genital tract. Nonulcerative sexually-transmitted diseases have also been associated as cofactors of HIV infection. Programs for the control of sexually transmitted diseases should be strengthened and should focus on eliminating chancroid, which is easily treated with antibiotics. Patients with genital ulcer disease should receive counseling, so that they will know that untreated genital ulcers increase the risk of HIV infection.

  13. A Technique for Airborne Aerobiological Sampling

    ERIC Educational Resources Information Center

    Mill, R. A.; And Others

    1972-01-01

    Report of a study of airborne micro-organisms collected over the Oklahoma City Metropolitan area and immediate environments, to investigate the possibility that a cloud of such organisms might account for the prevalence of some respiratory diseases in and around urban areas. (LK)

  14. An epidemic model for the interactions between thermal regime of rivers and transmission of Proliferative Kidney Disease in salmonid fish

    NASA Astrophysics Data System (ADS)

    Carraro, Luca; Bertuzzo, Enrico; Mari, Lorenzo; Gatto, Marino; Strepparava, Nicole; Hartikainen, Hanna; Rinaldo, Andrea

    2015-04-01

    Proliferative kidney disease (PKD) affects salmonid populations in European and North-American rivers. It is caused by the endoparasitic myxozoan Tetracapsuloides bryosalmonae, which exploits freshwater bryozoans (Fredericella sultana) and salmonids as primary and secondary hosts, respectively. Incidence and mortality, which can reach up to 90-100%, are known to be strongly related to water temperature. PKD has been present in brown trout population for a long time but has recently increased rapidly in incidence and severity causing a decline in fish catches in many countries. In addition, environmental changes are feared to cause PKD outbreaks at higher latitude and altitude regions as warmer temperatures promote disease development. This calls for a better comprehension of the interactions between disease dynamics and the thermal regime of rivers, in order to possibly devise strategies for disease management. In this perspective, a spatially explicit model of PKD epidemiology in riverine host metacommunities is proposed. The model aims at summarizing the knowledge on the modes of transmission of the disease and the life-cycle of the parasite, making the connection between temperature and epidemiological parameters explicit. The model accounts for both local population and disease dynamics of bryozoans and fish and hydrodynamic dispersion of the parasite spores and hosts along the river network. The model is time-hybrid, coupling inter-seasonal and intra-seasonal dynamics, the former being described in a continuous time domain, the latter seen as time steps of a discrete time domain. In order to test the model, a case study is conducted in river Wigger (Cantons of Aargau and Lucerne, Switzerland), where data about water temperature, brown trout and bryozoan populations and PKD prevalence are being collected.

  15. Mars Airborne Prospecting Spectrometer

    NASA Astrophysics Data System (ADS)

    Steinkraus, J. M.; Wright, M. W.; Rheingans, B. E.; Steinkraus, D. E.; George, W. P.; Aljabri, A.; Hall, J. L.; Scott, D. C.

    2012-06-01

    One novel approach towards addressing the need for innovative instrumentation and investigation approaches is the integration of a suite of four spectrometer systems to form the Mars Airborne Prospecting Spectrometers (MAPS) for prospecting on Mars.

  16. Stable Isotopes Suggest Low Site Fidelity in Bar-headed Geese (Anser indicus) in Mongolia: Implications for Disease Transmission

    PubMed Central

    Bridge, Eli S.; Kelly, Jeffrey F.; Xiao, Xiangming; Batbayar, Nyambayar; Natsagdorj, Tseveenmyadag; Hill, Nichola J.; Takekawa, John Y.; Hawkes, Lucy A.; Bishop, Charles M.; Butler, Patrick J.; Newman, Scott H.

    2016-01-01

    Population connectivity is an important consideration in studies of disease transmission and biological conservation, especially with regard to migratory species. Determining how and when different subpopulations intermingle during different phases of the annual cycle can help identify important geographical regions or features as targets for conservation efforts and can help inform our understanding of continental-scale disease transmission. In this study, stable isotopes of hydrogen and carbon in contour feathers were used to assess the degree of molt-site fidelity among Bar-headed Geese (Anser indicus) captured in north-central Mongolia. Samples were collected from actively molting Bar-headed Geese (n = 61), and some individual samples included both a newly grown feather (still in sheath) and an old, worn feather from the bird’s previous molt (n = 21). Although there was no difference in mean hydrogen isotope ratios for the old and new feathers, the isotopic variance in old feathers was approximately three times higher than that of the new feathers, which suggests that these birds use different and geographically distant molting locations from year to year. To further test this conclusion, online data and modeling tools from the isoMAP website were used to generate probability landscapes for the origin of each feather. Likely molting locations were much more widespread for old feathers than for new feathers, which supports the prospect of low molt-site fidelity. This finding indicates that population connectivity would be greater than expected based on data from a single annual cycle, and that disease spread can be rapid even in areas like Mongolia where Bar-headed Geese generally breed in small isolated groups.

  17. Stable isotopes suggest low site fidelity in Bar-Headed Geese (Anser indicus) in Mongolia: Implications for disease transmission

    USGS Publications Warehouse

    Bridge, Eli S.; Kelly, Jeffrey F.; Xiangming Xiao,; Batbayar, Nyambayar; Natsagdorj, Tseveenmyadag; Hill, Nichola J.; Takekawa, John Y.; Hawkes, Lucy A.; Bishop, Charles M.; Butler, Patrick J.; Newman, Scott H.

    2015-01-01

    Population connectivity is an important consideration in studies of disease transmission and biological conservation, especially with regard to migratory species. Determining how and when different subpopulations intermingle during different phases of the annual cycle can help identify important geographical regions or features as targets for conservation efforts and can help inform our understanding of continental-scale disease transmission. In this study, stable isotopes of hydrogen and carbon in contour feathers were used to assess the degree of molt-site fidelity among Bar-headed Geese (Anser indicus) captured in north-central Mongolia. Samples were collected from actively molting Bar-headed Geese (n = 61), and some individual samples included both a newly grown feather (still in sheath) and an old, worn feather from the bird's previous molt (n = 21). Although there was no difference in mean hydrogen isotope ratios for the old and new feathers, the isotopic variance in old feathers was approximately three times higher than that of the new feathers, which suggests that these birds use different and geographically distant molting locations from year to year. To further test this conclusion, online data and modeling tools from the isoMAP website were used to generate probability landscapes for the origin of each feather. Likely molting locations were much more widespread for old feathers than for new feathers, which supports the prospect of low molt-site fidelity. This finding indicates that population connectivity would be greater than expected based on data from a single annual cycle, and that disease spread can be rapid even in areas like Mongolia where Bar-headed Geese generally breed in small isolated groups.

  18. Stable Isotopes Suggest Low Site Fidelity in Bar-headed Geese (Anser indicus) in Mongolia: Implications for Disease Transmission

    PubMed Central

    Bridge, Eli S.; Kelly, Jeffrey F.; Xiao, Xiangming; Batbayar, Nyambayar; Natsagdorj, Tseveenmyadag; Hill, Nichola J.; Takekawa, John Y.; Hawkes, Lucy A.; Bishop, Charles M.; Butler, Patrick J.; Newman, Scott H.

    2016-01-01

    Population connectivity is an important consideration in studies of disease transmission and biological conservation, especially with regard to migratory species. Determining how and when different subpopulations intermingle during different phases of the annual cycle can help identify important geographical regions or features as targets for conservation efforts and can help inform our understanding of continental-scale disease transmission. In this study, stable isotopes of hydrogen and carbon in contour feathers were used to assess the degree of molt-site fidelity among Bar-headed Geese (Anser indicus) captured in north-central Mongolia. Samples were collected from actively molting Bar-headed Geese (n = 61), and some individual samples included both a newly grown feather (still in sheath) and an old, worn feather from the bird’s previous molt (n = 21). Although there was no difference in mean hydrogen isotope ratios for the old and new feathers, the isotopic variance in old feathers was approximately three times higher than that of the new feathers, which suggests that these birds use different and geographically distant molting locations from year to year. To further test this conclusion, online data and modeling tools from the isoMAP website were used to generate probability landscapes for the origin of each feather. Likely molting locations were much more widespread for old feathers than for new feathers, which supports the prospect of low molt-site fidelity. This finding indicates that population connectivity would be greater than expected based on data from a single annual cycle, and that disease spread can be rapid even in areas like Mongolia where Bar-headed Geese generally breed in small isolated groups. PMID:27695389

  19. Source of drinking water supply and transmission of guinea worm disease in Nigeria.

    PubMed

    Ilegbodu, V A; Christensen, B L; Wise, R A; Ilegbodu, A E; Kale, O O

    1987-12-01

    During 1982, ecological factors associated with freshwater pollution were investigated in Idere, a rural Nigerian community with endemic guinea worm infection. Data were collected on the quality of all pond water sources, and on rainfall patterns and potable piped water available in the community. Pond water provided 76% of the total water used in Idere. This source of drinking water provided the classical ecological environment for the transmission of Dracunculus medinensis, other helminth parasites and bacterial enteric infections. The bacteriological analysis of drinking water from the ponds reflects the absence of sanitary arrangements for human waste disposal in the community, as the ponds are collectors of storm run-offs. Okina, the spring-fed pond which was nearest to the households, was the most reliable year-round source of water to the community; however, Okina also contained the highest density of infective Thermocyclops and the highest faecal coliform (FC) to faecal Streptococcus (FS) ratio (FC/FS), thus providing a central reservoir for guinea worm and bacterial infections. The transmission season of guinea worm infection corresponded with the period of greatest water scarcity in Idere. The amount of portable water available to Idere residents in 1981 was 3.6 litres per person per day. Frequent mechanical breakdowns, electric power failures, lack of fuel to run the water pumping engines and the direct link of the water pipeline supplying water to Idere with a water pipeline serving another major city in the same district were some of the reasons for potable water shortage in the community.

  20. Disease dynamics of Montipora white syndrome within Kaneohe Bay, Oahu, Hawaii: distribution, seasonality, virulence, and transmissibility.

    PubMed

    Aeby, G S; Ross, M; Williams, G J; Lewis, T D; Works, T M

    2010-07-26

    We report on an investigation of Montipora white syndrome (MWS), which is a coral disease reported from Hawaii, U.S.A., that results in tissue loss. Disease surveys of Montipora capitata within Kaneohe Bay (Oahu) found colonies that were affected by MWS on 9 reefs within 3 regions of Kaneohe Bay (south, central, north). Mean MWS prevalence ranged from 0.02 to 0.87% and average number of MWS cases per survey site ranged from 1 to 28 colonies. MWS prevalence and number of cases were significantly lower in the central region as compared to those in the north and south regions of Kaneohe Bay. There was a positive relationship between host abundance and MWS prevalence, and differences in host abundance between sites explained approximately 27% of the variation in MWS prevalence. Reefs in central Kaneohe Bay had lower M. capitata cover and lower MWS levels. MWS prevalence on reefs was neither significantly different between seasons (spring versus fall) nor among 57 tagged colonies that were monitored through time. MWS is a chronic and progressive disease causing M. capitata colonies to lose an average of 3.1% of live tissue mo(-1). Case fatality rate was 28% after 2 yr but recovery occurred in some colonies (32%). Manipulative experiments showed that the disease is acquired through direct contact. This is the first study to examine the dynamics of MWS within Hawaii, and our findings suggest that MWS has the potential to degrade Hawaii's reefs through time. PMID:20853736

  1. Global Climate Teleconnections to Forecast Increased Risk of Vector-Borne Animal and Human Disease Transmission

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We willexamine how climate teleconnect ions and variability impact vector biology and vector borne disease ecology, and demonstrate that global climate monitoring can be used to anticipate and forecast epidemics and epizootics. In this context we willexamine significant worldwide weather anomalies t...

  2. Effects of Newcastle disease virus vaccine antibodies on the shedding and transmission of challenge viruses

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Different genotypes of avian paramyxovirus serotype-1 virus (APMV-1) circulate in many parts of the world. Traditionally, Newcastle disease virus (NDV) is recognized as having two major divisions represented by class I and class II, with class II being further divided into eighteen genotypes. Alth...

  3. Congenital Chagas' disease transmission in the United States: Diagnosis in adulthood.

    PubMed

    Murillo, Jorge; Bofill, Lina M; Bolivar, Hector; Torres-Viera, Carlos; Urbina, Julio A; Benhayon, Daniel; Torres, Jaime R

    2016-01-01

    Two brothers with congenitally-acquired Chagas' disease (CD) diagnosed during adulthood are reported. The patients were born in the USA to a mother from Bolivia who on subsequent assessment was found to be serologically positive for Trypanosoma cruzi. Serologic screening of all pregnant women who migrated from countries with endemic CD is strongly recommended. PMID:27516969

  4. Reductions in human Lyme disease risk due to the effects of oral vaccination on tick-to-mouse and mouse-to-tick transmission.

    PubMed

    Voordouw, Maarten J; Tupper, Haley; Önder, Özlem; Devevey, Godefroy; Graves, Christopher J; Kemps, Brian D; Brisson, Dustin

    2013-04-01

    Vaccinating wildlife is becoming an increasingly popular method to reduce human disease risks from pathogens such as Borrelia burgdorferi, the causative agent of Lyme disease. To successfully limit human disease risk, vaccines targeting the wildlife reservoirs of B. burgdorferi must be easily distributable and must effectively reduce pathogen transmission from infected animals, given that many animals in nature will be infected prior to vaccination. We assessed the efficacy of an easily distributable oral bait vaccine based on the immunogenic outer surface protein A (OspA) to protect uninfected mice from infection and to reduce transmission from previously infected white-footed mice, an important reservoir host of B. burgdorferi. Oral vaccination of white-footed mice effectively reduces transmission of B. burgdorferi at both critical stages of the Lyme disease transmission cycle. First, oral vaccination of uninfected white-footed mice elicits an immune response that protects mice from B. burgdorferi infection. Second, oral vaccination of previously infected mice significantly reduces the transmission of B. burgdorferi to feeding ticks despite a statistically nonsignificant immune response. We used the estimates of pathogen transmission to and from vaccinated and unvaccinated mice to model the efficacy of an oral vaccination campaign targeting wild white-footed mice. Projection models suggest that the effects of the vaccine on both critical stages of the transmission cycle of B. burgdorferi act synergistically in a positive feedback loop to reduce the nymphal infection prevalence, and thus human Lyme disease risk, well below what would be expected from either effect alone. This study suggests that oral immunization of wildlife with an OspA-based vaccine can be a promising long-term strategy to reduce human Lyme disease risk.

  5. Prion transmission

    PubMed Central

    Maddison, Ben C

    2010-01-01

    Prion diseases range from being highly infectious, for example scrapie and CWD, which show facile transmission between susceptible individuals, to showing negligible horizontal transmission, such as BSE and CJD, which are spread via food or iatrogenically, respectively. Scrapie and CWD display considerable in vivo dissemination, with PrPSc and infectivity being found in a range of peripheral tissues. This in vivo dissemination appears to facilitate the recently reported excretion of prion through multiple routes such as from skin, feces, urine, milk, nasal secretions, saliva and placenta. Furthermore, excreted scrapie and CWD agent is detected within environmental samples such as water and on the surfaces of inanimate objects. The cycle of “uptake of prion from the environment—widespread in vivo prion dissemination—prion excretion—prion persistence in the environment” is likely to explain the facile transmission and maintenance of these diseases within wild and farmed populations over many years. PMID:20948292

  6. Training the Next Generation of Scientists: System Dynamics Modeling of Chagas Disease (American Trypanosomiasis) transmission.

    NASA Astrophysics Data System (ADS)

    Goff, P.; Hulse, A.; Harder, H. R.; Pierce, L. A.; Rizzo, D.; Hanley, J.; Orantes, L.; Stevens, L.; Justi, S.; Monroy, C.

    2015-12-01

    A computational simulation has been designed as an investigative case study by high school students to introduce system dynamics modeling into high school curriculum. This case study approach leads users through the forensics necessary to diagnose an unknown disease in a Central American village. This disease, Chagas, is endemic to 21 Latin American countries. The CDC estimates that of the 110 million people living in areas with the disease, 8 million are infected, with as many as 300,000 US cases. Chagas is caused by the protozoan parasite, Trypanosoma cruzi, and is spread via blood feeding insect (vectors), that feed on vertebrates and live in crevasses in the walls and roofs of adobe homes. One-third of the infected people will develop chronic Chagas who are asymptomatic for years before their heart or GI tract become enlarged resulting in death. The case study has three parts. Students play the role of WHO field investigators and work collaboratively to: 1) use genetics to identify the host(s) and vector of the disease 2) use a STELLA™ SIR (Susceptible, Infected, Recovered) system dynamics model to study Chagas at the village scale and 3) develop management strategies. The simulations identify mitigation strategies known as Ecohealth Interventions (e.g., home improvements using local materials) to help stakeholders test and compare multiple optima. High school students collaborated with researchers from the University of Vermont, Loyola University and Universidad de San Carlos, Guatemala, working in labs, interviewing researchers, and incorporating mulitple field data as part of a NSF-funded multiyear grant. The model displays stable equilibria of hosts, vectors, and disease-states. Sensitivity analyses show measures of household condition and presence of vertebrates were significant leverage points, supporting other findings by the University research team. The village-scale model explores multiple solutions to disease mitigation for the purpose of producing

  7. Vector-transmitted disease vaccines: targeting salivary proteins in transmission (SPIT).

    PubMed

    McDowell, Mary Ann

    2015-08-01

    More than half the population of the world is at risk for morbidity and mortality from vector-transmitted diseases, and emerging vector-transmitted infections are threatening new populations. Rising insecticide resistance and lack of efficacious vaccines highlight the need for novel control measures. One such approach is targeting the vector-host interface by incorporating vector salivary proteins in anti-pathogen vaccines. Debate remains about whether vector saliva exposure exacerbates or protects against more severe clinical manifestations, induces immunity through natural exposure or extends to all vector species and associated pathogens. Nevertheless, exploiting this unique biology holds promise as a viable strategy for the development of vaccines against vector-transmitted diseases.

  8. [Chagas' disease in patients in chronic hemodialysis. Prevalence and risk of transmission by blood transfusion].

    PubMed

    Lorca, M; Lorca, E; Atías, A; Plubins, L

    1989-06-01

    A serologic study of Chagas disease was performed in 110 patients submitted to chronic hemodialisis and blood transfusions. Immunofluorescence antibody testing (IgG and IgM) was positive in 6 out of 62 patients receiving multiple blood transfusions (9.7%), but negative in all 48 subjects without transfusions. Thus, repeated blood transfusion is a significant risk for T cruzi infection in chronic hemodialized patients. PMID:2501847

  9. Dysbiotic gut microbiota causes transmissible Crohn's disease-like ileitis independent of failure in antimicrobial defence

    PubMed Central

    Clavel, Thomas; Calasan, Jelena; Lagkouvardos, Ilias; Haange, Sven Bastiaan; Jehmlich, Nico; Basic, Marijana; Dupont, Aline; Hornef, Mathias; von Bergen, Martin; Bleich, André; Haller, Dirk

    2016-01-01

    Objectives Dysbiosis of the intestinal microbiota is associated with Crohn's disease (CD). Functional evidence for a causal role of bacteria in the development of chronic small intestinal inflammation is lacking. Similar to human pathology, TNFdeltaARE mice develop a tumour necrosis factor (TNF)-driven CD-like transmural inflammation with predominant ileal involvement. Design Heterozygous TNFdeltaARE mice and wildtype (WT) littermates were housed under conventional (CONV), specific pathogen-free (SPF) and germ-free (GF) conditions. Microbial communities were analysed by high-throughput 16S ribosomal RNA gene sequencing. Metaproteomes were measured using LC-MS. Temporal and spatial resolution of disease development was followed after antibiotic treatment and transfer of microbial communities into GF mice. Granulocyte infiltration and Paneth cell function was assessed by immunofluorescence and gene expression analysis. Results GF-TNFdeltaARE mice were free of inflammation in the gut and antibiotic treatment of CONV-TNFdeltaARE mice attenuated ileitis but not colitis, demonstrating that disease severity and location are microbiota-dependent. SPF-TNFdeltaARE mice developed distinct ileitis-phenotypes associated with gradual loss of antimicrobial defence. 16S analysis and metaproteomics revealed specific compositional and functional alterations of bacterial communities in inflamed mice. Transplantation of disease-associated but not healthy microbiota transmitted CD-like ileitis to GF-TNFdeltaARE recipients and triggered loss of lysozyme and cryptdin-2 expression. Monoassociation of GF-TNFdeltaARE mice with the human CD-related Escherichia coli LF82 did not induce ileitis. Conclusions We provide clear experimental evidence for the causal role of gut bacterial dysbiosis in the development of chronic ileal inflammation with subsequent failure of Paneth cell function. PMID:25887379

  10. Parameterizing Spatial Models of Infectious Disease Transmission that Incorporate Infection Time Uncertainty Using Sampling-Based Likelihood Approximations.

    PubMed

    Malik, Rajat; Deardon, Rob; Kwong, Grace P S

    2016-01-01

    A class of discrete-time models of infectious disease spread, referred to as individual-level models (ILMs), are typically fitted in a Bayesian Markov chain Monte Carlo (MCMC) framework. These models quantify probabilistic outcomes regarding the risk of infection of susceptible individuals due to various susceptibility and transmissibility factors, including their spatial distance from infectious individuals. The infectious pressure from infected individuals exerted on susceptible individuals is intrinsic to these ILMs. Unfortunately, quantifying this infectious pressure for data sets containing many individuals can be computationally burdensome, leading to a time-consuming likelihood calculation and, thus, computationally prohibitive MCMC-based analysis. This problem worsens when using data augmentation to allow for uncertainty in infection times. In this paper, we develop sampling methods that can be used to calculate a fast, approximate likelihood when fitting such disease models. A simple random sampling approach is initially considered followed by various spatially-stratified schemes. We test and compare the performance of our methods with both simulated data and data from the 2001 foot-and-mouth disease (FMD) epidemic in the U.K. Our results indicate that substantial computation savings can be obtained--albeit, of course, with some information loss--suggesting that such techniques may be of use in the analysis of very large epidemic data sets. PMID:26731666

  11. Parameterizing Spatial Models of Infectious Disease Transmission that Incorporate Infection Time Uncertainty Using Sampling-Based Likelihood Approximations

    PubMed Central

    Malik, Rajat; Deardon, Rob; Kwong, Grace P. S.

    2016-01-01

    A class of discrete-time models of infectious disease spread, referred to as individual-level models (ILMs), are typically fitted in a Bayesian Markov chain Monte Carlo (MCMC) framework. These models quantify probabilistic outcomes regarding the risk of infection of susceptible individuals due to various susceptibility and transmissibility factors, including their spatial distance from infectious individuals. The infectious pressure from infected individuals exerted on susceptible individuals is intrinsic to these ILMs. Unfortunately, quantifying this infectious pressure for data sets containing many individuals can be computationally burdensome, leading to a time-consuming likelihood calculation and, thus, computationally prohibitive MCMC-based analysis. This problem worsens when using data augmentation to allow for uncertainty in infection times. In this paper, we develop sampling methods that can be used to calculate a fast, approximate likelihood when fitting such disease models. A simple random sampling approach is initially considered followed by various spatially-stratified schemes. We test and compare the performance of our methods with both simulated data and data from the 2001 foot-and-mouth disease (FMD) epidemic in the U.K. Our results indicate that substantial computation savings can be obtained—albeit, of course, with some information loss—suggesting that such techniques may be of use in the analysis of very large epidemic data sets. PMID:26731666

  12. Synaptic Mitochondria in Synaptic Transmission and Organization of Vesicle Pools in Health and Disease

    PubMed Central

    Vos, Melissa; Lauwers, Elsa; Verstreken, Patrik

    2010-01-01

    Cell types rich in mitochondria, including neurons, display a high energy demand and a need for calcium buffering. The importance of mitochondria for proper neuronal function is stressed by the occurrence of neurological defects in patients suffering from a great variety of diseases caused by mutations in mitochondrial genes. Genetic and pharmacological evidence also reveal a role of these organelles in various aspects of neuronal physiology and in the pathogenesis of neurodegenerative disorders. Yet the mechanisms by which mitochondria can affect neurotransmission largely remain to be elucidated. In this review we focus on experimental data that suggest a critical function of synaptic mitochondria in the function and organization of synaptic vesicle pools, and in neurotransmitter release during intense neuronal activity. We discuss how calcium handling, ATP production and other mitochondrial mechanisms may influence synaptic vesicle pool organization and synaptic function. Given the link between synaptic mitochondrial function and neuronal communication, efforts toward better understanding mitochondrial biology may lead to novel therapeutic approaches of neurological disorders including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and psychiatric disorders that are at least in part caused by mitochondrial deficits. PMID:21423525

  13. Spinocerebellar ataxia type 3/Machado-Joseph disease: segregation patterns and factors influencing instability of expanded CAG transmissions.

    PubMed

    Souza, G N; Kersting, N; Krum-Santos, A C; Santos, A S P; Furtado, G V; Pacheco, D; Gonçalves, T A; Saute, J A; Schuler-Faccini, L; Mattos, E P; Saraiva-Pereira, M L; Jardim, L B

    2016-08-01

    Controversies about Mendelian segregation and CAG expansion (CAGexp) instabilities during meiosis in spinocerebellar ataxia type 3/Machado-Joseph disease (SCA3/MJD) need clarification. Additional evidence about these issues was obtained from the cohort of all SCA3/MJD individuals living in South Brazil. A survey was carried out to update information registered since 2001. Deaths were checked with the Public Information System, and data was made anonymous. Anticipation and delta-CAGexp from parent-offspring pairs, and delta-CAGexp between siblings were obtained. One hundred and fifty-nine families (94% of the entire registry) were retrieved, comprising 3725 living individuals as of 2015, 625 of these being symptomatic. Minimal prevalence was 6:100,000. Carriers of a CAGexp represented 65.6% of sibs in the genotyped offspring (p < 0.001). Median instability was larger among paternal than maternal transmissions, and instabilities correlated with anticipation (r = 0.38; p = 0.001). Age of the parent correlated to delta-CAGexp among 115 direct parent-offspring CAGexp transmissions (ρ = 0.23, p = 0.014). In 98 additional kindreds, the delta-CAGexp between 269 siblings correlated with their delta-of-age (ρ = 0.27, p < 0.0001). SCA3/MJD was associated with a segregation distortion favoring the expanded allele in our cohort. Instability of expansion during meiosis was weakly influenced by the age of the transmitting parent at the time of conception. PMID:26693702

  14. The alternate role of direct and environmental transmission in fungal infectious disease in wildlife: threats for biodiversity conservation.

    PubMed

    Al-Shorbaji, Farah N; Gozlan, Rodolphe E; Roche, Benjamin; Britton, J Robert; Andreou, Demetra

    2015-05-20

    Emerging fungal pathogens have substantial consequences for infected hosts, as revealed by the global decline of amphibian species from the chytrid fungus. According to the "curse of the Pharaoh" hypothesis, free-living infectious stages typical of fungal pathogens lengthen the timespan of transmission. Free-living infectious stages whose lifespan exceeds the infection time of their hosts are not constrained by virulence, enabling them to persist at high levels and continue transmitting to further sensitive hosts. Using the only Mesomycetozoea fungal species that can be cultured, Sphaerothecum destruens, we obtained tractable data on infectivity and pathogen life cycle for the first time. Here, based on the outcomes of a set of infectious trials and combined with an epidemiological model, we show a high level of dependence on direct transmission in crowded, confined environments and establish that incubation rate and length of infection dictate the epidemic dynamics of fungal disease. The spread of Mesomycetozoea in the wild raise ecological concerns for a range of susceptible species including birds, amphibians and mammals. Our results shed light on the risks associated with farming conditions and highlight the additional risk posed by invasive species that are highly abundant and can act as infectious reservoir hosts.

  15. Persistence of Ebola virus in various body fluids during convalescence: evidence and implications for disease transmission and control.

    PubMed

    Chughtai, A A; Barnes, M; Macintyre, C R

    2016-06-01

    The aim of this study was to review the current evidence regarding the persistence of Ebola virus (EBOV) in various body fluids during convalescence and discuss its implication on disease transmission and control. We conducted a systematic review and searched articles from Medline and EMBASE using key words. We included studies that examined the persistence of EBOV in various body fluids during the convalescent phase. Twelve studies examined the persistence of EBOV in body fluids, with around 800 specimens tested in total. Available evidence suggests that EBOV can persist in some body fluids after clinical recovery and clearance of virus from the blood. EBOV has been isolated from semen, aqueous humor, urine and breast milk 82, 63, 26 and 15 days after onset of illness, respectively. Viral RNA has been detectable in semen (day 272), aqueous humor (day 63), sweat (day 40), urine (day 30), vaginal secretions (day 33), conjunctival fluid (day 22), faeces (day 19) and breast milk (day 17). Given high case fatality and uncertainties around the transmission characteristics, patients should be considered potentially infectious for a period of time after immediate clinical recovery. Patients and their immediate contacts should be informed about these risks. Convalescent patients may need to abstain from sex for at least 9 months or should use condoms until their semen tests are negative. Breastfeeding should be avoided during the convalescent phase. There is a need for more research on persistence, and a uniform approach to infection control guidelines in convalescence. PMID:26808232

  16. Persistence of Ebola virus in various body fluids during convalescence: evidence and implications for disease transmission and control.

    PubMed

    Chughtai, A A; Barnes, M; Macintyre, C R

    2016-06-01

    The aim of this study was to review the current evidence regarding the persistence of Ebola virus (EBOV) in various body fluids during convalescence and discuss its implication on disease transmission and control. We conducted a systematic review and searched articles from Medline and EMBASE using key words. We included studies that examined the persistence of EBOV in various body fluids during the convalescent phase. Twelve studies examined the persistence of EBOV in body fluids, with around 800 specimens tested in total. Available evidence suggests that EBOV can persist in some body fluids after clinical recovery and clearance of virus from the blood. EBOV has been isolated from semen, aqueous humor, urine and breast milk 82, 63, 26 and 15 days after onset of illness, respectively. Viral RNA has been detectable in semen (day 272), aqueous humor (day 63), sweat (day 40), urine (day 30), vaginal secretions (day 33), conjunctival fluid (day 22), faeces (day 19) and breast milk (day 17). Given high case fatality and uncertainties around the transmission characteristics, patients should be considered potentially infectious for a period of time after immediate clinical recovery. Patients and their immediate contacts should be informed about these risks. Convalescent patients may need to abstain from sex for at least 9 months or should use condoms until their semen tests are negative. Breastfeeding should be avoided during the convalescent phase. There is a need for more research on persistence, and a uniform approach to infection control guidelines in convalescence.

  17. The alternate role of direct and environmental transmission in fungal infectious disease in wildlife: threats for biodiversity conservation.

    PubMed

    Al-Shorbaji, Farah N; Gozlan, Rodolphe E; Roche, Benjamin; Britton, J Robert; Andreou, Demetra

    2015-01-01

    Emerging fungal pathogens have substantial consequences for infected hosts, as revealed by the global decline of amphibian species from the chytrid fungus. According to the "curse of the Pharaoh" hypothesis, free-living infectious stages typical of fungal pathogens lengthen the timespan of transmission. Free-living infectious stages whose lifespan exceeds the infection time of their hosts are not constrained by virulence, enabling them to persist at high levels and continue transmitting to further sensitive hosts. Using the only Mesomycetozoea fungal species that can be cultured, Sphaerothecum destruens, we obtained tractable data on infectivity and pathogen life cycle for the first time. Here, based on the outcomes of a set of infectious trials and combined with an epidemiological model, we show a high level of dependence on direct transmission in crowded, confined environments and establish that incubation rate and length of infection dictate the epidemic dynamics of fungal disease. The spread of Mesomycetozoea in the wild raise ecological concerns for a range of susceptible species including birds, amphibians and mammals. Our results shed light on the risks associated with farming conditions and highlight the additional risk posed by invasive species that are highly abundant and can act as infectious reservoir hosts. PMID:25992836

  18. Spinocerebellar ataxia type 3/Machado-Joseph disease: segregation patterns and factors influencing instability of expanded CAG transmissions.

    PubMed

    Souza, G N; Kersting, N; Krum-Santos, A C; Santos, A S P; Furtado, G V; Pacheco, D; Gonçalves, T A; Saute, J A; Schuler-Faccini, L; Mattos, E P; Saraiva-Pereira, M L; Jardim, L B

    2016-08-01

    Controversies about Mendelian segregation and CAG expansion (CAGexp) instabilities during meiosis in spinocerebellar ataxia type 3/Machado-Joseph disease (SCA3/MJD) need clarification. Additional evidence about these issues was obtained from the cohort of all SCA3/MJD individuals living in South Brazil. A survey was carried out to update information registered since 2001. Deaths were checked with the Public Information System, and data was made anonymous. Anticipation and delta-CAGexp from parent-offspring pairs, and delta-CAGexp between siblings were obtained. One hundred and fifty-nine families (94% of the entire registry) were retrieved, comprising 3725 living individuals as of 2015, 625 of these being symptomatic. Minimal prevalence was 6:100,000. Carriers of a CAGexp represented 65.6% of sibs in the genotyped offspring (p < 0.001). Median instability was larger among paternal than maternal transmissions, and instabilities correlated with anticipation (r = 0.38; p = 0.001). Age of the parent correlated to delta-CAGexp among 115 direct parent-offspring CAGexp transmissions (ρ = 0.23, p = 0.014). In 98 additional kindreds, the delta-CAGexp between 269 siblings correlated with their delta-of-age (ρ = 0.27, p < 0.0001). SCA3/MJD was associated with a segregation distortion favoring the expanded allele in our cohort. Instability of expansion during meiosis was weakly influenced by the age of the transmitting parent at the time of conception.

  19. The alternate role of direct and environmental transmission in fungal infectious disease in wildlife: threats for biodiversity conservation

    PubMed Central

    Al-Shorbaji, Farah N.; Gozlan, Rodolphe E.; Roche, Benjamin; Robert Britton, J.; Andreou, Demetra

    2015-01-01

    Emerging fungal pathogens have substantial consequences for infected hosts, as revealed by the global decline of amphibian species from the chytrid fungus. According to the “curse of the Pharaoh” hypothesis, free-living infectious stages typical of fungal pathogens lengthen the timespan of transmission. Free-living infectious stages whose lifespan exceeds the infection time of their hosts are not constrained by virulence, enabling them to persist at high levels and continue transmitting to further sensitive hosts. Using the only Mesomycetozoea fungal species that can be cultured, Sphaerothecum destruens, we obtained tractable data on infectivity and pathogen life cycle for the first time. Here, based on the outcomes of a set of infectious trials and combined with an epidemiological model, we show a high level of dependence on direct transmission in crowded, confined environments and establish that incubation rate and length of infection dictate the epidemic dynamics of fungal disease. The spread of Mesomycetozoea in the wild raise ecological concerns for a range of susceptible species including birds, amphibians and mammals. Our results shed light on the risks associated with farming conditions and highlight the additional risk posed by invasive species that are highly abundant and can act as infectious reservoir hosts. PMID:25992836

  20. A rigorous approach to investigating common assumptions about disease transmission: Process algebra as an emerging modelling methodology for epidemiology.

    PubMed

    McCaig, Chris; Begon, Mike; Norman, Rachel; Shankland, Carron

    2011-03-01

    Changing scale, for example, the ability to move seamlessly from an individual-based model to a population-based model, is an important problem in many fields. In this paper, we introduce process algebra as a novel solution to this problem in the context of models of infectious disease spread. Process algebra allows us to describe a system in terms of the stochastic behaviour of individuals, and is a technique from computer science. We review the use of process algebra in biological systems, and the variety of quantitative and qualitative analysis techniques available. The analysis illustrated here solves the changing scale problem: from the individual behaviour we can rigorously derive equations to describe the mean behaviour of the system at the level of the population. The biological problem investigated is the transmission of infection, and how this relates to individual interactions.

  1. Lymphocyte contamination of laryngoscope blades--a possible vector for transmission of variant Creutzfeldt-Jakob disease.

    PubMed

    Hirsch, N; Beckett, A; Collinge, J; Scaravilli, F; Tabrizi, S; Berry, S

    2005-07-01

    Variant Creutzfeldt-Jakob disease (vCJD) is associated with extensive prion infection of lymphoreticular tissues during the prolonged asymptomatic incubation period. Instruments exposed to infected tissues of preclinically infected individuals during medical or surgical procedures represent a potential risk of iatrogenic transmission of vCJD prions. We assessed the frequency of contamination with lymphoid tissue of single-use laryngoscope blades used for tracheal intubation for general anaesthesia. Using a cyto-centrifugation technique, lymphocytes were detected from 30% of laryngoscope blades studied. As prions resist routine sterilisation procedures, the use of non-disposable laryngoscope blades poses a risk of transmitting vCJD from patient to patient. The use of such instruments should be abandoned and disposable alternatives used.

  2. The landscape configuration of zoonotic transmission of Ebola virus disease in West and Central Africa: interaction between population density and vegetation cover.

    PubMed

    Walsh, Michael G; Haseeb, Ma

    2015-01-01

    Ebola virus disease (EVD) is an emerging infectious disease of zoonotic origin that has been responsible for high mortality and significant social disruption in West and Central Africa. Zoonotic transmission of EVD requires contact between susceptible human hosts and the reservoir species for Ebolaviruses, which are believed to be fruit bats. Nevertheless, features of the landscape that may facilitate such points of contact have not yet been adequately identified. Nor have spatial dependencies between zoonotic EVD transmission and landscape structures been delineated. This investigation sought to describe the spatial relationship between zoonotic EVD transmission events, or spillovers, and population density and vegetation cover. An inhomogeneous Poisson process model was fitted to all precisely geolocated zoonotic transmissions of EVD in West and Central Africa. Population density was strongly associated with spillover; however, there was significant interaction between population density and green vegetation cover. In areas of very low population density, increasing vegetation cover was associated with a decrease in risk of zoonotic transmission, but as population density increased in a given area, increasing vegetation cover was associated with increased risk of zoonotic transmission. This study showed that the spatial dependencies of Ebolavirus spillover were associated with the distribution of population density and vegetation cover in the landscape, even after controlling for climate and altitude. While this is an observational study, and thus precludes direct causal inference, the findings do highlight areas that may be at risk for zoonotic EVD transmission based on the spatial configuration of important features of the landscape.

  3. Glyceraldehyde 3-phosphate dehydrogenase augments the intercellular transmission and toxicity of polyglutamine aggregates in a cell model of Huntington disease.

    PubMed

    Mikhaylova, Elena R; Lazarev, Vladimir F; Nikotina, Alina D; Margulis, Boris A; Guzhova, Irina V

    2016-03-01

    The common feature of Huntington disease is the accumulation of oligomers or aggregates of mutant huntingtin protein (mHTT), which causes the death of a subset of striatal neuronal populations. The cytotoxic species can leave neurons and migrate to other groups of cells penetrating and damaging them in a prion-like manner. We hypothesized that the glycolytic enzyme glyceraldehyde 3-phosphate dehydrogenase (GAPDH), previously shown to elevate the aggregation of mHTT, is associated with an increased efficiency of intercellular propagation of mHTT. GAPDH, on its own or together with polyglutamine species, was shown to be released into the extracellular milieu mainly from dying cells as assessed by a novel enzyme immunoassay, western blotting, and ultrafiltration. The conditioned medium of cells with growing GAPDH-polyQ aggregates was toxic to naïve cells, whereas depletion of the aggregates from the medium lowered this cytotoxicity. The GAPDH component of the aggregates was found to increase their toxicity by two-fold in comparison with polyQ alone. Furthermore, GAPDH-polyQ complexes were shown to penetrate acceptor cells and to increase the capacity of polyQ to prionize its intracellular homolog containing a repeat of 25 glutamine residues. Finally, inhibitors of intracellular transport showed that polyQ-GAPDH complexes, as well as GAPDH itself, penetrated cells using clathrin-mediated endocytosis. This suggested a pivotal role of the enzyme in the intercellular transmission of Huntington disease pathogenicity. In conclusion, GAPDH occurring in complexes with polyglutamine strengthens the prion-like activity and toxicity of the migrating aggregates. Aggregating polygluatmine tracts were shown to release from the cells over-expressing mutant huntingtin in a complex with glyceraldehyde 3-phosphate dehydrogenase (GAPDH). The enzyme enhances the intracellular transport of aggregates to healthy cells, prionization of normal cellular proteins and finally cell death, thus

  4. The response of ducks to V4 Newcastle disease virus and its transmission to contact ducks and domestic chickens.

    PubMed

    Bouzari, Majid

    2014-01-01

    Experimental infection of Muscovy ducks with V4 strain of Newcastle disease virus was undertaken to determine the response of the ducks to the virus and the possibility of virus transmission to ducks and chickens in village like conditions. Twelve ducks were randomly and equally divided into three groups of control, inoculated and in-contact. Additionally, the chickens were placed into two groups of four animals each, namely in-contact and control. The inoculated and in-contact ducks and in-contact chickens were kept together. The eye drop route was used for inoculation and hemagglutination inhibition (HI) antibodies were measured for assessment of antibody response and cloacal and pharyngeal swabs were used for detection of the virus. The primary antibody response of inoculated ducks was very high and rapid (geometric mean titers [Log base 2] of up to 5.75 ± 0.50). The in-contact ducks showed antibody response with the same pattern but lower titers than the inoculated ducks (geometric mean titers [Log base 2] of up to 3.25 ± 1.70). The in-contact chickens showed a slight increase of HI antibody (geometric mean titers [Log base 2] of up to 2.25 ± 1.25) while the control chickens did not show any increase. The antibody response indicated the transmission of the virus to contact ducks and chickens. A single isolation of virus confirmed the ability of ducks to excrete the virus. It was concluded that the V4 strain of Newcastle disease virus was highly antigenic for ducks, and ducks can transmit it to other ducks and also in-contact chickens.

  5. A Distributed Platform for Global-Scale Agent-Based Models of Disease Transmission

    PubMed Central

    Parker, Jon; Epstein, Joshua M.

    2013-01-01

    The Global-Scale Agent Model (GSAM) is presented. The GSAM is a high-performance distributed platform for agent-based epidemic modeling capable of simulating a disease outbreak in a population of several billion agents. It is unprecedented in its scale, its speed, and its use of Java. Solutions to multiple challenges inherent in distributing massive agent-based models are presented. Communication, synchronization, and memory usage are among the topics covered in detail. The memory usage discussion is Java specific. However, the communication and synchronization discussions apply broadly. We provide benchmarks illustrating the GSAM’s speed and scalability. PMID:24465120

  6. Chronic wasting disease and atypical forms of bovine spongiform encephalopathy and scrapie are not transmissible to mice expressing wild-type levels of human prion protein.

    PubMed

    Wilson, Rona; Plinston, Chris; Hunter, Nora; Casalone, Cristina; Corona, Cristiano; Tagliavini, Fabrizio; Suardi, Silvia; Ruggerone, Margherita; Moda, Fabio; Graziano, Silvia; Sbriccoli, Marco; Cardone, Franco; Pocchiari, Maurizio; Ingrosso, Loredana; Baron, Thierry; Richt, Juergen; Andreoletti, Olivier; Simmons, Marion; Lockey, Richard; Manson, Jean C; Barron, Rona M

    2012-07-01

    The association between bovine spongiform encephalopathy (BSE) and variant Creutzfeldt-Jakob disease (vCJD) has demonstrated that cattle transmissible spongiform encephalopathies (TSEs) can pose a risk to human health and raises the possibility that other ruminant TSEs may be transmissible to humans. In recent years, several novel TSEs in sheep, cattle and deer have been described and the risk posed to humans by these agents is currently unknown. In this study, we inoculated two forms of atypical BSE (BASE and H-type BSE), a chronic wasting disease (CWD) isolate and seven isolates of atypical scrapie into gene-targeted transgenic (Tg) mice expressing the human prion protein (PrP). Upon challenge with these ruminant TSEs, gene-targeted Tg mice expressing human PrP did not show any signs of disease pathology. These data strongly suggest the presence of a substantial transmission barrier between these recently identified ruminant TSEs and humans.

  7. Studies on disease transmission in spacecraft environments. [as experienced onboard Skylab 1

    NASA Technical Reports Server (NTRS)

    Kenyon, A. J.

    1974-01-01

    The effects of the Skylab gas mixtures on general health and immunocompetence of mice and ferrets subjected to the Skylab space cabin environment (SCE) were initially studied in a stainless steel low pressure facility which was maintained at gas ratios of 30% nitrogen and 70% oxygen under 5 psia, and which consisted of two subchambers, that permitted mutual isolation of experimental groups and/or selective removal of animals without return of the entire cabin to ambient pressure was developed. The studies demonstrated that ferrets immunized with Brucella Strain 19 prior to being housed in SCE had decreased synthesis of IgG compared to their respective controls. The possibility of latent infections being responsible for stress-induced upper respiratory diseases of astronauts required that the role of neutralizing antibody as a function of antibody affinity/avidity be investigated. The model consisted of Aleutian disease virus (ADV) which infects ferrets and mink resulting in nonneutralized immune complexes. These studies demonstrated that early antibody to ADV had lower affinity/avidity than late antibody with respect to chronicity. These studies culminated in a description of antibody affinity, first isolation of ADV and its cultivation in vitro.

  8. Heart Disease in Disorders of Muscle, Neuromuscular Transmission, and the Nerves

    PubMed Central

    Stöllberger, Claudia

    2016-01-01

    Little is known regarding cardiac involvement (CI) by neuromuscular disorders (NMDs). The purpose of this review is to summarise and discuss the major findings concerning the types, frequency, and severity of cardiac disorders in NMDs as well as their diagnosis, treatment, and overall outcome. CI in NMDs is characterized by pathologic involvement of the myocardium or cardiac conduction system. Less commonly, additional critical anatomic structures, such as the valves, coronary arteries, endocardium, pericardium, and even the aortic root may be involved. Involvement of the myocardium manifests most frequently as hypertrophic or dilated cardiomyopathy and less frequently as restrictive cardiomyopathy, non-compaction, arrhythmogenic right-ventricular dysplasia, or Takotsubo-syndrome. Cardiac conduction defects and supraventricular and ventricular arrhythmias are common cardiac manifestations of NMDs. Arrhythmias may evolve into life-threatening ventricular tachycardias, asystole, or even sudden cardiac death. CI is common and carries great prognostic significance on the outcome of dystrophinopathies, laminopathies, desminopathies, nemaline myopathy, myotonias, metabolic myopathies, Danon disease, and Barth-syndrome. The diagnosis and treatment of CI in NMDs follows established guidelines for the management of cardiac disease, but cardiotoxic medications should be avoided. CI in NMDs is relatively common and requires complete work-up following the establishment of a neurological diagnosis. Appropriate cardiac treatment significantly improves the overall long-term outcome of NMDs. PMID:27014341