Neurotropism in blackcaps (Sylvia atricapilla) and red-billed queleas (Quelea quelea) after highly pathogenic avian influenza virus H5N1 infection.

PubMed

Breithaupt, A; Kalthoff, D; Dale, J; Bairlein, F; Beer, M; Teifke, J P

2011-09-01

The epidemiologic role of passerine birds in the spread of highly pathogenic avian influenza virus (HPAIV) remains controversial. However, confirmed natural infections with HPAIV in Passeriformes, their close contact to poultry and humans, and their role as a human food source indicate a need for increased research on passerines. To date, there are only a few studies on viral shedding and pathomorphologic changes in songbirds infected with HPAIV. To investigate susceptibility, clinical outcome, virus spread, and pathomorphology, the authors inoculated oculo-oronasally 22 red-billed queleas (Quelea quelea) and 11 blackcaps (Sylvia atricapilla) with A/Cygnus cygnus/Germany/R65/2006 (H5N1) using 2 different doses of either 10(4) EID50 (50% egg infective dose) or 10(6) EID50 per animal. They monitored all birds for clinical signs and oropharyngeal and cloacal virus shedding. They also performed immunohistochemistry and obtained molecular virologic data by real-time reverse transcription polymerase chain reaction in tissue samples. In contrast to blackcaps, where 100% of the infected individuals died, queleas were much less susceptible, with a mortality of 82% and 18%, depending on the doses applied. In both species, the virus was shed within 3 to 6 days postinfection, mainly via the respiratory tract. Viral antigen was detected in 100% of the succumbed birds, particularly in the central nervous system. In blackcaps, the heart, lungs, and pancreas were mainly infected. In contrast, the pancreas was predominantly affected in queleas, whereas the heart and the lower respiratory tract were of minor relevance. The authors hypothesize that neurotropism should be considered a main factor for the fatal course of disease in Passeriformes after infection with HPAIV.

Bridge hosts for avian influenza viruses at the wildlife/domestic interface: an eco-epidemiological framework implemented in southern Africa.

PubMed

Caron, A; Grosbois, V; Etter, E; Gaidet, N; de Garine-Wichatitsky, M

2014-12-01

Wild terrestrial birds can act as potential local spreaders or bridge hosts for avian influenza viruses (AIVs) between waterfowl (the maintenance hosts of AIVs) and domestic avian populations in which AIVs may cause disease. Few studies have investigated this hypothesis, although it is an important knowledge gap in our understanding of AIV spread within socio-ecosystems. We designed a simple and reproducible approach in an agro-ecosystem in Zimbabwe based on: (1) bird counts at key target sites (i.e., wetlands, villages, intensive poultry production buildings and ostrich farms) to identify which wild birds species co-occur in these different sites and seasons when the risk of AIV transmission through these potential bridge hosts is maximal and (2) targeted sampling and testing for AIV infection in the identified potential bridge hosts. We found that 12 wild bird species represented the vast majority (79%) of co-occurrences in the different sites, whereas 230 bird species were recorded in this ecosystem. Specifically, three species - barn swallow, Hirundo rustica, red-billed quelea, Quelea quelea and cattle egret, Bubulcus ibis - represented the main potential bridge host species (65% of co-occurrences). In two out of these three species (i.e., barn swallow and red-billed quelea), we detected AIV infections, confirming that they can play a bridge function between waterfowl and domestic species in the ecosystem. Our approach can be easily implemented in other ecosystems to identify potential bridge hosts, and our results have implications in terms of surveillance, risk management and control of AIV spread in socio-ecosystems. Copyright © 2014 Elsevier B.V. All rights reserved.