Avian influenza surveillance in wild birds in the European Union in 2006

Abstract

Background Infections of wild birds with highly pathogenic avian influenza (AI) subtype H5N1 virus were reported for the first time in the European Union in 2006. Objectives To capture epidemiological information on H5N1 HPAI in wild bird populations through large‐scale surveillance and extensive data collection. Methods Records were analysed at bird level to explore the epidemiology of AI with regard to species of wild birds involved, timing and location of infections as well as the applicability of different surveillance types for the detection of infections. Results In total, 120,706 records of birds were sent to the Community Reference Laboratory for analysis. Incidents of H5N1 HPAI in wild birds were detected in 14 EU Member States during 2006. All of these incidents occurred between February and May, with the exception of two single cases during the summer months in Germany and Spain. Conclusions For the detection of H5N1 HPAI virus, passive surveillance of dead or diseased birds appeared the most effective approach, whilst active surveillance offered better detection of low pathogenic avian influenza (LPAI) viruses. No carrier species for H5N1 HPAI virus could be identified and almost all birds infected with H5N1 HPAI virus were either dead or showed clinical signs. A very large number of Mallards (Anas platyrhynchos) were tested in 2006 and while a high proportion of LPAI infections were found in this species, H5N1 HPAI virus was rarely identified in these birds. Orders of species that appeared to be very clinically susceptible to H5N1 HPAI virus were swans, diving ducks, mergansers and grebes, supporting experimental evidence. Surveillance results indicate that H5N1 HPAI virus did not establish itself successfully in the EU wild bird population in 2006.

Variation in viral shedding patterns between different wild bird species infected experimentally with low-pathogenicity avian influenza viruses that originated from wild birds

“…This observation is consistent with historic surveillance results of higher isolation rates from mallards, and supports the important role that this species plays in the natural history of AI. The mallard is distributed worldwide and, as previously mentioned, more AI viruses have been isolated from this species than any other wild avian species (Hinshaw et al, 1980;Stallknecht et al, 1990;Krauss et al, 2004;Munster et al, 2005;Olsen et al, 2006;Hesterberg et al, 2009). Mallards in the H5N2 and H3N8 treatment groups had an extended period of viral shedding, primarily via the cloaca.…”

Ecological Modeling of the Spatial Distribution of Wild Waterbirds to Identify the Main Areas Where Avian Influenza Viruses are Circulating in the Inner Niger Delta, Mali

“…Experimental infections with H5N1 HPAIV (Brown et al, 2006(Brown et al, , 2008Keawcharoen et al, 2008) showed that most Anatids species are able to replicate and shed H5N1 HPAIV, half of the time without any clinical sign (Gaidet et al, 2010). Furthermore, almost all of healthy, free-living wild birds that have tested positive for H5N1 HPAI with no apparent clinical signs were Anatids (Chen et al, 2006;Saad et al, 2007;Hesterberg et al, 2009;OIE, 2009). The highest circulation rates of LPAIV in the field also have been detected for Anatids species (Olsen et al, 2006).…”

Within-host variation of avian influenza viruses

“…The prevalence of H5N1 in wild birds has been studied intensively in Europe since 2006, and the results of a 2006 survey have been reported recently (Hesterberg et al 2009). The survey showed that H5N1 viruses were found only rarely in dabbling ducks, but swans, diving ducks, mergansers and grebes showed higher rates of infection and usually associated with disease.…”