West Nile virus monitoring of migratory and resident birds in Germany.

West Nile virus (WNV) is a mosquito-borne flavivirus naturally circulating in wild bird populations. The virus is also capable to infect a broad range of vertebrate species. Humans and equines are highly susceptible and can develop mild flu-like illnesses as well as severe encephalitis leading to fatalities. Most recently, WNV was found to circulate in countries close to Germany, such as France, Czech Republic, Italy, Austria, and Hungary. Given this epidemiological situation its spread to Germany cannot be ruled out. As no data on the WNV situation were available for Germany for the most recent past, we have conducted a serological survey to reveal WNV antibodies in wild birds. More than 2700 blood samples from migratory and resident birds representing 72 species that were collected during 2005-2009 were tested using an immunofluorescence assay and partly by micro-virus neutralization test. By immunofluorescence assay WNV-reactive antibodies could be demonstrated in 11 wild bird species. Similarly, WNV-neutralizing antibodies were revealed in migratory birds belonging to 10 species, but not in resident birds. According to the absence of WNV-reactive antibodies in resident birds and the absence of WNV-specific RNA in all investigated bird samples, there is currently no evidence for a WNV circulation in Germany.