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.
Summary West Nile virus (WNV) is a flavivirus that is maintained in an enzootic cycle between ornithophilic mosquitoes, mainly of the Culex genus, and certain wild bird species. Other bird species like ravens, jays and raptors are highly susceptible to the infection and may develop deadly encephalitis, while further species of birds are only going through subclinical infection. The objective of this study was to continue in years 2009–2011 the serological and molecular surveillance in wild birds in Germany (see Vector Borne Zoonotic Dis. 10, 639) and to expand these investigations for the first time also to sera from domestic poultry and horses collected between 2005 and 2009. All three cohorts function as indicators for the endemic circulation of WNV. The presence of WNV‐specific antibodies was detected in all samples by virus neutralization test (VNT), indirect immunofluorescence test (IFT) and/or enzyme‐linked immunosorbent assay (ELISA). The presence of WNV genomes was monitored in relevant sera using two qRT‐PCRs that amplify lineage 1 and 2 strains. A total of 364 migratory and resident wild bird serum samples (with emphasis on Passeriformes and Falconiformes) as well as 1119 serum samples from domestic poultry and 1282 sera from horses were analysed. With the exception of one hooded crow, antibody carriers were exclusively found in migratory birds, but not in resident birds/domestic poultry or in local horses. Crows are facultative, short‐distance winter migrants in Germany. WNV‐specific nucleic acids could not be demonstrated in any of the samples. According to these data, there is no convincing evidence for indigenous WNV infections in equines and in wild/domestic birds in Germany. However, since a few years, WNV infections are endemic in other European countries such as Austria, Hungary, Greece and Italy, a state‐of‐the‐art surveillance system for the detection of incursions of WNV into Germany deems mandatory.
West Nile virus (WNV) is a mosquito-transmitted flavivirus with wild birds as its natural hosts. Ravens, falcons and jays are highly susceptible for WNV and develop deadly encephalitis, while other bird species undergo only subclinical infections. Migratory birds are efficient vectors for geographic spreading of WNV. Until now, WNV infections have not been diagnosed in Germany, but infections in humans and horses have occurred recently in Austria, Hungary and Italy. To investigate potential WNV introduction by infected wild birds, we have monitored the serological status of ducks in three national sentinel stations. No WNV-positive reactions were found, whereas sera from coots from northern Iran were positive.
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