Monitoring of West Nile Virus Infections in Germany

Abstract

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.

Epizootic Emergence of Usutu Virus in Wild and Captive Birds in Germany

“…Neutralizing antibodies against USUV were also demonstrated in birds from the United Kingdom [5]. In contrast, no serological evidence for USUV circulation was found in birds from Germany between 2007 and 2011 [6], [7]. In 2009, two human cases with an USUV-related neuroinvasive illness were reported from Italy [8], [9].…”

Tick-borne encephalitis virus (TBEV) – findings on cross reactivity and longevity of TBEV antibodies in animal sera

“…One example of known cross-reactivity between members of the flavivirus genus comes from serological West Nile virus (WNV) diagnostics [29]. WNV is considered to be the most widespread flavivirus in the world and is transmitted and maintained in an enzootic mosquito-bird cycle [30,31].…”

West Nile Virus Antibody Prevalence in Horses of Ukraine

“…False positive ELISA results caused by TBE cross-reactive antibodies had been observed in earlier serological studies looking at horses from Germany and Austria [26,27,28] which impede the interpretation of the ELISA results. However, no TBEV-NT positive horse serum was found among the Ukrainian horse sera.…”

“…As the WNV ELISA used also detects cross-reacting antibodies induced by other flaviviruses, e.g. TBEV [26,27,28], all sera negative in the WNV NT were also screened using a TBEV NT as well as a Japanese encephalitis virus (JEV) NT, all with negative outcomes (data not shown). The reason for ELISA reactivity of the seven sera (positive WNV ELISA, but negative in all conducted NTs, Table 3) is unclear at present.…”