Veterinary/zoology session

West-Nile virus (WNV) belongs to the family of Flaviviridae, and an important human- and animal pathogen virus. It has caused mortality in wild birds in Hungary since 2004. The virus was first isolated in Africa, but within the years it was also detected in Europe, in Asia, and in Australia, and emerged in America. In some countries it caused serious outbreaks among wild birds, horses and humans. Mosquitoes are the principal vectors of the virus. Two main and further three smaller genetic lineages of WNV have been identified so far.

In this study we collected dead wild birds from different regions of Hungary in 2008 and in 2009, and we have investigated the presence of West-Nile virus nucleic acid in their brain samples by reverse-transcription polymerase chain reaction (RT-PCR). Within these two years we have analyzed 161 wild birds, which belonged to 53 species. In 2008 26 birds proved positive for WNV out of 91 investigated, and in 2009 we detected 15 infected birds out of 70. Goshawks (Accipiter gentilis) were the most sensitive for the virus infection, since there were 24 infected goshawks amongst the 41 infected birds. Furthermore we have detected the WNV in 2 Harris hawks (Parabuteo unicinctus), in 3 gryfalcons (Falco rusticolus), in 1 sparrowhawk (Accipiter nisus), in 1 peregrine falcon (Falco peregrinus), in 1 red-footed falcon (Falco vespertinus), in 1 barn owl (Tyto alba), in 1 europaean roller (Coracias garrulus), in 1 house sparrow (Passer domesticus), in 2 robins (Erithacus rubecula), in 1 black redstart (Phoenicurus ochruros), in 1 sedge warbler (Acrocephalus schoenobaenus), in 1 Savi’s warbler (Locustella luscinoioides), and in 1 raven (Corvus corax). In line with the birds mortality WNV cases in humans and in horses were also detected in Hungary.

The results of the phylogenetic analysis indicate that a particular, lineage 2 WNV strain, which emerged in Hungary in 2004, has spread to several regions of the country within the last five years. WNV strains belonging to this lineage have been detected only in the sub-Saharan region of Africa and in Madagascar before. This strain was most probably introduced into Hungary by migratory birds. We have recorded a particularly quick and significant spread of the strain in 2008, when it emerged even in the eastern regions of Austria. Mortality was recorded mainly in birds of prey, but the detection of the virus in small songbirds indicates that those species may also contribute the maintenance and spread of the virus in the region. Due to the wild bird mortality, besides the public- and animal health consequences, the presence of WNV in Hungary raise serious nature conservation concerns.