Surveillance on antibodies against West Nile virus, Usutu virus, tick-borne encephalitis virus and Tribeč virus in wild birds in Drienovská wetland, Slovakia

Searching for specific antibodies in bird serum could reveal arbovirus activity in certain localities. To date, no systematic surveillance for arbovirus infection in autochthonous population of wild birds has been conducted in Slovakia. Present study includes birds captured on spring migration and birds of the autochthonous nesting population of the Drienovská wetland (Slovakia). Serum samples were tested for West Nile virus (WNV), Usutu virus (USUV), Tick-borne encephalitis virus (TBEV) and Tribeč virus (TRBV) neutralizing antibodies (NAb). Blood samples were collected during 2017 spring migration (March – April) and from local breeders and hatched juveniles (May – July) caught by Constant Effort site ringing method. Specific NAb were detected by micro-titration virus neutralization test. WNV NAb were detected in 11.7% (18/153) of sampled birds. Ten WNV seropositive were migrants (Eurasian Robins, Eurasian Blackcap and a Great Tit), 5 were nesting adults (Song Thrush, White Throat, Eurasian Jay, Hawfinch and Eurasian Blackbird) and 3 were juveniles (Song Thrush, Common Starling and a Great Tit). There was not confirmed USUV infection in any of the examined birds. TBEV NAb were detected during breeding season in the adult Eurasian Blackcap, which means 1.1% (1/93) seropositivity. TRBV NAb was detected in 7.4% (5/68) of adult birds (Eurasian Blackbirds and a Common Starling) and in one juvenile Great Tit, which had also WNV Nab as well. These results suggest active transmission of at least two arboviruses in the autochthonous avifauna in Slovakia.