The common coot as sentinel species for the presence of West Nile and Usutu flaviviruses in Central Europe

We examined 146 common coots (Fulica atra) on fishponds in central Moravia, Czech Republic, for antibodies to West Nile (WNV) and Usutu (USUV) flaviviruses. Eighteen birds reacted in the plaque-reduction neutralization test against WNV; these WNV seropositive samples were then titrated in parallel against USUV and tick-borne encephalitis virus (TBEV) to exclude flavivirus cross-reactivity. Two birds (1.4% overall) had the highest titers against WNV while 9 birds (6.2% overall) were seropositive for USUV, and in 7 birds the infecting flavivirus could not be differentiated with certainty. Our results indicate that both WNV and USUV infections occur in common coots; these birds might serve as a 'sentinel' species indicating the presence of these viruses at fishpond and wetland habitats in Central Europe.