Further circulation of West Nile and Usutu viruses in wild birds in Italy

Usutu virus (USUV) and West Nile virus (WNV) are emerging pathogens that can cause neurological disease in humans. From March 2012 to June 2013, a sero-survey on wild birds was carried out to investigate the circulation of both viruses in Northwest (NW) Italy. Samples belonging to 47 different bird species have been collected using a volunteer based network and a wildlife rehabilitation center. Four of 297 serum samples had neutralizing antibodies against USUV (P = 1.34%, IC 95% 0.36-3.4), while 10 of 233 samples tested positive for WNV (P = 4.29%, IC 95% 2.07-7.75). Neutralizing antibodies for WNV were significantly more prevalent (p < 0.001) in trans-Saharan migrants (P = 21%, IC 95% 9.55-37.3) than in resident and short-distance birds, but no migratory habit-related differences were found for USUV. Antibodies in resident bird species suggest that both viruses are circulating in NW Italy.