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

Abstract

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.

Are tree squirrels involved in the circulation of flaviviruses in Italy?

“…USUV‐specific neutralizing antibodies were observed in all the three sampled years, while seropositivity to WNV and TBEV was only found in 2011. The presence of antibodies against WNV and USUV in young animals trapped in Piedmont indicates circulation of these viruses in 2011 and 2012, respectively, which is consistent with serological data from wild birds over the same geographical area (Llopis et al., ). However, WNV cases in the region were reported for the first time in horses and birds only in 2014, while USUV cases in horses were detected already in 2010, suggesting a more intense circulation of USUV compared to WNV (Calzolari et al., ; CESME, ), which may explain the higher seroprevalence to USUV observed in tree squirrels (CESME, ).…”

Serological Evidence for Japanese Encephalitis and West Nile Virus Infections in Domestic Birds in Cambodia

“…Due to the cross-reactivity, retrospective seroprevalence studies for flaviviruses are challenging in regions where more than one of these viruses circulate. The HIA is characterized by a high crossreactivity which generally only allows a qualitative conclusion about the presence of flavivirus antibodies (48)(49)(50)(51). Our HIA analysis and the moderate correlation of HIA titers among all viruses also demonstrated a high cross-reactivity especially between the two DENV serotypes 2 and 3 (Spearman r = 0.8999).…”

Geographic variations of the bird-borne structural risk of West Nile virus circulation in Europe

“…However our analyses focused on short-lived bird species, where the proportion of birds borne during the year of sampling is high, therefore blood-sampled before their first migration to Africa. An additional possible explanation may be the inclusion of studies done during West Nile outbreaks or intense circulation periods, for example in Italy between 2006 and 2013 [57,58] when resident species may present very high prevalence of antibodies.…”