Mosquito, bird and human surveillance of West Nile and Usutu viruses in Emilia-Romagna Region (Italy) in 2010

• Published in: PloS one Vol. 7; no. 5; p. e38058
• Main Authors: Calzolari, Mattia, Gaibani, Paolo, Bellini, Romeo, Defilippo, Francesco, Pierro, Anna, Albieri, Alessandro, Maioli, Giulia, Luppi, Andrea, Rossini, Giada, Balzani, Agnese, Tamba, Marco, Galletti, Giorgio, Gelati, Antonio, Carrieri, Marco, Poglayen, Giovanni, Cavrini, Francesca, Natalini, Silvano, Dottori, Michele, Sambri, Vittorio, Angelini, Paola, Bonilauri, Paolo
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 30-05-2012; Public Library of Science (PLoS)
• Subjects: Aedes albopictus; Analysis; Animals; Aquatic insects; Asian tiger mosquito; Biology; Birds; Birds - virology; Climate; Culex; Culicidae; Culicidae - virology; Diffusion; Drought; Drought conditions; Ecological and Environmental Phenomena; Epidemics; Flavivirus; Health policy; Humans; Italy; Medicine; Meningoencephalitis; Meteorological conditions; Mosquitoes; Mutation; Overwintering; Polymerase Chain Reaction; Pools; Public health; Relative abundance; Surveillance; Surveillance equipment; Temperature range; Veterinary Science; Viruses; West Nile fever; West Nile virus; West Nile virus - genetics; West Nile virus - isolation & purification; Italy
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0038058

In 2008, after the first West Nile virus (WNV) detection in the Emilia-Romagna region, a surveillance system, including mosquito- and bird-based surveillance, was established to evaluate the virus presence. Surveillance was improved in following years by extending the monitoring to larger areas and increasing the numbers of mosquitoes and birds tested.
A network of mosquito traps, evenly distributed and regularly activated, was set up within the surveyed area. A total of 438,558 mosquitoes, grouped in 3,111 pools and 1,276 birds (1,130 actively sampled and 146 from passive surveillance), were tested by biomolecular analysis. The survey detected WNV in 3 Culex pipiens pools while Usutu virus (USUV) was found in 89 Cx. pipiens pools and in 2 Aedes albopictus pools. Two birds were WNV-positive and 12 were USUV-positive. Furthermore, 30 human cases of acute meningoencephalitis, possibly caused by WNV or USUV, were evaluated for both viruses and 1,053 blood bags were tested for WNV, without any positive result.
Despite not finding symptomatic human WNV infections during 2010, the persistence of the virus, probably due to overwintering, was confirmed through viral circulation in mosquitoes and birds, as well as for USUV. In 2010, circulation of the two viruses was lower and more delayed than in 2009, but this decrease was not explained by the relative abundance of Cx. pipiens mosquito, which was greater in 2010. The USUV detection in mosquito species confirms the role of Cx. pipiens as the main vector and the possible involvement of Ae. albopictus in the virus cycle. The effects of meteorological conditions on the presence of USUV-positive mosquito pools were considered finding an association with drought conditions and a wide temperature range. The output produced by the surveillance system demonstrated its usefulness and reliability in terms of planning public health policies.