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

doi: 10.1371/journal.pone.0038058. Epub 2012 May 30.

Paolo Gaibani, Romeo Bellini, Francesco Defilippo, Anna Pierro, Alessandro Albieri, Giulia Maioli, Andrea Luppi, Giada Rossini, Agnese Balzani, Marco Tamba, Giorgio Galletti, Antonio Gelati, Marco Carrieri, Giovanni Poglayen, Francesca Cavrini, Silvano Natalini, Michele Dottori, Vittorio Sambri, Paola Angelini, Paolo Bonilauri

Affiliations

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

Mattia Calzolari et al. PLoS One. 2012.

Abstract

Background: 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.

Methodology/principal findings: 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.

Conclusions/significance: 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.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1

Figure 1. Emilia-Romagna regional map of mosquito sampling stations and locations of PCR–positive pools.

Circle, plan trap; square, Modena trap; diamond, extra-plan trap; red, WNV– and USUV–positive station; orange, USUV–positive station; green, negative station. Province abbreviations: PC, Piacenza; PR, Parma; RE, Reggio Emilia; MO, Modena; BO, Bologna; FE, Ferrara; RA, Ravenna; FC, Forlì Cesena; RN, Rimini.

Figure 2

Figure 2. Seasonal distribution of positive USUV mosquito pools (bi-weekly collection) per kind of trap.

Figure 3

Figure 3. Molecular Phylogenetic analysis by Maximum Likelihood method based on the Kimura two-parameter model of the WNV sequences of amplified fragments and homologous fragment obtained in GenBank library.

The tree with the highest log likelihood (−720.3421) is shown. Initial tree for the heuristic search were obtained automatically by Neighbor-joining method with Maximum Composite Likelihood distance matrix. The analysis involved 22 nucleotide sequences, there were a total of 409 positions in the final dataset. Evolutionary analyses were conducted in MEGA5 , the tree was rooted in RO97 50. Percentages of bootstrap test (1000 replicates) are shown next to the branches.

Figure 4

Figure 4. USUV “hot spots” obtained by kernel density estimation of positive mosquito pools (a); overlaying of 95% contour perimeter and quartile maps of temperature range (b); and of hydro-climatic balance (c); from July to September 2010.

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