Human and entomological surveillance of West Nile fever, dengue and chikungunya in Veneto Region, Italy, 2010-2012

Abstract

BackgroundSince 2010 Veneto region (North-Eastern Italy) planned a special integrated surveillance of summer fevers to promptly identify cases of West Nile Fever (WNF), dengue (DENV) and chikungunya (CHIKV). The objectives of this study were (i) To increase the detection rate of imported CHIKV and DENV cases in travellers from endemic areas and promptly identify potential autochthonous cases.(ii) To detect autochthonous cases of WNF, besides those of West Nile Neuroinvasive Disease (WNND) that were already included in a national surveillance.MethodsHuman surveillance: a traveler who had returned within the previous 15 days from endemic countries, with fever >38°C, absence of leucocytosis (leukocyte count <10,000 μL), and absence of other obvious causes of fever, after ruling out malaria, was considered a possible case of CHIKV or DENV. A possible autochthonous case of WNF was defined as a patient with fever >38°C for <7 days, no recent travel history and absence of other obvious causes of fever. Entomologic surveillance: for West Nile (WNV) it was carried out from May through November placing CDC-CO2 traps in five provinces of Veneto Region, while for DENV and CHIKV it was also performed around residences of viremic cases.ResultsHuman surveillance: between 2010 and 2012, 234 patients with fever after travelling were screened, of which 27 (11,5%) were found infected (24 with DENV and 3 with CHIKV). No autochthonous case of DENV or CHIKV was detected. Autochthonous patients screened for WNF were 408, and 24 (5,9%) were confirmed cases. Entomologic surveillance: the WNV was found in 10, 2 and 11 pools of Culex pipiens from 2010 to 2012 respectively, in sites of Rovigo, Verona, Venezia and Treviso provinces). No infected Aedes albopictus with DENV or CHIKV was found.ConclusionsVeneto is the only Italian region reporting WNV human cases every year since 2008. WNV is likely to cause sporadic cases and unforeseeable outbreaks for decades. Including WNF in surveillance provides additional information and possibly an early alert system. Timely detection of DENV and CHIKV should prompt vector control measures to prevent local outbreaks.

Isolation of infectious Zika virus from saliva and prolonged viral RNA shedding in a traveller returning from the Dominican Republic to Italy, January 2016

“…Ae. albopictus is established in Europe, especially in Mediterranean countries, including northern Italy [17], where the case reported in this study was imported. Due to the risk of emergence of outbreaks of vector-borne viruses following the introduction of a viraemic individual in areas where the vector is present [18], an integrated surveillance programme for imported dengue, chikungunya, and Zika virus infections has been implemented in Italy, along with veterinary and entomologic surveillance [17].…”

Phylogenetic characterization of Central/Southern European lineage 2 West Nile virus: analysis of human outbreaks in Italy and Greece, 2013–2014

“…This adaptation occurred in Italy and in Greece, where divergent phylogenetic groups, characterized by the acquisition of a set of conserved amino acid substitutions and corresponding to distinct geospatial areas, were identified. Favourable environmental conditions for the emergence of WNV probably included the presence of competent mosquitoes at a high density and the decline of immunity in the local bird population, as occurred in the affected areas in Italy [25]. In addition, the genetic changes in the viral genome might have provided enhanced transmissibility and increased virulence, contributing to the emergence of pathogenic strains.…”

Understanding West Nile virus ecology in Europe: Culex pipiens host feeding preference in a hotspot of virus emergence

“…Ten mosquito sampling localities were selected where one trap was positioned in a rural environment and the other one in a peridomestic environment (Figure 1 ). Data on WNV occurrence in mosquitoes at each locality was obtained from a regional surveillance program [ 38 ] with three of the sampling localities (6 traps) recorded as WNV positive and the other seven (14 traps) as WNV negative (Figure 1 ). Mosquitoes were collected from May to October 2012, using BG-sentinel traps baited with BG-lure attractant (Biogents AG, Regensurg, Germany).…”

“…Finally, we used the same method to compare feeding preference indices between sites where WNV occurrence in mosquitoes has, or has not, been observed ( P i.WNV+ , or P i.WNV- , respectively) during 2010-2012 [ 38 ]. Simulations were performed using MATLAB 7.10.0 (The Mathworks, Inc.).…”