Comparative study on the effectiveness of different mosquito traps in arbovirus surveillance with a focus on WNV detection.

The selection of the ideal trap for arbovirus surveillance is an issue of primary importance to increase the sensitivity of virus detection and the cost-effectiveness of the entomological surveillance. During the summer 2011, the effectiveness of five types of mosquito traps (CDC gravid trap, CO2(-)baited trap, BG-Sentinel™ and two experimental prototypes) to attract females potentially infected with West Nile virus were assessed. The study was carried out in three natural wetland sites located in the Emilia-Romagna Region (Northern Italy), using a Latin square scheme. Single night collections of adult females were performed and determination of species and physiological state (gravid, nulliparous or parous) was made upon return to the laboratory. The species most frequently collected in the gravid trap was Culex pipiens sl. L., being gravid females the large majority of the individuals. Species diversity was much higher in CO2(-)baited traps, which may therefore enable a more comprehensive description of the vector species composition and their role in arboviruses circulation. Our findings indicate that gravid traps can be a valid tool and should be integrated in the West Nile virus surveillance system in the Emilia-Romagna region, mainly based on collections made with CO2-baited traps.