The results of this study contribute to current understanding of the epidemiology of Dirofilaria spp. in an endemic area of north-eastern Italy. Based on the dog/human attractiveness, on the survival after feeding on dogs with high microfilariae concentrations and on the overall rate of positive mosquitoes, Cx pipiens was the most efficient natural vector of D. immitis in the studied area, where highly microfilaraemic dogs are expected [7,23]. Although the small number of Oc. caspius collected does not allow any definitive conclusion to be drawn, the high mortality rate of this species following a blood meal on a highly microfilaraemic dog indicates that Oc. caspius might be an effective vector in non-endemic areas. Indeed, the survival of different vectors was linked to Dirofilaria microfilariae concentration in the mosquito species [24].