Vector competence of Culex quinquefasciatus say from different regions of Brazil to Dirofilaria immitis

The vector competence of Culex quinquefasciatus from five localities in Bra zil to Dirofilaria immitis was evaluated experimentally. Females from each locality were fed on an infected dog (similar to 6 microfilariae/mul blood) . A sample of blood fed mosquitoes were dissected approximately 1 h after b lood meal. These results demonstrated that all had ingested microfilariae ( mean, 4.8 to 24.6 microfilariae/mosquito). Fifteen days after the infected blood meal, the infection and infective rates were low in all populations o f Cx. quinquefasciatus. The mean number of infective larvae detected in the head and proboscis of these mosquitoes was 1-1.5. The vector efficiency, t he number of microfilariae ingested/number of infective larvae, was low for all populations of Cx. quinquefasciatus. However, the survival rate for al l populations was high (range 50-75%). The survival rate of Aedes aegypti a ssayed simultaneously for comparison was low (24.7%), while the vector effi ciency was much higher than for Cx. quinquefasciatus. These data suggest th at the vector competence of all assayed populations of Cx. quinquefasciatus to D. immitis in Brazil is similar and that this species is a secondary ve ctor due to its low susceptibility Nevertheless, vector capacity may vary b etween populations due to differences in biting frequency on dogs that has been reported in Brazil.