Host-biting rate and susceptibility of some suspected vectors to Leishmania braziliensis

BACKGROUND: American tegumentary leishmaniasis is a serious Brazilian public health problem. This diseases is attributed to seven species of Leishmania, however, the majority of cases are associated with Leishmania braziliensis. Some phlebotomine species have been implicated in the transmission of this parasite, nonetheless only Psychodopygus wellcomei has had its vectorial competence demonstrated. Thus this study sought to assess some parameters related to the vectorial capacity of anthropophilic species of sand fly occurring in São Paulo state: Pintomyia fischeri, Migonemyia migonei Nyssomyia intermedia, Nyssomyia whitmani, Expapillata firmatoi and Psychodopygus ayrozai, under laboratory conditions. These parameters were the duration of the gonotrophic cycle, proportion of females which feed on hamster, the rate of infection by L. braziliensis and the duration of the extrinsic incubation period. METHODS: The sandflies were collected in three regions of the São Paulo state: Greater São Paulo and the Mogi Guaçu and Iporanga municipalities. To assess the proportion of engorged females the insects were fed on hamsters to estimate the duration of the gonotrophic cycle. To estimate the susceptibility to infection of each species, their females were fed on hamsters infected with Leishmania braziliensis and dissected to ascertain the localization of the flagellates and estimate the extrinsic incubation period. RESULTS: Low hamster attractiveness to Ps. ayrozai was observed. A high proportion of engorged females was observed when the hamster had its whole body exposed. The gonotrophic cycle ranged between three and eight days. Mg. migonei, Pi. fischeri, Ny. neivai, Ny. intermedia, Ny. whitmani and Ex.firmatoi presented susceptibility to infection by L. braziliensis. The highest infection rate (34.4%) was observed for Ny. whitmani and the lowest for Ny. intermedia (6.6%). Mg. migonei presented late-stage infection forms on the fifth day after feeding, but in the other species these forms were observed as from the fourth day. CONCLUSIONS: Our results, together with other parameters of their behavior under natural conditions, suggest the potential role of Ex. firmatoi as vector of this parasite and reinforce that of Mg. migonei, Pi. fischeri, Ny. neivai, Ny. intermedia and Ny. whitmani in the areas in which they occur.