ComunitaÂria, Universidade Federal do PiauõÂ, and Hospital de DoencËas Infecto-Contagiosas, Teresina, 3Departamento de Parasitologia,

The failure of control programs for visceral leishmaniasis (VL) that depend on elimination of infected dogs suggests that other reservoir hosts may participate in the transmission cycle. To determine whether persons infected with Leishmania chagasi can infect the vector sand ¯y, laboratory-reared Lutzomyia longipalpis were allowed to feed on Brazilian subjects with active, cured, and asymptomatic VL and on asymptomatic residents of houses of persons with active VL. Of 3747 insects that had fed, 26 acquired infection from 11 of the 44 persons with active VL, but none acquired infection from the 137 asymptomatic persons. Among persons!4 years old with active VL, a history of diarrhea and higher peripheral blood neutrophil counts were independent predictors of infectivity. Further experiments using larger numbers of insects are necessary to evaluate the reservoir competence of persons with asymptomatic infections, who represent a large segment of the population of several Brazilian cities. In Brazil, visceral leishmaniasis (VL) is a zoonosis caused by Leishmania chagasi and transmitted by phlebotomine sand ¯ies from wild and domestic canines. This is in contrast to VL in India, where sand ¯ies transmit L. donovani from person t