Leishmania infection in humans, dogs and sandflies was examined in the endemic visceral leishmaniasis (VL) municipality of Raposa, state of Maranhão, Brazil. In this study, we examined
Leishmania chagasi
infection in the blood serum of both humans and
Canis familiaris
and the natural
Leishmania
sp. infection rate in the sandfly vector,
Lutzomyia longipalpis
. Enzyme-linked immunosorbent assay, indirect immunofluorescence reaction and polymerase chain reaction were performed to detect
Leishmania infections in humans, dogs and sandflies, respectively. Overall, 186 out of 986 studied human beings were infected with
L. chagasi parasites, representing an infection prevalence of 18.9%. An even higher infection rate was detected in dogs, where 66 (47.8%) out of 138 were infected. Among all
Lu. longipalpis captured (n = 1,881), only 26.7% were females. The
Leishmania infection frequency for the vector
Lu. longipalpis was 1.56%. Remarkably, all infected sandflies were found in the peridomiciliary area. Furthermore, a high incidence of asymptomatic forms of VL in the human and canine populations was observed. The results of this study suggest autochthonous transmission of
L. chagasi in this endemic area for visceral leishmaniasis because infection by Leishmania sp. was identified in all important elements of the transmission chain
