Epidemiological aspects of vector, parasite, and domestic reservoir in areas of recent transmission and no reported human cases of visceral leishmaniasis in Brazil.

Abstract

About 97% of the human cases of the American visceral leishmaniasis (VL) occur in Brazil. In the last fewyears, the disease expanded to medium- and large-sized cities, in which surveillance and control actionshave been intensified, in an effort to control VL spreading. Our two-year study was conducted in BeloHorizonte, the sixth most populous city in Brazil, which is endemic for VL. We focused in two particulardistricts of recent transmission of the disease, with no reported human cases and submitted to minorsurveillance and control actions. Our aim was to draw an epidemiological profile of the local situationconcerning Lutzomyia vector, Leishmania parasites, and the main domestic reservoirs (dogs). Lutzomyialongipalpis comprised 96.5% of the total phlebotomine sand flies captured and displayed an expressiveminimal infection rate by Leishmania infantum (16.7%). Positive correlations were found between the pop-ulation densities of L. longipalpis, rainfall and temperature. L. infantum was also detected in the cortelezziicomplex and, for the first time, in Lutzomyia lloydi. Leishmania braziliensis, an etiological agent of theAmerican cutaneous leishmaniasis, was also identified in L. longipalpis. Among the 1408 dogs serologi-cally tested by standard enzyme-linked and fluorescence immune assays (ELISA/IFA) 3.6% were positivefor VL. L. infantum DNA and Leishmania parasites were identified in 100% and 72.5% of the seropositivedogs, respectively. The co-positivity of other diagnostic tests for VL—Leishmania-nested PCR, imprintand myeloculture—was compared to the standard serology. Both symptomatic or asymptomatic dogsdisplayed an equal average number of positive diagnostic tests for VL. The districts studied display favor-able conditions for the rapid spreading of human infection, in terms of L. longipalpis population density,and presence of L. infantum in both vector and main reservoir.