Exploration of Potential Reservoir Hosts and Vectors of Leishmania in Nicaragua

Abstract

Leishmaniasis is caused by infection with protozoan parasites within the genus Leishmania and, in the New World, is transmitted by the bites of female sand flies within the genus Lutzomyia. The occurrence of leishmaniasis in rodent species, the geographic distribution of sand fly species in Nicaragua, and environmental factors associated with the distribution of human cases of typical cutaneous leishmaniasis were investigated. Three hundred ninety five rodents representing 17 species were collected from 13 localities from August 2001–March 2006 and screened for Leishmania infections. One Heteromys desmarestianus and one Peromyscus mexicanus were found to be positive for leishmanial infections by PCR. This is the first report of Leishmania infections in rodents in Nicaragua. Five hundred fifty six sand flies representing 12 species were collected from 8 localities, including Lutzomyia hartmanni, a new record for this species in Nicaragua. The predominant sand fly species captured in western Nicaragua were Lutzomyia longipalpis and Lutzomyia evansi. The predominant species captured in central and eastern Nicaragua was Lutzomyia cruciata. The geographic distribution of sand flies in this study provides additional support to previouslypublished reports of suspected vectors of Leishmania species that cause typical and atypical forms of cutaneous leishmaniasis in Nicaragua. Distribution data of human cases of typical cutaneous leishmaniasis obtained from the Nicaraguan Ministry of Health, along with GIS and remotely sensed data of elevation, precipitation, temperature, soil types and land use/cover classes, were used to develop predictive logistic regression models for the presence or absence of human cases within 151 municipalities. Mean annual precipitation and land use/cover were determined to be the best environmental variable predictors for the occurrence of typical cutaneous leishmaniasis.