Molecular detection of Leishmania donovani, Leishmania major, and Trypanosoma spp. in Sergentomyia squamipleuris sandflies from a visceral leishmaniasis focus in Merti sub-County, eastern Kenya

Abstract

BackgroundVisceral leishmaniasis (VL) and zoonotic cutaneous leishmaniasis (ZCL) are of public health concern in Merti sub-County, Kenya, but epidemiological data on transmission, vector abundance, distribution, and reservoir hosts remains limited. To better understand the disease and inform control measures to reduce transmission, we investigated the abundance and distribution of sandfly species responsible for Leishmania transmission in the sub-County, and their blood-meal hosts. MethodsWe conducted an entomological survey in five villages with reported cases of VL in Merti sub-County, Kenya, using CDC miniature light traps and castor oil sticky papers. Sandflies were dissected and identified to the species level using standard taxonomic keys and PCR analysis of the cytochrome c oxidase subunit 1 (COI) gene. Leishmania parasites were detected and identified by PCR and sequencing of internal transcribed spacer 1 (ITS1) genes. Bloodmeal sources of engorged females were identified by high-resolution melting analysis of vertebrate cytochrome b (cyt-b) gene PCR products. ResultsWe sampled 526 sandflies consisting of eight species, Phlebotomus orientalis (1.52%; n = 8) and seven Sergentomyia spp. Sergentomyia squamipleuris was the most abundant sandfly species (78.71%; n = 414) followed by Sergentomyia clydei (10.46%; n = 55). Leishmania major, Leishmania donovani, and Trypanosoma DNA were detected in S. squamipleuris specimens. Humans were the main sources of sandfly bloodmeals. However, we also detected mixed bloodmeals; one S. squamipleuris specimen had fed on both human and mouse (Mus musculus) blood, while two Ph. orientalis specimens fed on human, hyrax (Procavia capensis), and mouse (Mus musculus) blood. ConclusionsOur findings implicate the potential involvement of S. squamipleuris in the transmission of Leishmania and question the dogma that human leishmaniases in the Old World are exclusively transmitted by sandflies of the Phlebotomus genus. The presence of Trypanosoma spp. may indicate mechanical transmission, whose efficiency should be investigated. Host preference analysis revealed the possibility of zoonotic transmission of leishmaniasis and other pathogens in the sub-County. Leishmania major causes ZCL while L. donovani is responsible for VL. However, the reservoir status of the parasites is not uniform. Further studies are needed to determine the reservoir hosts of Leishmania spp. in the area.