Molecular detection of Leishmania donovani, Leishmania major, and Trypanosoma species in Sergentomyia squamipleuris sand flies from a visceral leishmaniasis focus in Merti sub-County, eastern Kenya

Abstract

Background: Visceral 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 remain limited. To better understand the disease and inform control measures to reduce transmission, we inves‑tigated the abundance and distribution of sand fy species responsible for Leishmania transmission in the sub-County and their blood-meal hosts.Methods: We conducted an entomological survey in fve villages with reported cases of VL in Merti sub-County, Kenya, using CDC miniature light traps and castor oil sticky papers. Sand fies were dissected and identifed to the species level using standard taxonomic keys and PCR analysis of the cytochrome c oxidase subunit 1 (cox1) gene. Leishmania parasites were detected and identifed by PCR and sequencing of internal transcribed spacer 1 (ITS1) genes. Blood-meal sources of engorged females were identifed by high-resolution melting analysis of vertebrate cytochrome b (cyt-b) gene PCR products. Results: We sampled 526 sand fies consisting of 8 species, Phlebotomus orientalis (1.52%; n=8), and 7 Sergentomyia spp. Sergentomyia squamipleuris was the most abundant sand fy species (78.71%; n=414) followed by Sergentomyia clydei (10.46%; n=55). Leishmania major, Leishmania donovani, and Trypanosoma DNA were detected in S. squami pleuris specimens. Humans were the main sources of sand fy blood meals. However, we also detected mixed blood meals; one S. squamipleuris specimen had fed on both human and mouse (Mus musculus) blood, while two Ph. orien talis specimens fed on human, hyrax (Procavia capensis), and mouse (Mus musculus) blood. Conclusions: Our fndings implicate the potential involvement of S. squamipleuris in the transmission of Leishma nia and question the dogma that human leishmaniases in the Old World are exclusively transmitted by sand fies of the Phlebotomus genus. The presence of Trypanosoma spp. may indicate mechanical transmission, whose efciency should be investigated. Host preference analysis revealed the possibility of zoonotic transmission of leishmaniasis and other pathogens in the sub-County. Leishmania major and L. donovani are known to cause ZCL and VL, respectively. 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