Association of Phlebotomus guggisbergi with Leishmania major and Leishmania tropica in a complex transmission setting for cutaneous leishmaniasis in Gilgil, Nakuru county, Kenya

Background Phlebotomus (Larroussius) guggisbergi is among the confirmed vectors for cutaneous leishmaniasis (CL) transmission in Kenya. This scarring and stigmatizing form of leishmaniasis accounts for over one million annual cases worldwide. Most recent CL epidemics in Kenya have been reported in Gilgil, Nakuru County, where the disease has become a public health issue. However, little is known about the factors that drive its transmission. Here, we sought to determine the occurrence, distribution and host blood feeding preference of the vectors, and to identify Leishmania species and infection rates in sandflies using molecular techniques. This information could lead to a better understanding of the disease transmission and improvement of control strategies in the area. Methodology/ Principal findings An entomological survey of sandflies using CDC light traps was conducted for one week per month in April 2016, and in June and July 2017 from five villages of Gilgil, Nakuru county; Jaica, Sogonoi, Utut, Gitare and Njeru. Sandflies were identified to species level using morphological keys and further verified by PCR analysis of cytochrome c oxidase subunit I (COI) gene. Midguts of female sandflies found to harbour Leishmania were ruptured and the isolated parasites cultured in Novy-MacNeal-Nicolle (NNN) media overlaid with Schneider’s insect media to identify the species. Leishmania parasite screening and identification in 198 randomly selected Phlebotomus females and parasite cultures was done by PCR-RFLP analysis of ITS1 gene, nested kDNA-PCR and real-time PCR-HRM followed by sequencing. Bloodmeal source identification was done by real-time PCR-HRM of the vertebrate cytochrome-b gene. A total of 729 sandflies (males: n = 310; females: n = 419) were collected from Utut (36.6%), Jaica (24.3%), Sogonoi (34.4%), Njeru (4.5%), and Gitare (0.1%). These were found to consist of nine species: three Phlebotomus spp. and six Sergentomyia spp. Ph. guggisbergi was the most abundant species (75.4%, n = 550) followed by Ph. saevus sensu lato (11.3%, n = 82). Sandfly species distribution across the villages was found to be significantly different (p
Author summary Leishmaniases are diseases caused by Leishmania parasites and transmitted through the bites of infected female sandflies during blood feeding. In Kenya, two main forms of the disease exist; visceral (VL) and cutaneous leishmaniasis (CL). Most recent CL epidemics in Kenya have been reported in Gilgil, Nakuru county, where the disease has become a public health problem. However, little is known about the factors that drive its transmission in the area. In this study, we investigated the occurrence, distribution, host preference and Leishmania infection rates in sandflies collected from Gilgil using molecular tools. This could lead to a better understanding of the disease and improvement of control strategies in the area. Our results revealed a high infection rate of L. tropica in two sandfly species (Ph. guggisbergi and Ph. saevus s.l.), which may indicate a high circulation level of this parasite in the area. However, we also identified L. major infection from Ph. guggisbergi species by PCR. Analysis of sandfly bloodmeal sources showed that Ph. guggisbergi fed on a diverse range of vertebrates including goats, rock hyraxes, rabbits, wild pigs and rodents whereas Ph. saevus s.l. fed mainly on humans. The potential of Ph. guggisbergi as a vector of L. major and whether other vertebrate hosts play a role in maintaining Leishmania parasites in this CL endemic area needs further investigation.