Natural Infection of Sandfly Vector and Reservoir Hosts Species with Leishmania Parasites in Mt. Elgon Cave Habitats in Kenya

Leishmaniasis is a major public health problem caused by a parasite of the genus Leishmania which is transmitted through the bite of an infected female phlebotomine sandfly. However, the disease epidemiology on interactions of causative agents, reservoir hosts, and vectors in areas where there is a high prevalence of the disease needs to be properly understood to inform effective control. The present study was conducted to determine natural infection by Leishmania parasites in phlebotomine sandfly vectors and suspected reservoir hosts found in caves in Mount Elgon in Kenya. Sandflies, bats and rock hyraxes were found inhabiting the assessed caves in the study area. A total of 5688 sandflies collected from caves were morphologically identified and analyzed for infectivity with Leishmania parasites by molecular characterization sequencing using Cytochrome c oxidase subunit 1 (COI). Giemsa-stained blood smears and spleen and liver impression smears prepared from bats, and hyraxes collected from the same caves were examined microscopically for Leishmania amastigotes. The sandflies, bats, and hyraxes were identified morphologically using taxonomic keys. The results showed that randomly selected COI sequences (n = 5) of three different morphologically identified Phlebotomus species were positive for Leishmania based on their molecular characteristics. Five species of bats were identified, and they were significantly more abundant compared to hyraxes (χ2 = 16.7845, df = 7, P = 0.0002). The bats’ species had a higher prevalence of Leishmania parasites compared to hyraxes (F = 7.342, P = 0.0043). Cardioderma cor, Chaerephon pumilus and Rhinolophus clivosus bat species had more than 5% Leishmania parasite prevalence rate. Leishmania amastigote density was significantly higher in the liver (F = 39.232, P < 0.001) compared to the density in the blood (F = 75.1124, P < 0.001) of bats and hyraxes. This study has shown that transmission of Leishmania parasites in Mt. Elgon caves involves vertebrate reservoir hosts (bats and hyraxes) and the insect vector species (sandfly). Therefore, disruption of the life cycle of the Leishmania parasites should be done by targeting these reservoir animals and the sandfly vector.