Publication: 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
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2021
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NRF
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BMC Parasites & Vectors
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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 fly species responsible for Leishmania transmission in the sub‑County
and their blood‑meal hosts.
Methods: We 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. Sand flies were dissected and identified 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 identified by PCR and sequencing of internal transcribed spacer 1 (ITS1)
genes. Blood‑meal sources of engorged females were identified by high‑resolution melting analysis of vertebrate
cytochrome b (cyt‑b) gene PCR products.
Results: We sampled 526 sand flies consisting of 8 species, Phlebotomus orientalis (1.52%; n = 8), and 7 Sergentomyia
spp. Sergentomyia squamipleuris was the most abundant sand fly 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 fly 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 findings 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 flies 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 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.
Keywords: Leishmania, Leishmaniasis, Sand fly, Trypanosoma, Sergentomyia, Phlebotomus, Zoonotic cutaneous
leishmaniasis, Visceral leishmaniasis, Kenya