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

Abstract

BackgroundPhlebotomus (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 findingsAn 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<0.001) with Jaica recording the highest diversity. The overall Leishmania infection rate in sandflies was estimated at 7.07% (14/198). Infection rates in Ph. guggisbergi and Ph. saevus s.l. were 9.09% (12/132) and 3.57% (2/56) respectively. L. tropica was found to be the predominant parasite in Gilgil with an overall infection rate of 6.91% (13/188) in Ph. guggisbergi (n = 11) and Ph. saevus s.l. (n = 2) sandflies. However, PCR analysis also revealed L. major infection in one Ph. guggisbergi specimen. Bloodmeal analysis in the 74 blood-fed sandflies disclosed a diverse range of vertebrate hosts in Ph. guggisbergi bloodmeals, while Ph. saevus s.l. fed mainly on humans.Conclusions/ SignificanceThe high infection rates of L. tropica and abundance of Ph. guggisbergi in this study confirms this sandfly as a vector of L. tropica in Kenya. Furthermore, isolation of live L. tropica parasites f...

Leishmaniasis Beyond East Africa

“…CL was first documented in 1969 and is caused by: L. tropica , predominantly found centrally and in the Rift Valley; L. major , reported in the lowlands of Kitui and Baringo ( 38 , 82 , 87 ); and L. aethiopica , detected in areas of high altitudes such as Mount Elgon ( 88 ). The vectors responsible for transmission in these regions are Phlebotomus duboscqi, Phlebotomus guggisbergi , and Phlebotomus pedifer ( 89 ). In some instances, there have been cases where individuals have been positive for both L. major and L. tropica ( 80 ).…”

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

“…Cutaneous leishmaniasis and VL are among the world’s most neglected tropical diseases (NTDs), occurring mainly in remote foci of the tropical, subtropical, and Mediterranean regions. Approximately 350 million people are at risk of infection [ 2 ]. Cutaneous leishmaniasis is the most common form with over 600,000 annual cases worldwide [ 3 ] and contributes to high psychological morbidities because of its scarring and stigmatising lesions [ 4 ].…”

“…In Kenya, both VL and CL are endemic in arid and semi-arid areas in the Rift Valley, eastern and north-eastern regions in the country [ 5 ]. Cutaneous leishmaniasis is caused mainly by three species of Leishmania : Leishmania tropica , Leishmania major , and Leishmania aethiopica [ 2 , 6 , 7 ]. Cutaneous leishmaniasis infections caused by L. aethiopica and L. tropica are predominant in highland areas, especially around the Mount Elgon and Rift Valley regions, respectively [ 7 ].…”

“…Sand flies of the Phlebotomus genus are the confirmed vectors of human leishmaniasis in the Old World [ 1 ]. In Kenya, the sand flies Phlebotomus guggisbergi , Phlebotomus duboscqi , and Phlebotomus pedifer are the confirmed vectors of L. tropica , L. major , and L. aethiopica , respectively [ 2 , 9 ]. In contrast, L. donovani is transmitted primarily by Phlebotomus martini , while Phlebotomus orientalis is regarded as a secondary vector of the parasite in Kenya [ 9 , 10 ].…”

“…However, Sergentomyia sand flies are the predominant species in most leishmaniasis endemic foci in the Old World, where they appear to be well adapted to different biotopes and environmental conditions [ 13 ]. Most of these species have been shown to feed on humans and other mammalian hosts [ 2 ] which may carry other pathogens in addition to Leishmania species.…”