Phlebotomus (Larroussius) orientalis (Diptera: Psychodidae) as a probable secondary vector of visceral leishmaniasis in Kenya.

According to the World Health Organization’s reports, leishmaniases in humans are caused by 20 species of protozoa, belonging to the genus Leishmania1. The parasites are transmitted by the bite of a female tiny, 2–3 mm long insect vector, the phlebotomine sandfly1. Leishmaniasis endemic areas in Kenya are—West Pokot, Kitui, Machakos, Meru, Koibatek and Kajiado districts2–6. Kala-azar (Visceral leishmaniasis) in these endemic sites is transmitted by Phlebotomus martini (Diptera: Psychodidae)5,6, which predominantly lives and breeds in termite mounds, while in Sudan the same disease is transmitted by P. orientalis which breeds in soil cracks7. Previous reports of the existence of P. orientalis in Kenya suggested that this species did not occur in large numbers to cause any transmission of visceral leishmaniasis4,8. However, in 2000, 2003 and 2006 some kala-azar epidemics were reported in Wajir District Hospital, north-eastern Province and Makagalla location, Merti division, Isiolo district, Eastern Province, Kenya9. Phlebotomus orientalis is the only member of the Larroussius Nitzulescu group that has been associated with L. donovani transmission in the sub-Saharan Africa10,11. It is for this reason the study was carried out to investigate its possible role in the transmission of kalaazar in an endemic area where P. martini, the known vector of the disease in other parts of Kenya was seemingly absent but transmission has been going on.