Leishmaniasis in the Jordan Valley II. Sandflies and transmission in the central endemic area.

Cutaneous leishmaniasis in the Jordan Valley is maintained within the close association of the rodent Psammomys obesus and sandfly Phlebotomus papatasi, which appear to be the exclusive host and vector species. The incidence of the disease was similar to the distribution of Psammomys colonies in the region, i.e., the plains of light stoneless soil. An infection rate of 93% was recorded in the very common P. obesus. Other potential host species, except for Mus musculus, were scarce and no infection with Leishmania was found in them. The only Phlebotomus species caught in significant numbers was Ph. papatasi and this was also the only species harbouring leishmanial parasites, up to 56% in one sample. All Leishmania isolates from Psammomys and from Ph. papatasi were identical to those from local human cases. The density of Ph. papatasi populations in uncultivated areas was correlated with soil conditions favouring high humidity in Psammomys burrows. A very low rate of engorged females among the Sergentomyia species collected suggests that the common species, S. antennata and S. africana asiatica, are highly autogenous.