Distinct transmission cycles of Leishmania tropica in 2 adjacent foci, Northern Israel

Abstract

Transmission of Leishmania tropica was studied in 2 adjacent foci in Israel where vector populations differ. Only Phlebotomus sergenti was found infected with L. tropica in the southern focus; P. arabicus was the main vector in the northern focus. Rock hyraxes (Procavia capensis) were incriminated as reservoir hosts in both foci. L. tropica strains from the northern focus isolated from sand flies, cutaneous leishmaniasis cases, and rock hyraxes were antigenically similar to L. major, and strains from the southern focus were typically L. tropica. Laboratory studies showed that P. arabicus is a competent vector of L. tropica, and P. sergenti is essentially refractory to L. tropica from the northern focus. Susceptibility of P. arabicus may be mediated by O glycoproteins on the luminal surface of its midgut. The 2 foci differ with respect to parasites and vectors, but increasing peridomestic rock hyrax populations are probably responsible for emergence of cutaneous leishmaniasis in both foci.

Figure 1

Leishmania tropica foci near Lake Kinneret in the Galilee region of Israel. Inset shows the location of the foci. W. Bank, West Bank.

Figure 2

A) PCR of Leishmania internal transcribed spacer region 1 (ITS1) of naturally infected Phlebotomus sergenti sand flies and cultured Leishmania spp. controls. B) HaeIII digestion of restriction fragment length polymorphisms of ITS1 PCR products shown in A. Lane 1, P. sergenti female 1; lane 2, P. sergenti female 2; lane 3, P. sergenti female 3; lane 4, L. tropica (Lt-L590); lane 5, L. major (Lm-L777); lane 6, L. infantum (Li-L699).

Figure 3

A) PCR of Leishmania internal transcribed spacer region 1 (ITS1) of cultured Leishmania promastigotes isolated from rock hyrax. B) HaeIII digestion of restriction fragment length polymorphisms of ITS1 PCR products shown in A. Lane MW, molecular mass marker; lane 1, L. infantum (Li-L699); lane 2, L. major (Lm-L777); lane 3, L. tropica (Lt-L590); lane 4, rock hyrax.

Figure 4

Artificial infection of laboratory-reared Phlebotomus arabicus and P. sergenti with Leishmania tropica isolates from 2 foci in Galilee, Israel. Note the high susceptibility of P. arabicus for both strains and refractoriness of P. sergenti for the northern strain. Nf, northern focus; Sf, southern focus.

Figure 5

Left, female sand fly midgut lysates separated by sodium dodecyl sulfate–polyacrylamide gel electrophoresis and blotted onto nitrocellulose membranes. Blots were incubated with biotinylated Helix pomatia agglutinin (HPA) that detects O-glycosylated proteins. Lane 1, molecular mass markers; lanes 2 and 3, Phlebotomus sergenti; lanes 4 and 5, P. arabicus; +, preincubation of lectin with 250 mmol/L N-acetyl-d-galactosamine; –, no preincubation. Right, reaction of fluorescein-conjugated HPA with P. arabicus and P. sergenti midgut cells.

Figure 6

Random amplified polymorphic DNA PCR banding patterns of Phlebotomus sergenti from 2 foci in Galilee, Israel. The PCR was performed with primer OPI 1. Lane MW, molecular mass marker; lane 2, P. sergenti from Turkey. Shown are 4 flies from the northern focus (Nf) and 4 flies from the southern focus (Sf).

Figure 7

Rock hyrax (Procavia capensis). Sand flies are attracted to these animals and prefer feeding on their snouts.