Environmental factors underlying spatial patterns of sand flies (Diptera: Psychodidae) associated with leishmaniasis in southern Sinai, Egypt

A GIS-based predictive map of the distribution of Phlebotomus alexandri in southern Sinai, Egypt. [Display omitted] ► Sand fly species collected from southern Sinai tended to cluster in space, except Phlebotomus papatasi which was found dispersed across the study area. ► There is a significant spatial association between Phlebotomus alexandri and Phlebotomus kazeruni. ► They are estimated to be the most widely distributed sand fly species in southern Sinai. ► GIS-assisted spatial analysis indicated that Phlebotomus kazeruni, Phlebotomus alexandri, Phlebotomus sergenti and Phlebotomus papatasi are ecological generalists, able to inhabit diverse environmental settings. ► Phlebotomus major, Phlebotomus arabicus and Phlebotomus orientalis had more limited distributions, suggesting that they have more restricted ecological conditions. Although Leishmania major is endemic in parts of the Sinai of Egypt, the ecology and distribution of Leishmania sand fly vectors in southern Sinai has not been well characterized. Accordingly, additional sand fly samples were obtained at 41 sites in the southern Sinai region during 1996–1997, and analyzed to improve the characterization of risk of sand fly-borne pathogens. Using a Geographic Information System (GIS), species-specific spatial distributions that might suggest zoonotic cutaneous leishmaniasis (ZCL) risk areas were determined in relation to contextual environmental factors, including geology, hydrogeology, climate variables and elevation. Southern Sinai was characterized by a diverse sand fly fauna (eight Phlebotomus species), probably attributable to highly variable landscape and environmental factors. Phlebotomus alexandri, Phlebotomus kazeruni and Phlebotomus sergenti were widespread and abundant, Phlebotomus papatasi and Phlebotomus bergeroti were less frequent, and Phlebotomus arabicus, Phlebotomus major and Phlebotomus orientalis had highly restricted distributions. Logistic regression models indicated that elevation and climatic conditions were limiting determinants for the distributions of sand flies in southern Sinai. Based on the predicted distribution of P. papatasi, a recognized vector of L. major, about one-quarter of southern Sinai may be at high risk of ZCL. Risk areas for the suspected ZCL vector P. bergeroti had a more patchy distribution. Results suggest that future studies should include other factors related to vector abundance, vector competence, human population, and parasite and reservoir host(s