Anthropogenic disturbances enhance occurrence of cutaneous leishmaniasis in Israel deserts: Patterns and mechanisms

A continuous and gradual increase in the incidence of cutaneous leishmaniasis (CL) has been reported in southern Israel over the last 20 years. The goal of our research was to determine if and how anthropogenic disturbances enhance the occurrence of the disease. To assess the effect of anthropogenic disturbances, we selected twelve 60 x 60 m plots, six in disturbed and six in undisturbed habitats at each of five study sites in southern Israel. We trapped rodents and sand flies, determined Leishmania major infection prevalence in rodents, and measured various environmental parameters. Infection prevalence in the reservoir host, the rodent Psammomys obesus, was significantly higher in disturbed habitats than in undisturbed ones. Infection prevalence was positively correlated with vector (Phlebotomus papatasi) density but not with host density. P. papatasi density was positively correlated with soil moisture. Soil in disturbed habitats had significantly more moisture, and plants were significantly more lush than in undisturbed habitats. P. obesus density was positively correlated with plant lushness. These results suggest that an important impact of anthropogenic disturbance, the addition of water, improves the conditions for vector breeding and promotes larger host populations by improving the quality of their food. These effects, in turn, should enhance disease transmission risk to humans.