The use of an Ecological Approach for the Study and Control of Zoonotic and Vector-borne Disease: Old-World Cutaneous Leishmaniasis as a Case System

It is becoming increasingly clear that the health of ecosystems, organisms, and humans are tightly interlinked. Anthropogenic disruption of natural ecosystems has been implicated as a major driver in the emergence of infectious diseases worldwide; the majority of which are zoonoses or vector-borne. This highlights the fact that an ecologically-based approach is essential in order to understand and control such diseases that cross the nexus of natural and human systems. In this talk, I will exemplify this principle using old-world zoonotic cutaneous leishmaniasis, in which the etiologic agent is Leishmania major, the vector is the sand fly Phlebotomus papatasi, and reservoir host is Psammomys obesus. In a study conducted in the Negev in the late 1990s, I demonstrate that anthropogenic disturbance of natural environments enhances disease risk to human by initiating a cascade of ecological processes triggered by direct and indirect enhancement of soil moisture. I also characterized habitat-related risk factors that helped inform local civilian and military public health authorities regarding strategies that could mitigate human exposure risk. Further studies into the vector-host interactions informed us regarding the demographic, spatial, and temporal underpinning of L. major transmission cycle, which in turn, guided us in the development of a novel individual-based-simulation model. One important prediction of this model is that transmission can be reduced by manipulating host density. A measure of reducing the epizootiologically-relevant density of the host without affecting their actual density (because sand rats are ecologically important in this system) is by using the rodent host as a “trojan horse” for delivering the insecticide directly to where the sand fly vector breeds and shelters. Another approach is using oviposition-site attractants as effective lures in an attract-and-kill oviposition trap. The use of these methods in the L. major system will be discussed.