Phlebotomine sand flies transmit protozoan parasites (Leishmania spp.), bacterial (Bartonella bacilliformis), and viral pathogens. An alternative approach to the traditional delivery of an insecticide to the vector is to bring the vector to the insecticide using an attractant. In the context of controlling vector-borne disease, oviposition-sie attractants are expected to be highly effective because they target gravid females that are responsible for transmission of the pathogen and amplifying vector populations. Decomposing organic matter is the main food source for sand fly larvae. Central to our ongoing and proposed research is the proposition that natural selection has tuned the olfactory system of gravid females to odorants emanating from optimal oviposition substrates that indicate suitable conditions and nutrients for larval development. We therefore hypothesize that gravid sand flies are differentially attracted in a dose-dependent manner to a blend of fecal- and microbially-derived chemical cues associated with the decomposition of fecal material, as well as to signals from eggs and larvae which indicate suitable oviposition sites. Our overall goal is to develop and optimize an attractive blend of semiochemicals that would function as a lure for oviposition-site seeking sand fly females using Ph. papatasi (vector of old-world cutaneous leishmaniasis) as a model system. We will apply an integrated interdisciplinary approach including behavioral, electrophysiological, and microbiological studies to address the following specific aims: (1) Identify the most attractive and oviposition stimulating conspecific stages, rearing medium, and saprophytic microbes; (2) Isolate and identify oviposition attractants and stimulants from the most attractive conspecific stage, rearing medium, and microbial isolates; and (3) Develop an optimal blend of oviposition attractants and stimulants and evaluate it at the micro- and meso-scales. This proposed study introduces several novel and innovative approaches including: (1) Application of an integrated approach including behavioral, electrophysiological, analytical and microbiological investigations; (2) Study a neglected aspect of oviposition - the role of saprophytic fungi as indicators of suitable oviposition sites; (3) Evaluate the effectiveness of th optimized blends at the scale of meters using a wind-tunnel. Success of this study will set the stage for the next project - a field test of these blends - and would eventually contribute to relieving morbidity and mortality due to sand fly transmitted pathogens.
Following Malaria and Dengue, human leishmaniases are the most important vector-borne diseases with population at risk estimated at approximately 350 million people with annual incidence estimated at 1-1.5 million cases of cutaneous leishmaniasis, 500,000 cases of visceral leishmaniasis, and DALY of 2.1 million. By developing an optimal attractant blend we will set the stage for the development of an attract-and-kill oviposition (egg-laying) trap, improve surveillance of sand fly borne diseases, and enhance the productivity of sand fly lab colonies. By targeting gravid (ready to lay eggs) females, attract-and kill oviposition traps have the potential to simultaneously affect disease transmission and sand fly population amplification by reducing the abundance of blood-fed females and the vector's fecundity.
