Project 2 "Studies of the sand fly vector" will challenge some of the dogma's guiding current vector and diseases control efforts for Visceral Leishmaniasis (VL). Phlebotomus argentipes, the sand fly vector of Leishmania donovani, is assumed to be a poor flyer that breeds and rests mainly indoor and bites around midnight;vector control efforts are planned based on assumptions about the seasonality of sand fly abundance.
The first aim of this study is to provide an accurate description of seasonal variation in vector abundance, feeding preferences, biting times and an estimate of the seasonal variation in the proportion of vectors infected with L. donovani. To be able to target not just the adult sand flies but also the earlier stages, the study also includes a component aimed at identifying breeding sites of P. argentipes. Coverage with indoor residual insecticide spraying (IRS), the main P. argentipes control method on the Indian subcontinent, was shown to be grossly inadequate in an eartier phase of the TMRC study. In this project reasons for low IRS coverage will be investigated through qualitative and quantitative research. In addition a sand fly saliva antibody test will be developed, this test is expected to provide a direct measure of vector exposure at the level of the individual. This new method can be used to monitor the effectiveness of vector control efforts, obviating the need of costly and cumbersome vector abundance studies. Another assumption this project will challenge is the assumption that only symptomatic patients and patients with post Kala Azar dermal Leishmaniasis (PKDL) are infectious to the sand fly vector. The number of VL cases in the current TMRC study area is so low that mathematically it seems unlikely they can sustain transmission;the number of asymptomatically infected persons however is much higher. The project will study the infectivity of asymptomatically infected persons to sand flies by conducting targeted xenodiagnosis experiments.
Though vector control is among the few strategies with proven effectiveness in VL control, current efforts are not yielding good results. This project will generate data that can be used to readjust the current vector control schemes as well as a tool to monitor their effectiveness. If asymptomatically infected persons can transmit VL, current VL control strategies need to be revised. This project will search for evidence.
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