Abstract
BackgroundInsecticide thermal fogging (ITF) is a tool to control vector borne diseases. Insecticide application success for vector control has been associated with housing materials and architecture. Vector abundance is correlated with weather changes. Nevertheless, housing quality and weather impacts on vector abundance have been unaccounted for in most New World insecticide control trials for leishmaniasis vectors.MethodsWe conducted a 15 month insecticide control trial that included two deltamethrin [6 mg a.i.m-2] based ITF interventions in 12 of 24 monitored houses at Trinidad de Las Minas, a hyperendemic cutaneous leishmaniasis transmission village in western Panamá. During the study we followed sand fly (SF) abundance, keeping track of rainfall and quantified housing quality using an index based on architecture and construction materials.ResultsWe found a 50 to 80% reduction in SF density in the fogged houses when compared with control houses, while controlling for seasonal changes in SF abundance associated with rainfall. We found heterogeneities in the reductions, as abundance changed according to SF species: Lutzomyia gomezi, Lu. panamensis, Lu. dysponeta and Lu. triramula reduced in density between 40% and 90% after ITF. In contrast, Lu. trapidoi density increased 5% after ITF. Differences in the impact of ITF were associated with housing quality, the most destitute houses, i.e., those with features that ease insect entrance, had a disproportionally larger SF abundance, in some cases with increased domiciliary SF density following the ITF.ConclusionOur results suggest the potential of insecticide application to control SF density and leishmaniasis transmission could depend on housing quality beyond insecticide efficiency.
Highlights
Insecticide thermal fogging (ITF) is a tool to control vector borne diseases
A key insight from the few long-term studies on sand fly (SF) population dynamics is that vector abundance is extremely sensitive to environmental changes, with different species having a distinctive sensitivity to particular meteorological components [12,15,17]
Our goal was to evaluate the impact of household insecticide thermal fogging (ITF) with deltamethrin (6 mg a.i.m-2) on domiciliary and peridomiciliary SF abundance
Summary
Insecticide thermal fogging (ITF) is a tool to control vector borne diseases. Insecticide application success for vector control has been associated with housing materials and architecture. Housing quality and weather impacts on vector abundance have been unaccounted for in most New World insecticide control trials for leishmaniasis vectors. Methods of insecticide application for SF control have included: fogging [19,22,34], residual spraying [21,23,24,25,26,27,31,32,33], insecticide diffusion devices [35], insecticide treated nets [28,29] and curtains [30] These studies have shown that insecticide application at the household level seems to be the most effective SF control method [7], because it can suppress both SF abundance [7] and CL transmission over short [36] and long term [37] time scales. Most insecticide control trials have ignored the importance of weather variability when evaluating the efficacy of insecticides on SF abundance [20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35]
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