A Standardized and Portable Field Bioassay to Evaluate Interior Residual Sprays for Control of Malaria
Uniformed Services University Of The Health Sciences Bethesda United States
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Interior or indoor residual spraying IRS is the practice of indoor application of residual insecticides or repellents as a way to halt the malaria life cycle either by insecticidal action or prevention of mosquito entrance Diabate et al. 2006 Bouma et al.2005 Rowland et al. 2000. The World Health Organization recommends the inclusion of IRS in malaria control programs where the sprays are appropriate WHO, 2006. However, there is currently no standardized field method to evaluate the susceptibility of vectors to available insecticides or repellents. Previous studies have used a variety of techniques to evaluate local abatement efforts, usually involving only one insecticide for evaluation of efficacy. The lack of a standardized field assay prevents comparison of these studies and it limits choice of control methods to one or two tested chemicals in a certain area of interest. After testing our standardized, field bioassay in northern Belize, we trapped 2193 mosquitoes belonging to seven species and five genera over the study period. However, no statistical differences with respect to trap rates were found between any of the insecticides, control, and standard tents, therefore, we conclude that IRS in military issued two-person tents are not effective or significant at stopping mosquito entrance. Further studies on implementation of a portable, field bioassay should include looking at the difference between contact irritants and spatial repellents in different sized tents, as spatial repellency may be more important in smaller sized tents.