Comparative efficacy of two rounds of indoor residual spraying of DDT 75% @ 1g/m2 with that of DDT 50% @ 1g/m2 against the malaria vectors in India

Abstract

While, dichlorodiphenyl-trichloroethane (DDT) water dispersible powder (WDP) 75% is considered as the high performance long lasting formulation for indoor residual spraying (IRS), no information is available regarding the comparative epidemiological effectiveness of the two DDT formulations when used for IRS in Indian conditions. The current study was undertaken to compare the effectiveness of IRS using DDT WDP 75% @ one g active ingredient (AI)/m² with that using DDT WDP 50% @ one g AI/m² in controlling Anopheles fluviatilis and An. culicifacies, the primary vectors of malaria in the selected endemic areas of Odisha State. Although, cone-bioassay mortality after 8 months of post spraying on DDT 75% sprayed surfaces as well as on sprayed but mud plastered surfaces was higher than DDT 50%, the six entomological parameters viz. resting density indoors and outdoors, trap density indoors, parous rate, human blood index and infection rate of An. fluviatilis and An. culicifacies did not show any statistically significant difference in reduction/ changes from pre- to post-spray period between the two DDT formulations.

Keywords: Anopheles culicifacies; Anopheles fluviatilis; Comparative efficacy; DDT 50%; DDT 75%; India.