Abstract
BackgroundDeltamethrin 62.5 polymer-enhanced suspension concentrate (SC-PE) is one of the World Health Organization-approved insecticides for indoor residual spraying and was recommended to evaluate its residual activity for determination of appropriate spray cycles in different eco-epidemiologic settings. In the current study, efficacy of deltamethrin 62.5 SC-PE was evaluated against vectors of malaria and its impact on malaria incidence in a Plasmodium falciparum hyper-endemic area in Koraput district, Odisha State, India.MethodsThe trial had two comparable arms, arm 1 with residual spraying of deltamethrin 62.5 SC-PE and arm 2 with deltamethrin 2.5% WP (positive control). Comparative assessment of the impact of each intervention arm on entomological (density, parity, infection and human blood index), epidemiological (malaria incidence) parameters, residual efficacy and adverse effects were evaluated.ResultsBoth the arms were comparable in terms of entomological and epidemiological parameters. While, deltamethrin 62.5 SC-PE was found to be effective for 150 days in mud and wood surfaces and 157 days in cement surfaces; deltamethrin 2.5% was effective only for 105 days on mud surfaces and 113 days on cement and wood surfaces.ConclusionsDeltamethrin 62.5 SC-PE had prolonged killing effectiveness up to 5 months. Hence, one round of IRS with deltamethrin 62.5 SC-PE would be sufficient to cover two existing malaria peak transmission seasons (July–August and October–November) in many parts of India.
Highlights
Deltamethrin 62.5 polymer-enhanced suspension concentrate (SC-PE) is one of the World Health Organization-approved insecticides for indoor residual spraying and was recommended to evaluate its residual activity for determination of appropriate spray cycles in different eco-epidemiologic settings
The current study evaluated the efficacy of deltamethrin 62.5 SC-PE at 20 mg/sq m mainly against the susceptible population of An. fluviatilis and its impact on malaria incidence in a falciparum hyper-endemic area in India
Spray coverage Out of 719 houses and 2231 rooms in the 7 study villages in arm 1, 96.2% (92.0–100.0%) of targeted houses and 93.5% (84.6–100.0%) of targeted dwelling rooms were sprayed with deltamethrin 62.5 SC-PE
Summary
Deltamethrin 62.5 polymer-enhanced suspension concentrate (SC-PE) is one of the World Health Organization-approved insecticides for indoor residual spraying and was recommended to evaluate its residual activity for determination of appropriate spray cycles in different eco-epidemiologic settings. Due to continuous use of DDT, An. culicifacies developed resistance to it all over the country [9], resulting in decline of use of DDT in IRS since the last two decades This prompted National Vector Borne Disease Control Programme (NVBDCP) to switch-over to other classes of insecticides, preferably synthetic pyrethroids, as they are cheap and longlasting with low mammalian toxicity [10]. The malaria control programme of India is facing a great challenge, as one of the malaria vectors in the country, An. culicifacies, has developed resistance to deltamethrin due to shared mechanisms with organochlorines and widespread use of this class of insecticide in treating the mosquito nets [9, 10]. To tackle the growing threat of pyrethroid resistance in malaria vectors in India and elsewhere [11], industries are manufacturing newer vector control tools, such as insecticide mixtures combining two active ingredients with different modes of action
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