Field evaluation of the residual efficacy of new generation insecticides for potential use in indoor residual spray programmes in South Africa

• Published in: Malaria Journal
• Main Authors: Rajendra Maharaj, Ishen Seocharan, Vishan Lakan, Zuziwe Nyawo, Moses Mkhabela, Yusentha Balakrishna
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2024
• Subjects: Actellic; SumiShield; Fludora® Fusion; Indoor residual spraying; Efficacy; Insecticide resistance; Arctic medicine. Tropical medicine; RC955-962; Infectious and parasitic diseases; RC109-216; Arctic
• Online Access: https://doi.org/10.1186/s12936-024-04963-6; https://doaj.org/article/0bc8499900694229b384f502829cae06

Abstract Background The decreasing residual efficacy of insecticides is an important factor when making decisions on insecticide choice for national malaria control programmes. The major challenge to using chemicals for vector control is the selection for the development of insecticide resistance. Since insecticide resistance has been recorded for most of the existing insecticides used for indoor residual spraying, namely, DDT, pyrethroids, organophosphates and carbamates, and new chemicals are necessary for the continued success of indoor residual spraying. The aim of this study was to assess the residual efficacy of Actellic 300CS, SumiShield™ 50WG and Fludora®Fusion by spraying on different wall surfaces. Methods One hundred and sixty-eight houses with different wall surface types (mud, cement, painted cement, and tin) which represented the rural house wall surface types in KwaZulu-Natal, South Africa were used to evaluate the residual efficacy of Actellic 300CS, SumiShield 50WG and Fludora®Fusion with DDT as the positive control. All houses were sprayed by experienced spray operators from the Malaria Control Programme. Efficacy of these insecticides were evaluated by contact bioassays against Anopheles arabiensis, a vector species. The residual efficacy of the insecticide formulations was evaluated against a susceptible insectary-reared population of An. arabiensis using WHO cone bioassays. Results Effectiveness of the three insecticides was observed up to 12 months post-spray. When assessing the achievement of 100% mortality over time, SumiShield performed significantly better than DDT on mud (OR 2.28, 95% CI 1.72–3.04) and painted cement wall types (OR 3.52, 95% CI 2.36–5.26). On cement wall types, Actellic was found to be less effective than DDT (OR 0.55, 95% CI 0.37–0.82) while Fludora®Fusion was less effective on tin wall types (OR 0.67, 95% CI 0.47–0.95). When compared to the combined efficacy of DDT on mud surfaces, SumiShield applied to each of the mud, cement and painted cement wall types and DDT ...