Evaluation of ICON Maxx, a long-lasting treatment kit for mosquito nets: experimental hut trials against anopheline mosquitoes in Tanzania.

Robert Malima,Stephen M Magesa,Mark Rowland,Issa Lyimo,Harparkash Kaur,Frank W Mosha,William N Kisinza,Patrick K Tungu,Caroline Maxwell,Matthew J Kirby

doi:10.1186/s12936-015-0742-z

Abstract

BackgroundInsecticide-treated nets are the primary method of preventing malaria. To remain effective, the pyrethroid insecticide must withstand multiple washes over the lifetime of the net. ICON® Maxx is a ‘dip-it-yourself’ kit for long-lasting treatment of polyester nets. The twin-sachet kit contains a slow-release capsule suspension of lambda-cyhalothrin plus binding agent. To determine whether ICON Maxx meets the standards required by the World Health Organization Pesticide Evaluation Scheme (WHOPES), the efficacy and wash fastness of ICON Maxx was evaluated against wild, free-flying anopheline mosquitoes.MethodsICON Maxx was subjected to bioassay evaluation and experimental hut trial against pyrethroid-susceptible Anopheles gambiae, Anopheles arabiensis and Anopheles funestus. Mosquito mortality, blood feeding inhibition and personal protection were compared between untreated nets, conventional lambda-cyhalothrin treated nets (CTN) washed either four times (cut-off threshold) or 20 times, and ICON Maxx-treated nets either unwashed or washed 20 times.ResultsIn bioassay, ICON Maxx demonstrated superior wash resistance to the CTN. In the experimental hut trial, ICON Maxx killed 75 % of An. funestus, 71 % of An. gambiae and 47 % of An. arabiensis when unwashed and 58, 66 and 42 %, respectively, when 20 times washed. The CTN killed 52 % of An. funestus, 33 % of An. gambiae and 30 % of An. arabiensis when washed to the cut-off threshold of four washes and 40, 40 and 36 %, respectively, when 20 times washed. Percentage mortality with ICON Maxx 20 times washed was similar (An. funestus) or significantly higher (An. gambiae, An. arabiensis) than with CTN washed to the WHOPES cut-off threshold. Blood-feeding inhibition with ICON Maxx 20 times washed was similar to the CTN washed to cut-off for all three species. Personal protection was significantly higher with ICON Maxx 20 times washed (66-79 %) than with CTN washed to cut-off (48-60 %).ConclusionsNets treated with ICON Maxx and washed 20 times met the approval criteria set by WHOPES for Phase II trials in terms of mortality and blood-feeding inhibition. This finding raises the prospect of conventional polyester nets and other materials being made long-lastingly insecticidal through simple dipping in community or home, and thus represents a major advance over conventional pyrethroid treatments.

Highlights

Insecticide-treated nets are the primary method of preventing malaria
This led to increased demand for long-lasting insecticidal nets (LLINs) by national malaria control programmes (NMCPs) to meet the target of at least 85 % protected by 2015, and led to international donors opting for LLIN as their preferred choice of net [5, 6]
This paper reports upon the Phase II experimental hut evaluations undertaken in Tanzania by the National Institute for Medical Research (NIMR) in Muheza against Anopheles gambiae and Anopheles funestus and by the Kilimanjaro Christian Medical College (KCMCo) in Moshi against Anopheles arabiensis

Summary

Introduction

Insecticide-treated nets are the primary method of preventing malaria. To remain effective, the pyrethroid insecticide must withstand multiple washes over the lifetime of the net. In 2005 the World Health Assembly (WHA) set a target of 85 % of those at risk of malaria should benefit from preventive interventions by the end of 2015 [4] This led to increased demand for LLINs by national malaria control programmes (NMCPs) to meet the target of at least 85 % protected by 2015, and led to international donors opting for LLIN as their preferred choice of net [5, 6]. Based on data from household surveys and reports on ITNs delivered by manufacturers and distributed by NMCPs, an estimated 49 % of the population at risk had access to an ITN in their household in 2013, compared to 3 % in 2004 [7] Despite this achievement, not all households have enough nets to meet family needs: an estimated 71 % of households have insufficient ITNs to protect all household members and one-third of households do not own even a single ITN [7]. More needs to be done to reach all families with ITNs, and supply enough ITNs for all household members [7]

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Discussion

Conclusion