Degradation of insecticides used for indoor spraying in malaria control and possible solutions

Show simple item record Sibanda, Mthokozisi Mayibongwe Focke, Walter Wilhelm Labuschagne, F.J.W.J. (Frederick Johannes Willem Jacobus) Moyo, Lumbidzani Nhlapo, N.S. (Nontete Suzan) Maity, Arjun Muiambo, H.F. (Herminio Francisco) Massinga, Pedro Horacio Crowther, N.A.S. (Nicolaas Andries Sadie), 1944- Coetzee, Maureen Brindley, Gordon W.A. 2012-03-19T06:16:09Z 2012-03-19T06:16:09Z 2011-10-18
dc.description.abstract BACKGROUND: The insecticide dichloro-diphenyl-trichloroethane (DDT) is widely used in indoor residual spraying (IRS) for malaria control owing to its longer residual efficacy in the field compared to other World Health Organization (WHO) alternatives. Suitable stabilization to render these alternative insecticides longer lasting could provide a less controversial and more acceptable and effective alternative insecticide formulations than DDT. METHODS: This study sought to investigate the reasons behind the often reported longer lasting behaviour of DDT by exposing all the WHO approved insecticides to high temperature, high humidity and ultra-violet light. Interactions between the insecticides and some mineral powders in the presence of an aqueous medium were also tested. Simple insecticidal paints were made using slurries of these mineral powders whilst some insecticides were dispersed into a conventional acrylic paint binder. These formulations were then spray painted on neat and manure coated mud plaques, representative of the material typically used in rural mud houses, at twice the upper limit of the WHO recommended dosage range. DDT was applied directly onto mud plaques at four times the WHO recommended concentration and on manure plaques at twice WHO recommended concentration. All plaques were subjected to accelerated ageing conditions of 40°C and a relative humidity of 90%. RESULTS: The pyrethroids insecticides outperformed the carbamates and DDT in the accelerated ageing tests. Thus UV exposure, high temperature oxidation and high humidity per se were ruled out as the main causes of failure of the alternative insecticides. Gas chromatography (GC) spectrograms showed that phosphogypsum stabilised the insecticides the most against alkaline degradation (i.e., hydrolysis). Bioassay testing showed that the period of efficacy of some of these formulations was comparable to that of DDT when sprayed on mud surfaces or cattle manure coated surfaces. CONCLUSIONS: Bioassay experiments indicated that incorporating insecticides into a conventional paint binder or adsorbing them onto phosphogypsum can provide for extended effective life spans that compare favourably with DDT’s performance under accelerated ageing conditions. Best results were obtained with propoxur in standard acrylic emulsion paint. Similarly, insecticides adsorbed on phosphogypsum and sprayed on cattle manure coated surfaces provided superior lifespans compared with DDT sprayed directly on a similar surface. en_US
dc.description.sponsorship The Bill & Melinda Gates Foundation through the Grand Challenges Exploration Initiative. en_US
dc.description.uri en_US
dc.identifier.citation Sibanda et al.: Degradation of insecticides used for indoor spraying in malaria control and possible solutions. Malaria Journal 2011 10:307. en_US
dc.identifier.issn 1475-2875
dc.language.iso en en_US
dc.publisher BioMed Central en_US
dc.rights © 2011 Sibanda et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. en_US
dc.subject Indoor residual spray en_US
dc.subject Pyrethroid en_US
dc.subject Carbamate en_US
dc.subject Stabilization en_US
dc.subject Dichloro-diphenyl-trichloroethane (DDT) en_US
dc.title Degradation of insecticides used for indoor spraying in malaria control and possible solutions en_US
dc.type Article en_US

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