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Micro-encapsulated pirimiphos-methyl shows high insecticidal efficacy and long residual activity against pyrethroid-resistant malaria vectors in central Côte d'Ivoire

Tchicaya, Emile S. and Nsanzabana, Christian and Smith, Thomas A. and Donzé, Jennifer and de Hipsl, Maiti Laserna and Tano, Yao and Müller, Pie and Briët, Olivier Jt and Utzinger, Jürg and Koudou, Benjamin G.. (2014) Micro-encapsulated pirimiphos-methyl shows high insecticidal efficacy and long residual activity against pyrethroid-resistant malaria vectors in central Côte d'Ivoire. Malaria journal, Vol. 13 , 332.

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Abstract

The wide-scale implementation of insecticide-treated nets and indoor residual spraying (IRS) has contributed to a considerable decrease of malaria morbidity and mortality in sub-Saharan Africa over the last decade. Due to increasing resistance in Anopheles gambiae sensu lato mosquitoes to dichlorodiphenyl trichloroethane (DDT) and pyrethroids, alternative insecticide formulations for IRS with long-lasting residual activity are required to sustain the gains obtained in most malaria-endemic countries.; Three experimental capsule suspension (CS) formulations of the organophosphate pirimiphos-methyl were evaluated together with Actellic 50 EC, an emulsifiable concentrate (EC) of pirimiphos-methyl, and the pyrethroid ICON 10 CS, a lambda-cyhalothrin CS formulation, in an experimental hut trial. The formulations were tested on two types of surfaces: mud and cement. The study with a 12-month follow-up was carried out in Bouaké, central Côte d'Ivoire, where An. gambiae mosquitoes show high levels of resistance against pyrethroids, DDT and carbamates. Residual activity was also tested in cone bioassays with the susceptible An. gambiae KISUMU strain.; One of the CS formulations of pirimiphos-methyl, CS BM, outperformed all other formulations tested. On cement surfaces, the odds ratios of overall insecticidal effect on An. gambiae s.l. of pirimiphos-methyl CS BM compared to Actellic 50 EC were 1.4 (95% confidence interval (CI): 1.2-1.7) for the first three months, 5.6 (95% CI: 4.4-7.2) for the second three months, and 3.6 (95% CI: 3.0-4.4) for the last six months of follow-up. On mud surfaces, the respective odds ratios were 2.5 (95% CI: 1.9-3.3), 3.5 (95% CI: 2.7-4.5), and 1.7 (95% CI: 1.4-2.2). On cement, the residual activity of pirimiphos-methyl CS BM measured using cone tests was similar to that of lambda-cyhalothrin and for both treatments, mortality of susceptible Kisumu laboratory strain was not significantly below the World Health Organization pre-set threshold of 80% for 30 weeks after spraying. Residual activity was shorter on mud surfaces, mortality falling below 80% on both pirimiphos-methyl CS BM and lambda-cyhalothrin treated surfaces at 25 weeks post-treatment.; CS formulations of pirimiphos-methyl are promising alternatives for IRS, as they demonstrate prolonged insecticidal effect and residual activity against malaria mosquitoes.
Faculties and Departments:09 Associated Institutions > Swiss Tropical and Public Health Institute (Swiss TPH) > Department of Epidemiology and Public Health (EPH) > Health Interventions > Vector Control Centre (Müller)
09 Associated Institutions > Swiss Tropical and Public Health Institute (Swiss TPH)
09 Associated Institutions > Swiss Tropical and Public Health Institute (Swiss TPH) > Department of Epidemiology and Public Health (EPH) > Infectious Disease Modelling > Infectious Disease Modelling (Smith)
09 Associated Institutions > Swiss Tropical and Public Health Institute (Swiss TPH) > Department of Epidemiology and Public Health (EPH) > Eco System Health Sciences > Health Impact Assessment (Utzinger)
UniBasel Contributors:Smith, Thomas A. and Müller, Pie and Briët, Olivier and Utzinger, Jürg
Item Type:Article, refereed
Bibsysno:Link to catalogue
Publisher:BioMed Central
ISSN:1475-2875
Note:Publication type according to Uni Basel Research Database: Journal article
Language:English
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Last Modified:31 Dec 2015 10:56
Deposited On:07 Nov 2014 08:28

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