The aim of this project was to develop a long lasting non pyrethroid IRS spray formulation using proprietary technology to provide 6 months residual activity on all typical wall surfaces. The level of residuality after indoor residual spraying of insecticides on house walls varies from one to six months for organophosphates, carbamates and pyrethroids to twelve months for DDT. This necessitates varying frequency of repeat application in order to maintain protection of the population from malaria transmission.
In addition, pyrethroid and DDT resistance is a major concern and increasing regulatory standards are driving the search for cost-effective alternatives to DDT. In cases where carbamates or organophosphates are used for IRS, applications are typically made every three months which can lead to increased product and logistical costs compared to longer lasting products. Therefore, a non pyrethroid/DDT product lasting six months or more offers a practical new tool for cost-effective IRS and an opportunity to replace DDT.
Syngenta developed formulations based on their proprietary technology which demonstrated at least 6 months residual activity in laboratory trials. Lab trials carried out on wood, concrete and wood surfaces have confirmed these results. Experimental hut trials carried out in three different sites, Tanzania, Benin and Côte D’Ivoire have confirmed that six months residual efficacy has been achieved on wood and concrete surfaces and four months residual efficacy on mud surfaces, this is a significant improvement on current products. Syngenta have decided to commercialise this formulation and will take it through the WHOPES process and develop a regulatory package for the formulation.