Residual Effects of Deltamethrin WG 25% as a New Formulation on Different Surfaces against Anopheles stephensi, in Southeastern Iran.

Background: Indoor residual spraying (IRS) is functioned as national interventions against malaria in southeastern foci of Iran and deltamethrin WP one of the insecticides have been used since past decade. In this study, the residual activity of the wettable granule (WG) was studied on different surfaces in hut scale trial against Anopheles stephensi in Iranshahr District, southeastern Iran.

Methods: Three dosages of 25, 40 and 50 mg a.i./m(2) of deltamethrin WG 25% formulation were applied on plaster, cement, mud, and wooden surfaces using Hudson(®) X-pert compression sprayer having 10 litters capacity.

Results: The residual effects of deltamethrin WG 25% on different surfaces was assessed based on reduction of mortality An. stepehnsi from 100% to about 70%. At 25, 40 and 50 mg a.i./m(2) the WG formulation of deltamethrin had a bioefficacy for about 2, 3 and 4 months respectively.

Conclusion: There was an expectable fluctuation in mortality of An. stephensi at different sprayed surfaces as well as dosages. The proposed 50 mg/m2 WG is the longest activity for up to 4 months which needs to be applied for two spraying cycles per year at the climatically condition of southwestern Iran.