Designing of a laboratory model for evaluation of the residual effects of deltamethrin (K-othrine WP 5%) on different surfaces against malaria vector, Anopheles stephensi (Diptera: Culicidae)

Abstract

Background & objectives: Deltamethrin plays an important role in controlling malaria vectors,and is used in indoor residual spraying and manufacture of long-lasting insecticidal mosquitonets. The residual activity of deltamethrin (K-othrine WP 5%) @ 25 mg/m2 was studied in laboratoryconditions on different surfaces.Methods: The surfaces were made artificially with different building materials such as mud, plaster,cement and wood in the laboratory. The surfaces were mounted inside petri-dishes (diam: 20 cm)and wood surface was prepared separately. The prepared surfaces were attached to the walls anddeltamethrin was applied using standard Hudson pump sprayer with a discharge rate of 757 ml/min or 0.2 gal/min. The spraying was conducted at standard rhythm as recommended by WHO.After application all the sprayed surfaces were transferred into the special wooden boxes designedfor this purpose. The surfaces were maintained at laboratory conditions. The WHO’s recommendedbioassay kit and method was used during this study.Results: Bioassays on Anopheles stephensi Liston showed that the persistence of deltamethrin ondifferent surfaces (>70% mortality) was around 4 months on plaster (Mortality = 77±6.2%), 2months on mud (76.9±6.8%), 4.5 months on cement (79±3.2%), 4 months on wood (71.7±6.8%)and 4 months on filter papers (82.3±5.4%).Interpretation & conclusion: The results of this study on residual effects of deltamethrin WP 5%(25 mg/m2) are highly concordant with two field bioassays carried out in a malarious area atsouth-eastern Iran. This method can be replaced by the field bioassay tests which are time consumingand costlier.

Keywords

• Anopheles stephensi
• bioassay
• deltamethrin
• Iran
• malaria
• vector