Factors associated with variation in insecticide quantity being used for indoor residual spraying (IRS) for visceral leishmaniasis (kala-azar) elimination in Bihar, India

Abstract

Background & objectives: Indoor residual spraying (IRS) is part of a key strategy for elimination of visceral leishmaniasis (kala-azar). IRS for kala-azar elimination in India uses 125 g 5% alpha-Cypermethrin wettable powder which is mixed with 7.5 litres of water and sprayed on walls using hand compression sprayers. Insecticide quantity is measured volumetrically through a container. Methods: A cross-sectional study design with cluster random sampling was adopted to select 272 IRS squads of 46 blocks across 12 districts in Bihar, India. The quantity of insecticide measured by the container used by each IRS squad was recorded. Results: Mean weight of insecticide measured was found to be 147 g (SD 33.9). One-thirds of squads were measuring less than the nationally recommended quantity of 125 g. Two-fifths of squads were overdosing with use of more than 150 g insecticide powder. Shoving the containers into a heap of insecticide powder resulted in heavier and less consistent measurements as compared to filling the containers from the top. Different types of measuring containers and different manufacturers of insecticide were shown to significantly account for the variation in the quantity of insecticide being measured. Interpretation and conclusion: Standardization of insecticide measurement by IRS squads is needed, both to prevent under-dosing and overdosing of insecticide residue on walls. Standard operating procedures for calibrating and using uniform measuring containers should be implemented. Further, use of measuring containers may be replaced altogether with manufacturer-packaged amounts of insecticide formulation which could be directly used to prepare one-tank load of insecticide suspension.

Keywords

• indoor residual spraying
• standardization
• calibration
• measuring containers
• wettable powder