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Background: Vector control through application of insecticides on bed nets and other surfaces in the house is one of the most effective means of controlling vector borne diseases. Information on performance of insecticides including DDT, Lambda cyhalothrin and Pirimiphos-methyl on soils is scanty. House modification is another method that can be employed in the control of vector diseases. The aim of this study was to evaluate indoor residual spray (IRS) on different mud wall surfaces, house characteristics based on factors associated with mosquito’s entry, exit and resting behavior like presence of eaves, ceiling; wall opening and widow mesh.
Methods: A cross sectional study was carried out in five villages, where by 1371 houses were characterized. Insectary reared mosquitoes were exposed to insecticides sprayed on mud wall surfaces according to standard WHO guidelines. Field information collecting tools included questionnaire for ascertaining information on household characteristics. A standard laboratory form was used to collect data from the Laboratory cone bioassay tests done in the laboratory.
Results: Out of 1371 houses, 940(68.6%) were made of bricks walls, 396(28.9%) mud, 27(2%) concrete, 5(0.36%) sticks and 2(0.15%) wood. 66.4% of house has no window mesh and 31.6% had window mesh. 81.7% has openings and 18.2% no openings. Grading of houses showed a statistical significance [χ²=237.505, P<0001] indicating differences across all villages either there was a significance association between eaves space within villages at [χ²=41.39 P<0.0001]. The proportion of mosquito mortality was 100% in the first week of exposure to treated surfaces while a change was observed in the fifth week of exposure with respective rates of 95.25%, 89.25% and 29.75% for Lambda cyhalothrin, DDT and Pirimiphos-methyl.
Conclusion: There were very high chances for vectors to enter the house and transmit vector borne diseases in the study area. House modification should be considered as one of the method to be implemented hand-to hand with other methods for vector control. Poor house construction is one of the factors that can reduce the effectiveness of IRS in this area. Selecting insecticides for IRS should be based on the type of wall surfaces to be targeted. |
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