Abstract: Introduction: In Eritrea, malaria remains a major vector-borne disease of significant public health concern. The disease exhibits high seasonality, focal distribution, and instability. Insecticides such as bendiocarb, pirimiphos-methyl, and a mixture of deltamethrin and clothianidin have been widely used for indoor residual spraying (IRS), with rotations occurring every two years based on the resistance status of local vectors. The objective of this study was to assess the residual efficacy of Fludora® Fusion WP-SB 56.25 (a mixture of clothianidin and deltamethrin).
Methods: Larvae of Anopheles, Culex, and Aedes mosquitoes were collected from both natural and artificial breeding habitats in the Tesseney district. The collected larvae were reared in the laboratory until they reached adulthood. Four-day-old female mosquitoes were used for cone tests following the WHO protocol. Cone tests were conducted on both cement and mud walls, with ten structures evaluated for each mosquito species. The residual activity of Fludora® Fusion WP-SB 56.25 (clothianidin + deltamethrin) against the different mosquito species was assessed at intervals of two, six, and twelve weeks post-IRS.
Results: Immediately following the spraying campaign, the residual efficacy of the insecticide exceeded the WHO’s 80% threshold. However, its efficacy dropped below 80% over a period of three months. A slightly higher efficacy was observed on cement walls compared to mud walls. The residual efficacy of Fludora® Fusion was more pronounced against Anopheles and Aedes mosquitoes than against Culex mosquitoes.
Conclusion: The new formulation of Fludora® Fusion demonstrated residual efficacy lasting up to three months, suggesting that a second round of IRS may be advisable in areas with long transmission periods.