Fenitrothion Bio-Efficacy on Different Intradomicile Surface Types Against Anopheles (Nyssorhynchus) Albimanus in the Main Malaria Endemic Regions of Panama

Background: The use of intradomicile residual insecticide on a large scale is a proven and efficacious intervention against malaria mosquito vectors. The objective of the study was determined the bio-efficacy and resistance of fenitrothion insecticide against the mosquito An. (Nyssorhynchus.) albimanus Wiedemann . Methods: This study included seven communities located in different endemic regions where fenitrothion is used to control An. (Nys.) albimanus populations. The test of bio-efficacy and susceptibility were conducted following the WHO standard bioassay methodology. Results: The average percent mortality of An. (Nys.) albimanus exposed to fenitrothion in the seven communities tested were 96% and 92% for the first two months. This bio-efficacy was maintained until the fifth month with 81% mortality in communities with high IRS coverage. Anopheles (Nys.) albimanus was susceptible to the organophosphate insecticides fenitrothion and malathion, as well as to carbamate propoxur but resistant to pirimiphos-methyl and chlorpyrifos. Conclusion: This study demonstrates that fenitrothion maintains an elevated insecticide residuality and toxic effect on different types of surfaces until the fifth month post-application. Furthermore, An. (Nys.) albimanus remains highly susceptible to this insecticide, providing a high degree of protection against mosquito bites inside households, and interrupting malaria transmission in places with high IRS coverage and where the mosquito is still susceptible to fenitrothion application.