Entomological surveillance on Aedes aegypti during covid 19 period in Cape Coast, Ghana: Risk of arboviral outbreaks, multiple insecticide resistance and distribution of F1534C, V410L and V1016I kdr mutations

Author summaryThe study assessed the risk of transmission of Aedes-borne arboviruses in a community in Cape Coast during the Covid-19 restriction period in 2020. Three larval indices were calculated from the household larval survey in 100 randomly selected houses in the community. Insecticide susceptibility of the female adult Ae. aegypti to four insecticides was performed. The results showed that the risk of a potential outbreak of Aedes-borne diseases in the Covid 19 restriction period was much lower than in 2017 when a similar assessment was done. The low risk was related to frequent clean-up exercises in the community during the Covid-19 restriction period. The mosquito population was resistant to deltamthrin, DDT, bendiocarb and fenitrothion insecticides. However, resistance level was higher in the mosquitoes collected in houses than the mosquitoes collected outside houses. Insecticide use in houses may have contributed to the different level of resistance observed. The study detected F1534C, V1016I and V410L kdr mutations in Ae. aegypti population. The combination of these mutations is known to generate high levels of pyrethroid resistance in the mosquito. The study agrees with sanitation improvement as a tool to control Ae. aegypti and could complement insecticide-based tools in controlling this vector. BackgroundThe study assessed the risk of transmission of Aedes-borne arboviruses in a community at Cape Coast during the Covid-19 restriction period in 2020 based on entomological indices. The spatial distribution of insecticide resistance was also assessed in Ae. aegypti population from Cape Coast. MethodsThree larval indices were calculated from a household larval survey in 100 randomly selected houses. WHO susceptibility bioassay was performed on female adult Ae. aegypti that were reared from the larvae collected from household containers and other receptacles located outside houses against four insecticides. The mosquitoes were also screened for F1534C, V1016I, and V410L kdr mutations. ResultsThe estimated larval indices in the study community were House index- 34%, Container index- 22.35%, and Breteau index- 2.02. The mosquito population was resistant to Deltamethrin (0.05%), DDT (4%), Fenitrothion (1%), and Bendiocarb (0.1%). A triple kdr mutation, F1534C, V410L and V1016I were detected in the mosquito population. ConclusionThe study found the risk of an outbreak of Aedes-borne diseases lower in the covid-19 lockdown period than before the pandemic period. The low risk was related to frequent clean-up exercises in the community during the Covid-19 restriction period. Multiple insecticide resistance couple with three kdr mutations detected in the study population could affect the effectiveness of control measures, especially in emergency situations. The study supports sanitation improvement as a tool to control Ae. aegypti and could complement insecticide-based tools in controlling this vector.