Microsporidia MB (MB), a promising biological control agent, suppresses Plasmodium falciparum transmission in Anopheles mosquitoes. This study examined the spatial distribution of MB infection in natural populations of An. gambiae s.l. mosquitoes collected in Nigeria and Niger Republic, and its association with insecticide susceptibility in the mosquitoes. Microsporidia MB has wide geographic distribution across Nigeria and Niger Republic. The overall prevalence of MB in F₀ mosquitoes was 12.25% (95% CI: 7.76–16.75%); 25 mosquitoes out of 204 were positive. Geographic variation was observed, with a higher prevalence (5/15 mosquitoes) in Ebonyi State (33.33%, CI: 9.48–57.19%, Fisher’s exact test, p = 0.008). Infection rates were higher in An. coluzzii mosquitoes (21/133 mosquitoes), estimated at 15.79% (CI: 9.59–21.99%) compared to An. gambiae s.s. mosquitoes (4/71), with approximately 5.63% (CI: 0.27–11.00%, χ² = 4.44; df = 1, p = 0.035). Resistant mosquitoes had a significantly higher prevalence of MB infection than susceptible mosquitos at 28.57% (CI: 16.74–40.40%) with an odds ratio of 3.33 (CI: 1.23–9.03, p = 0.017). These findings suggests that MB can be exploited as an alternative for vector control in Nigeria and Niger, but its possible association with pyrethroid resistance suggests that it should be taken into account as a potential confounder when designing insecticide resistance management strategies.

Insecticide-based interventions continue to serve as the cornerstone of Aedes mosquito control, the primary vectors of arboviruses. This study assessed the insecticide resistance profiles of four Aedes mosquitoes in three rural areas in southern Nigeria, where arbovirus outbreaks recently occurred. Using WHO tube tests and CDC bottle bioassays, four Aedes species (Aedes aegypti, Ae. albopictus, Ae. simpsoni complex and Ae. luteocephalus) were evaluated for susceptibility to commonly used public health insecticides, including deltamethrin, alphacypermethrin, permethrin, pirimiphos-methyl, chlorfenapyr and clothianidin. Biochemical assays were conducted using Ae. albopictus to establish the role of metabolic resistance mechanism. Amplification and sequencing of fragment of Ae. luteocephalus ITS1 gene molecularly confirmed its species identity. Aedes aegypti exhibited possible resistance to pirimiphos-methyl but remained susceptible to all other insecticides across study sites. Aedes albopictus showed resistance to DDT and possible resistance to pirimiphos-methyl, while remaining susceptible to pyrethroids. Aedes luteocephalus was resistant to pirimiphos-methyl but susceptible to all other insecticides. Aedes simpsoni complex was fully susceptible to all insecticides. Biochemical assays revealed elevated 𝛼-esterase and monooxygenase activities (3.4-fold and 2.54-fold, respectively) in exposed females of Ae. albopictus compared to the unexposed cohort. Overall, the low resistance levels observed underscore the need for sustained insecticide resistance monitoring and management to maintain the effectiveness of insecticide-based vector control strategies in Nigeria.

Background: Microsporidia MB (MB), a promising biological control agent suppresses Plasmodium falciparum transmission in Anopheles mosquitoes. Methods: This study examined the spatial distribution of MB infection in natural populations of An. gambiae s.l. mosquitoes collected in Nigeria and Niger Republic, and its potential modulation of insecticide susceptibility in the Anopheles mosquitoes. Results: The overall prevalence of MB in F₀ mosquitoes was 12.25% (95% CI: 7.76%-16.75%); 25 mosquitoes out of 204 were positive. Geographic variation was observed, with a higher prevalence (5/15 mosquitoes) in Ebonyi State (33.33%, 95% CI: 9.48%-57.19%, Fisher's exact test, p = 0.008). Infection rates were higher in An. coluzzii mosquitoes (21/133 mosquitoes), estimated at 15.79% (95% CI: 9.59%-21.99%) compared to An. gambiae s.s. mosquitoes (4/67), approximately 5.63% (95% CI: 0.27%-11.00%), χ² = 4.44; df = 1, p = 0.035)]. Resistant mosquitoes had a significantly higher prevalence of MB infection at 28.57% (95% CI: 16.74%-40.40%) and OR of 3.33 (95% CI: 1.23-9.03, p = 0.017) compared with susceptible mosquitoes. Conclusion: MB has wide geographic distribution across Nigeria and Niger Republic. An. coluzzii and resistant mosquitoes are more infected with this fungi. Understanding the geographic and species-specific infection patterns and implication in insecticide resistance could guide targeted vector control strategies using this biological agent.