Spatial Distribution of Microsporidia MB Along Clinal Gradient and the Impact of Its Infection on Pyrethroid Resistance in Anopheles gambiae S.L. Mosquitoes from Nigeria and Niger Republic

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.