Different agroecosystems have similar Anopheles–Microsporidia MB infection dynamics in the Ahero region of Western Kenya: implications for symbiont control strategies

Background Microsporidia MB is a maternally inherited symbiont of several Anopheles species. In An . arabiensis , it is characterized by strong Plasmodium falciparum transmission blocking, stable vertical transmission, and no detectable virulence, making it a promising candidate for a symbiont-based malaria control intervention. Previous studies have shown that Microsporidia MB prevalence varies across regions of Kenya; however, the scale at which Microsporidia MB prevalence varies is unknown. Methods Longitudinal sampling was conducted simultaneously in 10 sentinel houses per area within an irrigated rice scheme and an adjacent non-irrigated sugarcane-growing zone located 8 km away. Collected mosquitoes were screened for Microsporidia MB and Plasmodium via PCR, and their abundance and infection rates were correlated with remote sensing-derived microhabitat variables. Results Both areas harbored similar Anopheles species pools, dominated by An. arabiensis , An. gambiae , and An. funestus . Larval surveys mirrored this composition, though An. funestus was absent. The irrigated rice scheme had a seven-fold greater Anopheles mosquito abundance, indicating strong spatial heterogeneity in abundance driven by location. Microsporidia MB was detected across both areas in all three major species and in other uncharacterized Anopheles species (prevalence 2–15.6%). Prevalence did not vary significantly in adult mosquitoes between areas (Chi−square test, χ ² = 1.716, df = 1, p = 0.1902) or across sentinel houses (Ahero: Kruskal−Wallis H−test, H = 10.02, df = 9, p = 0.35; Miwani: H = 8.89, df = 9, p = 0.45), nor between larvae in Ahero and Miwani (Chi−square test, χ² = 0.01612 , df = 1, p = 0.8990). The vegetation index (NDVI) positively influenced Microsporidia MB prevalence, while wind speed had a negative influence. Furthermore, the higher vector-producing rice scheme also had greater spatio-temporal detection of Plasmodium. Discussion These findings provide vital context on Microsporidia MB and its hosts; consistent prevalence across contrasting agroecosystems, despite a seven-fold variance in host population density, indicates that its transmission is resilient to local ecological shifts. While specific to this study’s spatial scale, this provides a crucial proof of concept that the efficiency of deploying the symbiont as a malaria control tool is therefore unlikely to be hindered by local-scale differences in landscape heterogeneity.