Larval ecology of Aedes spp. mosquitoes and arbovirus transmission risk in four mid-sized cities of southern Cameroon

Vector-based surveillance is crucial for monitoring arboviral diseases such as dengue, chikungunya, yellow fever, and Zika. In Cameroon, data on the distribution and bionomics of Aedes species in medium-sized cities within the equatorial forest region are limited. This study assessed the distribution, larval habitats, and bionomics of immature Aedes spp. stages across four mid-sized cities of southern Cameroon. Larval surveys were conducted from March 2022 to March 2023 in Bertoua, Kribi, Sangmelima, and Abong-Mbang during rainy and dry seasons. Water-holding containers were inspected using the dipping method, and collected larvae and pupae were reared to adults for morphological identification. Entomological indices were used to estimate arboviral transmission risk, and species co-occurrence in larval habitats was recorded. A generalized linear model was used to compare abundance and distribution among sites, seasons, and breeding site. From 758 larval habitats inspected (214 in Bertoua, 213 in Sangmelima, 184 in Kribi, 147 in Abong-Mbang), 3820 mosquitoes belonging to four genera and 11 species were emerged. Aedes spp. mosquitoes were the most abundant (n = 2903), with Aedes albopictus and Aedes aegypti as dominant species that often co-occurred. Seasonal variation in the abundance of all mosquito genera was significant, with peak Aedes spp. abundance in the rainy season (n = 2359; 81.3%). Tires were the most common larval habitats, mostly located within 10 m of human dwellings. Kribi and Bertoua exhibited the highest container, house, and Breteau indices, suggesting high potential risk. The study supports the need for regular vector-based surveillance to control arboviral disease in Cameroon. Such studies could also provide critical information for strengthening integrated vector management.