Intense malarial transmission during the dry season in irrigated rice-growing areas: a case study in Sakassou, Côte d'Ivoire

The health district of Sakassou is one of the 83 health districts in Côte d'Ivoire, located in a zone with very high malarial transmission rates, with an incidence rate of ≥40% Therefore, to guide vector control methods more effectively, it was crucial to have a good understanding of the vectors in the area. This study aimed to determine the level of malarial transmission during the dry season in Sakassou, Côte d'Ivoire. Female Anopheles mosquitoes were sampled using human landing catches (HLCs) and pyrethrum spraying catches (PSCs). The larvae were collected using the ‘dipping’ method. A total of 10,875 adult female mosquitoes of Anopheles gambiae were collected. The PCR analysis revealed that all individuals were Anopheles coluzzii. The geographical distribution of potential breeding sites of Anopheles showed the presence of An. coluzzii in all the wetlands of the city of Sakassou. During the dry season, the human-biting rate of An. coluzzii was 139.1 bites/person/night. An exophagic trend was displayed by an adult female of An. coluzzii. The entomological inoculation rate during the dry season was 1.49 infectious bites/person/night. This study demonstrated that An. coluzzii was the main vector of malarial transmission in Sakassou, and the intensity of transmission remains high throughout the dry season.