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

Abstract

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 <i>Anopheles</i> 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 <i>Anopheles gambiae</i> were collected. The PCR analysis revealed that all individuals were <i>Anopheles coluzzii</i>. The geographical distribution of potential breeding sites of <i>Anopheles</i> showed the presence of <i>An. coluzzii</i> in all the wetlands of the city of Sakassou. During the dry season, the human-biting rate of <i>An. coluzzii</i> was 139.1 bites/person/night. An exophagic trend was displayed by an adult female of <i>An. coluzzii</i>. The entomological inoculation rate during the dry season was 1.49 infectious bites/person/night. This study demonstrated that <i>An. coluzzii</i> was the main vector of malarial transmission in Sakassou, and the intensity of transmission remains high throughout the dry season.