Diversity, abundance of anopheline species, and malaria transmission dynamics in high-altitude areas of western Cameroon

Background : Assessing vector bionomics is crucial to improving vector control strategies. Several entomological studies have been conducted to describe malaria transmission in different eco-epidemiological settings in Cameroon; knowledge gaps persist, particularly in highland areas. This study aimed to characterize malaria vectors in three localities along an altitudinal gradient in the western region: Santchou (700 m), Dschang (1400 m), and Penka Michel (1500 m). Methods : Human landing catches were conducted from May to June 2023 from 6:00 pm to 9:00 am. Mosquitoes were sorted into genera, and all Anopheles species were identified using morphological taxonomic keys and species-specific Polymerase Chain reaction (PCR). Entomological indicators were assessed including species composition and abundance, biting behavior, infection rate, and entomological inoculation rate (EIR). Genomic DNA from the head and thoraces were tested for Plasmodium infection by real-time PCR. Results : 2,835 Anopheles mosquitoes were identified, including An. gambiae, An. coluzzii, An. funestus, An. leesoni, An. nili, and An. ziemanni , with An. gambiae being the most prevalent at all sites. The human-biting rate of An. gambiae s.l. was significantly higher (p-value < 0.001) in Penka Michel compared to Santchou and Dschang (45.25 b/h/n vs 3.1 b/h/n and 0.41 b/h/n), and appears to be the most infected vector, and infectious vector distribution is highly focal, with entomological inoculation rates 13-fold higher in Penka Michel compared to Santchou (1.11 vs 0.08ibites/human/night). P. falciparum was the dominant malaria parasite (67% at Santchou, 62% at Penka Michel), but P. malariae (30%) and P. ovale (1.21%) infections were also detected. Conclusion : The study highlights a difference in mosquito composition and host-seeking behavior with altitude and the need for continued surveillance to monitor vector populations and prevent potential malaria outbreaks in these highland areas.