Malaria transmission dynamics in four ecoepidemiological settings in Cameroon

Introduction : In Cameroon, malaria remains a major health problem. Despite the increased scale-up of ITNs, persistence of malaria transmission remains a challenge in most epidemiological settings. Updated data on factors driving malaria transmission in these ecological context are unavailable. Our study aimed to evaluate the dynamic and level of malaria transmission based on entomological parameters.
Methods : A longitudinal entomological study was carried out from August 2019 to May 2021 during five periods in the localities of Kaélé, Tibati, Bertoua and Santchou in Far-North, Adamawa, East and West Regions respectively. Mosquitoes were caught in the rainy season using human landing catches (HLC) and CDC light traps. Mosquitoes were identified using morphological taxonomic keys. PCR techniques were used to identify the species of the Anopheles gambiae complex. The Plasmodium sporozoite infection status of female mosquitoes were determined by ELISA methods.
Results : A total of 19662 mosquito was caught. Anopheline represented 25, 29% of total mosquito collected (n = 4650). Kaélé had the highest number of Anopheles specimens caught (65.44%) followed by Tibati (19.39%) and Santchou (9.42%) while Bertoua had the lowest contribution (5.74%). Four Anopheles morphological species leading were identified namely An. gambiae s.l., An. ziemanni, An. pharoensis, An. funestus. An. pharoensis species was only found in Kaélé. The average biting rates of anopheline were high outdoor than indoor in all localities. Seasonal variation in mosquito abundance and biting rate was recorded during the study. The infection rate by  Plasmodium falciparum was 3.7% in Bertoua, 2.32% in Santchou, 0.7% in Tibati and 0.33% in Kaélé. The annual entomological inoculation rate (EIR) was 7.24, 25.55, 10.95 and 18.25 infected bites/man/year (ib/m/y) in Kaélé, Tibati, Bertoua and Santchou respectively. Malaria transmission risk was high outdoor than indoor.
Conclusion : The study suggests heterogeneous pattern of malaria transmission in the four localities
Key words : Malaria ; transmission ; dynamics ; ecoepidemiological; Cameroon