Altitudinal variation in the parasitological and entomological indices of malaria around Mount Cameroon, South West Region of Cameroon

This study aimed to define the heterogeneity in the parasitological and entomologic indices of malaria transmission from sites of contrasting altitudes in the Mt. Cameroon region. Blood samples were collected by pricking the finger. Thick and thin blood films were prepared and Giemsa-stained. Slides were examined under x100 objective for the identification of asexual and sexual stages of malaria parasites. Quantification of asexual stages and gametocytes was done against 200 WBC and 500 WBC, respectively assuming a WBC count of 8000 leucocytes/µl blood. Mosquitoes were collected by the landing catch method by human bait. All mosquitoes caught were separated into Anopheles, Culex, Aedes or Mansonia. Man biting rate (MBR), vectorial capacity and entomological inoculation rate (EIR) were calculated using standard formulae. The data generated was analyzed using SPSS version 15. Overall, 876 pupils aged 4-16 years of both sexes were enrolled in this study. The prevalence of asexual stages of malaria was 45.31% while that of sexual stages was 24.69%. Tiko, the locality at the lowest altitude recorded the highest prevalence of malaria while Bonakanda at the highest altitude recorded the lowest and the difference was significant, p=0.01. The geometric mean parasite density (GMPD) of infection was highly heterogeneous amongst the different localities, p=0.02. Age significantly affected the prevalence of malaria, p=0.02. Sex did not affect the prevalence nor the GMPD of malaria infection, p>0.05. P. falciparum was found to be the most prevalent Plasmodium species infecting children. An. gambiae was the most aggressive anopheline species. The highest EIR and vectorial capacity of anophelines was recorded in Tiko. The malaria epidemiology is highly heterogeneous among the different localities. Malaria control programmes should be based on evident spatial and temporal heterogeneity of Anopheles mosquitoes and Plasmodium species in a particular area so as not to waste resources which would be of limited effectiveness to the populations at risk.   Key words: Altitudinal variation, parasitological, entomological, indices, malaria, Mount Cameroon region.