Seasonal variations of malaria transmission in Western Cameroon highlands: entomological, parasitological and clinical investigations.

A cross-sectional study on malaria transmission was carried out in Mangoum, a village situated in the western highland region of Cameroon in October 2005 and May 2006, to assess malaria parasite prevalence in a cohort of children and vectors biting habits and entomological inoculation rate. Mosquitoes were collected by landing catches on volunteers. Members of the Anopheles gambiae complex and molecular forms were identified using Polymerase Chain Reaction method.Infection intensity was determined by counting the number of infected red blood cells against 200 leucocytes. A total of 1195 Anopheles were collected, 183 and 1012 respectively in the dry and rainy seasons. Two Anopheles species were identified: A. gambiae s.l. and Anopheles funestus. A. gambiae s.s. was the only member of the A. gambiae complex found and the main malaria vector in this region. The sporozoite rate of A. gambiae was higher in the rainy season (9%). The average inoculation rate was 90 infective bites per man per year. A total of 699 children were examined. Two parasites species were identified: Plasmodium falciparum and Plasmodium malariae. The mean parasite rate was 41. 3%. In the age range of 2 - 9 years, the parasite rates were 49% in the dry season and 34.7% in the rainy season. The mean spleen rate of the age range 2 - 9 years varies from 26. 7% in rainy season to 22. 3% in the dry season, and was not significantly different (p = 0, 3). The Western highlands region can be considered as an area of high malaria transmission intensity.   Key words: Malaria, transmission, Anopheles vectors, biting habits, sporozoite rate, parasites species, western Cameroon highlands.