Low dispersion of anopheline malaria vectors in the African equatorial forest

Previous studies showed that the anophelines, vectors of human malaria, had densities especially high on the banks of the large rivers flowing through the rain forest in the South of Cameroon. In order to establish if these mosquitoes enter or not into the forest, samplings were performed with CDC light traps placed in houses distant of less than 200 m from the banks of the Sanaga river and in houses at 1.5 km from this river. In houses at less than 200 m from the bank, the mean densities of Anopheles nili and An. gambiae were respectively 40 and 5 limes higher than at 1.5 km. Thus the rain forest constitute a significant obstacle for the dispersion of anophelines. Therefore confining of anophelines at the immediate surroundings of the river permits to explain why anopheline densities are such important at low distances of the river and not in the rest of the forest.