Malaria and urbanization in central Africa: the example of Brazzaville. Part II: Results of entomological surveys and epidemiological analysis.

92 night-bite collections on human bait (550 man-nights) and 234 collections of the house-resting fauna were carried out from October 1982 to May 1984 in Brazzaville. A total of 19,531 Culicidae were captured, of which 1,893 were Anopheles, almost exclusively A. gambiae. An average sporozoite rate of 3.41% was found from dissection of 1,291 A. gambiae: one female A. moucheti was also found to be infected. Considerable differences in the intensity of transmission of malaria were observed in the different districts of the town. Whereas the inhabitants of Brazzaville received on average 22.5 infective bites per person per year, in reality this number varies according to the district, from over 100 infective bites per person per year, to less than one infective bite per person every three years. With the help of classical quantitative epidemiological models, the authors analyse here the over-all results, as well as those of two areas of the town, the first area characterized by a high anopheline density, and the second by the rarity of anopheles.