A national survey of Ascaris lumbricoides and Trichuris trichuria was carried out in Cameroon on more than 22,000 children from a random sample of 512 schools. Prevalence rates of both A. lumbricoides and T. trichuria infection were very low in the tropical zone (below 5%). They increased markedly in the equatorial zone, Guinea-type climate, to 60-85% for A. lumbricoides and 85-95% for T. trichuria. In the equatorial zone with Cameroon-type climate, prevalences were slightly lower: 50-70% for A. lumbricoides and 70-90% for T. trichuria infections. Environmental conditions are the main factors explaining these differences. Other factors (altitude, population density and urbanization) were not important. The entire population of villages selected from distinct climatic zones of Cameroon were also examined. The age group distribution of A. lumbricoides and T. trichuria infections indicated acquisition early in life, reaching a peak in early childhood, followed by a stable prevalence rate.

An estimate of the number of schistosomiasis infections in Cameroon was based on a statistically representative national prevalence survey carried out in the entire country. The number of cases of infection by Schistosoma haematobium was estimated to be 393,900, and 419,600 for S. mansoni, a total of 813,500. Taking into account the dual infections the total number of cases was 719,100 (95% confidence interval: 392 900-1 027,800). A current World Health Organization estimate extrapolating from the results of limited epidemiological surveys showed 2,239 591 cases for Cameroon, an estimate 3.1 times higher than the more accurate estimate based on the national survey. Schistosomiasis being a focal disease, prevalences observed in limited foci are not representative of regional prevalences. Prevalence survey data in the literature are biased toward reporting only positive results. Therefore extrapolations made on limited surveys may lead to an overestimation of the number of cases of schistosomiasis.