Ascariasis and trichuriasis in Cameroon.

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.