The epidemiology of Ascaris lumbricoides and other soil-transmitted helminths in primary school children from Ile-Ife, Nigeria.

An epidemiological survey of intestinal helminthiases was conducted on 766 primary school children aged 5-16 years from Ile-Ife, Nigeria. On the basis of stool examinations, the prevalence of Ascaris lumbricoides, Trichuris trichiura, hookworm and Strongyloides stercoralis was 88.5, 84.5, 33.1 and 3% respectively. Intensity of infection was measured indirectly by egg counts for each species of helminth and also by counting worms passed after chemotherapy in the case of A. lumbricoides. The influence of host age and sex on infection levels was assessed. Relationships between the intensities of A. lumbricoides, T. trichiura and hookworm in individual children were identified. After anthelmintic treatment with levamisole, the frequency distribution of A. lumbricoides per host and the relationship between parasite fecundity and worm burden were investigated. Reinfection patterns of A. lumbricoides were assessed at two 6-monthly intervals and even within the narrow age range described, differences were found. In addition, evidence was obtained for predisposition of individuals to heavy or light infection with A. lumbricoides.