The prevalence and intensity of Ascaris lumbricoides infections in Moslem children from northern Bangladesh

Abstract

The results are presented of a horizontal epidemiological survey of intestinal infections of children aged between six months and 15 years in three adjacent villages in northern Bangladesh. On the basis of 203 stool sample examinations, the prevalence of Ascaris lumbricoides, Trichuris trichiura, hookworm and amoebic infections was estimated as 68, 56, 53 and 19%, respectively. Age-specific prevalence data indicated that approximately 90% of the children were harbouring patent Ascaris infections by the time they were four years old and there was some evidence to suggest differences in the pattern of age-prevalence between male and female children. The intensity of Ascaris infection was found to rise to its maximum value within the first four years of life. No significant differences were detected in the mean worm burdens of children aged between four and 15 years. Each child in this age-group harboured on average 10 worms. The frequency distribution of numbers of A. lumbricoides per host was found to be overdispersed, with a value of the negative binomial parameter, k, of 0 · 44. The degree of aggregation was found to be approximately the same for each age-class of the population between one and 15 years (0 · 26 ⩽ k ⩽ 0 · 82). No evidence was found to suggest a density-dependent reduction in the weight of either male or female Ascaris within the range one to 43 worms per host. The sex-ratio of worms recovered (male:female) from individual hosts harbouring burdens greater than 3 was 1·2 ± 0·2, with no correlation between sex-ratio and number of worms recovered. Correlation of the number of Ascaris eggs detected in stool samples with the number of worms recovered after anthelmintic treatment suggested a marked density-dependent decrease in egg output with increasing worm burden.