ASSOCIATIONS AMONG MULTIPLE GEOHELMINTH SPECIES INFECTIONS IN SCHOOLCHILDREN FROM PEMBA ISLAND

In order to estimate the potential benefits of interventions against m ultiple geohelminth species in endemic areas, an improved understandin g of the population biology of multiple infections is required. This p aper presents a detailed analysis of the associations among Ascaris lu mbricoides, Trichuris trichiura and hookworm infections in 1539 school children on Pemba Island, Tanzania, where 58% of the sampled children carried infections of all 3 parasites at the time of the study. Infect ion intensities of different species were positively correlated, and i ndividuals with single-species infections had generally lower species- specific egg counts than individuals with multiple-species infections. There was no age- or sex-related clustering of infections. A weak clu stering of intense infections among individuals with multiple-species infections was observed, which became more pronounced as the threshold defining an intense infection increased for each species. The results suggest that individuals with multiple species infections are likely to be at highest risk of geohelminth-related morbidity, not only becau se of the number of infections they harbour, but also because they gen erally carry heavier infections of each species.