Density-dependent fecundity in Schistosoma mansoni infections in man

An analysis is presented of autopsy data collected by Cheever in 1968 on the association between Schistosoma mansoni worm burdens and faecal egg counts. Significant negative relationships are found between the number of eggs/worm pair/g faeces and both the number of worm pairs and the total number of worms. A general, non-linear, statistical routine is shown to be the most practical method of fitting non-linear models to the observed density-dependent fecundity relationship. The conceptual and practical implications of density-dependence are discussed in the context of epidemiological field studies and chemotherapy programmes.