Host genetic factors do not account for variation in parasite loads in Strongyloides fuelleborni kellyi.

Previous work in Papua New Guinea has shown considerable variation in egg counts between different people infected with Strongyloides fuelleborni kellyi, although individual egg loads remained relatively constant over a 14-month period. Possible explanations include genetic predisposition, a surprising longevity of the worms, or external auto-infection. We have now analysed the pedigrees of 177 individuals for whom egg counts were available, and find no evidence for polygenic inheritance of factors related to egg counts. The use of genetic models postulating the segregation of a single unknown susceptibility gene did not enable us, using the data available, to distinguish between this hypothesis and environmental determination of egg counts; nor did we find any association between egg load and the class 1 HLA genotype of the host.