Geographical variation in Ascaris lumbricoides fecundity and its implications for helminth control

The observation by microscopy of nematode eggs in human faeces is used to diagnose a helminthic infection, while the concentration of those eggs is used to estimate the number of worms in the host. Within a community, the prevalence of infection and the mean egg count provide useful information about the extent of a public health problem, and are being used to guide the growing efforts to control disease caused by helminths. Here, Andrew Hall and Celia Holland examine data on the relationship between the worm burdens of Ascaris lumbricoides and the concentration of eggs in faeces, and discuss the implications of the variation found for using such data to plan helminth control programmes.