Studies on the hatchability of Schistosoma mansoni eggs from a naturally infected human community on St Lucia, West Indies.

A relatively simple, standardized hatching test was devised, tested and used to estimate the Schistosoma mansoni hatching rate for 88 St Lucian subjects selected by age, sex and intensity of infection. The hatching rate was dependent on the intensity of infection and rose proportionately with it. The rate also decreased with increasing age of the subject. Sex alone had no direct effect but there was a suggestion of an interaction between sex and age. These results suggest that several hatching tests are necessary, before and after treatment in schistosomicidal drug trials, to permit valid conclusions to be drawn. The hatching data are used in conjunction with survey results to calculate the contamination potential of different age groups in a population. School children (5-14 years old) are about twice as important as young adults (15-29 years old) who, nevertheless, contribute over a quarter of the total contamination potential. However, whereas school children are fairly accessible for mass chemotherapy control programmes, young adults often are not and, furthermore, involve problems associated with the treatment of women of child-bearing age.