Stability of faecal egg excretion in Schistosoma mansoni infection.

Stability of Schistosoma mansoni egg excretion was studied in 23 residents of a rural endemic area in North-east Brazil where the over-all prevalence rate was 87% and the peak geometric mean egg excretion was 308 eggs/ml (Bell method) in the 10 to 14-year-old age group. Stool examinations by the Kato method were performed for three to four consecutive days each month for three consecutive months. Both raw and transformed data showed significant stability of S. mansoni egg excretion from day to day and month to month in this population. A single Kato examination detected 68% of individuals who were excreting more than 400 eggs per gramme. Although S. mansoni egg excretion is stable over time, identifying individuals with high egg excretion in endemic populations requires sensitive quantitative methods.