DAY-TO-DAY EGG COUNT FLUCTUATION IN SCHISTOSOMA-MANSONI INFECTION ANDITS OPERATIONAL IMPLICATIONS

In a study group of 183 people in a Schistosoma mansoni-endemic area i n Burundi, stool examinations were performed with duplicate 25-mg Kato -Katz slides on seven occasions (days 1, 3, 5, 8, 10, 32, and 37). Poi nt prevalences detected by single examinations of 25 mg and 50 mg of s tool varied from 41.0% to 57.9% and from 55.7% to 63.9%, respectively. The cumulative prevalence for all seven measurements was 82.0%. The i ndividual day-to-day variation in egg output was important. The majori ty of infections missed by the examination of single slides and specim ens were light ones. The Kato-Katz method applied on a single stool sp ecimen is more suitable for morbidity control, but less suitable for c ontrol of infection. When a precise quantitative diagnosis on the indi vidual level is required, several measurements on different days are n ecessary. The data presented validate recently developed statistical m odels and charts predicting true prevalences.