Control of Morbidity Due to Schistosoma haematobium on Pemba Island: Egg Excretion and Hematuria as Indicators of Infection

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  • Ministry for Foreign Affairs, Direzione Generale per la Cooperazione allo Sviluppo, Schistosomiasis Control Programme, Swiss Tropical Institute Field Laboratory, World Health Organization, Ministry of Health of Zanzibar, Pemba Island, Zanzibar, Italy

The variability of Schistosoma haematobium egg excretion using a quantitative syringe filtration technique and the variability of hematuria detected visually and by reagent strips were studied in a population of 520 subjects from the village of Pujini (Pemba Island, Zanzibar, Tanzania) for 6 consecutive days. A high degree of day-to-day variability of egg excretion within subjects was found both in the whole population and in the 5–19 year age group. Subjects with 1 urinary egg count of ≥50 eggs/10 ml urine were not similarly classified in 36–61% of the other 5 examinations and 4–16% of their other examinations were negative. Gross hematuria had a specificity of almost 100%, when related to a positive filtration on any day, and was closely related to egg counts of ≥ 50 eggs/10 ml urine. The finding of a strongly positive reaction for hematuria on a given single day was closely associated with the subject having a high egg count (≥50 eggs/10 ml urine) on at least one of the 6 days of the study. At the primary health care level, single highly positive semiquantitative values for hematuria were a more useful diagnostic indicator than a single egg count to select patients with heavy infections for selective population chemotherapy.