Egg viability in urinary schistosomiasis. II. Simplifying modifications and standardization of new methods.

Two new methods were recently introduced for the determination and quantification of egg viability in Schistosoma haematobium infections by staining eggs filtered from urine on Nytrel filters with mercurochrome and iodine. Both methods showed reasonable agreement with the best currently available method, centrifugation hatching, but it appeared that improved agreement could be obtained by modifications of timing and technique. The present paper describes the standardization of staining times and microscopic counting techniques; the modifications made gave substantially improved agreement with the reference method and achieved the most important objective, not to have zero estimates of viability when the centrifugation method detected hatching.