Schistosoma mansoni and S. japonicum: méthylène blue test for the viability of schistosomula in vitro.

Abstract Methylene blue staining has already been used to help in determining the viability of schistosomula, but precise criteria were lacking. Such criteria have now been established using the schistosomula of Schistosoma mansoni and S. japonicum , Living schistosomula, depending on the time of reading, are either (1) unstained and motile or (2) a deep blue, contracted, and motionless. Dead organisms are (1) a light green-blue and flattened or (2) colorless and degenerate. Optimum readings are made in uncovered preparations, 50–60 min after addition of the dye, when all initially motile schistosomula will have contracted and been stained.