Miracidia-Immobilizing Substances in Extracts Prepared from Snails Infected with Schistosoma Mansoni

Edward H. Michelson Department of Tropical Public Health, School of Public Health, Harvard University, Boston, Massachusetts

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Summary

A miracidia-immobilizing substance has been demonstrated in tissue extracts of the snail Australorbis glabratus subsequent to infection with Schistosoma mansoni. Detection of the immobilizing substance in snail extracts occurred as early as 9 days postinfection. The immobilizing activity of the extracts was not diminished by brief periods of freezing, storage at 5°C, or heating to 56°C for 30 minutes. Absorption of up to 67% of the immobilizing activity of the extracts could be accomplished by exposure to either living or formalin-fixed cercariae. With two exceptions, extracts prepared from other species of snails refractory to S. mansoni infection gave no evidence that immobilizing substances were present.

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