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Summary and Conclusions
Female albino mice were re-exposed to cercariae of Schistosoma mansoni at intervals of one hour, five hours, one day, two days, one week, one month and two months after an original exposure, together with previously unexposed control mice. Exposures were to 50 cercariae per mouse by tail for one hour. For all except the longest interexposure interval the parasites of the initial and challenging infections were tagged by their sex, and the mice were initially exposed at the age of about six weeks. When the interval between exposures was two months, each exposure was to both male and female cercariae, and the initial infection was presented to the mice when they were one week old. In all studies autopsies were performed six weeks after the second exposure.
The following conclusions have been drawn: