Resistance to cercarial challenge upon transfer of Schistosoma mansoni into mice.

: Various numbers of 25- to 28-day-old schistosomes of both sexes were surgically transferred into the mesenteric veins of mice. Recipient animals (plus sham-operated controls) were percutaneously challenged with cercariae at various times after transfer, and the number of surviving worms was subsequently determined by portal perfusion. Significantly fewer challenge parasites were recovered from mice which had received a worm transfer than from sham controls; the reduction was comparable to that observed in mouse recipients of a percutaneous primary infection with cercariae. Resistance of mice to cercarial challenge was dependent upon the number of schistosome pairs transferred, and upon the time interval between transfer and challenge.