The importance of collateral portal veins for resistance to schistosomiasis in mice.

Mice with portal hypertension and collateral circulation caused by partial portal vein ligation yielded fewer worms than intact or sham-operated controls when infected with 50 Schistosoma mansoni cercariae for 8 weeks. The collateral circulation probably diverted arriving immature worms back to the general circulation where they died as the result of being out of their natural habitat rather than from immune killing. The present data strongly support the concept that a leaky portal system is the main factor in resistance to reinfection in murine schistosomiasis.