The biology of Angiostrongylus cantonensis larvae in immune rats.

Rats acquired protective immunity to Angiostrongylus cantonensis after a single infection with 50 infective larvae. Immunity was stronger after subsequent infections. Fewer worms were recovered which were shorter and produced fewer progeny after secondary and tertiary infections. However, the growth of A. cantonensis during the early developmental stages in the brain and the ability of the young adult parasites to migrate to the lungs was not affected in the immune host.