Studies on Angiostrongylus cantonensis in Molluscan Intermediate Hosts

Abstract

First-stage larvae of Angiostrongylus cantonensis from rat feces developed to infective third-stage larvae in 20 of 26 species of freshwater mollusks experimentally exposed. Numbers of larvae up to 2, 000 per snail and survival of larvae for a year were observed in Biomphalaria glabrata. First-stage larvae were susceptible to drying but survived at least 3 weeks in freshwater and were infective to snails after at least 2 weeks in either freshwater or seawater. B. glabrata was routinely infected by ingestion of infected rat feces, and first-stage larvae were observed penetrating the wall of the intestine. A cellular reaction enclosed the developing larvae in tissue nodules. Isolated third-stage larvae were susceptible to drying but survived up to 11 days in B. glabrata removed from water, larvae remaining alive 4 days after death of the snails. Rats became infected by drinking water containing third-stage larvae, and larvae were observed active in freshwater for up to a week. Infected B. glabrata died a few minutes after immersion in seawater, but yielded by digestion numerous infective larvae after 4 days in seawater, and a few infective larvae after 5 days. Results suggest the potential importance of freshwater mollusks as intermediate hosts and the possibility of infection of marine hosts.