Failure of Certain Clams and Oysters to Serve as Intermediate Hosts for Angiostrongylus cantonensis^

Several species of invertebrate animals have been reported as intermediate or as paratenic hosts for the rat lungworm, Angiostrongylus cantonensis. Intermediate hosts which have been found naturally infected include: the land snails, Bradybaena stmMaris, Opeas javanicum, Macrochlamys resplendens, Achatina fulica, Pupina complanata, and Subulina octona; the slugs, Deroceras laeve, Vaginalus plebeius, Veronicella alte, Girasia peguensia, and Microparmarion malayanum; and the amphibious snail, Pila ampullacea. Naturally infected paratenic hosts include: the land planarian, Geoplana septemlineata; the freshwater prawn, Macrobrachiiim sp.; the land crab, Cardisoma hirtipes; and the coconut crab, Birgiis latro. Also, several land and aquatic snails and slugs have been reported as experimental hosts (Alicata, 1965). Of particular interest have been the recent reports (Cheng and Burton, 1965 and Cheng, 1966) that the American oyster, Crassostrea virginica, and the soft-shell clam, Mercenaria mercenaria, could serve as intermediate hosts of A. cantonensis under experimental conditions. This finding could have special significance especially in some of the Pacific islands where the rat lungworm exists and clams and oysters may be eaten raw or imperfectly cooked.