Paragonimus westermani: a comparative study on the migration route of the diploid and triploid types in the final hosts.

Recent studies on chromosomes have shown the presence of diploid and triploid types of Paragonimus westermani. To determine any possible biological differences between them, the migration route and development of the diploid type in the final hosts were compared with those of the triploid type. In the cat, the definitive host, larvae of the diploid type migrated to the abdominal wall, remained there for two weeks, and then migrated to the lung. In the rat, the abnormal host, some orally administered metacercariae of the diploid type made cysts in the lung and laid eggs, but the triploid type did not lay any eggs. Neither type of P. westermani migrated to the liver of the rat, in contrast to the previously reported fact that P. miyazakii and P. ohirai migrate to the liver and develop there. From these results, it seems likely that the two types of P. westermani are closely related.