Sequence analyses of ITS2 and CO1 genes of Paragonimus proliferus obtained in Yunnan province, China and their similarities with those of P. hokuoensis.

Among about 50 Paragonimus species, Paragonimus proliferus is a rare species characterized by extremely large metacercariae, most of which are present excysted in the crab hosts. Recently, this species was discovered by us in northern Vietnam as the first record outside of China. DNA sequences of both second internal transcribed spacer region (ITS2) and cytochrome oxidase subunit 1 gene (CO1) genes of the metacercariae and adult worms of P. proliferus of the Vietnamese isolates were identical with those of Paragonimus hokuoensis in the DNA database of the GenBank. To confirm those observations and to clarify the molecular phylogenetic status of P. proliferus, we determined the ITS2 and CO1 sequences of the metacercariae of P. proliferus obtained in Yunnan province, China where the original specimen was discovered. The results show that both ITS2 and CO1 sequences of P. proliferus of the Chinese isolates are identical with those of P. proliferus of the Vietnamese isolates and are also identical with those of P. hokuoensis that appeared in the DNA database (obtained in Yunnan province), suggesting the synonymy of P. hokuoensis with P. proliferus. By phylogenetic tree analyses, all samples of P. proliferus from China and Vietnam together with P. hokuoensis constructed a distinct group within, or very close to, Paragonimus skrjabini complex in both trees.