Accurate identification of aspermic Fasciola forms in Japan remains difficult because of their morphological variations. In order to characterize the forms genetically, nucleotide sequences of ribosomal internal transcribed spacer (ITS1 and ITS2) and mitochondrial cytochrome c oxidase I (COI) and NADH dehydrogenase I (NDI) genes in 34 liver flukes from 16 prefectures in Japan were analysed. Two major forms represented by Fsp 1 and Fsp 2 had sequences identical to or closely resembling those of F. hepatica and F. gigantica, respectively, in all the 4 DNA markers and were mainly distributed in northern and eastern-western parts of Japan, respectively. Fsp 1 and Fsp 2 would have been introduced into Japan with infected cattle of 2 distinct lineages via the Korean Peninsula and spread through limited parts of Japan (northern and eastern-western parts) together with the movement of each cattle lineage. The Japanese form (Fsp 1/2), which showed heterozygosity in ribosomal DNA and Fsp 2 haplotype in mitochondrial DNA, may have originated in interspecific cross hybridization between paternal F. hepatica and maternal F. gigantica.

ABSTRACT. Nucleotide sequences of ribosomal internal transcribed spacer (ITS1) and mitochondrial NADH dehydrogenase I (NDI) gene were analyzed to genetically characterize aspermic Fasciola forms in Korea. From the difference in ITS1 sequences, Korean flukes were divided into 3 haplotypes represented by Kor1, Kor2 and Kor1/2, which had nucleotides identical to F. hepatica, F. gigantica and those overlapped between the two species, respectively. NDI sequences also showed that Korean flukes could be classified into 3 distinct haplotypes (Kor1: F. hepatica-type, . The sequences of Kor1 and Kor2a were 100% identical to those of the haplotypes Fsp1and Fsp2, respectively, which are major Fasciola forms in Japan. These findings strongly suggest that aspermic Fasciola forms in Korea and Japan originated from same ancestors and have recently spread throughout both countries. KEY WORDS: Fasciola sp., haplotype, ITS1, Korea, NDI.