Molecular evidence of the absence of Metagonimus yokogawai (Katsurada, 1912) in Europe: report of Metagonimus sp. in cyprinoid fish from the River Danube in Hungary

Trematodes of the genus Metagonimus Katsurada, 1912 (Digenea: Heterophyidae) are zoonotic parasites that cause infections in humans, with most cases reported in Southeast Asia. Larvae from the second intermediate host, called metacercariae, of one of human-infecting species, M. yokogawai (Katsurada, 1912), have been reported from cyprinoid fish in Europe. In the present study, we provided DNA-based evidence that metacercariae of Metagonimus , which are commonly found in the scales of various cyprinoids in Central Europe (Danube River in Hungary) do not belong to M. yokogawai . Sequence analysis of the ITS region, 28S rDNA, and cox1 genes showed that this species is clearly distinct from all Asian species, including M. yokogawai , which probably does not occur in Europe. Metacercariae from cyprinoids might belong to Metagonimus romanicus (Ciurea, 1915), an insufficiently known species described from Romania.