Molecular genetic characterization of the Fennoscandian cervid strain, a new genotypic group (G10) of Echinococcus granulosus.

The northern biotype of Echinococcus granulosus occurs in North America and northern Eurasia in life-cycles involving cervids. Previously, cervid isolates of E. granulosus from North America have been characterized using molecular genetic techniques as the G8 genotype. In this study, 5 isolates of E. granulosus were collected from 4 reindeer and 1 moose in north-eastern Finland. DNA sequences within regions of mitochondrial cytochrome c oxidase I (COI) and NADH dehydrogenase I (NI)I) genes and the internal transcribed spacer 1 (ITS-1) fragment of the ribosomal DNA were analysed. The mitochondrial nucleotide sequences were identical in all isolates, but high sequence variation was found in the ITS-1 region. Mitochondrial and nuclear sequences of the Finnish cervid E. granulosus and the camel strain (G6) of E. granulosus resembled closely each other. According to phylogenetic analyses, the Finnish isolates have close relationships also with the pig (G7) and cattle (G5) strains. Although some similarities were found with the previously published North American cervid strain (G8), particularly in the NDI sequence and some of the ITS-1 clones, the Finnish E. granulosus form represents a distinct, previously undescribed genotype of E. granulosus. The novel genotype is hereby named as the Fennoscandian cervid strain (G10).