[Taxonomic revision of the genus Orloffia (Nematoda: Ostertagiinae) based on an ITS-2 rDNA study].

A comparative study of ITS-2 rDNA of the nematodes of the genera Orloffia, Ostertagia, Teladorsagia, and Trichostrongylus was performed. The obtained results allow us to consider Orloffia, Ostertagia, and Teladorsagia as closely related but distinct genera. The results of the study indicate that O. bisonis is the only valid species in the genus Orloffia, which has two morphologically distinct forms of males: O. bisonis (major morph) and O. kasakhstanica (minor morph). The percentage of similarity of ITS-2 sequences was 83.3-84.5% between Orloffia spp. and Ostertagia ostertagi, 84.9-86.1% between Orloffia spp. and Teladorsagia circumcincta, and 73.8-74.6% between Orloffia spp. and Trichostrongylus colubriformis.