[On the conspecificity of Ostertagia ostertagi and Ostertagia lyrata (Nematoda: Ostertagiinae)].

Partial sequences of the second internal transcribed spacer (ITS-2) rDNA were obtained for Ostertagia ostertagi and O. lyrata, which are supposedly constitute two morphologically distinct variants of the species. The 1.4% level of difference between the ITS-2 sequences of O. ostertagi and O. lyrata was reported, whereas the sequences derived from worms of the same morph were completely identical. The data obtained prevent an attribution of O. ostertagi and O. lyrata to the same species.