Genetic evidence indicating that Cooperia surnabada and Cooperia oncophora are one species.

Sequences of the second internal transcribed spacer (ITS-2) of ribosomal DNA were determined for the trichostrongylid nematodes Cooperia surnabada and Cooperia oncophora, to test the hypothesis that they represent one species. Also included for comparison were other morphologically distinct species within the genus, namely Cooperia punctata and Cooperia curticei. There were no differences in the consensus ITS-2 sequences between C. oncophora and C. surnabada, whereas each taxon differed from C. punctata and C. curticei by 1.7% and 4.1%, respectively. Also, C. punctata differed from C. curticei by 5.0%. Based on these results and the DNA studies of other trichostrongylid species, it is proposed that C. oncophora and C. surnabada represent a single species.