Lack of intraspecific variation in the second internal transcribed spacer (ITS-2) of Trichostrongylus colubriformis ribosomal DNA.

The nucleotide sequence of the second internal transcribed spacer (ITS-2) was determined for three populations of the parasitic nematode Trichostrongylus colubriformis which differed in their susceptibility to benzimidazole anthelmintics and/or in their geographical origin. No intraspecific variation was found in the ITS-2 sequence, indicating that this region of rDNA is inadequate to discriminate between resistant and susceptible populations of T. colubriformis, but it may prove useful for distinguishing between species of Trichostrongylus.