Abstract:

To understand whether the characters of Haemonchus contortus were related to the variations of the internal transcribed spacer (ITS) sequences, the strains resistant to benzimidazole, ivermectin and moxidectin; strains isolated from giraffe, cattle, sheep, goat and yak; isolates from China, USA, Italy, France, Yemen, Malaysia and Australia, and other nematodes in the family of trichostrongylidae were collected and their ITS sequences were analyzed. The results showed that the ITS2 sequences in the worms of family trichostrongylidae were similar. The phylogentic tree based on ITS2 sequences indicated that different genus in the family could be distinguished by the tree. The variations of H. contortus ITS1 were not related to the drug resistance or susceptivity. Comparisons of the sequences of ITS2 of the isolates from different place in the world did not show too many variations. However, the ITS1 of H. contortus isolated from domestic hosts seems to be different from that of the wild giraffe. These results indicated that ITS sequences of H. contortus were conserved in the parasites and could be used in the molecular taxonomy.