Molecular identification and phylogenesis analysis of gastrointestinal nematode in different populations of Kazakh sheep

Three dominant species of gastrointestinal nematodes, Haemonchus contortus , Trichostrongylus spp., and Teladorsagia circumcincta from the various populations of Kazakh sheep were subjected to molecular identification and phylogenetic analysis. The internal transcribed spacer 2 (ITS-2) sequences of ribosomal DNA (rDNA) was used as the target sequence and specific primers. The results showed that all the three species had their ITS-2 specific bands amplified. The infection rates based on fecal DNA were 35.59% of H. contortus , 25.55% of Trichostrongylus spp., and 11.24% of T. circumcincta respectively, and the infection rates based on larva DNA were 19.75% of H. contortus , 23.54% of Trichostrongylus spp., and 10.03% of T. circumcincta respectively. The results were consistent with the PCR results of fecal samples and larval DNA from Trichostrongylus spp. and T. circumcincta , except H. contortus . The phylogenetic tree showed that the ITS-2 sequences of the three species were on the same branch as the ITS-2 sequences of the same species in NCBI, and on different branches from those of the ITS-2 sequences of different families, genera and species. The same 93 fecal samples were analyzed by molecular identification and saturated saline solution floatation method respectively. The molecular identification of hatched larva from fecal samples exhibited an infection rate of 100.00% with respect to the three dominant species, higher than the infection rate of 96.77% by the saturated saline solution floatation method. Therefore, the present molecular identification is more reliable in specificity and accuracy of these three species.