Characterization of Bunostomum trigonocephalum and Bunostomum phlebotomum from sheep and cattle by internal transcribed spacers of nuclear ribosomal DNA

In the present study, samples representing Bunostomum trigonocephalum and Bunostomum phlebotomum from sheep and cattle in Heilongjiang Province, China, were characterized and grouped genetically by the first (ITS-1) and second (ITS-2) internal transcribed spacers (ITS) of nuclear ribosomal DNA (rDNA). The rDNA region including the ITS-1, 5.8S, ITS-2, and flanking 18S and 28S rDNA sequences was amplified by polymerase chain reaction (PCR), then sequenced and compared with that of other members of the hookworms available in GenBank™, and phylogenetic relationships between them were reconstructed using the Maximum-Parsimony method. The ITS-1, 5.8S, and ITS-2 sequences of the sheep hookworm were 381, 153, and 231 bp in length, respectively, and the corresponding sequences of the cattle hookworm were 392, 153, and 240 bp in length. The identity of ITS sequences of B. trigonocephalum and B. phlebotomum from sheep and cattle was 87.4%. A PCR-linked restriction fragment length polymorphism (PCR-RFLP) assay using restriction endonuclease Nde I was established for the unequivocal differentiation of the two hookworm species. Phylogenetic analyses based on the ITS sequences revealed that B. trigonocephalum and B. phlebotomum were closely related, but they represent two different species.