title: Differentiation of Haemonchus placei from H. contortus (Nematoda: Trichostrongylidae) by the ribosomal DNA second internal transcribed spacer.
abstract: There has been much debate as to whether H. placei is a separate species to H. contortus. The aim of this study is to provide molecular information to assess the species status of H. placei. Using the polymerase chain reaction, the second internal transcribed spacer (ITS-2) of ribosomal DNA was amplified and sequenced. Comparison of the 231 base pair ITS-2 sequences showed no intraspecific variation in H. contortus, among one isolate from each of the United Kingdom. Switzerland and China and 5 isolates from within Australia, or among 3 Australian isolates of H. placei. Three (1.3%) nucleotide differences were detected between the ITS-2 sequences of H. contortus and H. placei. In addition, 2 diagnostic sites for the endonucleases BfaI and FokI allowed the delineation of H. placei from H. contortus. The data presented herein support previous morphological and genetic evidence that H. placei is a separate species to H. contortus.
authors.affiliation: Department of Veterinary Science, University of Melbourne, Werribee, Victoria, Australia.
authors.forename: L A
authors.initials: LA
authors.lastname: Stevenson
authors.forename: N B
authors.initials: NB
authors.lastname: Chilton
authors.forename: R B
authors.initials: RB
authors.lastname: Gasser
mesh_terms: D000818:Animals; D001483:Base Sequence; D002417:Cattle; D004275:DNA, Ribosomal / Q000235:genetics*; D004591:Electrophoresis, Polyacrylamide Gel; D006189:Haemonchus / Q000145:classification* / Q000235:genetics; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid; D012756:Sheep; D014158:Transcription, Genetic
chemical_list: D004275:DNA, Ribosomal