title: Comparison of internal transcribed spacers and intergenic spacer regions of five common Iranian sheep bursate nematodes.
abstract: BACKGROUND
  Accurate identification of sheep nematodes is a critical point in epidemiological studies and monitoring of drug resistance in flocks. However, due to a close morphological similarity between the eggs and larval stages of many of these nematodes, such identification is not a trivial task. There are a number of studies showing that molecular targets in ribosomal DNA (Internal transcribed spacer 1, 2 and Intergenic spacer) are suitable for accurate identification of sheep bursate nematodes. The objective of present study was to compare the ITS1, ITS2 and IGS regions of Iranian common bursate nematodes in order to choose best target for specific identification methods.
  
  
  METHODS
  The first and second internal transcribed spacers (ITS1and ITS2) and intergenic spacer (IGS) of the ribosomal DNA (rDNA) of 5 common Iranian bursate nematodes of sheep were sequenced. The sequences of some non-Iranian isolates were used for comparison in order to evaluate the variation in sequence homology between geographically different nematode populations.
  
  
  RESULTS
  Comparison of the ITS1 and ITS2 sequences of Iranian nematodes showed greatest similarity among Teladorsagia circumcincta and Marshallagia marshalli of 94% and 88%, respectively. While Trichostrongylus colubriformis and M. marshalli showed the highest homology (99%) in the IGS sequences. Comparison of the spacer sequences of Iranian with non-Iranian isolates showed significantly higher variation in Haemonchus contortus compared to the other species.
  
  
  CONCLUSIONS
  Both the ITS1 and ITS2 sequences are convenient targets to have species-specific identification of Iranian bursate nematodes. On the other hand the IGS region may be a less suitable molecular target.
authors: Dept. of Pathobiology, Faculty of Veterinary Medicine, University of Zabol, Zabol, Iran.
authors: Reza
authors: R
authors: Nabavi
authors: School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland ; Teagasc, Animal Production Research Centre, Athenry, Co Galway, Ireland.
authors: Brendan
authors: B
authors: Conneely
authors: School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.
authors: Elaine
authors: E
authors: McCarthy
authors: Teagasc, Animal Production Research Centre, Athenry, Co Galway, Ireland.
authors: Barbara
authors: B
authors: Good
authors: Dept. of Parasitology, Faculty of Veterinary Medicine , University of Tehran, Tehran, Iran.
authors: Parviz
authors: P
authors: Shayan
authors: School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.
authors: Theo
authors: T
authors: DE Waal
keywords: Bursate nematodes; Intergenic spacer; Internal transcribed spacers; Similarity score