Genetic markers for strongylid nematodes of livestock defined by PCR-based restriction analysis of spacer rDNA.

Twenty-four species of parasitic nematode (order Strongylida) from sheep, goats, cattle or pigs were characterised using a polymerase chain reaction-linked restriction fragment length polymorphism technique (PCR-RFLP). The ribosomal (r)DNA region spanning the first internal transcribed spacer (ITS-1), 5.8S rRNA gene and the second internal transcribed spacer (ITS-2) (designated ITS) was amplified from genomic DNA by polymerase chain reaction (PCR), digested separately with four restriction endonucleases (RsaI, HinfI, DraI or NlaIII) and the fragments separated by agarose gel electrophoresis. The PCR products amplified from all species appeared as a single band of approximately 870 bp in size, except for Ostertagia ostertagi whose product was approximately 1250 bp. The PCR-RFLP analysis of ITS revealed characteristic restriction patterns for all species, except for C. surnabada and C. oncophora which had identical patterns. The study demonstrated that ITS contains useful genetic markers for the identification of a range of strongylid nematodes of livestock. These markers should be of use in specific PCR assays for the identification of developmental stages of the parasites where morphological characters are unreliable.