Use of random amplified polymorphic DNA for identification of ruminant trichostrongylid nematodes.

The aim of this work was to evaluate random amplified polymorphic DNA (RAPD) as a source of markers for species identification and phylogenetic analysis of ruminant trichostrongylid nematodes. As these nematodes are often polymorphic, species identification may be difficult. We tested eight species and several of their morphs: Haemonchus contortus (three vulvar morphotypes: flap, smooth, and knobbed), Teladorsagia circumcincta, Ashworthius gagarini, Spiculopteragia boehmi, Ostertagia leptospicularis (and its morph Ostertagia kolchida), Cooperia oncophora (and its morph C. surnabada), Trichostrongylus colubriformis, and T. vitrinus. With five chosen 10-mer primers, genetic variations were assessed among individuals of each species or morphotype. In trichostrongylid nematodes, the identification of species is possible by means of RAPD on adult or larva DNA extracts, although the variability observed within species was very important for most species studied. The use of RAPD in phylogenetics studies is conversely questionable for this superfamily of parasitic nematodes. The interspecific distances were always larger than the intraspecific ones and did not vary much (between 0.8 and 0.9); they would not be of much use in the construction of a phylogenetic tree, at least for the species and the primers involved in this study.