Ostertagia, Haemonchus, Cooperia, and Oesophagostomum: construction and characterization of genus-specific DNA probes to differentiate important parasites of cattle.

Partial genomic DNA libraries for four common cattle parasites, Ostertagia ostertagi (Oo), Haemonchus placei (Hp), Cooperia oncophora (Co), and Oesophagostomum radiatum (Or), were generated and differentially screened with radiolabeled homologous and heterologous genomic DNA. Clones were identified from each parasite species which did not cross react with DNA from the heterologous genera by Southern blot or slot-blot analyses. Four clones, pOo2, pHp2.1, pCo2, and pOr14 were chosen for further examination. Genomic DNA from other species within the genera were screened with the cloned segments, and the clones were shown to be genus specific. The cloned fragments ranged in size from 195 to 669 base pairs and were approximately 50% in AT content. The cloned segments, pOo2 and pCo2, were approximately equally represented within their parasite genomes at 0.40 and 0.62%, respectively, whereas pHp2.1 and pOr14 were significantly higher at 1.61 and 3.39%, respectively. Sequence analysis demonstrated that pOr14 contained three 180-base pair tandemly repeated units with minor sequence variability between the repeats. Results presented here suggest that these sequences can detect as few as 25 eggs, and hence, may be used as diagnostic probes for the antemortem differentiation of trichostrongyle infections in cattle.