RESTRICTION-ENDONUCLEASE PROFILES OF ORF VIRUS ISOLATES FROM THE BRITISH-ISLES

A comparison of DNA profiles of representative isolates of orf virus, obtained using four different restriction endonucleases (RE), showed t hat the enzyme ECORI could be used to discriminate between wild-type v irus isolates and vaccine strains, The enzyme was used to compare the RE profiles of orf virus isolates from 43 outbreaks of orf that occurr ed in vaccinated flocks between 1988 and 1993; 21 outbreaks yielded wi ld-type virus, 10 yielded vaccine viruses, three produced both vaccine and wild-type viruses and no clear result was obtained from nine of t he outbreaks. From the 21 outbreaks yielding wild-type viruses, 28 orf virus isolates had clear RE profiles and 15 distinct RE profiles were recorded, Usually only one virus type was associated with each outbre ak but from two farms, two different wild-type viruses were recovered, No predominant genotype was identified, with four RE profile types be ing recovered for more than one outbreak. From the more severe form of orf involving the buccal cavities of lambs only wild-type viruses wer e recovered, with at least four different genotypes being represented.