Analysis of the genetic diversity of ovine herpesvirus 2 in samples from livestock with malignant catarrhal fever

•Segments of three ovine herpesvirus-2 genes were characterised from MCF diagnostic samples.•Case samples included head and eye, alimentary and neurological presentations of MCF.•The newly-annotated Ov9.5 gene was highly polymorphic.•No association was found between OvHV-2 variants and presentation in MCF cases.•This approach has potential for use in epidemiological studies of MCF.

In order to define better virus isolates from animals with malignant catarrhal fever (MCF), segments of three genes of ovine herpesvirus-2 were amplified from diagnostic samples representing MCF cases with a range of clinical presentations in cattle, including head and eye, alimentary and neurological. The variation within each gene segment was estimated by DNA sequencing, which confirmed that the newly-annotated Ov9.5 gene was significantly more polymorphic than either of the other loci tested (segments of ORF50 and ORF75), with alleles that differed at over 60% of nucleotide positions. Despite this, the nine Ov9.5 alleles characterised had identical predicted splicing patterns and could be translated into Ov9.5 polypeptides with at least 49% amino acid identity. This multi-locus approach has potential for use in epidemiological studies and in charactering chains of infection. However there was no association between specific variants of OvHV-2 and the clinical/pathological presentation of MCF in the cattle analysed.