First complete coding sequence of ovine herpesvirus 2 from a malignant catarrhal fever case of Formosan sambar deer in Taiwan: Genomic characterization and molecular epidemiology.

Malignant catarrhal fever (MCF) is a highly fatal disease of cattle and other cloven-hoofed animals, most commonly caused by ovine herpesvirus 2 (OvHV-2), a member of the subfamily Gammaherpesvirinae. Despite nearly four decades since its identification, coding-complete genomic data for OvHV-2 remain limited. Recently, a Formosan sambar deer, an endemic subspecies in Taiwan, presented with characteristic MCF lesions and tested positive for OvHV-2 by PCR. We reconstructed the first coding-complete OvHV-2 genome from Taiwan (OvHV-2 TW01) using a hybrid whole-genome sequencing approach. The TW01 genome spans approximately 131 kb and encodes 74 predicted open reading frames (ORFs). Comparative genomic analysis with three available OvHV-2 reference genomes revealed high amino-acid identity (93-100%); however, two loci, ORF73 and Ov9.5, exhibited marked divergence, with identities of 77.7% and 50.9%, respectively. Notably, ORF73 exhibited characteristic features of the latency-associated nuclear antigen (LANA), including a C-terminal glutamate/glycine-rich insertion and two flanking repeat regions comprising 37-43 heptapeptide repeats. Phenetic clustering and ordination analyses based on these conserved structural features revealed host-associated clustering patterns. In addition, the Ov9.5 gene of TW01 showed 100% identity with a sequence within allele*02 + 04, previously reported exclusively in the United Kingdom, indicating close evolutionary affinity with European strains. Consistently, biogeographic analyses by Haplotype network assay placed TW01 within a European-associated lineage, distinct from OvHV-2 sequences reported from China. In summary, this study reports the first coding-complete OvHV-2 genome from Taiwan and provides novel insights into the genetic diversity, evolutionary relationships, and epidemiological origin of OvHV-2. These data expand current genomic resources and contribute to improved molecular surveillance and understanding of MCF transmission.