Isolation and characterization of Ovine gammaherpesvirus type 2 from an outbreak of Malignant Catarrhal Fever in Artiodactyla and horses in Mexico

Ovine gammaherpesvirus 2 (OvHV-2), a member of the Macavirus genus, causes sheep-associated malignant catarrhal fever (SA-MCF), a fatal lymphoproliferative disease that affects a wide variety of ungulates in addition to horses.This study described an outbreak of SA-MCF that occurred in Mexico and the identification of the OvHV-2 virus through viral isolation and different laboratory techniques such as immunofluorescence (IF), immunoperoxidase (IP), immunohistochemistry (IHC), end point PCR and partial sequencing of the ORF75 gene. The animals involved in this outbreak showed head and eye clinical signs and lesions. Based on the clinical-pathological outcome, buffy coats were taken, and virus isolation was attempted on primary cell cultures of the rabbit testicle. Small clusters of refractile cytomegalic cells characterized the cytopathic effect between 48 and 72 hours postinfection. In addition, inclusion bodies were identified, and cytoplasmic immunoreactivity was observed in the infected cells. The sequences obtained were aligned with OvHV-2 sequences reported in GenBank and revealed a nucleotide identity higher than 98%. The results indicate that the outbreak was caused by OvHV-2 and the horses are susceptible to SA-MCF.