Abstract / Summary
Sheep-associated malignant catarrhal fever (SA-MCF) is a frequently fatal, pantropic, lymphoproliferative disease caused by ovine gammaherpesvirus 2 (OvGHV2), with sheep serving as the asymptomatic reservoir host. Although the Rusa deer (Cervus timorensis) are known to be highly susceptible to OvGHV2 in other regions, cases have not been documented in this species from Brazil. This report describes the spontaneous occurrence of OvGHV2 infection in a captive Rusa deer from Southern Brazil and discusses possible impacts on wildlife. Three deer from the same property died suddenly without prior clinical signs. These animals had no known contact with sheep or goats, but were maintained in an epidemiological niche where OvGHV2 was detected in subclinically infected free-ranging wild boars (FRWBs) and cattle. One of these was submitted for routine post-mortem evaluations. Gross lesions included ulcerative and erosive lesions of the alimentary tract, pulmonary edema, and marked meningeal congestion. Histopathology revealed erosive and ulcerative esophagitis, abomasitis, omasitis, and rumenitis, with nonsuppurative meningoencephalitis, and vasculitis in several organs, consistent with SA-MCF. Molecular testing of brain tissue detected OvGHV2 DNA by qPCR. Furthermore, PCR assays amplified the partial fragments of the OvGHV2 tegument protein (ORF75) and the glycoprotein (gB) genes. Other neurological pathogens of ruminants including BoAHV5, BVDV, Listeria monocytogenes, Histophilus somni, and rabies virus were not detected. Additionally, phylogenetic analyses, based on ORF75 and gB genes, revealed that the nucleotide sequences derived from this study clustered with and had elevated sequence homology with the OvGHV2 reference strains and other strains derived from ruminants maintained in different geographical locations. The absence of contact with sheep, combined with prior evidence of subclinical OvGHV2 infection in FRWBs and cattle within the same epidemiological niche, suggests the involvement of alternative wildlife reservoirs or bridge hosts in viral transmission. Additionally, these results expand the host range of OvGHV2 in Brazil, highlight the vulnerability of exotic cervids to SA-MCF, and underscore the need for integrated wildlife–livestock surveillance strategies in regions where multiple susceptible species coexist.