Detection of Ursid Gammaherpesvirus 2 in Asiatic Black Bears (Ursus thibetanus) With Keratoconjunctivitis

To investigate the potential contribution of herpesvirus infection in the development of ocular surface disease in Asiatic black bears (Ursus thibetanus).

Eight captive Asiatic black bears housed at a wildlife sanctuary were examined during routine health assessments.

Fourteen cytobrush conjunctival samples were collected from eight subjects. A first bear was sampled in January 2024 with a pooled sample acquired from both eyes. Seven more animals underwent a full ophthalmic exam and conjunctival cytobrush sampling in February 2024. From those animals, one cytobrush sample per eye was acquired. DNA was extracted from the samples and tested for the presence of herpesviruses by polymerase chain reaction (PCR).

All but one animal showed evidence of active or past ocular surface disease. Nested PCR on a highly conserved region in herpesvirus genomes showed the presence of herpesvirus DNA in six samples obtained from 5 individuals. Three animals tested negative. PCR products from positive cases were subjected to Sanger sequencing, and results were aligned against the NCBI nucleotide collection. Sequences returned with over 95% similarity to Ursid gammaherpesvirus 2 (UrHV-2). Five of the positively tested eyes (5/6, 83%) and two of the negatively tested eyes (2/9, 22%) showed active ocular surface disease.

This study represents the first report of ursid gammaherpesvirus identification in bears with keratoconjunctivitis. The findings indicate a potential association between UrHV-2 and active ocular surface disease in Asiatic black bears. Further research is warranted to clarify its role in the pathogenesis of ocular surface disease in this species.