Epstein-Barr virus (EBV) infection is a global infection associated with lymphoma in humans. In a 2005 study, EBV was identified in Taiwanese canine samples by both polymerase chain reaction (PCR) in canine leukocytes and antibody detection to the EBV thymidine kinase protein. This recent study examined other geographic canine populations for the presence of EBV, assessed EBV infection in cats, and evaluated potential associations with lymphoma in dogs. Serum samples from UK and U.S. dogs and cats were collected for analysis. Canine palatine tonsil samples from a cohort of UK dogs with respiratory disease and UK lymphoma biopsy samples were also evaluated. Residual whole blood samples and DNA extracted from whole blood were included. Immunofluorescence and PCR were performed on appropriate samples. Antibodies to EBV or an EBV-type virus were identified in UK dog sera (38.4%), U.S. dog sera (64%), and cat sera (38%). EBV was detected by PCR in a single tonsil sample. A canine herpesvirus was detected in several tonsil and biopsy samples. EBV antibody-positive dogs were PCR-negative for transcripts denoting EBV lytic or latent infection. This paper provided evidence of exposure to EBV or an EBV-like virus in a subset of dogs and cats without evidence of EBV tonsillar or peripheral blood mononuclear cell infection.

Commentary: This interesting study supported evidence of EBV exposure in dogs and cats from the UK and U.S. based on antibody presence to an EBV or EBV-like virus. The palatine tonsil usually serves as an EBV reservoir in latently infected humans; however, only 1 of 104 canine tonsils was EBV positive. In addition, EBV was not detected in canine whole blood samples. This collectively suggested that persistent EBV infection was not identified in dogs and cats, although examination of additional lymphoid tissues will help determine this. Interestingly, the prevalence of EBV antibodies was significantly higher in pet cats than stray cats, suggesting that cats may have been infected by human contacts. While this study does provide evidence of companion animal exposure to EBV or an EBV-like virus, future epidemiologic and in vitro laboratory studies will characterize the potential for and prevalence of EBV infection in small animals.—Indu Mani, DVM, DSc

Serological detection of Epstein-Barr virus infection in dogs and cats. Milman G, Smith KC, Erles K. VET MICROBIOL doi:10.1016/j.vetmic.2010.12.013.