Gammaherpesviruses (GHVs) affect a very broad range of species including humans and other primates, ruminants, squirrels, badgers and sea lions. Like all herpesviruses they cause persistent infection but have variable pathogenicity and are often kept at bay by the immune response.
In the absence of an effective immune response, due to immune dysfunction or infection of non-adapted host, GHVs may cause devastating diseases including lymphoma and malignant catarral fever.
The discovery of Felis catus gammaherpesvirus 1(FcaGHV1) followed a long search that was grounded in Beatty’s clinical suspicion that cats harbour cancer-causing viruses other than FeLV and FIV. With major collaborator Ryan Troyer and Sue VandeWoude from Colorado State University, the team investigated samples from Australian cats. This work culminated in the discvery of three novel gammaherpesviruses in domestic cats, bobcats and pumas. The prevalence of FcaGHV1 in free-ranging domestic cats in the US, recently published in Journal of Virology,was found to be 16 per cent.
In the most recent study, Beatty led a team looking at the prevalence of Felis catus gammaherpesvirus 1 (FcaGHV1) in whole blood of cats in Australia and Singapore, as detected by PCR. The prevalence was found to be 11.4 and 9.6 per cent respectively. When combined with the US study, the overall prevalence is 12.8 per cent.
“Its likely a widely endemic virus,” Beatty said. “We’ve only looked for this virus in three regions and found it in every single one at a similar prevalence. We have sampled around 500 cats to date. When we sequenced isolates from Australia and the US they were exactly the same, and isolates from Singapore differed by one amino acid. They appear to be strains of the same virus.”
While there is no confirmation that FcaGHV1 causes clinical disease in cats, cats that were positive for FcaGHV1 were 2.8 times more likely to be assessed as clinically unwell by a veterinarian at the time of sampling than FcaGHV1-negative cats.
Risk factors for infection include being male, increased age and concurrent infection with the retroviruses feline immunodeficiency virus (FIV) or feline leukaemia virus (FeLV). Cats with FIV and FcaGHV1 coinfection had significantly higher FcaGHV1 viral loads than those without FIV infection.
“This is similar to the increased gammaherpesvirus loads seen in HIV affected humans coinfected with Epstein-Barr virus,” Beatty said.
There is currently no vaccination for Epstein-Barr virus, which is associated with glandular fever and numerous neoplastic conditions in human patients.
Beatty said that aside from elucidating the pathogenesis of feline diseases, FcaGHV1 could be a useful model for studying gammaherpesvirus infection in humans.
The virus is transmitted horizontally with biting the most plausible route of infection.
Further work is being undertaken to develop an antibody test and to understand whether and how this virus impacts feline healthThe infectious diseases research team at the Valentine Charlton Cat Centre, University of Sydney has recently enrolled three more veterinarians in PhD projects.
Visit tinyurl.com/vm06a to learn how to make a tax-deductable contribution to this project.
Beatty JA, Troyer RM, Caryer S, Barrs VR, Espinasse F, Conradi O, Stutzman-Rodriguez K, Chan CC, Tasker S, Lappin MR & VandeWoude S (2014) Felis catus gammaherpesvirus 1: a widely endemic potential pathogen of cats. Virology 460-461:100-107.