Study: We’re finding new feline viruses faster than we can figure them out

Things are moving fast in the world of feline pathogens.

The authors of a recent review article in the Journal of Feline Medicine and Surgery say “the rate at which novel [or previously unknown] viruses are being discovered now exceeds our understanding of their clinical relevance.”

And it’s not just happening to cats: A 2008 paper in Nature described the discovery of 335 infectious diseases in the global human population between 1940 and 2004.

The authors of the review article note that new technologies for gene sequencing, combined with computer-based algorithms that allow for sequence assembly and analysis, have revolutionized infectious disease research in veterinary medicine, just as they have in human medicine.

They’ve also raised important questions, the authors say, because the potential pathogenic role of novel viruses can be difficult to determine.

To get some perspective on what this means for the practicing veterinary professional, NEWStat contacted Julia Beatty, BVetMed, PhD, FANZCVS (feline medicine), RCVS, Recognized Specialist in Feline Medicine, professor of feline medicine at the University of Sydney in Australia, and lead author of the study.

“The traditional paradigm of virus discovery is in the context of a disease outbreak where the epidemiology suggests an infectious etiology,” Beatty told NEWStat. “If that novel virus reliably causes disease in naive animals, then it can be identified as a pathogen pretty quickly.”

If the virus remains subclinical, things get a lot trickier.

“The difficulty in assigning relevance to a virus comes when infection is not reliably followed by disease,” Beatty said. “We know that individuals are infected with a diverse population of viruses. These viruses can act as pathogens, symbionts, or just be hanging out as passengers and these roles can change.”

Beatty points to gammaherpesvirus, or FcaGHV1, first reported in 2014. FcaGHV1 is a common infection in domestic cats; Beatty says it’s likely that more than 80% of cats are infected. But she says it’s also likely that most cats, maybe all, will remain asymptomatic.

That doesn’t mean researchers can let down their guard.

“As an occasional consequence of chronic infection, FcaGHV1 could cause a range of cancers and other diseases,” Beatty says. Which means that if a lot of those normally asymptomatic cats start showing symptoms, “The total disease burden may be high.”

The fact is, science doesn’t really know what kind of damage FcaGHV1 or other novel viruses are capable of doing.

“Feline morbilliviruses (FeMV) were postulated to play a role in chronic kidney disease when the virus was discovered,” Beatty says. That was in 2012, and the perceived connection to kidney disease took root, even though scientific evidence to support it remains limited.

Like FcaGHV1, the clinical relevance of FeMV is unclear, as it has shown up in both healthy and sick cats.

Meanwhile, Beatty says, the novel viruses just keep on coming.

“We reported a feline hepadnavirus earlier this year, a virus similar to hepatitis B virus in humans,” Beatty says. That particular virus was especially intriguing to researchers because while they couldn’t immediately identify its particular pathology, other viruses in the same family are known to cause liver pathologies in their hosts. “So we're focusing our efforts on collecting biopsies of liver cancers to look for [signs of the] virus in the cells.”

The researchers also write in their report that, “Practicing veterinarians have a role to play in progressing clinical research.” NEWStat asked Beatty to elaborate; what can our readers be doing to help the cause?

“The future of veterinary research must value and support the expert input of veterinary clinicians,” Beatty said. “Veterinarians are experts in diagnosis; no one else can perform this role. In this case, we're talking about deciphering the role of an increasing number of viruses in a broad range of diseases. If there is a particular clinical presentation that is potentially linked to infection with a novel virus, then case material is collected for investigation in the laboratory.”

That means that the cases must be well curated or the whole project falls over. And that means all hands on deck:

“Laboratory results must be viewed in the context of what makes clinical sense. My preference is to have clinicians and support staff embedded in the research team, with everyone engaged in a common goal,” Beatty said.

For example, Beatty said, with the domestic cat gammaherpesvirus, “We had a disease [and were] looking for a virus. We needed to collect fresh-frozen lymphoma tissue and blood samples from [feline immunodeficiency virus]–infected cats.”

Beatty said they got it done by reaching out to veterinarians across Australia. And not just veterinarians, Beatty noted—veterinary technicians and support staff were pitching in as well: “It was a tremendous team effort.”

When it comes to hunting down and identifying new feline viruses, everybody in the hospital has a part to play.

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