Roughly two thirds of all domestic cats in the US have a virus called feline foamy virus (FFV), according to a recent joint study led by researchers at Colorado State University (CSU).

Published this fall in Journal of Feline Medicine and Surgery Open Reports, the study is the first large-scale research on the prevalence of FFV in the US and the first to suggest that the majority of the nation’s domestic cats have it.

FFV is an asymptomatic, complex retrovirus that infects cats, apparently without causing disease. But the high prevalence of the virus has researchers concerned that it could leave cats more susceptible to other deadly bugs, such as feline leukemia virus. Possible transmission to the nation’s wildcat population is another concern.

Cats transmit FFV through their saliva when they nuzzle or bite one another. A major concern with these kinds of easily transmitted viruses is that outdoor domestic cats can transmit them to wildcats, such as mountain lions, says study leader Sue VandeWoude, DVM, DACLAM, associate dean for research in CSU’s College of Veterinary Medicine and Biomedical Sciences.

VandeWoude poses this scenario: a mountain lion attacks and kills a domestic cat who’s infected with the virus. According to VandeWoude, that wildcat would be at risk of contracting the virus.

“We’re generally very interested in looking at how diseases of domestic animals are spread to wildlife and we’re worried about that,” said VandeWoude. “The risk that diseases will be transmitted from wildlife to people and their animals and vice versa increases as wildlife territories become more urbanized,” she added.

VandeWoude and her colleagues took 308 blood samples from domestic cats in eight animal shelters in Southern California, Florida, and Colorado between 2009 and 2011, then analyzed them for the presence of FFV.

Their findings show that FFV is widespread in cats in all three regions, which researchers say provides a fairly representative picture of the virus’ spread among US cats. Cats in Southern California showed the greatest incidence of FFV, with 75% of the samples testing positive. And older, outdoor cats were more likely to be infected than younger ones.

Additionally, the study notes that other studies have associated FFV with chronic diseases of cats, including kidney disease and arthritis, and urge that more research be done on FFV’s clinical relationship to other infections to assess risks of infection for domestic cat health as well as develop guidelines for FFV surveillance.

“The way we treat our cats has a big impact on whether or not they get diseases [like FFV],” said VandeWoude; even letting your cat outside could be a risk, she said—both for the cat and wildlife.

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