Study: Lab cats can contract equine flu virus H3N8

Ten years ago the equine influenza virus (EIV) A/H3N8, a common cause of respiratory infections in horses, turned up in dogs. Now Chinese researchers report that domestic cats in a lab setting are susceptible to the same virus and can spread it to other cats.

Writing in Emerging Infectious Diseases, the researchers report that they inoculated six cats intranasally with H3N8. A day later, they placed five pathogen-free cats in the same cages, and they kept three other cats in a separate room to serve as controls.

Both the inoculated cats and the contact cats became infected, as evidenced by typical signs of influenza, virus shedding, and histopathologic changes in the trachea and lungs, the report says. Clinical signs of illness developed from 2 to 9 days after infection in the inoculated cats and from 4 to 9 days after infection in the contact cats, but the illness was less severe in the contact cats. The control cats showed no evidence of infection.

The authors said it’s not surprising that the cats became infected, since feline infections with various influenza A viruses have been reported before.

“However, our finding of horizontal transmission of EIV among cats is significant,” they added. “If transmission occurs outside the laboratory, and if the basic reproduction rate is higher than 1.0, then EIV could potentially establish itself and circulate in this new host species.”

Why cats, unlike dogs, have not been infected naturally by H3N8 remains to be determined, but it could be because of lower transmission efficiency or feline behavior, the authors wrote.




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