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Cat Owners Beware: Dog Flu Has Spread to Cats

Four Indiana shelter cats were sickened; although none died, it's a reminder of a looming menace.

Dr. Eric Barchas  |  May 10th 2016


On June 28, 1914, a Yugoslavian nationalist assassinated Archduke Franz Ferdinand of Austria in Sarajevo. That event was the trigger for a conflict of previously unimaginable proportions. During the next four years, military actions in World War I claimed the lives of an estimated 8.2 million combatants and 2.2 million civilians. It was a war so terrible that it was called “the war to end all wars,” although its final result was little more than setting the stage for an even bigger war a couple of decades years later.

Those who know anything about World War I might have been taken aback by the death tolls listed in the above paragraph. Hadn’t many more than 11 million people perished in the war, or at least during it? Indeed, many had.

In 1918, another world event, incredibly, caused far more deaths than the war (although the conditions of the war certainly contributed to the fatalities). An unusually deadly strain of influenza, colloquially called Spanish Flu and known more formally as H1N1, began to spread around the world. By the time the pandemic ended, every place on Earth except for the island of Marajó, at the mouth of the Amazon, had been affected. The death toll was estimated to be between 50 million and 100 million people. Some believe that more soldiers died in the trenches from influenza than from bullets. It’s detailed in a 2005 book called The Great Influenza.

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An illustration of the H1N1 virus.

Influenza is serious business. Although it generally causes only temporary misery and inconvenience for young, healthy people, the potential for another serious pandemic is a major cause of worry for public health authorities.

So what does this have to do with cats? Influenza is a zoonotic disease. This means that it can affect animals as well as people. Birds and pigs commonly are infected with the virus. And the virus mutates frequently, meaning that new strains are constantly emerging. (In fact, scientists theorize that the 1918 pandemic started when influenza harbored in birds mutated in pigs to a strain that could spread among people.)

Despite influenza’s proclivity to jump species, historically it hasn’t been much of an issue for cats. In 2003-2004 big cats and domestic cats were sickened and in some cases killed by H5N1 avian influenza. However, these cases appeared to be the result of direct contact with birds. The cats appeared capable of becoming infected, but they did not appear to spread the disease.

Unfortunately, a recent news release from the American Veterinary Medical Association indicates that influenza might be emerging as a more serious threat to felines. Canine influenza is capable of spreading to cats.

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In fact, influenza was not known to be much of a risk to pets until the 2000s. Shortly after the turn of the century an equine version of influenza spread to dogs in Florida, leading to a significant canine outbreak. In the past few years, another canine outbreak has occurred primarily in the Midwestern United States. This more recent outbreak appears to have been imported from Asia when dogs were moved from Korea to the U.S.

The news release discusses the sickening of four cats in a shelter in Indiana. Dogs in the shelter had been sickened by influenza, and then it spread to cats. Crucially and unfortunately, it did more than just spread to cats. It spread among them. Analysis of the situation indicated that the cats were shedding the virus and spreading it to others in the facility.

Cats sickened with influenza developed symptoms that included “runny noses, congestion, malaise, excessive salivation, and ‘lip smacking’ behavior.” Fortunately there were no reports of deaths.

At this time, the outbreak and the threats it pose appear to be limited. This strain of influenza is not especially virulent, and it also doesn’t seem to spread very effectively.

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However, for me it is a chilling reminder of the ever-looming menace of influenza viruses. And it raises a significant fear in my mind: What if a virulent, highly contagious influenza strain emerged that could sicken not just cats and dogs, but also people?

Such a scenario could lead to a major disaster. There would be a time at the start of such a scenario when nobody realized what was happening. Pets sickened by the virus would be taken to veterinary offices, where veterinarians might assume that a species-specific bug was causing respiratory illness. Veterinary staff would become infected, and they in turn would infect other patients and clients. This could result in a huge pandemic, and a crisis in veterinary medicine that might result in the temporary closure of many of the world’s veterinary offices, just when they would be needed most.

Although such scenarios are chilling to imagine, I’m happy to report that the 1918 pandemic is not likely to repeat itself in cats, dogs, and humans. Advances in medicine and especially vaccines would probably reduce the lethality and transmission of the disease. Furthermore, the world does not currently have millions of stressed, freezing, malnourished young men festering in trenches like sitting ducks for the virus to kill, as it did in World War I.

I hope medical science will evolve more rapidly than influenza. But for now, the risk posed by the nearly ubiquitous virus is real.