There was so much dog flu in the Louisville, Kentucky, in 2017 that veterinarians were concerned there was a new strain responsible for sickening so many dogs, or, at the very least, some sort of variation of the existing strains and/or that the vaccine is ineffective. It turns out, if anything, what occurred in Louisville only demonstrated the importance of proactively vaccinating before dog flu or canine influenza virus (CIV) overwhelms a community.
“It was absolutely an outbreak,” says Dr. Scott Rizzo in Louisville. He guesses that there were at least 500 to 600 dogs with flu from early summer until now.
There was so much flu occurring that Cornell University College of Veterinary Medicine got involved and Dr. Jason Stull, internal medicine specialist at the Ohio State University College of Veterinary Medicine was even deployed to Louisville.
After studying the pathogen responsible for sickening the Louisville-area dogs under a microscope, the culprit turned out to be almost identical to all other H3N2 around America. No new flu strain is the good news.
Then why such an overwhelming outbreak when a vaccine is available? Rizzo says, “Most dogs weren’t vaccinated going into the summer when this happened. As a community, we just weren’t vaccinating. There are many variables to further explain what happened. One is that the public really didn’t understand that dogs needed a booster (shot) several weeks after the initial injection or to keep their dogs away from others until fully protected. So, dogs were going into public too soon.”
Not only were dogs going out in public, they were being boarded at kenneling facilities, a common occurance in the summer. And boarding facilities didn’t proactively mandate the vaccine.
Arguably the most significant explanation regarding how flu spread so overwhelmingly is simply the nature of the H3N2 virus says Rizzo.
Nearly all unvaccinated dogs (who haven’t been recently sickened by H3N2) that happen to be exposed get the bug since it is still a novel virus. However, about 20 percent of dogs with the flu virus actually don’t show signs of illness, but they do still spread flu. Their owners have no way to know that their dog is contagious, so these dogs are wagging tails as they’re out and about and unknowingly spreading the virus to others. Also, the virus can be shed or spread for about a month. That means a dog may be sick for a few weeks, then get medically better, but may still be contagious. This dog flu virus can even live on objects, like shoes or dog toys at a pet store, and spread to unprotected dogs who happen to come by for a sniff.
As this summer moved into fall, and finally a significant enough population of dogs became vaccinated, and the public was educated on how the flu is spread and fewer dogs were boarded (as people traveled less), the numbers of sick dogs in the Louisville metro area have dissipated.
However, Rizzo feels there is now a permanent price paid in his community, as the H3N2 strain of dog flu is now endemic or there to stay, which also happened in Chicago following an outbreak in 2015. “H3N2 is here and I have zero expectation that it’s going anywhere,” he says.
In 2017, the H3N2 (or H3N8) strain of dog flu was identified in 46 states.