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Dog Flu or Imposter: What Is it?


What seems to be the dog flu is appearing everywhere in Bozeman, Montana. But, if it quacks like a dog, it might not be a duck. Imagine around 20 percent of the dogs in the community where you live suffering from sneezing, coughing, runny noses, and a small percent of them transitioning to pneumonia. That describes the epidemic happening now in Bozeman, Montana.

Dr. Jarrod Moss says, “This has been going on for four to eight weeks. I haven’t had a dog die at any of our practices (he has three), but, according to colleagues, some have died. This is very infectious, because, by now, I estimate up to 200 cases in our community of 40,000. That’s a lot of dog flu.”

But is it the dog flu? Actually, according to experts at both the Cornell and IDEXX labs, the answer is no.

Edward Dubovi, Cornell Director Virology Section Diagnostic Center, said only two of the samples of around 18 dogs came up positive for dog flu or canine influenza virus (CIV), which is a low positive value. “It looks like flu, it smells like flu, but I don’t know that it is flu,” he said.

The tests at both labs focused on any influenza A-type virus, and came up short, except for those two barely positive results, which are described as “borderline.” Could it be a B-flu (a human flu)? “Not likely. It’s not shown up in dogs before,” said Dr. Chrstian Leutenegger, director of molecular diagnostics at IDEXX Laboratories.

There are actually different strains of H3N2 (dog flu). Could the strain that was introduced to Los Angeles from dogs at a Chinese meat market earlier this year (which differs from the strain of H3N2 originally introduced into Chicago from South Korea in 2015) go unidentified? Also, interestingly, even the original H3N2 strain that entered the U.S. in Chicago has evolved. Could current testing technology miss these changes in H3N2? “Good questions,” said Leutenegger, “But very unlikely.”

Some clinics are vaccinating outside to limit exposure in the clinics

Asked about a long line of “usual suspect” infectious respiratory diseases, Leutenegger said none have been identified. The IDEXX panel is inclusive, covering 11 infectious agents.

Something is definitely going on in Bozeman; it’s infectious, and it has happened fast. “People in our community love to hunt and fish with dogs, and they hike trails, and meet other dogs,” said Moss. “Most stores downtown allow dogs and have communal water bowls. People board their dogs here, too. All this helps support the spread of CIV.”

While mimicking CIV, and perhaps even as contagious as CIV, it’s apparently not CIV sickening dog (at least most dogs). Making matters even more complicated, H3N2 has been identified in the state, and it might be that some of the dogs have indeed had the dog flu.

Dr. Christian Leutenegger

The search continues, as IDEXX tested for an additional six infectious agents, including the recently discovered canine polyomavirus, which have all been ruled out.

IDEXX lab testing is now being focused on “zebras,” looking for something totally unexpected.  How about a canine retrovirus? For years, researchers have attempted to isolate this possibility. After all, if retroviruses appear commonly in other species, why not dogs? “At the bottom of the list,” Leutenegger said and laughed.

Maybe it’s not even a virus, but instead a fungal disease. “Highly unlikely because whatever is going on is acting like a viral infection,” Leutenegger said.

So, what is the mysterious cause of all these sickened dogs? “It may be that we have another new virus,” said Leutenegger.  “We don’t know what we don’t know.”

And, to date, no one knows. Certainly, veterinarians are telling dog owners in Bozeman to stay away from other dogs, and also to vaccinate for dog flu. After all, even if most dogs aren’t getting flu, CIV does occur in Montana.

The dog flu (and likely the mysterious Bozeman virus) can be passed from dog to dog via public water bowls

What is known is that H3N2 continues to spread around the country, hitting some communities particularly hard, including Louisville, Kentucky; Los Angeles, California; Houston, Texas; Galveston, Texas; and various cities throughout Florida.

According to the Orlando Sentinel, the recent outbreak of canine influenza virus has led to the closure of at least four central Florida dog boarding and daycare facilities. Veterinarians believe there are likely many facilities that know they have flu, but attempt to keep what they know quiet, manage the fallout, and remain open.

Veterinarians, including Drs. Cynda Crawford and Julie Levy at University of Florida College of Veterinary Medicine, have called for complete transparency, rather than facilities keeping their doors open knowing they have flu.

Some boarding and daycare facilities have had 30 (and likely over twice that many) cases of dog flu, according to various printed reports. At least one boarding facility, called Woof, closed its doors for several days, pointing out that it was the responsible thing to do.

The boarding association, the International Boarding & Pet Services Association, provides education and certification and encourages working with local veterinary professionals. But they don’t mandate vaccines. And, unfortunately, many kennels and daycares aren’t even members of this association.

The dog flu can be better controlled if pet stores, groomers, dog daycares, and boarding facilities are transparent

Of course, if dogs are required to show proof of CIV vaccine (including the booster) before being boarded or allowed at daycare, far less flu would occur in the first place.

There are additional “hot spots” of sporadic H3N2 throughout the U.S. And, in Chicago, H3N2 dog flu exists and is going nowhere. The truth is that positive lab results are likely only a drop in the bucket or the tip of an iceberg. After all, most dogs suspected of dog flu are not tested.

While most dogs don’t require hospitalization as a result of the flu, plenty do. And three to five percent may die. The percentage may be small, but consider this: In 2017, likely thousands of dogs have been sickened as a result of the flu. If only a thousand have been sickened (and likely the number is at least twice that), it means conservatively at least 30 to 50 dogs have died. And, helping to enhance the spread of CIV, around 20 percent of dogs never display any signs of illness but still spread virus. Their owners have no way to know their dog is contagious.

“That’s one reason I am for vaccination,” said Leutenegger. “Inoculated dogs don’t shed much virus. And even if the vaccine doesn’t prevent infection, the vaccine ameliorates clinical signs and makes it very unlikely the dogs advance to pneumonia, and therefore vaccine reduces deaths.”

Dubovi adds to remind clients to be proactive and understand that a booster is required (about three weeks after the initial shot) for the CIV vaccine, and therefore it’s important to plan ahead before boarding or traveling.

Cornell’s diagnostic lab’s mapping of where CIV has been identified.

More information regarding dog flu.

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