Dog Flu Update: The Asian Dog Flu Attacks Chicago


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Leave it to the Chicago area to be hit by an obscure canine influenza (dog flu) virus – one never previously seen in the U.S. as far anyone knows.

This virus, according a dog flu update, and further detailed laboratory testing at Cornell University College of Veterinary Medicine, with the New York State Animal Diagnostic Laboratory at Cornell and the Wisconsin Veterinary Diagnostic Laboratory in Madison, WI identifies the Chicago area epidemic as influenza A H3N2. The same strain of the virus is currently in wide circulation in Southern China and South Korean dog populations, since being identified there is 2006.

How it got to Chicago, no one knows, and is one of the many mysteries which researchers are now beginning to seek answers for. What is known is that over 1,000 Chicago area dogs have been sickened, and at least five have died, according to Dr. Donna Alexander, administrator for the Cook County Department of Animal and Rabies Control.

Previously, reports here and among veterinarians was that the epidemic in the Chicago area had been attributed to the H3N8 strain of virus, which was first identified in the U.S. dog population in 2004 (at first in Florida) and has been circulating since, including an outbreak in Chicago in 2008.

“While it’s still an H3 virus (the strain impacting Chicago now from Asia), it  is antigenically different from  the H3N8 virus strain so it is likely to be seen differently by the immune system,” says Dr. Amy Glaser, director of molecular diagnostic center at the animal health diagnosis Center at Cornell. The big question that follows is will the current dog flu vaccines work for this specific bug? “I wouldn’t expect the H3N8 vaccine to offer significant protection against the H3N2 virus,” she says. “I won’t say it won’t; we just don’t know. The problem is that we have no data.” It might be that the vaccine will offer some protection, how much – if any – remains unknown. The jury is still out.”

No doubt research to answer that question will begin soon.

Still she adds, “Vaccinating for influenza for a dog in an urban population is never a bad idea, and that’s an important point.  Just as in people new strains pop up which makes our vaccines less effective.” Though it’s fair to say that in this instance no one yet knows if the vaccine will offer any cross protection.

According to research conducted on the strain of flu originating in the U.S. in 2004, the H3N8 strain, Dr. Cynda Crawford, a clinical assistant professor of Shelter Medicine with Maddie’s Shelter Medicine Program at the University of  Florida College of Veterinary Medicine, Gainesville,notes that nearly all dogs exposed to the strain will get the flu, as they have no built-in immunity. A lucky 2o to 25 percent of dogs will suffer no symptoms but will shed the virus to other dogs with ease. The largest percent of dogs get sick, but symptoms are so mild they require little or no veterinary care. However, about 7 to 10 percent can get very sick, even developing pneumonia and some of those individuals may succumb. The dog flu vaccines created for this strain also happens to have some built in anti-pneumonia protection.

Is all of that true for this Asian dog flu, H3N2 strain? Glaser says what is known is that this virus strain is also naive to all dogs – so there is no built-in immunity. It’s strongly suspected that ANY exposed dog will get the virus (except any dogs that may be vaccinated and as discussed – it’s unclear if the vaccine may be helpful or if so, how helpful).

Glaser says it is too early to tell what the infection dynamics of this virus are in the dog population. “Just as with the H3H8 strain, there is a spectrum of outcomes following infection from no clinical signs to severe disease but we do not know what that means in terms of percent risk ,” she says. Similarly, it’s unclear what the percent of dogs who get sick or seriously sick when they have the H3N2 strain. “It seems (with the Asian strain of the virus) anecdotally we are hearing  that dogs seem to be sicker with this virus than the historical experience in the same setting with H3N8 ,” she says. “And that is a major concern.”

Another concern, notes Glaser, is that this Asian strain may even be more easily spread than the original canine flu – which was easy enough to spread as well. This is reflected in the rapid way this virus has spread and the intensity of the outbreak.

So, what can people do to slow the dog flu epidemic? Glaser says she hopes the virus spread will slow down on it’s own. And she still suggests that vaccine isn’t a bad idea. “The best thing Chicago area residents can do to protect their own dogs, and to benefit the community is to limit sociability,” she says. She very much liked to hear that the  and Chicago Park District continues to strongly discourage dogs from using the park district Dog Friendly Areas, a decision supported by the Chicago Veterinary Medical Association. The same is true for dog daycare, boarding, dog training classes, even visiting pet stores with dogs.

The good news is that via good luck or precautions taken, based on anecdotal reports – for the first time in weeks, many clinics are reporting fewer cases of the dog flu.

However, the more people adhere to the restrictions – the greater the opportunity for the new flu bug to burn out in the Chicago area, but meanwhile the risk is real that the virus will appear in other geographic locations. Glaser says, “I wouldn’t be surprised,” as she already received a report from Wisconsin. “After all, dogs do travel,” she adds.  There are also unconfirmed reports of one flu virus or another, if for sure even the flu, in New York and New Jersey.

The Asian strain, H3N2 (unlike the original H3N8) can affect cats, based on what has been seen with the virus in Asia. Glaser says that cats exhibit similar clinical signs similar as dogs. While no feline cases has been reported in the Chicago area, upper respiratory problems are common in cats; it’s possible cats with the flu weren’t tested specifically for influenza, and responded to treatment. As far she knows, no feline deaths have been attributed influenza  in Asia.  People are not susceptible to either canine influenza virus strain.

Note the early onset symptoms are the same for either flu virus strain in dogs:

 Coughing

 Lethargy

 Lack of Appetite

 Nasal Discharge

 Trouble Breathing

Any time you observe a change in your pets behavior, or any of the above symptoms, contact your veterinarian.

Cornell Press Release regarding canine influenza virus