My Pet World: Dog flu outbreak in the Midwest could spread

A dog flu epidemic has sickened over 1,000 dogs and has been responsible for the death of at least five dogs in the Chicago area since mid-March, according to Dr. Donna Alexander, administrator for the Cook County Department of Animal and Rabies Control.

Alexander concedes that these numbers may be conservative and are likely to continue to grow, as some Chicago area veterinary clinics continue to see as many as 50 or more new cases of confirmed or suspected canine influenza virus (CIV) weekly. Some emergency clinics are filled with sick dogs.

As of this writing, the outbreak is restricted to the Chicago metropolitan area. However, many dogs travel with their owners, especially now during spring break. Dog sport competitions to family vacations send pets across state lines. There have been several suspected but yet to be confirmed CIV cases in Missouri, Wisconsin and Indiana.

"Of course, the canine influenza virus could easily spread to other cities, especially where there are dense canine populations," says veterinary immunologist 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. Crawford was among the first to identify the virus back in 2004, when a flu virus jumped species. The canine influenza virus (or dog flu) mutated from an equine influenza virus (horse flu) at a Florida racetrack.

While CIV outbreaks have occurred sporadically across the country, including in Chicago in 2008, the vast majority of dogs have never been exposed to this virus.

"There's no built-in immune protection for most dogs," says Dr. Brooke Bartell, who works in the ER at Chicago Veterinary Emergency and Specialty Center. "The result is that nearly all dogs exposed to the virus will get the virus."

The tricky part is that all the dogs who get the virus don't get sick. Crawford says about 20 percent to 25 percent of dogs infected with CIV are asymptomatic.

"These dogs feel fine, they act fine and have no symptoms. That's good, except they are highly infectious and are particularly effective at spreading the virus because they continue their usual activities without anyone suspecting how contagious they are," explains Dr. Natalie Marks, a Chicago veterinarian. Dogs can easily spread the virus to other dogs. In fact, people can perpetuate the spread of the virus.

"The virus can live on clothing for 24 hours or on objects for up to 48 hours," Marks notes. As one example, if a dog carrying the virus licks your hand or face (unless you wash your hand or face), even hours later a healthy dog licking the same place can pick up the virus.

The good news is, relative to the number of dogs infected, most recover well. About a quarter of infected dogs don't get sick at all. Most who do get sick suffer coughing, lethargy and lack of appetite.

"Just like people (with) respiratory flu, we get better on our own in three or four days without calling the doctor. Many dogs recover without veterinary assistance," Crawford says.

However, some dogs don't get better or even worsen. About 5 percent to 10 percent of dogs need veterinary intervention, or even hospitalization. Sometimes their conditions deteriorate quickly into pneumonia. Surprisingly, these seriously compromised pets are usually not elderly individuals in fragile health, or puppies; they tend to be younger, active, healthy dogs.

All breeds are equally prone to CIV, although, Bartell says she's always particularly worried about the ability of brachycephalic dog breeds (dogs with pushed-in faces like the Pekingese, Pug, Bulldog or French Bulldog) to bounce back from respiratory problems.

People and cats cannot contract CIV.

In an effort to limit the spread of CIV, the Chicago Park District is cooperating with the Chicago Veterinary Medical Association to post signs warning dog owners to enter dog-friendly areas at their own risk. Some dog-training classes have been postponed, a handful of pet stores are discouraging visits from dogs, and a small number of dog day cares have closed their doors until the outbreak subsides.

"Limiting social contact keeps individual dogs safe, and also slows the virus circulation in the community," Crawford says.

Of course, if more dogs were pre-emptively vaccinated for CIV, the epidemic may not have occurred in the first place.

"That (would be true) if we had about 70 percent of dogs vaccinated, based on the human model for vaccination for flu," says Crawford. "Certainly, with any significant number of dogs vaccinated, not as many dogs would have been affected, which means it's possible fewer would have died."

Like the vaccine for human flu, the CIV vaccine may prevent infection or reduce severity of symptoms. Importantly, the dog flu vaccine (which requires a booster shot 2-3 weeks after the initial shot) also seems protective against pneumonia. That's important because when dogs succumb to CIV, pneumonia often plays a role, and certainly is a cause for hospitalization.

"Many veterinarians think if we don't see it, we don't need to vaccinate," says Dr. Derrick Landini, of Chicago. "Boy, now most of us wish we'd been more proactive."

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