Tests show Midwestern canine flu outbreak stems from new strain

Canine influenza virus (CIV) has affected at least 1,000 dogs in Illinois, Wisconsin, Ohio and Indiana in the last month, including one confirmed case in the Madison area. Previously thought to be caused by the H3N8 strain, which has been circulating in North America since 2004, recent tests from the Wisconsin Veterinary Diagnostic Laboratory (WVDL) and the New York State Animal Diagnostic Laboratory at Cornell University have identified the strain as H3N2.

"It's believed that the H3N2 strain was introduced here from Asia, but how it happened is not known," says Keith Poulsen, WVDL diagnostic and case outreach coordinator and clinical assistant professor at the UW School of Veterinary Medicine (SVM). "The commercially available vaccines for CIV are made to protect against the H3N8 strain, and their effectiveness against the H3N2 strain is unknown at this time, but it is likely to be less effective."

Both CIV strains can cause persistent cough, runny nose, and fever. A small percentage of dogs will develop more severe clinical signs; some will not show any symptoms at all. The infection has been associated with some deaths.

Neither CIV strain is related to the highly pathogenic H5N2 avian flu, which was recently reported in a commercial flock in Jefferson County; they are completely different strains that affect separate species.

Currently, there is no evidence that either CIV strain is contagious to humans. While the more familiar H3N8 strain is not known to affect cats, H3N2 has caused infection and respiratory illness in felines.

"We're advising pet owners to seek veterinary medical care, including diagnostic testing and potential treatment, for dogs and cats exhibiting clinical signs of CIV," says Sandi Sawchuk, primary care veterinarian at UW Veterinary Care (UWVC) and SVM clinical instructor.

For pet owners, UWVC recommends the following:

• If possible, get your dog vaccinated. Although it is unknown if commercial vaccines will be effective against the H3N2 strain, they will reduce the incidence and severity of disease in dogs infected with the H3N8 strain, which is still in circulation. There is no feline vaccine at this time.
• Avoid bringing your dog into close contact with other dogs.
• Wash your hands and change your clothes if you work with or are exposed to sick dogs before handling your own pets at home. Soap and water is very effective at inactivating influenza virus.
• Call your veterinarian for further instructions if your dog or cat is showing signs of persistent cough, runny nose and fever.

In addition, the WVDL has compiled information and sampling guidelines for veterinarians.