Canine influenza was first reported in 2004 at a Florida greyhound track, probably imported by a dog coming from Asia. Dogs are the only known susceptible species. This strain (H3N8) is not known to infect humans. The influenza is thought to be transmitted by an infected dog sneezing or coughing on another dog, much the same way as influenza is spread among humans. It can also be transmitted via contaminated inanimate objects and by people who touch infected dogs and then touch uninfected dogs.

The incubation period is usually two to five days. Infected dogs shed the virus for seven to 10 days after clinical signs appear. Since the virus is new, all dogs are considered susceptible to infection, and most dogs exposed to canine influenza become infected. About 80 percent of infected dogs develop clinical signs. Infected dogs that do not exhibit clinical signs can still shed the virus and spread the infection.

The disease may be mild or severe. Most dogs exhibit the mild form of the disease. The most common clinical sign is a cough that lasts 10 to 30 days despite treatment with antibiotics and cough suppressants. Many dogs have a purulent nasal discharge and a low-grade fever. Some dogs are more severely affected and may develop pneumonia with a high fever and difficult breathing.

A rapid test is available that can be used to tentatively diagnose an active infection. The test can be run on a nasal swab and is most sensitive during the first two to three days of illness.

Treatment is mostly supportive. In the mild form of the disease, many dogs are treated with a broad-spectrum antibiotic to prevent secondary bacterial infections. Intravenous fluids may be needed for dehydrated dogs.

Dogs showing signs of canine influenza should be isolated as soon as possible to prevent spread of the disease to other dogs. Do not take dogs with canine influenza to dog parks, boarding facilities or other places where other dogs can be exposed to the virus. Wash your hands thoroughly after handling any dog with influenza. Thoroughly disinfect areas where the dog is housed with dilute bleach or other suitable disinfectant.

There is a new vaccine for canine influenza that drastically decreases the potential for your dog to get this disease. Ask your veterinarian if you should protect your dog by administering the vaccine.

Most dogs with canine influenza have a good prognosis, though about 5 percent of clinically ill dogs die of this disease.

Dr. Karsten Fostvedt is a veterinarian at St. Francis Pet Clinic in Ketchum.

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