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Canine Influenza

Canine influenza is extremely contagious in dogs.

Influenza viruses affect humans, wildlife, and domestic animals. Dogs were, by and large, not the target of these bugs until around 2004, when a new influenza virus was found in a group of racing greyhounds in Florida. From there, it began to appear in dogs that were boarded at kennels. Canine influenza appears to have mutated from equine influenza. The designation of the canine influenza virus is H3N8.

(*Please see the addendum below.)

What Is Influenza?

Influenza is a respiratory illness that is caused by a group of viruses. These viruses are divided into three sections: Type A, Type B, and Type C. Canine influenza falls into the Type A group.

Influenza infection causes fever, sore joints, and respiratory signs such as coughing. Death from canine influenza is very rare, but it can happen due to complications, usually pneumonia. It is usually very young or elderly dogs that die from influenza or those that were not treated with supportive care early enough in the disease process.

How Is Canine Influenza Spread?

Canine influenza is spread easily and rapidly through exposure to the virus in the air. Dogs that are affected will cough, dispersing the virus in droplets through the air. Nearby dogs breathe in these droplets and may become infected. The virus does not last long outside of the dog, so this is an illness that is spread when dogs are close to one another.

Signs of Canine Influenza

Many dogs that are infected with influenza will clear the disease without developing illness. Of the dogs that are infected with canine influenza, 50 to 80% will develop clinical signs including:

  • Lethargy
  • Inappetance
  • Coughing
  • Nasal discharge
  • Rapid breathing (this is a sign of a more severe infection)

From the time of infection, signs of influenza may appear in 2 to 5 days. The illness may then last for 2 to 4 weeks.

Diagnosis of Canine Influenza

The diagnosis of canine influenza is generally based on clinical signs and history. The signs can closely mimic those of other illnesses, especially bordetella infection. There are two types of testing available for canine influenza:

  • Serology testing: Canine influenza can be diagnosed by testing for antibodies to the virus in the dog's blood. This is a paired sample test. This means that two consecutive blood tests are done in order to confirm the diagnosis. One sample is taken within a week of the development of clinical signs. The second sample is taken two to three weeks after the first. If the antibodies increase by four times in the second sample, it is strongly suggestive of infection. However, negative results do not mean that the animal definitely is not infected.
  • Elisa tests are available for canine influenza. These are tests that a veterinarian can run in-clinic on a nasal swab sample. False negatives do occur, but a positive result is a definite case of canine influenza.

Treatment of Canine Influenza

Most dogs with canine influenza get better with supportive care including:

  • The use of a humidifier
  • Saline nose drops
  • Hand-feeding
  • Rest
  • Other symptomatic care as needed, including the treatment of secondary bacterial infections with antibiotics

Some dogs infected with canine influenza develop secondary pneumonia and a high fever, and these dogs need further care. They are the most at risk of dying from influenza, and they require hospitalization, IV fluid therapy, oxygen therapy, and close monitoring.

Prevention of Canine Influenza

There is a vaccine available for canine influenza. This vaccine does not need to be changed every year the way human flu vaccines do because canine influenza is relatively rare comparatively, and it has not yet shown mutations the way that human influenza does. You can discuss with your veterinarian whether vaccination is a good idea for your dog.

Dogs that go to kennels, grooming facilities, and dog parks are at higher risk of contracting canine influenza than those that are mostly home.

Any dog that develops signs of canine influenza should be isolated from other dogs immediately to decrease the spread of the virus.

Some Comments on the Current (April, 2015) Canine Influenza Outbreak in Chicago

Currently, there is an outbreak of canine influenza in the Chicago, USA area. At the time of this writing, around one thousand dogs have been infected and five have died. Below are some important things to know about this outbreak:

  • It is important to remember that this virus spreads quickly and easily, sickening many dogs. Outbreaks usually spike, then die out in a few weeks.
  • If you are in the Chicago area during the time of this outbreak, keep your dog at home as much as possible. Try not to take your dog to dog parks, the kennel, or the groomer at this time.
  • If you have traveled to Chicago during the outbreak, watch your dog closely. Go to the veterinarian at the first sign of illness, and tell him or her that you were in the canine influenza outbreak area.
  • If your dog develops ANY signs of illness, but especially a cough, go to the veterinarian immediately. When dogs receive the proper care early in the disease process, canine influenza is not usually fatal.
  • Though losing even a single dog to this virus is heart-breaking, it's important to remember that canine influenza has a very low mortality rate. The number of dogs that die compared to the number that are infected is very low, usually somewhere around 5%. These dogs usually die from pneumonia.
  • People, cats, and other animals are not at risk of contracting canine influenza.

*Addendum: Lab scientists at Cornell University and the University of Wisconsin have determined that the current outbreak of canine influenza in and around Chicago is caused by a different strain of canine influenza than has been previously seen in the US. The new strain is closely related to the strain H3N2, which is common in Southern China and South Korea and has not been identified in North America before. Some important differences to note between the previously common H3N8 virus and the H3N2 are:

  • The symptoms are the same as those seen in H3N8 (listed above), but they can be more severe in cases caused by H3N2.
  • Some infected dogs may not show any signs of illness.
  • H3N2 has caused illness in cats.
  • It is not known whether the previously-available canine influenza vaccine will provide any cross-protection to H3N2.
  • Current paired serology tests (as discussed above) will not yield positive results for H3N2.
  • All of the previous recommendations remain the same, but now extend to cats.
  • Idexx laboratories, as of 5/7/15, has a Real PCR test available for the detection of H3N2. Veterinarians can order this test along with a panel that screens for other causes of respiratory signs.

5/15/15: A dog in Beach City, Texas, near Houston, has tested positive for the H3N2 strain of canine influenza virus. The family recently moved to Beach City from Chicago.

5/4/16: A group of cats in a shelter in Indiana tested positive for H3N2 after showing signs of respiratory illness. Dogs in the shelter were also infected, though the species were kept in two separate areas of the building. As of this writing, the cats were all recovering and no deaths had occurred in the group from the virus.

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