Canine Influenza by Laura McLain Madsen, DVM

Influenza viruses have been in the news recently, from “swine flu” H1N1 to the recent human outbreak in China of avian influenza H7N9. (The H’s and N’s are a way to specifically identify the strain of influenza.) Dogs have a flu strain also, called H3N8.

Canine influenza didn’t exist before 2004. That year, the virus “jumped” from horses (equine influenza) to dogs. The first outbreak was in a racing greyhound kennel in Florida and many dogs died. The virus spread across the country over the next few years. There have been outbreaks at doggy day cares, boarding facilities, pet stores, veterinary hospitals, animal shelters, etc. It is currently considered to be “endemic” (meaning well-established in the local dog population) in urban areas of Pennsylvania, Florida, New York and Colorado.

Like human influenza, canine influenza is highly contagious and targets the respiratory tract. The virus is spread through sneezing, coughing, direct contact with another dog, and from contaminated surfaces and objects (floors, cages, toys, bowls, etc.). A dog can actually spread virus before he starts to show symptoms; this can lead to outbreaks because the dog appears healthy.

Symptoms develop a few days after infection. In mild cases, dogs are still active and eating but may have a mild fever, sneezing, coughing, and watery or mucusy discharge from the nostrils. In more severe cases, a bacterial infection can develop on top of the viral infection, leading to high fever, lethargy, decreased appetite, and pneumonia (lung infection). In rare cases (1-5% of infected dogs) canine flu can be fatal.

Treatment depends on how sick the dog is. Mild cases can be treated symptomatically with oral antibiotics and cough suppressants. For severe cases, your veterinarian may recommend diagnostic testing, including a blood test to check levels of white blood cells (infection-fighting cells), and chest x-rays to determine if pneumonia is present. Treatment for severe cases may require hospitalization, intravenous fluids, intravenous antibiotics, and oxygen therapy.

There is a vaccine available against canine flu. It is given as two doses initially (2-4 weeks apart) and then annual boosters. It’s important to realize that the dog won’t be immune until about 2 weeks after the second injection, so if you decide to have your dog vaccinated before he goes to a boarding kennel, you’ll need to start at least 4-6 weeks before the kennel stay.


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