Canine InfluenzaCanine influenza is a newly emerging infectious disease caused by a “flu” virus. In dogs, a highly contagious strain of the influenza A virus known as H3N8 is able to cause respiratory illness. Canine influenza virus only affects dogs, although it originated in horses.

How contagious is canine influenza?

Just like the human “flu,” canine influenza is highly contagious. In fact, unless a dog has already had the illness and recovered, virtually every dog exposed to the virus will become infected. This is because the virus is relatively new and dogs have no natural immunity to it. While 100% of dogs are susceptible to influenza infection, about 80% will become ill from the virus. The other 20% of infected dogs will show no signs of infection but can still spread the virus to other dogs. The incubation period is usually two to four days from exposure to onset of clinical signs. The highest amounts of viral shedding occur during this time; therefore, dogs are most contagious during this period when they are not exhibiting signs of illness. Virus shedding decreases dramatically during the first 4 days of illness but may continue up to 7 to 10 days in some dogs.

What are the signs of canine influenza?

The most common sign of canine influenza is a persistent cough. About 80% of dogs who show signs of influenza will have mild disease. Signs in this case include a low-grade fever, nasal discharge, lack of energy, loss of appetite, and a cough that can last for up to a month. Approximately 72% of infected dogs will have some form of pneumonia. The mortality rate is 1-5% for Canine Influenza virus, with a higher mortality rate in racing greyhounds.

How is canine influenza spread?

Canine Influenza has been documented in over 30 states including New Jersey, New York and Pennsylvania. Canine influenza spreads the same way that human flu spreads-through direct contact (kissing, licking, nuzzling); through the air (coughing or sneezing from 20+ feet away); and via contaminated surfaces (surfaces such as concrete where the virus can live for up to 48 hours). The disease can also contaminate bowls, leashes, collars, and the hands and clothing of people who handle ill dogs, so just as with human influenza, frequent hand washing and disinfection may help in preventing the spread of CIV. Most common cleaners such as bleach, disinfectants, alcohol and soap kill the virus.

How can I protect my dog from canine influenza?

Protection starts by keeping your dog in good general health. A well-nourished, well-rested and well-cared for pet will have a stronger immune system to help fight off infection. Asking questions of kennel owners, groomers, show event managers and veterinary staff among others is important as well. You should be able to find out whether any cases of respiratory disease have been reported and what the facility’s policies are regarding disinfection, quarantine, and disease prevention. Dog owners should be aware that any situation where dogs are brought together increases the risk of exposure, so if an outbreak is underway, keep your pet close to home if possible. If you think your dog is sick with a respiratory disease, isolate it until you can consult with your veterinarian.

Canine Influenza Vaccine is available. Although the vaccine may not prevent infection altogether, it significantly reduces the severity and duration of clinical illness, including the incidence and severity of damage to the lungs. In addition, the vaccine reduces the amount of virus shed and shortens the shedding interval; therefore, vaccinated dogs that become infected develop less severe illness and are less likely to spread the virus to other dogs. The initial vaccination requires 2 doses, 2-4 weeks apart, followed by annual revaccination.

Is the canine influenza vaccine safe?

Canine Influenza Vaccine, H3N8 has been shown to reduce viral shedding, thereby minimizing spread; lessen the occurrence and severity of clinical signs; and decrease the likelihood of serious complications like pneumonia. It has also been proven safe and well tolerated in more than 700 dogs.

We can help can advise you whether this new influenza vaccine should be added to your dog’s vaccination schedule. Please call us with any questions or concerns.

Canine Influenza Fast Facts

  • Unlike most human influenza, canine “flu” is not seasonal. It can occur at any time of the year

  • Virtually all exposed dogs will become infected

  • Of those dogs, 80% will develop respiratory illness while the remaining 20% will not

  • While the overall mortality rate is low and most dogs recover with supportive care within 2 weeks, a small percentage will become severely ill and some may even die

  • Dogs of any age, breed, or size are susceptible to infection

For More Information

ASPCA: Canine Influenza Virus/Canine Flu


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