The canine influenza virus is a highly contagious, newly emerging pathogen in the dog population. The virus appears to have mutated from the equine influenza virus. Canine influenza virus infections can be mistaken for infections caused by Bordetella bacteria / Parainfluenza viruses, part of the traditional “kennel cough” complex.

2. When was canine influenza disease first identified?

Canine influenza was first identified in racing greyhounds in 2004. The virus appears to have been responsible for widespread respiratory disease affecting dog tracks throughout the USA for the last two to three years. Cornell University first isolated the influenza virus from an animal that died during one of these outbreaks. Evidence of infection of non-greyhounds has been found in Florida (as of May 2005) as part of ongoing research by Dr. Cynda Crawford (University of Florida). Veterinary clinics, boarding facilities and humane shelters have all experienced positive-testing cases. Confirmed cases are also now reported from New York State (New York City 2005). Testing of some ill dogs from other states such as Massachusetts has also produced positive tests to influenza virus, but widespread screening is still in the early phase.

3. Are all dogs at risk of contracting the canine influenza virus?

Yes, all dogs, regardless of breed or age, are susceptible to infection. They have no naturally acquired or vaccine-induced immunity. Virtually 100 per cent of exposed dogs become infected. Nearly 80 per cent of infected dogs will contract a form of the disease which will produce obvious signs of illness. Of these, a small percentage of dogs will experience more severe clinical progression, including pneumonia.

4. What are the clinical signs of canine influenza?

In the milder clinical picture, the most common sign is a cough typically lasting from 10 to 21 days. It continues despite therapy. Most dogs have a soft, moist cough, while others have a dry cough, typical of a kennel cough. Many dogs have heavy discharge from the nostrils and a low-grade fever. The nasal discharge may be associated with other bacterial infections which move in to take advantage of the ill dog. The discharge generally resolves with antibiotic therapy.

Some dogs develop a more severe disease with clinical signs of pneumonia such as a high fever (> 40º C or 104º F), and fast and difficult breathing. Chest X-rays may show lung changes when pneumonia is present. Dogs with pneumonia often have a secondary bacterial infection and have responded to a combination of antibiotics and supportive care, including intravenous fluid therapy in hospital.

An infected dog will begin to exhibit clinical signs of the disease 2-5 days after being exposed to the virus.

5. Will all dogs infected with the virus exhibit clinical signs/symptoms?

No. About 20 percent of dogs infected with the virus do not exhibit clinical signs.

6. Will these dogs eventually get sick? Are they contagious to other dogs?

Infected dogs, which appear healthy and do not exhibit clinical signs, for reasons unknown, do not progress to a state of clinical illness. It is believed that these dogs are contagious to other dogs, with shedding of infectious virus particles starting at the onset of clinical signs and lasting another 7 to 10 days.

7. What is the fatality rate for dogs infected with the canine influenza virus?

Fatal cases of pneumonia have been documented. In those dogs where the cause of death was verified by diagnostic testing, reported death rates for dogs with pneumonia ranged from 1 to 8 percent. Some of the popular media outlets are reporting 10 percent death rates overall for infected/exposed dogs, but to date, this is not supported by clinical data.

8. How is canine influenza diagnosed?

Antibodies to the canine influenza virus are measured. Paired blood samples are required for diagnosis of recently acquired infection. The second sample is collected at least two weeks following the first. When collection of an early illness sample is not feasible, testing of a late (convalescent) sample will at least indicate whether the dog was infected at some time in the past.

Serology tests are very useful, not only because they diagnose individual infections, but also alert veterinarians that the virus is present in their community where precautions and testing can then begin.

Post-mortem, the lungs and windpipes from dogs that died of pneumonia can be tested for influenza virus by direct tissue testing.

9. Is there a vaccine for canine influenza virus?

No. There is no vaccine for canine influenza virus at this time. Work has begun on vaccine development.

10. How many strains of the canine influenza virus have been identified?

To date, only one strain of the virus has been identified.

11. How is canine influenza virus spread?

This virus is spread through respiratory secretions and contaminated surfaces. People can provide excellent pathways for disease spread (ex. kennel workers, pet store workers, friends) when they move between infected and uninfected dogs. The virus spreads easily in close proximity, but can also be spread outside of enclosed or crowded environments.

12. What can your veterinarian do to protect against the spread of canine influenza?

Because of the highly contagious nature of this illness and widespread susceptibility of patients, veterinarians, boarding facilities, shelters and pet stores should institute effective isolation protocol for dogs that have any “kennel-type cough” or undiagnosed pneumonia.

Equally important is the protection of other dogs while any infected dogs are undergoing diagnosis, treatment, and hospitalization.

Veterinarians will also monitor the spread of the new influenza infection closely. Though it is not widespread in North America at this time, it is likely to spread quickly and front-line awareness will be essential to contain future outbreaks.

13. What precautions should dog owners take to protect their dogs from canine influenza? Should they avoid walking their dogs with other dogs? Visiting groomers, boarding kennels or dog parks?

Pet owners should use common sense and take reasonable precautions to protect their dogs, and other dogs from contracting the canine influenza virus.

• Dog owners who have a dog with an active respiratory illness or one that has recently recovered from a respiratory infection should keep their dog at home for a couple of weeks. This will allow rest so that the dog fully recovers from their illness, and also helps prevent potential infection transmission to other dogs.
• If a dog is exhibiting coughing, laboured breathing, nasal discharge, fever or lethargy, isolate the dog and seek veterinary advice promptly.
• Inform your veterinarian if your dog has stayed at a boarding kennel recently or has been out to shows or trials.
• If your dog will be staying in a boarding kennel in the near future, be sure that the kennel is well-known to you and ask them if any kennel cough has gone through the facility recently, or is currently a concern.
• Be aware that vaccination for kennel cough agents (Bordetella, Parainfluenza) required by many boarding kennels will not protect against this new virus.
• Remain alert to potential outbreaks of canine influenza in your area.
• Otherwise, dog owners should continue their routine activities with their dogs. This includes visiting dog parks, walking their dogs and visiting the veterinarian or groomer.

14. What are the implications for public health?

The H3N8 equine influenza virus has been present in domestic horses for over 40 years without report of human infection documented. All cases of possible human exposure to the canine influenza virus will be monitored, but at this point, there is no reason to believe that the virus will cross to humans as with avian influenza.