Last month, a respiratory illness broke out in a King County boarding facility. Initially thought to be a bad case of “kennel cough”, subsequent testing has shown that it was actually a virus relatively new to dogs, Canine Influenza. This outbreak became the first of its kind (so far) in Washington State, infecting over 80 dogs at the facility. More cases are expected.
What is dog flu?
Influenza encompasses multiple viral strains, usually specific to a particular host species. It was not previously seen in dogs until about 2004, when a strain that normally infects horses jumped species and adapted to dogs. The first cases of H3N8 first appeared in racing greyhounds in Florida, then gradually spread to several other states. Last year, an influenza strain that normally infects birds, crossed species and also adapted to dogs. This strain, H3N2, hit Chicago area shelters last year, then spread to other nearby states. It appears to spread even more easily between dogs, and thousands of dogs have been positively confirmed with influenza since that time. There is no established population immunity to either strain, and nearly all dogs, if exposed, are vulnerable.
Like people with the flu, dogs have similar clinical signs; usually a high fever, snotty nose and a cough. It can look similar to other much more common respiratory diseases in dogs including “kennel cough,” but may be more severe. Some cases may develop into pneumonia.
What is my dog’s risk, and how is it spread?
All dogs are highly susceptible to the virus, with up to 80% of exposed animals becoming ill. A small percentage of infected dogs will develop mild or no observable signs of disease but can still be a source of transmission to other dogs.
Dogs at most risk of getting sick would be those that go to boarding kennels, public dog parks, dog shows, field trials and any other event where dogs and their people gather. Though I have not yet seen any reports of positive cases in Skagit County, dogs do travel. I expect it is just a matter of time.
The flu can be spread by aerosol contact, contaminated objects, clothing and people if they have had contact with an infected dog. Incubation of the virus is 1-5 days, and the virus can be spread on to other dogs before your dog even looks sick.
Should I vaccinate?
There are two vaccines available, to protect against each of the two dog flu strains. These two viral strains are genetically different, so the vaccine for one is not expected to be cross protective to the other strain. To establish immunity, your dog will need both vaccines, with boosters 3-4 weeks later.
The decision to vaccinate for any disease should take into consideration the risk of exposure, the current health status of the dog, and the potential seriousness of the disease if exposed. Since my personal dogs go everywhere with me, including dog events from time to time, I have decided to be safe rather than sorry and vaccinate them. Both the H3N8 and H3N2 strain vaccines are available at our practice.