What You Need to Know about the Doggie Flu…Canine Influenza

Recently, the one year anniversary of the emergence of a second strain of canine flu here in North America occurred.   So, what have we learned in the last 12 months?

Canine flu virusFirst and foremost, it’s important to understand that there are significant differences between the strain of canine flu (Canine Influenza Virus, or CIV) originally found in 2004 (hereafter known as H3N8) and the newer strain (known as H3N2).   H3N8 was originally a flu virus found in horses (where it had been stable for about 40 years) when it suddenly jumped to dogs around 2004.  Since 2004, CIV H3N8 has been found in more than 40 states.   By contrast, H3N2 is an avian virus, normally seen in Asia.  When it emerged in Chicago a year ago, it had never been seen in the United States before.  In this past year, H3N2 has now been found in 25 states.  You can see more about the spread of both viruses here.

H3N8 (the original  virus) generally infects only dogs while the newer strain can infect both dogs and cats.  Perhaps the most concerning difference between the two virus strains is that dogs with the newer strain (H3N2) can remain infectious for up to 24 days while the older strain generally only remains infectious for about 14 days.  That difference is substantial, both for owners of pets who are recuperating from infection as well as businesses, such as doggie daycare facilities or boarding kennels, who may need to shut down until the outbreak is past.

Beagle with ice packDogs with either virus will show signs of coughing, sneezing, nasal discharge and may be running a fever.  One of the scariest aspects of these viruses is that your pet may be spreading or transmitting the virus without showing any signs of clinical disease.  In fact, dogs might be going to their normal doggie daycare visits or training appointments for 3 or 4 days before the first cough, sneeze or nasal drip starts!!  Once clinical signs start, the amount of viruses being shed into the environment starts to drop off and this might make a diagnosis difficult.  Pets that are exposed to either strain of CIV may start showing signs as soon as 2 or 4 days after exposure.  Most pets will exhibit a mild disease and will recover without issue, but up to 20% of unvaccinated pets might develop a more severe disease and require hospitalization.  Mortality is not high, but some reports do show up to 8% of dogs might die from CIV.

Although most exposure is from direct contact, pet owners should know that the virus can be spread via aerosolization and while exact numbers aren’t known, it is estimated that viral particles may spread more than 20 feet, even from non-coughing pets.  In addition, dogs can be exposed to the virus indirectly due to viral particles on food/water bowls, leashes, owner’s clothing, etc.  Pets who are at highest risk will be those recently adopted from a shelter environment, those who frequent boarding/daycare or grooming facilities or pets who go places where there are lots of other dogs (like dog parks).

So, what can you do to insure that your pup doesn’t contract the “doggie flu”?

First and foremost, talk with your veterinarian about your dog’s risk factors and the prevalence of canine influenza in your hometown.  Next, consider routine vaccination, especially if your pet frequents places where other dogs congregate.   There are TWO vaccines available, one for the H3N8 and one for the H3N2 virus.  Your dog should receive both vaccines and have a booster done about 2 – 4 weeks later in order to develop proper immunity.  Annual boosters are then recommended.

The good news about the vaccines is that vaccinated pets, while not immune from getting the disease, will get less serious cases, show fewer signs of coughing and, most importantly, have fewer days of shedding the virus, possibly preventing your pet from sharing the bug with other dogs.


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