Update on Dog Flu

By Megan Kelley, DVM, CVA, CVSMT

People worry about getting sick with the flu every flu season. Should you be worried about canine influenza infection in your dog? The dog flu, or canine influenza, has many differences in comparison to the flu we humans experience, including the history of how it came to be.

Prior to 2014 the only strain of influenza seen in dogs was H3N8. This strain had mutated from a horse strain that was passed from race horses to racing gray hounds in a race track in Florida. However, in 2015 an avian influenza strain mutated and created an outbreak of canine influenza, H3N2. The good news is those are the only two strains dogs need to worry about.

Both strains cause a cough, nasal discharge and in severe cases result in the development of pneumonia, fever, breathing difficulties and sometimes death. Similar to human influenza, dog flu is highly contagious and also has a high infection rate. That means almost 100% of dogs will get infected after coming in contact with another sick dog. Of those dogs, 80% will show some type of clinical sign. Most will not need treatment, just like with humans. Some dogs will get infected and not show clinical signs. They are still contagious and can get other dogs sick. About 8-10% will experience a complicated infection and require veterinary care. Of those 8-10%, the mortality rate is 4-6%. The dogs most affected are the young, the old and the small. Yes, small dogs are at higher risk of getting a more complicated case of influenza because of their small airways. So are flat faced breeds. Sorry Bulldogs, Frenchies and Bostons. And, both strains are circulating the nation, including Washington State.

Why is there such a high infection rate? It is because once a dog in exposed to the virus, they will start to shed the virus within 24 hours. This is usually 2-3 days before they start to show any clinical signs of coughing.

Is there a difference between the two strains of canine influenza? The biggest difference is in severity of the sickness. The H3N2-bird strain causes more severe signs of respiratory illness (coughing, nasal discharge, difficulty breathing and fever). Also, with H3N2-bird strain, the length of time that dogs are sick and shedding virus is twice the length of the sickness from the strain from horses. This means dogs with the H3N2-bird strain can show signs of sickness and be contagious for up to a month.

How is the dog flu diagnosed? Often it is diagnosed based on clinical signs and a history of being around other dogs. This includes dog parks, boarding facilities or even vet clinics. For a more definitive diagnosis veterinarians can be measure antibodies or they can send off samples of secretions to check for the DNA of the virus.

Can canine influenza be prevented? Yes, it can. The dog flu vaccinations are safe and effective. Studies show that the vaccine had a 100% success rate in preventing illness. The vaccinations also shorten the length of time the dogs are contagious.

Can you get the flu from your dog, or visa versa? Luckily there have been no known cases of the virus being spread between dogs and humans. There have been two documented cases of cats getting the H3N2-bird strain from dogs. Normally cats are resistant to the influenza virus, which is why you haven’t heard about feline influenza.

Is your dog at risk? The flu virus likes still, warm, humid air. And exposure to other dogs is the major source of infection. This means that outbreaks usually occur in kennels, doggy day-cares, parks and vet clinics. This also means that the dog flu season is typically during the spring and summer months where a lot of traveling and boarding is taking place. If your dog is being boarded while you travel, or you decide to take him along, or if she goes to doggy day-care, or to a vet clinic, or to a dog show, or is young, or is old, or is small or has a smooshed face, you may want to consider vaccinating your dog.

The good news is there is no guessing game with the dog flu vaccine. There are only two virus strains present. Your vet may have a combo vaccine that covers both strains or possibly just the H3N2-bird strain, because infection is more severe. Though you can’t get sick from your dog, and your dog can’t get sick from you, you can prevent your dog from getting the flu. Your dog would do the same for you.

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