We’re not finished with the flu

2015 was notable for the usual litany of memorable events: Syria was in crisis, terrorists struck in Paris, deflated footballs made the national news, the United States and Cuba are speaking again. And we’ll remember 2015 as being the year of Bill Cosby, Caitlyn Jenner, and The Donald.

Those of us with dogs will also remember 2015 as the year of a nasty outbreak of canine influenza in Illinois. It took some time to figure out that this wasn’t the familiar H3N8 strain of flu, but rather a new strain -- H3N2 --  so the existing vaccine was not effective.  Routine frolics in the dog park were curtailed, as were vacations, walks in the neighborhood, and visits to the groomer. 

You probably haven’t heard much about the flu lately, but it’s still a viable concern in Lake and surrounding counties; we continue to see small outbreaks in and around Chicago. A disease is classified as endemic when it’s constantly present within a given geographic area over a long period of time. Epidemiologists now consider H3N2 canine influenza to be endemic in our area of the country. For dog owners, that means we have to consider this new flu a continuing threat.

So the bad news is that the flu has not flown. The good news is that there’s a new vaccine against the H3N2 strain that is safe and effective. 

Puppies as young as 8 weeks can be immunized. After the initial dose, another dose is given two to four weeks later, and then boosters are given yearly. Full immunity occurs two weeks after the second vaccine. If you do the math, you’ll see that it takes a minimum of four weeks to full immunity, so now is a good time to protect your dog.

During the clinical trials for the new vaccine, both vaccinated and unvaccinated dogs were challenged with the H3N2 influenza virus. 42% of the unvaccinated group developed severe clinical signs and had to be euthanized.¹ None of the vaccinated dogs developed serious symptoms, and the vaccine prevented secondary pneumonia and lung damage. No adverse reactions or swelling at the injection site were noted. However, as with all vaccines, once they are given to thousands of dogs we’re likely to see the occasional vaccination reaction. 

The older H3N8 strain of flu is still alive and kicking, and there’s a good vaccine for that, too. It probably doesn’t provide much, if any, protection against the newer flu strain, so experts advise giving your dog both vaccines. Both contain inactivated viruses and can be given together safely. I’ve learned that several drug companies are working on a vaccine that contains both strains.

Does your four-legged friend need to be protected against the flu? It depends on his or her lifestyle. Dogs that go to doggy day care, boarding kennels, grooming facilities, the dog park, dog shows or agility trials, or that are otherwise in close contact with others of their species, are most at risk.

Another consideration is whether any cases have been reported in your area. The problem with waiting for that to happen, though, is that if there’s a local outbreak, you may have to halt your dog’s visits to the park or groomer. Or you may have to cancel your vacation. 

Most upper respiratory infections we see are caused not by the flu but by Parainfluenza, Bordetella, and Adenovirus Type 2.  Like the flu, they are spread by close contact. At-risk dogs should also get the vaccine for those agents. It’s an intranasal, injectable, or oral vaccine that we offer to all of our clients.

I’m conservative regarding vaccines; there are some that we don’t even have at our hospital. But given the severity of last year’s flu epidemic, I think all healthy dogs in our area that are at risk should be vaccinated. As events develop, the doctors at Vernon Hills Animal Hospital may change this recommendation. But for now, it seems like the prudent thing to do. 

^1.    In a natural outbreak of the H3N2 influenza, 100% of exposed dogs will contract the virus. 20% will have no clinical signs (but will still shed the virus and spread the infection). That means 80% will get sick. The mortality rate is less than 10%, which, although not even close to the 42% in the study, is still scary.