One day a few weeks ago, my animal hospital was suddenly swamped with calls from worried pet owners about reports they had been hearing regarding outbreaks of canine influenza in larger cities in Ohio. Before I even had time to check into these reports, I was getting texts from a sales rep asking if I wanted to order vaccines for canine Influenza to try to head off the spread from these larger cities to Lima area dogs. I quickly did some research into these reports to decide how real the risk truly was and if I needed to start making some recommendations to dogs that came to me for preventive health care.
Canine influenza is a highly contagious respiratory tract infection primarily caused by two subtypes of the influenza A virus, H3N8 and H3N2. H3N8 was first recognized in the USA in greyhounds at 20 racetracks across eight states between 2003 and 2005. It is believed to have originated from a mutation of equine influenza. Since it initially appeared in the USA, it has been diagnosed in 39 states and is now considered endemic in Colorado, Florida, Pennsylvania, New Jersey, Wyoming, and New York.
H3N2 was first discovered in South Korea and China between 2005 and 2007. It is believed to have originated from a mutation of avian influenza. H3N2 was first diagnosed in the USA during an outbreak in the Midwest in 2015. Since then, it has been reported in at least 30 states. I remember this outbreak in 2015. Cases were primarily centered in and around Chicago. There was some concern at that time that it might really take off and spread quickly to other states. There were some media reports that caused concern for dog owners prompting calls to my animal hospital. We did vaccinate a few dogs for it to prevent it, but these were primarily dogs that traveled to Chicago or that went to large dog shows. After a few months, the hype settled down and I really didn’t hear anything more about it until just a few weeks ago.
The recent outbreak that has been reported in Ohio and other areas of the country is of the H3N2 strain. The reports I have read make this outbreak more worrisome than the outbreak in the Chicago area in 2015. Dogs have been diagnosed with H3N2 in Toledo, Dayton and Columbus. Specialty clinics and emergency clinics in these cities have seen enough cases that they often no longer even test dogs suspected of having canine influenza, they just begin treatment. Just the fact that it is even in Ohio makes it a greater concern to the dogs I see every day in my practice. Many of the dogs in this area travel with pet owners, not to mention dogs from theses bigger cities traveling to the Lima area.
Canine influenza virus is spread most easily in areas such as shelters, boarding centers, dog parks, pet stores, dog shows and grooming facilities. Areas where there are larger numbers of dogs in confined spaces make transmission more likely. The virus can be spread thru the air, on items shared by dogs, or by direct oronasal contact. Once exposed to the influenza virus, the incubation period before clinical signs are seen is 2-5 days. The peak level of viral shedding where an infected dog is contagious to other dogs is 2-4 days after exposure. The fact that an infected dog is highly contagious before showing clinical signs is a huge concern and makes it much harder to prevent spread of this virus.
The clinical signs of canine influenza can be somewhat mild with a soft, moist cough that persists for 10-30 days, decreased appetite, and a fever. Sneezing and discharge from the eyes and nose may be also seen. Some dogs show more severe clinical signs with fevers of 104-106, pneumonia, and labored respirations. These more severe signs often are due to secondary bacterial infections. Fatal cases of pneumonia have been reported, but this is in less than 10 percent of dogs. Most dogs recover in 2-3 weeks.
There is a new vaccine that covers H3N8 and H3N2 all in one vaccination. Dogs initially get two vaccinations 3-4 weeks apart and then it is boostered yearly. The vaccine hasn’t necessarily been shown to completely stop illness, but if a vaccinated dog does show signs of illness the signs typically are very mild and only last 2-3 days compared to the 2-3 weeks in unvaccinated dogs. If your dog is at risk for exposure as described in this article, call your veterinarian for vaccination recommendations for your dog.
Chad Higgins, DVM has owned Amanda Animal Hospital for the last 20 years and sees dogs, cats, ferrets and other little furry critters.