Influenza in Canines

by Bruce W. Little, DVM

Canine Influenza

Much has been written about canine influenza (dog flu) over the past two years, and one might wonder why we continue to write about a dog disease that has been around for some time and has infected dogs in 41 states. The reason, in my opinion, is that almost every day we read where another outbreak has occurred in some area of North America that did not have a significant problem only a few weeks before the outbreak. The University of Florida College of Veterinary Medicine reported last month that more than a dozen dogs had been seen at its animal clinic that tested positive for canine influenza virus. These dogs had attended one of two dog shows, one in Perry, Georgia on May 19-21 or Deland, Florida on the following weekend, that has now spread to several states including Florida, Georgia, Tennessee, Kentucky, South Carolina, North Carolina, Texas, Louisiana, Minnesota, Missouri, and Illinois. Just this week there was a report about a new outbreak of this disease in Minnesota. Apparently, most of these confirmed cases have had contact that traces back to the dog shows listed above. These types of events have increased concerns about this disease throughout the United States.

Canine influenza is a relatively new, highly contagious viral disease that can affect dogs of any breed, age, sex, or health status. It can occur year-round and currently has been shown to infect dogs only, although there are signs that it may have the potential to infect cats. To date there have been no diagnosed cases of canine influenza in cats. Also, there is no evidence the virus can infect people. Canine influenza spreads rapidly through direct contact with infected dogs by licking or nuzzling each other, air transmission through coughing and sneezing, or on contaminated surfaces such as a shared toy or water bowl, or when the virus is transported by their handlers by not washing their hands or contaminated clothing. This contact typically creates clinical signs in approximately 80% of unvaccinated dogs that come into contact with the virus. So, one in five dogs that are exposed to the virus do not show signs of the disease; however, they can serve as carriers of the virus and can infect other dogs with whom they come into contact. Fortunately, less than 10% of those dogs that exhibit symptoms die from the disease. There are two known strains of the canine influenza virus, H3N8 that was discovered in 2004 by University of Florida veterinarians and a more recent strain, H3N2 that had previously been diagnosed only in Asia before making an appearance in the Upper Midwest in the spring of 2015. The H3N2 virus first discovered in the Chicago area in March 2015 infected hundreds of dogs causing the death of dozens of them.

Most dogs, regardless of breed or age, are susceptible to canine influenza. With the older version of H3N8 dog flu, it was thought that much like human influenza the very young and the very old, or those dogs that had a pre-existing condition such as a compromised immune system were more vulnerable. However, it is generally thought today that dogs of any age or breed are at risk for both strains of canine influenza. Dogs that show a high level of social interaction are at more risk than those pets who tend to remain alone and separated from other dog populations. Visits to dog parks, boarding kennels or daycare facilities, group dog training sessions, grooming parlors, dog show and agility events and dogs that travel with you to various places both in your home town or inter-state places, the dog is at greater risk for exposure to canine influenza. It is thought that about 4 in every 5 cases of canine influenza is contracted in boarding kennels and dog daycare facilities. Seasonal events such as holidays and spring break from school when families travel more frequently seem to be conducive to the spread of canine influenza. These are the times when dogs are left at boarding facilities or placed with dog-sitters who migrate from one dog walking job to another increasing the potential for transmitting this highly contagious disease.

The signs of illness include symptoms to which people can relate in human influenza infections; such as a lasting cough, low-grade fever, nasal discharge, loss of appetite and lethargy. About one-fifth of the dogs that show clinical signs after exposure develop more severe illness such as pneumonia and high fever. Less than 10% will develop more complicated symptoms and some may die. If your dog shows signs of illness, especially respiratory illness, you should consult your veterinarian immediately. To confirm a diagnosis of canine influenza your veterinarian will send a sample of blood or nasal swab to a laboratory. She or he will then establish the best course of treatment options if your dog is diagnosed with canine influenza. As is the case for all viral diseases, treatment is mostly supportive with good care and nutrition that can assist dogs in developing an effective immune response to the disease. Antiviral drugs are approved for use in humans only, and little is known about their use or safety in dogs. The presence of secondary bacterial infection as evidenced by fever, dehydration and nasal discharge may need a course of antibiotics, fluids to correct and maintain hydration and/or anti-inflammatory medications to reduce fever. Your dog should be kept isolated from other dogs in the house and in the neighborhood during the symptoms stage of this disease.

Preventing your dog from contracting canine influenza is the best scenario possible. Talk to your veterinarian about the risk factors that may affect your dog. Find out if there are widespread cases of canine influenza in the area in which you live or in places that you are contemplating visiting. Make sure boarding kennels, dog day care facilities, groomers and dog-sitters are aware of the potential for your dog regarding canine influenza, and that they take all precautions necessary to keep the disease contained as well as possible. Ask your veterinarian if your dog should be vaccinated against canine influenza as there has been a government approved vaccine against H3N8 influenza since 2009 and a more recent approval for vaccine to immunize dogs against the H3N2 virus. The vaccine for your dog may not stimulate a total preventative for the disease; however, records show it provides complete immunity to approximately 90% of the dogs who receive it. It also relieves the severity and duration of the illness. The vaccine reduces the period that an infected dog may shed the virus in its respiratory secretions, as well as the amount of virus shed, thus making them less contagious to other dogs.

There is some misinformation in the dog care world that the canine influenza vaccine is not effective. That is false information and should be discounted. The USDA has fully licensed these vaccines, and they do not pose significant side-effects to dogs when vaccinated. Not all dogs may need to be vaccinated. Canine influenza is not a devastating disease unless your pet is in the 10% or less that develops complications and dies. However, we must be aware of the disease and the problems it can create. If your dog never goes outside your own home and yard, and if there are no stray dogs or other visiting dogs coming into your home environment, your veterinarian may advise that your dog does not need the vaccine. Seek out and follow the advice of your veterinary professional and canine influenza can be mitigated or contained altogether. Canine influenza, like human influenza, can make a dog very sick for a period. Most dogs recover in 2 to 3 weeks. Consult with your veterinarian to assess the specific needs of your dog and the environment in which it lives, and take all necessary precautions. Prevention is always better than treating the disease once it has been infected. Your dog deserves the very best of care, and will continue to show its unconditional love regardless.


Bruce W. Little, DVM