If you have a dog that you've had to board or take to the groomer's in the last year, you've no doubt heard about the "flu" as most facilities are requiring dogs to be vaccinated against it. We’ve had a lot of clients call us in confusion about whether or not their dog needs the “flu” vaccine—hopefully this post will clear things up.
Canine influenza virus (CIV) causes respiratory symptoms similar to those experienced by humans with flu, including coughing, sneezing, lethargy, fever, and discharge from the nose and eyes. Unlike seasonal flu in people, canine influenza can occur year round. It is spread through the air via coughing or sneezing or physical contact with infected dogs, contaminated objects (floors, walls, bowls, etc) and people. Most dogs infected with CIV will only experience a mild upper respiratory tract illness and recover within a few days. Dogs with more severe cases of influenza are often suffering from additional viral or bacterial infections. So far, there is no evidence that canine influenza infects people. However, H3N2 has infected cats in Asia and more recently in Indiana in 2016.
There are two known influenza viruses that can infect and spread between dogs in the United States. CIV H3N8 was first identified in racing greyhounds in Florida in 2004. The virus has been declared to be endemic in areas of Colorado, Florida, New York and Pennsylvania. Since 2004 outbreaks have continued to occur. More recently, in early 2015, a new strain of CIV (H3N2) was identified as the cause of a severe respiratory outbreak in Chicago, IL. First diagnosed in Asia in 2007, CIV H3N2 is derived from an avian influenza virus that gained the ability to infect dogs. Infected dogs were seen in many states and more than 2,000 dogs were confirmed positive for the CIV H3N2 virus. CIV H3N2 has been found in household dogs, dogs in shelters, and in breeding facilities.
There are vaccines available in the US for both CIV H3N2 and CIV H3N8. It is important to understand that they are different viruses requiring separate vaccinations. To date, there is no information indicating that dogs vaccinated for one strain will be protected for the other. Each vaccine requires a booster two to three weeks after the initial vaccination--this means that your dog will receive two vaccinations for either H3N8 or H3N2. Despite some boarding and grooming facilities only requiring the initial vaccination to accept your dog into their facility, you need to know that your dog will NOT have maximum immunity to the virus if it does not receive the booster. Once the H3N2 vaccine became available late fall 2015, we stopped purchasing the H3N8 vaccine as the H3N2 strain was much closer to home, and spreading, and H3N8 is non-endemic in Missouri, with the risk of H3N8 exposure being extremely low unless traveling.
The influenza vaccine is considered a "lifestyle" vaccine, which means that the decision to vaccinate a dog against CIV is based on the risk of exposure. A veterinarian should determine whether vaccination is needed based on related risks and benefits, and should administer these vaccinations at least 2 weeks prior to planned visits to dog activity and care facilities (e.g., kennels, veterinary clinics, dog day care centers, training facilities, dog parks). This differs from "core" vaccines - such as distemper, parvo and rabies that are recommended for all dogs, regardless of lifestyle.
Vaccination against other pathogens causing respiratory disease (Bordetella, adenovirus and parainfluenza) may help prevent more common respiratory pathogens from becoming secondary infections in a respiratory tract already compromised by influenza infection.
To learn more about canine influenza, visit the American Veterinary Medical Association site.