An Update on Canine Influenza

Winter is usually known for respiratory illnesses in humans, especially influenza. Humans’ best friend can also get their own influenza viruses, which are not seasonal, and should not be ignored. The dog flu, as it’s commonly known, is thankfully not known to spread to people, and is thought to be of low risk to people but can cause severe disease in a select number of dogs.

The clinical signs associated with canine influenza are nonspecific and may include cough, fever, eye discharge, thick nasal discharge, loss of appetite, and general not feeling well. Fevers can reach upward of 105! These signs are similar to tracheobronchitis, also known as “kennel cough”. Many dogs will have the virus and not display any abnormalities but are still capable of transmitting it. Severity can range from happy wagging tails, to pneumonia, and even death, although this is rare. Most dogs fully recover within two to three weeks, with no lingering aftereffects.

Dogs that are in danger usually present with classic coughing, but then rapidly decline. Treatment consists of supportive care, with the goal of providing the body enough time to mount an effective immune response. Severe cases require oxygen supplementation, intravenous fluid support, possibly antibiotics, and other medications. Mild cases are treated as outpatient.

The disease is caused by Type A influenza strains known to infect dogs, not humans. Two distinct strains exist, H3N8 virus and the other is an H3N2 virus. Influenza viruses do commonly mutate, so the Centers for Disease Control and Prevention (CDC) and World Health Organization is monitoring canine influenza carefully, to assess if there is any species jump from dogs to people.

The H3N8 virus strain has been known in horses for more than 40 years, and in 2004, it is believed to have jumped from horses to dogs at a racetrack in Florida. After infecting dogs it adapted to spread within the canine population, and is now considered to be a species-specific virus. H3N2 strains originated in birds before spreading to dogs, most likely in South Korea around 2007. This particular virus has been documented to be transmissible from dogs to cats, but not causing significant clinical illness.

As with human influenza, canine influenza is rapidly spread between individuals. Dogs are most contagious for two to four days during the incubation period, before any significant signs of illness are evident. It is highly contagious, with an estimate of 80% of infected dogs displaying flu-like signs. Thankfully the percentage of dogs who succumb to the virus is low. Being that this is a novel virus for dogs, there is no built-up immunity within the canine population, therefore most dogs are susceptible to infection.

Transmission is via nasal and respiratory secretions, and contaminated surfaces, similar to human influenza viruses. High-density areas, such as kennels, dog parks, dog daycares, are prime areas for the virus to rapidly spread.

Prevention consists of vaccination, hygiene, quarantine, and common sense. If your dog is coughing, prevent their exposure to other dogs or cats until such time as the coughing has resolved. Should there be suspicion or confirmation of influenza, that period should be extended to two or three weeks. Wash hands frequently and keep all kennels and shared spaces clean. The virus usually does not survive more than two days on surfaces and is readily deactivated by commonly used disinfectants. Stay away from dog parks, daycare, and social situations until clear of the isolation period.

A combination H3N8 and H3N2 canine influenza vaccination has been approved and is manufactured by several companies. Although considered a “lifestyle” vaccination, it is advisable that your dog be vaccinated, especially if they are social and if they go to daycare, boarding, or the dog park. Vaccination consists of a series of two injections, two to four weeks apart. Ask your veterinarian about the vaccination, especially of you have a social pup.

Dan Teich, DVM