Downeast Dog News


By Gail D. Mason, DVM, MA, DACVIM | Nov 01, 2018

Canine influenza is a highly contagious (Influenza Type A) viral infection affecting dogs (though infection in cats has been reported). Presently, two strains of the virus known as H3N2 and H3N8 have been documented in 40 states in the U.S. Influenza viruses are known for their ability to “mutate” to different strains that can affect different species. Humans are not a host for these viruses, but future mutations are possible. The viruses are easily spread through coughing, sneezing, or barking and target the entire respiratory system of dogs. Infected dogs start shedding the virus before they show any symptoms and will usually manifest illness within 3 days after exposure. In mild cases, the dog may develop a hacking (sometimes moist) cough, with some clear or light-colored nasal discharge. A decrease in appetite and energy may be noted, which helps to distinguish it from the more commonly known “kennel cough complex.” Many cases of this type will resolve without further treatment. However, symptoms of the severe form of canine influenza often escalate quickly. Fever (104-106 F), moist cough, “red eyes,” and significant nasal discharge are the hallmarks of this more dangerous form. In addition, there is general malaise, lack of energy, and possibly increased respiratory rate and effort. The lining of the lungs becomes inflamed and “leaky,” such that fluid and blood may enter the lower airways. This often leads to the complication of bacterial pneumonia and reduced oxygenation which can be life-threatening.

DIAGNOSIS: If you suspect that your dog has a respiratory infection, contact your veterinarian. Diagnosis is generally made from a physical examination of the pet, plus supporting evidence such as an elevated white blood cell count, and abnormalities visible on chest (thoracic) x-rays. Specific tests that detect viral infection include virus isolation, antibody detection, or PCR nuclei acid assays, but the lag time for test results (or false negatives) can be problematic.

TREATMENT: Fortunately, treatment for dogs who are systemically ill with respiratory infections does not depend on identifying the specific infection per se. Therefore, hospitalization with 24-hr. care would be recommended for patients in this category. Your dog would likely receive intravenous antibiotics (for secondary bacterial infections), fluid therapy, anti-inflammatories, and careful monitoring. For some patients (especially very young or very elderly ones), supplemental oxygenation and nebulization (medications delivered directly into the airways by aerosols) may be recommended. Tamiflu ® is an antiviral drug used in human medicine but has apparent utility in treating canines as well. With appropriate treatment and support care, rapid recovery can be achieved in all but 10% of patients.

PREVENTION: Because the influenza viruses are highly contagious, keep an eye out for news reports regarding outbreaks in your region. It is of note that a few cases have been reported in Massachusetts and Connecticut, so the threat exists for dog owners in Maine. Dogs that travel, that are boarded, or that frequent public places have a higher risk of exposure. The influenza viruses can survive 48 hrs. on surfaces and 12-24 hrs. on clothing or hands. Any dog suspected to have the flu should be isolated from other dogs (and cats) for at least 30 days.

There is now a combination H3N2 & H3N8 vaccine that is approved for use in dogs over 7 weeks of age. The initial vaccination is followed by a booster in 3-4 weeks and is generally well tolerated. An annual booster is recommended as immunity is not long lasting. While no vaccine is 100% effective, it can greatly reduce your dog’s chances of developing severe respiratory disease. Consider talking with your veterinarian to assess if the vaccination is recommended for your pup. Here’s hoping for a “sneeze free” season for you and your best friend!


Gail D. Mason, DVM, MA, DACVIM

Small Animal Internal Medicine/

Portland Veterinary Specialists