10 Things to Know About the H3N8 Dog Flu
Dr. Cynda Crawford, DVM, PhD
Q: What is canine influenza?
A: Canine influenza is a highly contagious respiratory infection of dogs caused by a novel influenza virus that was first discovered in 2004. We do not use the general term "dog flu" because it could refer to any flu-like illness in dogs due to various causes. Rather, canine influenza is a specific disease caused by a particular subtype, H3N8, of the influenza A virus.
Q: Where does influenza occur?
A: Canine influenza has been documented in 30 states and the District of Columbia. At this time, the canine influenza virus is prevalent in Colorado, Florida, New York and Pennsylvania. There is no evidence that canine influenza H3N8 is currently infecting dogs in other countries.
Q: What type of infection does canine influenza virus cause?
A: Like influenza viruses that infect other mammals, canine influenza virus causes an acute respiratory infection in dogs. It is one of several viruses and bacteria that are associated with canine infectious respiratory diseases, or what is commonly referred to as "kennel cough". The canine influenza virus can cause respiratory disesase by itself or along with other canine respiratory pathogens. Unlike human influenza, canine influenza is not a "seasonal" infection and infections occur year round.
Q: What are the symptoms and clinical signs of canine influenza?
A: Like influenza viruses in other species, canine influenza virus causes a flu-like illness consisting of cough, sneezing, mucoid nasal discharge. Fever can also occur but is usually transient and rarely is noticed by pet owners. There are no clinical signs that distinguish canine influenza from other respiratory infections. That is why diagnostic tests must be performed to determine the cause of the respiratory infections in dogs. Virtually all dogs exposed to the canine influenza virus become infected; about 80% develop flu like symptoms while the remaining 20% do not become ill. Fortunately, most dogs recover within two weeks without further health complications. However, some dogs progress to pneumonia, which is usually due to secondary bacterial infections. While the death rate for canine influenza is very low, the secondary pneumonia can be life-threatening in some cases. There is no evidence that dogs of particular age or breed are more susceptible to developing pneumonia from canine influenza.
Q: Who is susceptible to canine influenza?
A: Because canine influenza is due to a virus that is novel to the canine population, dogs lack preexisting immunity to the virus. Dogs of any breed, age, or vaccination status are therefore susceptible to infection. It is likely that dogs that have recovered from infection retain immunity to re-infection for an undetermined time period, although studies have not verified how long. Canine influenza is most likely to spread in facilities where dogs are housed together and where there is a high turnover of dogs in and out of the facility. Dogs in shelters, boarding and training facilities, day care centers, veterinary clinics, pet stores, and grooming salons are at highest risk for exposure to the virus. Dogs that mostly stay at home and walk around the neighborhood are at low risk. Canine influenza virus does not infect people, and there is no documentation that cats have become infected by exposure to dogs with canine influenza.
Q: How is canine influenza transmitted?
A: As with other respiratory pathogens, the most efficient transmission occurs by direct contact with infected dogs and by aerosols generated by coughing and sneezing. The virus can also contaminate kennel surfaces, food and water bowls, collars and leashes, and the hands and clothing of people who handle infected dogs. Fortunately, the virus is easily inactivated by washing hands, clothes and other items with soap and water.
Q: How is canine influenza treated?
A: Since canine influenza is a viral infection, treatment consists mainly of supportive care while the virus runs its course much like human influenza. Supportive care includes IV fluids, IV antibiotics for secondary bacterial infection, nebulization, and coupage.
Q: How is canine influenza diagnosed?
A: Canine influenza cannot be diagnosed by clinical signs because other respiratory pathogens cause similar signs of coughing, sneezing and nasal discharge. For dogs that have been ill for less than four days, a swab from the nose or throat is submitted for PCR testing. The most accurate method for confirmation of infection is a blood sample drawn during the first week of illness followed by a second sample drawn 10-14 days later. The paired serum samples are submitted to a diagnostic laboratory for measurement of antibodies to canine influenza virus that were found in response to infection.
Q: Is there a vaccine for canine influenza?
A: In May, 2009 the United States Department of Agriculture approved for licensure the first influenza vaccine for dogs. The canine influenza vaccine contains inactivated whole virus, so there is no chance that the vaccine will cause a respiratory infection. During tests to evaluate vaccine performance, there were no side effects or safety issues in a field trial of more than 700 dogs ranging in age from 6 weeks to 10 years and representing 30 breeds. The vaccine is intended as an aid in the control of canine influenza virus infection. Although the vaccine may not prevent infection, it does significantly reduce the severity and duration of clinical illness including the incidence and severity of damage to the lungs. In addition, the vaccine reduces the amount of virus shed and shortens the shedding interval. This means that vaccinated dogs that become infected are less likely to have severe symptoms and are not as contagious to other dogs. These benefits are similar to those provided by influenza vaccines used in other species, including people. The canine influenza vaccine is intended for dogs who go to a boarding facility, groomer, dog day care, or show events.
Q: How do I get an influenza vaccine for my dog?
A: The vaccine is available at Yorkshire Veterinary Clinic and the cost is $20. The vaccine is given once and is boostered 2-4 weeks later and then given yearly thereafter. If your pet has not been seen within the past year then an examination will need to be performed prior to the administration of the vaccine.