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Canine Influenza

H3N8

What is Canine Influenza?
Canine influenza (CIV) is a highly contagious respiratory infection in dogs. CIV is caused by an influenza virus, type A H3N8. The H3N8 strain originated in horses over forty years ago before it jumped species (from horses to dogs) to form a new canine-specific virus. CIV was first discovered among racing greyhounds at a Florida racetrack in 2004. From June to August of 2004, outbreaks of the disease were reported at fourteen tracks across six states (Florida, Texas, Alabama, Arkansas, West Virginia, and Kansas). Since then, canine influenza has been documented in thirty states and Washington, D.C., with the most prevalent in areas of Florida, Colorado, New York, and Pennsylvania.
Symptoms and Severity of Canine Influenza Virus
Virtually all dogs that are exposed to CIV become infected, but about 80% develop clinical signs of disease. The approximate 20% that do not show signs of disease can still shed the virus and spread infection. The majority of dogs infected show a mild form of CIV. In the mild form, the most common clinical symptoms are: a persistent cough, runny nose, and fever. A small proportion of dogs can develop serious illness such as, pneumonia, high grade fever, and increased respiratory rate and effort. Deaths occur mainly in dogs with the severe form of the disease and the mortality rate is thought to be 1-5%. Higher case fatality rates have been reported in small groups of the greyhounds that developed hemorrhagic pneumonia during outbreaks.
Diagnoses and Treatment
Diagnosing CIV cannot be done solely by clinical signs, because the symptoms (coughing, nasal discharge, and sneezing) are similar to those associated with all of the other respiratory diseases. Antibodies to CIV may be detected in the blood as early as seven days after symptoms occur, the virus may be identified in nose or throat swabs during the first four days of illness. The most reliable and sensitive method for confirmation of infection is through blood testing.

Since CIV is a viral infection, treatment consists mainly of supportive care while the virus runs its course. In the milder forms of disease, this care may include either IV or subcutaneous fluids to avoid dehydration. Broad spectrum antibiotics may be prescribed if a secondary infection is suspected. Most dogs recover from canine influenza within 2 - 3 weeks.
Prevention and Control
Canine influenza virus can be spread by direct contact with infected dogs, by contact with contaminated objects, and by people moving between infected and non-infected dogs. Dog owners whose dogs are coughing, or showing other signs of respiratory infection should not participate in activities or bring their dogs to pet facilities where other dogs can be exposed to the virus. The CIV appears to be easily killed by disinfectants commonly used in veterinary and boarding facilities such as ammonia or bleach solutions. Protocols should be established for thoroughly cleaning and disinfecting cages, bowls, and other surfaces between uses. The virus may be persistent in the environment for about two days and on clothing for up to 24 hours. CIV is very contagious, infected dogs can shed the virus for 7-10 days, during which the time the dog is contagious to other dogs. Dogs that have been exposed or showing any signs of respiratory disease should be isolated for two weeks.

In May 2009, the USDA approved for licensure the first influenza vaccine for dogs. The vaccine is intended as an aid in the control of disease associated with CIV. Like the flu shot for humans, the CIV vaccine may not prevent infection altogether, but efficacy trials have shown that the vaccination may significantly reduce the severity and duration of the illness. In addition, the vaccine reduces the amount of virus shed and shortens the shedding interval. Vaccinated dogs that become infected develop less severe illness and are less likely to spread the virus to other dogs.
Which Dogs Should Get the Canine Influenza Vaccine?
The canine influenza vaccine is a “lifestyle” vaccine and is not recommended for every dog. In general, the vaccine is intended for the protection of dogs at risk to exposure of CIV. Dogs at risk include dogs that participate in activities with many other dogs (i.e. doggie daycare, or dogs that go to dog parks), dogs that do grooming, and dogs that do any boarding at kennel or resort facilities. Dogs that may benefit from the CIV vaccine include those that already receive the Bordetella/ Para influenza, also known as the kennel cough vaccine, because the risk groups are similar. Dog owners should consult with their veterinarian to determine whether their dog’s lifestyle includes risks for exposure to the canine influenza virus, and if the vaccine is appropriate for their dog.
Courtesy of AVMA “Canine Influenza Virus Backgrounder” 09/07/09