Canine influenza is a highly contagious respiratory infection of dogs that is caused by a virus. The canine influenza virus is closely related to the virus that causes equine influenza and it is thought that the equine influenza virus mutated to produce the canine influenza virus.
Two clinical syndromes have been seen in dogs infected with the canine influenza virus, a mild form of the disease and a more severe form that is accompanied by pneumonia.
- About the mild form—Dogs suffering with the mild form of canine influenza develop a soft, moist cough that persists for 10 to 30 days. Some dogs have a dry cough similar to the “kennel cough” caused by Bordetella bronchiseptica/parainfluenza virus complex. For this reason, canine influenza virus infections are frequently mistaken for “kennel cough.” Dogs with the mild form of influenza may also have a thick nasal discharge, which is usually caused by a secondary bacterial infection.
- About the severe form—Dogs with the severe form of canine influenza develop high fevers (104ºF to 106ºF) and have clinical signs of pneumonia, such as increased respiratory rates and effort. Pneumonia may be due to a secondary bacterial infection.
Because this is a newly emerging disease, almost all dogs, regardless of breed or age, are susceptible to infection and have no immunity. Virtually all dogs that are exposed to the virus become infected and nearly 80% show clinical signs of disease. Fortunately, most affected dogs have the mild form.
Fatal cases of pneumonia resulting from infection with canine influenza virus have been reported in dogs, but the fatality rate (5% to 8%) has been low so far.
The first recognized outbreak of canine influenza in the world is believed to have occurred in racing greyhounds in January 2004 at a track in Florida. From June to August of 2004, outbreaks of respiratory disease were reported at 14 tracks in 6 states (Alabama, Arkansas, Florida, Kansas, Texas, and West Virginia). Between January and May of 2005, outbreaks occurred at 20 tracks in 11 states (Arizona, Arkansas, Colorado, Florida, Iowa, Kansas, Massachusetts, Rhode Island, Texas, West Virginia, and Wisconsin). Infection has also been confirmed in pet dogs in California, Connecticut, Florida, Georgia, Massachusetts, North Carolina, New Jersey, New York, Ohio, Oregon, Pennsylvania, Washington State, and Washington, DC. These cases occurred in animal shelters, humane societies, rescue groups, pet stores, boarding kennels, and veterinary clinics.
As with any disease caused by a virus, treatment is largely supportive. Good animal care practices and nutrition assist dogs in mounting an effective immune response. In the milder form of the disease, a thick green nasal discharge, which most likely represents a secondary bacterial infection, usually resolves quickly after treatment with a broad-spectrum bactericidal antimicrobial. In the more severe form of the disease, pneumonia is thought to often be caused by bacterial superinfection, and responds best to hydration (sometimes via intravenous administration of fluids) and a broad-spectrum bactericidal antimicrobial.
Canine influenza is not known to be transmissible from dogs to people. However, caretakers can inadvertently transmit canine influenza virus from infected dogs to susceptible dogs by not following good hygiene and infection control practices. To prevent spread of canine influenza virus, caretakers should take the following precautions:
- Wash hands with soap and water (if soap and water are unavailable, use an alcohol-based hand cleaner)
- Before and after handling each animal
- After coming into contact with animal saliva, urine, feces or blood
- After cleaning cages
- Before eating meals, taking breaks, smoking or leaving the facility
- Before and after using the restroom
- Before and after handling each animal
- Wear a barrier gown over your clothes and wear gloves when handling sick animals or cleaning cages. Discard gown and gloves before working with other animals
- Consider use of goggles or face protection if splashes from contaminated surfaces may occur
- Bring a change of clothes to wear home at the end of the day
- Thoroughly clean clothes worn at the animal facility
- Do not allow animals to “kiss” you or lick your face
- Do not eat in the animal care area
- Separate newly arriving animals from animals that have been housed one week or longer.
- Routinely monitor animals for signs of illness. Separate sick animals from healthy animals, especially animals with signs of respiratory disease.
- There is no evidence of transmission of canine influenza virus from dogs to people. However, because of concerns about diseases that are transmissible from dogs to people, in general, it may be prudent for young children, the elderly, pregnant women, and immunocompromised persons to limit or avoid contact with animals that are ill.