Pawsitively Helpful Pet Tips

with DR. DEB


CAUSITIVE AGENT: Dog flu is a highly contagious infection caused by an influenza virus.  The two known strains are H3N8 and H3N2.

The first canine flu outbreak in the US occurred in 2004 and involved racing greyhounds caused by H3N8 virus.

This year, a canine flu outbreak in Chicago and other parts of the Midwest, is associated with a new strain of the virus to the US--an H3N2 virus originating in Asia.

TRANSMISSION:  Outbreaks are more commonly seen in situations where groups of susceptible dogs are in close contact such as shelters, kennels, dog daycare facilities, and boarding facilities.

The two strains of canine are not contagious to humans, but the newer H3N2 virus has been associated with infection and respiratory illness in cats. 

Canine flu is spread via aerosolized respiratory secretions and contaminated objects ( kennel surfaces, food and water bowls, collars, and leashes), and people moving between infected and uninfected dogs.  The virus can remain alive and able to infect on surfaces for up to 48 hours, on clothing for 24 hours and on hands for 12 hours.

The incubation period is usually 2-4 days from exposure to onset of clinical signs.  The highest amount of viral shedding occurs during this time--therefore dogs are most contagious during this 2-4 day incubation when they are not exhibiting any signs of illness.  Though the amount of virus shedding decreases after the first 4 days it will continue up to 7-10 days.

As an emerging pathogen, all dogs are susceptible to inflection as they have no naturally acquired or vaccine induced immunity when first exposed to canine flu.  Virtually all dogs exposed in a closed group, such as a kennel, will become infected.  Most dogs have a miler form of canine flu and recover without complications, though some may develop severe pneumonia.  About 20-25% of infected dogs will have no symptoms but still shed and spread the virus.

CLINICAL SIGNS: Common signs of canine flu include sinus inflammation, sore throats, and bronchitis.  Due to damage to the lining cells of the respiratory tract by the flu virus, secondary bacterial infections occur contributing to nasal discharge, and coughing.

Unlike other mammalian flu viruses, canine flu virus is not "seasonal" flu--infections occur year round.

Canine flu virus infection often resembles the illness known as kennel cough.  In mild versions of flu a common clinical sign is a cough that persists for 10-21 days despite treatment with antibiotics and cough suppressants.  Nasal and/or ocular discharge, sneezing, lethargy, fever, and lack of appetite may be seen.

Severe infections can result in bronchopneumonia and some dogs can die.

DIAGNOSIS: Specific tests must be submitted to outside labs for an absolute diagnosis of canine flu.

TREATMENT: As for all viral diseases, treatment is largely supportive including good husbandry and nutrition.  Most dogs recover from canine flu within 2-3 weeks.  The presence of secondary bacterial infection, pneumonia, dehydration, or other health factors (such as pre-existing lung disease) may warrant more aggressive veterinary care.

Antibiotics, non-steroidal anti-inflammatory medications, fluids to correct dehydration and cough suppressants are often part of the treatment for canine flu.

PREVENTION: Isolation protocols of at least 2 weeks are very important  once dogs show clinical signs of respiratory disease.  If outbreaks of canine flu occur, avoid group settings where close contact with other dogs can occur such as dog parks.

There are currently two H3N8 canine influenza vaccines available.  Much like the human flu vaccines, the canine flu vaccines are intended to aid in the control of disease by significantly reducing the severity and duration of clinical illness.  In addition, the vaccine reduces the amount of virus shed and shortens the shedding interval.  Therefore, vaccinated dogs that become infected develop less severe illness and are less likely to spread the virus to other dogs.

There is no US commercial vaccine for the newest H3N2 strain of canine influenza virus, and it is not yet known whether the H3N8 vaccines will provide any cross-protection against H3N2.

The canine flu 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 for exposure to the canine influenza virus, which include those that either participate in activities with many other dogs, or are housed in communal facilities, particularly where the virus is prevalent. Dog owners should consult their veterinarian to determine whether their dog's lifestyle includes risks for exposure.

Unfortunately, canine flu vaccine is very short supply presently.

We will continue monitoring recommendations for AVMA regarding canine flu.

Thank you to The American Veterinary Medical Association for the information above.


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