Canine Influenza Virus Alert

Situation:  University of Florida researchers report that outbreaks of canine influenza virus, which causes an acute respiratory infection, have been identified in dogs in shelters, humane societies, boarding facilities, and veterianry clinics in Florida, predominantly in Broward, Dade, Palm Beach, and Duval counties.  This highly contagious virus is a newly emerging respiratory pathogen in dogs and causes a clinical syndrome that mimics "kennel cough".  Canine influenza virus infections are frequently mistaken for infections due to the Bordetella bronchiseptica/parainfluenza virus complex.

Clinical Signs:  Because this is a newly emerging pathogen, all dogs, regardless of breed or age, are susceptible to infection and have no naturally acquired or vaccine-induced immunity.  Virtually 100% of exposed dogs become infected.  Nearly 80% have clinical signs.  There are two general clinical syndromes-the milder syndrome and the more severe pneumonia syndrome.  The milder disease syndrome occurs in most dogs.

In the milder disease, the most common clinical sign is a cough that persits for 10-21 days despite therapy with antibiotics and cough suppressants.  Most dogs have a soft, moist cough, while others have a dry cough similar to that induced by Bordetella bronchiseptica/parainfluenza virus infection.  Many dogs have purulent nasal discharge and a low-grade fever.  The nasal discharge likely represents a secondary bacterial infection that quickly resolves with treatment with a broad-spectrum, bactericidal antibiotic.

Some dogs develop a more severe disease with clincal signs of pneumonia, such as a high fever (104F-106F) and increased respiratory rate and effort.  Thoracic radiographs may show consolidation of lung lobes.  Dogs with pneumonia often have a secondary bacterial infection and have responded best to a combination of broad-spectrum, bactericidal antibiotics and maintenance of hydration with IV fluid therapy.

Fatality Rate: Fatal cases of pneumonia have been documented, but the fatality rate so far is low, at 1%-5%.

Incubation/Shedding Period:  The incubation period is two to five days after exposure before clinical signs appear.  Infected dogs may shed virus for 7-10 days from the initial day of clinical signs.  Nearly 20% of infected dogs will not display clinical signs and become the silent shedders and spreaders of the infection.

Diagnosis:  There is no rapid, real-time test for diagnosis of dogs with an acute influenza virus infection.  Current diagnostic tests rely on detection of antibodies to canine influenza virus, which are detected as early as seven days after onset of clinical signs. 

Prevention: There is no vaccine for canine influenza virus at this time.  This virus is spread by aerosolized respiratory secretions, contaminated inanimate objects, and even by people moving back and forth between infected and uninfected dogs.  This is an enveloped virus that is most likely killed by routine disinfectants.  Because the virus is highly contagious and all dogs are susceptible to infection, veterinarians, boarding facilities, shelters, and pet stores should use isolation protocols for dogs that have "kennel cough".

Contact Hallett Veterinary Hospital with any questions or concerns you have about canine influenza.