SITUATION: 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 veterinary clinics in throughout the USA.
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, alt dogs, regardless of breed or age, are susceptible
to infection and have no naturally acquired or vaccine-induced
immunity. Virtually all exposed dogs become infected. Nearly 80
percent have clinical signs. There are two general clinical syndromes
- the milder syndrome and a 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 persists for 10 to 30 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 Bordatella 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
clinical signs of pneumonia, such as a high fever (1 040F to 1
060F) 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 intravenous fluid therapy.
FATALITY RATE: Fatal cases of pneumonia
have been documented, but the fatality rate so far is at 1 percent
to 5 percent.
INCUBATION/SHEDDING PERIOD: The incubation
period is two to five days after exposure before clinical signs
appear. Infected dogs may shed virus for seven days from the initial
day of clinical signs. Nearly 20 percent of infected dogs will
not display clinical signs and become the silent shedders and
spreaders of the infection.
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, such as quaternary ammoniums and dilute
bleach. 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 a “kennel cough.”
