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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 veterinary 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 infectious 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 percent of 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 10-21 days despite therapy with antibiotics and
cough suppressants. Most dogs have a soft, moist cough, while others have a
dry cough similar to that induces by the Bordetella
bronchieseptical/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, bacterial antibiotic.
Some dogs develop a more severe disease with clinical
signs of pneumonia, such as a high fever (1040F to 1060F) 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 low, 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 to 10 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.
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.
Paired acute and convalescent serum samples are necessary for diagnosis of
recent infection. The convalescent sample is collected at least two weeks
after the acute sample. There are many situations in which collection of an
acute sample is not feasible. In this case, testing of a convalescent sample
will indicate whether the dog was infected at some time in the past.
Serology tests not only indicate if a dog was infected, but also serve to
alert veterinarians that the virus is present in their community so they can
take precautions with dogs presenting for “kennel cough.”
In addition to serology, the lungs and distal trachea
from dogs that died of pneumonia can be tested for influenza virus by PCR
analysis and virus culture.
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 10 percent 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”. |
