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
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 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 to 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 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.
WHAT VETERINARIANS CAN DO:
Veterinarians can submit serum samples for canine influenza antibody
titers. Paired acute and convalescent samples are preferable for
confirmation of infection, while single samples collected after
seven days of clinical disease are also useful. In addition to
determining infection, these samples will contribute toward virus
surveillance in Florida. Currently, there is no fee for this
testing. The turnaround time for results is less than two weeks.
Please see the ""Serum Collection and Shipping"" form for further
instructions.
Veterinarians may also submit fresh (no formalin or freezing) lung
and tracheal tissues from dogs that die from pneumonia. Canine
influenza virus culture and PCR analysis will be performed on these
tissues. Virus recovered from these samples will greatly contribute
toward development of vaccines and diagnostic tests. If you have
samples for submission, please contact Dr. Cynda Crawford for
instructions on handling of the tissues.
FOR MORE INFORMATION: Contact Dr.
Crawford in the Department of Small Animal Clinical Sciences at the
University of Florida College of Veterinary Medicine for sample
submission via phone (352) 392-4700, ext. 5731; fax (352) 392-6125;
or e-mail crawfordc@mail.vetmed.ufl.edu.
