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An
Overview of Canine Kennel Cough Complex
Infectious
tracheobronchitis (ITB), more commonly referred to as “kennel
cough,” is an acute, highly contagious respiratory infection.
The disorder affects the larynx, trachea, bronchi, and sometimes spreads
to the nasal mucosa, lower airways, and lungs. The infection may be
triggered by a variety of different pathogens, but canine adenovirus
type-2 (CAV-2), and the bacteria Bordetella bronchiseptica
are among the most prevalent. Vaccination and other preventative measures
have rendered ITB less common than it once was. Thankfully, most cases
of ITB come to a natural end and are not fatal.
Why and how might my dog become infected?
Whether
an individual dog becomes infected is a result of a complex interaction
between the animal, the pathogen, and the environment. If each factor
is just right, an animal will contract a virus, bacteria, or both and
become ill.
Transmission
of both B. bronchiseptica and CAV-2 is aerosol; the bacteria
are suspended in the air and enter the body and respiratory system via
the nose or mouth. Because direct contact is not necessary for the virus
or bacteria to be passed from one animal to another, ITB in general
and B. bronchiseptica and CAV-2 more specifically are highly
contagious.
It has
been speculated that an initial invasion of a viral pathogen clears
the way and makes infection with disease-causing bacteria easier. Once
in the body CAV-2 particles invade and irritate the respiratory system.
B. bronchiseptica bacteria form attachments to the respiratory
cilia, irritating and reducing the effectiveness of the respiratory
system. In addition, the bacterium secretes a substance that likely
serves to decrease the effectiveness of the body’s immune response,
allowing for the bacteria to live longer.
Incubation
time between day of infection and day of onset of symptoms often varies.
The disease is not systemic and will not affect other organs or parts
of the body.
How will my vet reach a diagnosis of ITB? How can he tell which
pathogen is the cause of the disease?
Most cases of ITB are labeled “uncomplicated” and
usually clear up spontaneously within 2 weeks. Symptoms commonly associated
with uncomplicated ITB include a dry, hacking cough followed by retching.
The cough has a sudden onset, is frequently paroxysmal,
and may produce a sort of high pitched “honking” sound.
The retching is generally accompanied by the production of a white,
foamy, mucoid discharge. Nasal discharge and conjunctivitis
may also occur. Appetite and energy level remain generally unchanged.
Dogs that
develop “complicated” ITB often have an underlying airway
or immunosuppressive
disorder. These more severe cases may include pneumonia or bronchopneumonia
and can prove life-threatening. Symptoms in dogs with complicated ITB
range from shortage of breath (dyspnea) and lethargy to weight loss,
fever, and decreased appetite.
Diagnosis
of ITB is based primarily upon clinical observations and history of
exposure to other dogs.
Laboratory
tests are often inconclusive and nonspecific. It is however possible
to determine the exact pathogen
behind the infection using isolation techniques on swabs from the respiratory
tract.
What are the treatment options for dogs with ITB?
Treatment
options for dogs suffering from ITB are varied. Glucocorticoids
may be administered as anti-inflammatories to help alleviate coughing.
These drugs may also reduce the volume of mucoid secretions, though
they do not shorten the course of the disease.
Antitussives,
when used in conjunction with bronchodilators, are often considered
the standard treatment for dogs with ITB. Antitussive drugs serve to
interrupt the cough cycle. Care must be used when administering narcotic
cough suppressants however, as excessive use may cause the animal to
have difficulty breathing. Bronchodilators are not especially effective
when used alone, but when used together with antitussives they can prevent
bronchospasm and thus serve as effective cough suppressants.
Finally,
dogs with excessive accumulations of respiratory secretions may benefit
from aerosol therapy. Here liquid is suspended in a carrier gas and
animals are given medication or antibiotics with a nebulizer.
This procedure must be completed in hospital. Though as with all treatments
aerosol therapy cannot completely eliminate symptoms, it can make them
less severe and in turn make the patient more comfortable.
Beyond
these specific treatments, supportive care is administered with the
aim of maintaining caloric and fluid intake and preventing any secondary
infections.
Is it possible to vaccinate my pet against pathogens that cause
kennel cough?
Vaccines
are complex substances and often raise many questions. For information
about vaccines in general, please goto An
Introduction to the World of Vaccines.
CAV-2
vaccines are administered as part of the combination shot meant to target
canine distemper and parvovirus. The majority of B. bronchiseptica are
packaged and administered separately from the combination shot. Vaccination
cannot totally prevent development of disease and will not forestall
ITB caused by other pathogens, but it will reduce the severity of clinical
signs to a much more manageable level. Vaccines for CAV-2, B. bronchiseptica
and other major canine pathogens are given every 3-4 weeks from the
time a puppy is 6 weeks old until he is at least 16 weeks of age.
How else can I help prevent the disease?
ITB did
not garner the nickname “kennel cough” out of coincidence.
Any environment in which large numbers of dogs are housed in potentially
ill-ventilated buildings creates an ideal environment for the spread
of this disease.
In order
to minimize the risk of an ITB outbreak, population densities of kennels
or other similar operations should be kept at a minimum. Further, ventilation
in all buildings that house dogs should be maximized.
If a confined
outbreak occurs within a kennel, infected animals should be isolated
and handlers should wear clean, disposable gloves whenever interacting
with the afflicted dogs.
All kennels
should be disinfected regularly with a bleach solution.
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