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.
Additional resources on the web:
Pet owners may find this article at VeterinaryPartner.com helpful.
The veterinary college at the University of California at Davis provides suggestions and sample protocols for managing infectious tracheobronchitis in shelters. It also contains information for foster homes, a sample client information handout, and Bordetella antibiotic resistance patterns.
Dr. Brad Fenwick at the Kansas State University College of Veterinary Medicine has produced an excellent scientific overview of ITB, including causative pathogens, available vaccines, and current research. A similar but slightly more detailed article is available to veterinarians from the International Veterinary Information Service. The Merck Veterinary Manual discusses many of the clinically relevant aspects of ITB.
For information on specific vaccines, visit the manufacturers' websites: