Infectious Canine Tracheobronchitis, Not Kennel Cough
“Kennel cough” is a misnomer.
No one knows how the name got started, but it’s simple and maybe a little catchy. so it stuck. One of the problems with the name is that the vast majority of the dogs afflicted with “kennel cough” have never even seen a kennel.
The syndrome is correctly termed ITB, or Canine Infectious TracheoBronchitis. Some experts also call it Canine Cough Syndrome. It is a complex disease. There are three main players: two viral and one bacterial. To further complicate matters, many lesser organisms may or may not be present in a given case of ITB.
The name Infectious Tracheobronchitis describes the body parts affected. “Itis” means inflammation. “Tracheo” refers to the windpipe or trachea and “bronch” refers to the bronchi, or first branches from the trachea. In uncomplicated cases of ITB the harsh, hacking cough typical of the disease results from inflammation of these parts of the airway.
Canine Parainfluenza Virus is a member of the Paramyxoviridae family of viruses. It is the first contributor to ITB for which we had a vaccine. You may remember it as part of the DHL”P” vaccine your dog got twenty years ago. Alone it can cause only the mildest of signs.
Later it was discovered that a “cousin” to the canine adenovirus that causes one form of hepatitis in dogs (CAV1) was a component of ITB. Its name, not surprisingly, is CAV2. Because CAV2 confers protection against CAV1-hepatitis, most vaccines now contain only CAV2. Therefore, the old DHLP vaccine is now called DA2LP. Adenovirus Type 2, alone, can cause only a mild and short-duration cough.
In the layman’s mind the vaccination for Bordetella bronchiseptica is “the kennel cough shot.” In fact, your dog can have a case of ITB without Bordetella even being a component of his particular case. That said, the worst cases of ITB typically do have Bordetella involved. While it was once thought that Bordetella could be only a secondary invader to a respiratory tract already infected by Parainfluenza and/or CAV2, researchers now know that Bordetella has no difficulty causing infection all on its own.
Bordetella induces illness by attaching itself to the cilia of the airway. Cilia are microscopic hairs lining the airway. They are a structure on the cells in that lining. They wave back and forth like tiny blades of seagrass and are charged with the duty of moving mucus and foreign materials up and out of the airway. Bordetella’s attachment to this organ interferes with its function, allowing materials normally transported out of the respiratory tract to build up.
Exotoxins are also produced by B. bronchiseptica. These toxins affect not only the lining cells of the respiratory tract but the protective mechanisms as well.
The cough associated with ITB is frequently described as “trying to cough something up,” or having “something caught in my dog’s throat.” Mucus and debris coughed up is usually swallowed by the canine patient, whereas a human patient with a similar infection would expectorate.
Coughing is actually curative in ITB cases not infected with Bordetella. The coughing action can remove CAV2 and Parainfluenza viruses and the patient can recover in as little as two weeks. Bordetella-complicated cases, however, require treatment and may remain infected for months.
Two forms of the condition occur. “Complicated” ITB is usually seen in patients with weak immune systems such as young puppies or dogs ill with other conditions such as concurrent illness, cancer, chemotherapy or other medications that suppress the immune system. Pneumonia is a common complication and in some cases may even be fatal.
“Uncomplicated” ITB would, by definition, not include Bordetella bronchiseptica as a component and would be a self-limiting disease that cured itself in about two weeks. However, this is purely an academic scenario, because in the real world Bordetella, Mycoplasma and other organisms commonly “complicate” the “uncomplicated” case, quickly turning your pet into a very sick puppy or dog.
Cats may also experience Bordetellosis. Those cats not too fastidious to associate with dogs may become infected that way. Likewise, cats can also infect dogs with the same organism, though infection and disease in cats is less common than in dogs.
Treatment usually consists of oral antibiotics. Severe cases may also be treated by nebulizing or aerosolizing antibiotics directly into the respiratory tract. Any of several cough suppressants may be used to break the coughing cycle. Rest is important to conserve energy needed for healing as well as to avoid inducing cough. If your dog must be walked during this illness be sure to use a harness that goes around his chest so as to avoid pressure on the cervical trachea that a collar would cause.
Complicated cases, especially those which have progressed to pneumonia, need rest, antibiotics, intravenous (IV) fluid therapy and bronchodilators.
Prevention is primarily through vaccination and avoidance of filthy conditions. Both injectable and intranasal Bordetella vaccination may take up to five days to effect protection, so be sure vaccinations are updated well in advance of boarding opportunities, dog shows or any other situation that puts your pet in contact with “strangers.” Vaccines should be repeated every six to twelve months.
See you tomorrow, Dr. Randolph.