Let’s just get it out there: for a dog, coughing is never “normal.”
As a small-animal veterinarian, I hear this all the time. Clients tell me that their dog has been coughing for a while/off and on/when he’s excited/after pulling on the leash/after going to the groomer and so forth, but that they think he’s “okay.” However, a healthy dog should not cough, and a history of coughing always raises a red flag with me.
Coughing is caused by an irritation or inflammation of one or more of the dog's respiratory organs. A problem anywhere in that system—the larynx, in the back of the throat; the windpipe; the airways (bronchi); or lungs—can cause your dog to cough. Heart disease, which is closely tied to the lungs and airways, also causes coughing.
Sometimes, the cause of a dog coughing is benign, like a small bout of tracheobronchitis (an infectious inflammation of the airways more commonly referred to as kennel cough) that resolves easily with medication and has a vaccine (Bordetella). Sometimes, the cause is more sinister; collapsing airways, pneumonia, a piece of grass or bone stuck in the back of the throat, parasites, the previously mentioned heart disease, laryngeal paralysis or a cancerous tumor that is pushing on respiratory structures can all cause a dog to cough.
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Why Dogs Cough
When coughing is due to a problem in the laryngeal area, it can be a real pain in the neck, both literally and figuratively, and new research is showing that more coughing dogs have laryngeal problems than previously thought.
The anatomy of a dog’s throat is much the same as that of a human’s. The larynx (the area between the nose and the trachea), trachea (windpipe), epiglottis (a flap of cartilage at the root of the tongue that is depressed during swallowing to cover the opening of the windpipe) and esophagus are the same in both. As well as housing the voice box, the larynx serves to protect the lower airways—trachea, bronchi and lungs —from foreign material and germs. The larynx is lined with secretory membranes, and comprises muscles, cartilage and ligaments.
Laryngitis in Dogs
Like humans, dogs can develop laryngitis, an inflammation and swelling of the larynx secondary to infection, irritation by dust or smoke, inhaled foreign bodies (grass, bones), or trauma due to excessive barking or pulling against a collar. Older dogs can also develop laryngeal paralysis, a condition in which the muscles that move the arytenoid cartilages (a pair of pyramidshaped pieces of cartilage that open and close during breathing) stop working.
Dogs with laryngeal disorders typically exhibit what are called “upper airway signs” such as changes in their bark; loud breathing that sounds like “roaring”; and a dry, hacking cough that can be exacerbated by pressure on the larynx. Other upper airway signs that clue veterinarians into a laryngeal problem include difficulty swallowing, bad breath and an extended neck. A dog with laryngitis looks like he has a sore throat. When veterinarians see these signs, we suspect laryngeal disease and point our efforts in that direction. If we don’t see them, we look for other causes of coughing farther down the respiratory tract
Generally, coughing dogs are not extensively evaluated for problems with their larynx. However, a study conducted by Lynelle Johnson, DVM, PhD, at the University of California, Davis, School of Veterinary Medicine and recently published in the Journal of the American Veterinary Medical Association* showed the importance of checking all chronically coughing dogs for signs of laryngeal issues. What’s interesting about the UC Davis study is that it found that a majority of coughing dogs who didn’t exhibit classical upper airway signs associated with the larynx had a laryngeal disease that may have gone undiagnosed. This study showed that they should be, and that we should be aware of the possibility of a hidden condition.
To investigate the prevalence of laryngeal abnormalities in this class of coughing dogs, Dr. Johnson enrolled 138 dogs in the study, which lasted for 13 years. Dogs were assigned to one of three groups, based on the duration of their cough: acute (less than two weeks), subacute (two weeks to two months) and chronic (more than two months). As part of the study, the dogs were sedated and their throat and airways were examined via endoscope (a medical device with a light attached), a procedure also known as “scoping.”
Interestingly, Dr. Johnson found that 19 percent of the dogs examined because of cough alone (no upper-airway signs) also had some form of laryngeal dysfunction, ranging from laryngitis to swelling to laryngeal paralysis. Dogs with an acute cough were not observed to have laryngeal inflammation, but it was noted in more than half of the dogs who had been coughing longer than two weeks.
Results also indicated that dogs with a cough of more than two weeks’ duration commonly have laryngeal swelling regardless of the underlying problem. This makes sense, as chronic coughing irritates the throat. Laryngeal paralysis or partial paralysis was also fairly common, seen in 19 percent of the dogs with a cough of more than two weeks’ duration. Remember, these dogs had none of the classic signs of laryngeal paralysis (such as excessive panting and loud breathing); the problem was only diagnosed when their throats were scoped.
Once their laryngeal problems were correctly diagnosed, the dogs received focused testing and treatment.
In dogs with laryngitis, treatment includes antibiotics if appropriate, as well as anti-inflammatories and pain medication. (Laryngitis hurts!) When the inflammation is caused by allergies, the allergies are addressed. A dog with a swollen larynx also benefits from humidified air; a warm, clean environment; and soft food. Dogs with a weak or paralyzed larynx can be treated surgically, or may require hormone therapy; there is anecdotal evidence that laryngeal paralysis may be related to hypothyroidism. Those whose dogs have laryngeal paralysis need to be advised on how to prevent overheating and aspiration pneumonia as well as informed of the links between paralysis and systemic neuromuscular diseases and megaesophagus.
The finding that dogs can have laryngeal disease even when they don’t have the classic signs has significant implications. If we as veterinarians aren’t scoping these coughing dogs, we might be missing something. The bottom line: if your dog has been coughing for more than two weeks, or if the cough doesn’t resolve with medication, talk to your vet about further medical evaluation.