Sarah Wooten is a small animal veterinarian and certified veterinary journalist. She practices in Greeley part time at Sheep Draw Veterinary Hospital, and writes for multiple online and print publications.
Wellness: Health Care
January 5 2017
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 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 is benign, like a small bout of tracheobronchitis (an paralysis or a cancerous tumor that is pushing on respiratory structures can all cause a dog to 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 f lap 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.
Also 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 infectious inflammation of the airways more commonly referred to as kennel cough) that resolves easily with medication. 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 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.*Johnson, L.R. 2016. Laryngeal structure and function in dogs with cough. JAVMA 249(2):195–201.
News: Guest Posts
July 26 2016
Have you ever thought about the athletic difference between dogs and cats? We already know that nutritional needs and personalities differ greatly between the two species, but what about their athletic prowess? We know they are both runners, but how long can they go? How fast? As it turns out, there are some interesting anatomic differences between the two, and it starts with a little-known tendon in the neck called the nuchal ligament.
The nuchal ligament attaches the head to the spine and is an adaptation designed to stabilize the head in animals that run fast and far. The nuchal ligament that dogs have is like the one that horses have. It supports the head without using muscles, thus saving energy and making the animal more efficient. Early canids like the extinct euycon canid show elongation of the leg bones, which also maximizes the efficiency of the dog’s stride.
We also know dogs relied upon a scent trail to hunt prey over long distances, while felines use hearing and eyesight to locate and hunt prey up close. Dogs must ‘follow their noses.’ As early dogs evolved longer legs, noses and necks, they needed the nuchal ligament to save energy while keeping their ‘nose to the ground’ posture, run and follow scent trails over miles and miles. And while dogs lost dexterity of their front limbs and evolved relatively weaker neck muscles needed to take down prey alone, they compensated by evolving group hunting techniques, according to Tedford Wang’s “Dogs: Their Fossil History and Evolutionary History.”
Dogs, humans and horses have nuchal ligaments and are unique long distance runners. You know who doesn’t have a nuchal ligament?
Cats, as we know, don’t hunt in packs, nor do they run their prey to exhaustion. Cats are solitary hunters and rely on stealth, explosive power and flexibility. From a sitting crouch, a cat can jump up to nine times their height, and in a split-second they can make sudden changes in direction and twist their spines mid-fall to land on all fours, according to the Cornell Feline Health Center. It’s true: cats almost always do land on their feet. Why can they do this?
A cat’s spine is much more flexible than that of a dog. Their vertebral bones have increased elasticity in the disc between bones when compared to a dog, which is why cats don’t have the back problems that dogs tend to have. A cat’s vertebrae also is less tightly connected than a dog’s, making the spine far more flexible, and a cat’s pelvis and shoulders are more loosely attached to its backbone than dogs. A cat can stretch their body and run with a stride length of three times their body length. A cat’s flexible spine, powerful muscles and retractable/extendable claws that provide traction like runner’s spikes all contribute to top speeds of 30 miles per hour. There’s a reason the cheetah is the fastest animal in the world. However, a cat can only sustain this kind of anaerobic activity for very short periods of time, which makes a cat a fantastic sprinter but a terrible distance runner.
The next time you see your dog or cat running, watch how they are different: Whether your companion animals are sprinting to pounce on a cat toy, jogging 10 miles with you, or prefer the strenuous athletic activity of couch surfing, all adult dogs and cats can benefit from daily exercise, a healthy weight and a high-quality joint supplement.
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