Why Is My Dog Coughing?

Ron Hines DVM PhD 10/23/03
I cannot think of a more difficult sign that I have to evaluate at my Hospital than a cough in your pet. You see, coughing can be due to an extremely minor problem - no more than drinking water too fast - or it can be the first sign of serious problems of the lungs or heart.

When I question owners about their pet’s cough I begin the interview with the same set of questions every time. We call this the History: Is your pet a cat or a dog? Is it a small breed less than 15 pounds or is it larger? How long has it been coughing? How old is your pet? Is the cough harsh and dry or is it moist and productive? Does your pet cough most when it is up and active or when it is lying down? Is your pet listless or more depressed than usual? Is it having trouble breathing or breathing rapidly? Does the problem occur this season every year? Does your pet sneeze too and have a runny nose? Has the pet been boarded or groomed recently? Are there any other changes you have noticed in your pet?

These questions give me a basis to begin my examination. I usually begin my exam by looking at the pet as it walks around the exam room. It is amazing how much a dog or cat will tell me through its mannerisms if I just observe them closely.

Then I look in the pet’s mouth. I check to see if its gums are pale or bluish or if blood vesicles in the gums stand out (injected gums). Injected gums can be associated with heart disease. I check the pet’s tonsils. Enlarged tonsils often cause a cough. I also check that the pet has nothing lodged in its throat.

I look for inflamed eyes and a crusty nose, which often accompany kennel cough and I massage the pet’s trachea (wind pipe) to see if that causes coughing. I check the dog’s neck to see if an abnormal pulse is present in the jugular vein and I feel the pet’s abdomen to detect fluids or an enlarged liver or spleen.

Then I use a stethoscope to listen to the heart and lungs. Lung sounds that are dry and harsh often accompany upper respiratory tract infections. Moist congested lung sounds can indicate pneumonia or lung congestion due to heart disease. Both these conditions cause coughing. I check to see if any of the superficial lymph nodes are enlarged and I take the pet’s temperature. The following are many of the causes of cough in dogs. The list is not complete, but it covers most of the cases that I have seen.

Breed Characteristics:

Dogs and cats with flat faces that snore often have elongated soft pallets in the rear of their mouths. This can cause coughing. Pekingese, Pugs, Bulldogs, Lhasa Apsos, Shia Tzu and some Persian cats fall into this category. When flare-ups occur, I put these pets on a short course of corticosteroid and antibiotic treatment. Occasionally the problem is so severe that the pet does not get enough air. When this is the case, I surgically remove a portion of the soft palate. One must be very cautious in performing this surgery. If too much tissue is removed coughing will become worse and the pet may inspire food and water into its lungs.

Tonsillitis:

Infectious tonsillitis is passed from pet to pet through close contact, coughing and sneezing and through contaminated food, water bowls and other objects. It is most common in toy breeds of dogs and puppies. Tonsillitis rarely causes coughing in cats. The two tonsils normally lie in deep crypts or crevices at the far back of the mouth. With certain infections such as kennel cough, the tonsils enlarge, partially obstructing the pet’s throat. Usually both tonsils are affected. When enlarged tonsils become inflamed and ulcerated the pet will spend hours trying to cough them up. This is a retching, violent cough that usually ends in a gag producing foam. These pets will sometimes paw at their mouths. I treat many of these animals with a two-week course of antibiotics. My favorite antibiotic for this problem is trimethoprim/sulfa. If the tonsillitis returns frequently, I remove the tonsils.

Furballs In Cats:

Longhaired cats that are infrequently groomed will periodically retch, cough and vomit up mats of hair. Brushing the cat frequently, cutting its hair or weekly administration of a petrolatum based hairball remedy usually solves this problem. Hairball cat food, high in fiber, also prevents this syndrome.

Tooth And Mouth Infections:

Small breeds of dogs, especially Toy poodles, Yorkshire terriers, Maltese and Pomeranians are very subject to periodontal disease, loose infected teeth and oral inflammation. This is partly due to their genetics but also due to feeding them soft table foods. These oral infections sometimes inflame the rear of the throat causing coughing. Often the problem is magnified by a flabby, narrow trachea or windpipe as well as tonsillitis due to the mouth infection. Many times the infection has migrated to the valves of the heart (mitral valve) damaging that organ as well. These pets need to have all diseased teeth removed. This is not major surgery in these pets because the teeth are already loose, lifeless and no longer used in eating. Many have already fallen out on their own. Subsequent to dental surgery, I place these pets on two weeks of antibiotics and try to get the owners to feed them balanced dog foods.

Kennel Cough In Dogs:

Kennel cough of dogs, also called infectious tracheobronchitis, is cause by the bacteria, Bordatella bronchiseptica. The signs of parainfluenza virus and Canine Adeno-2 virus can be indistinguishable from kennel cough and often the two or three organisms work in tandem along with mycoplasma to cause the cough.

Soft dry coughs and sneezing are the two most common signs of this disease. They begin 3-7 days after the dog was exposed to another sick pet. Some dogs with this problem only cough when they are excited. Kennel cough is highly contagious and passes directly from dog to dog at kennels, grooming parlors, pet stores, doggy parks and humane societies. Dogs with this disease rarely feel ill although they may vomit food and foam due to enlarged tonsils and tracheal irritation. In healthy dogs, the cough lasts seven days to three weeks. But it can persist much longer in flat-faced breeds or dogs with narrow tracheas (windpipes).

I have never seen a case of kennel cough that endangered a pet’s life. It is not clear that antibiotics speed recovery from this disease. But I place many dogs on antibiotics for a week or two, chiefly because owners are so annoyed by the constant racket. If the cough is not too severe I dispense a guanfacine-based cough syrup. If guanfacine is not sufficient to control the cough I put them on the narcotic cough suppressant, Hycodan. Humidifiers help clear mucous from the throat allowing the dog to breath easier.

Dogs that are frequently exposed to other pets should receive a kennel cough vaccination every six to twelve months. The intranasal vaccine is more effective than injectable products. Vaccinating a dog the day it goes to the kennel is valueless – it takes a good week to ten days for the vaccine to protect.

Collapsed Trachea:

Toy breeds of dogs are very prone to a genetic abnormality called tracheal collapse. I believe I have seen this problem in more Pomeranians than any other breed. The trachea is made up of cartilaginous rings in the shape of a C( that are fibrous and soft on their innermost side - represented by the parenthesis. In collapsing trachea the inner soft portion of the windpipe is sucked into the airway during inspiration, partially occluding it. With time, the membranes lining the trachea become inflamed causing a chronic dry, hacking cough. The condition is easily diagnosed by massaging the trachea near the dog’s chest for a minute or two. Dogs with this problem go into a coughing spell as soon as you finish the massage.

When the problem flares up, I place these dogs on a cough suppressant and an anti-inflammatory drug such as prednisone until the problem resolves. Air humidifiers are also helpful. I suggest these dogs wear harnesses rather than collars and I limit exercise until the cough is better. Various surgical techniques are used to attempt to cure this condition. They meet with mixed success.

Migrating Hook And Roundworm Larva:

Canine and feline hookworms and roundworms can also cause a cough. We call this a verminous cough. This problem is primarily a concern in young dogs, kittens and puppies. When a dog or cat accidentally eats a hookworm or roundworm larva or egg, the larva burrows through pet’s stomach or intestine into the blood stream. When it reaches the lungs it is coughed up, re-swallowed and then matures in the pet’s intestine. If the pet becomes infested with large numbers of larva due to an unsanitary environment the owners will notice the cough.

Preventing verminous coughs is a mater of sanitation. Dog feces need to be collected and disposed of properly. Hookworm larva thrive in damp shaded soil. One of the best ways to prevent this problem is to keep all your pets on a monthly heartworm medication, which contains pyrantel pamoate.

Allergies And Irritants:

Some dogs and cats, like people, experience throat and nasal irritation due to chemicals in perfumes, cigarette smoke, new bedding, carpeting, etc. Dust mite allergy is said to occasionally cause coughing. These cases are uncommon and I do not recall any seen in my practice. Coughing can be a multifaceted problem and it is quite likely that allergies and irritants have made many of the cases of cough that I due treat worse

Heartworm Disease:

Heartworms are transmitted to dogs and cats by mosquitoes. The disease is common in dogs and rarer in cats. Mosquitos that bites an infected dog, ingests microscopic heartworm larva or microfilaria. When they next bite a dog or cat these larva migrate through the new host’s body and lodge in the upper right side of the heart. Depending on the number of heartworms present and the length of time they are there, the heart is slowly damaged and enlarges.

The presence of heartworms also causes inflammatory changes in the lungs. In dogs, these changes, along with pressure from the enlarged heart on the windpipe cause a dry to moderately moist cough. In cats the signs are more similar to asthma. By the time a cough is present the disease is quite advanced and some of the changes to the heart and lungs are irreversible. Dogs with heartworm coughs are noticeably ill. They are thin and their hair coat is dry and musty.

They have a worn-out look about them and are often prematurely grey around their mussel and toes. They are usually pot bellied due to an enlarged liver and excess fluid in their abdomens and are positive on a heartworm antigen test. Their cough is worse when the dog is lies down. The pet’s history includes the fact that they are not receiving heartworm preventative.

After assessing the degree of damage to the body, I treat these dogs with Immiticide, an arsenic-containing medication that kills the adult parasites. If the dog’s liver, heart and kidneys are strong enough to withstand the side effects of this powerful medication, I give them the standard two injections at twenty-four hour intervals. If the disease has caused marked damage to the liver and heart I try to stabilize and improve the pet’s health before the injections.

If that cannot be done I have two alternatives. I can give a single injection and then place the dog on monthly heartworm preventative or I can just place them on the monthly preventative. Recent studies have shown that dogs placed on monthly ivermectin are free of adult heartworms within a year. Coughs can take up to six months to resolve.

Heart Problems:

Congestive Heart Disease

Coughing is one of the most consistent signs of heart disease. The most common form of heart disease in dogs and cats begins with damage to the mitral valve on the left side of the heart. When I listen to the heart with my stethoscope, I can detect abnormal sounds on the left upper quadrant of the heart – the area where this valve is located. X-rays of the pet’s heart show a typical globular, enlarged heart shape with elevation of the trachea. Pressure on the trachea and fluid in the lungs are the primary causes of the cough. The pets’ gums are often bluish (cyanotic) and slow to return to normal color when my fingers blanch them.

The livers of these pets are enlarged with pooled blood and they may have fluid in their abdomens. Mitral valve insufficiency is the most common heart disease in older dogs. It affects over one-third of the dogs that are older than ten.

Early in this disease, placing the pet on the diuretic, furosemide, eliminates the cough and improves the function of a weakened heart. These dogs and cats do well when placed on a sodium-restricted diet. As the disease progresses, the pet will need other medications. One of the most effective medications is the ACE inhibitor, enalapril maleate

Dilated Cardiomyopathy

Cardiomyopathy is a form of heart disease that affects larger breeds of dogs. Doberman Pinchers and boxers have a high incidence of this condition. In cats it has long been associated with a lack of dietary Taurine. Most recently, Taurine deficiencies due to feeding lamb and rice diets have been shown to cause the same disease in dogs. It is very rare in dogs that weigh less than 28 pounds.

The onset of this disease is very rapid. Pets begin to cough and show general weakness and exercise intolerance all within a matter of weeks. When I listen to the chests of these dogs their heart rate is very fast and weak. Often the heartbeat is very irregular. The usual lack of heart murmurs distinguishes this condition from congestive heart failure. X-rays of these animals chest show a huge heart – often with an enlarged left upper chamber (atrium) and the lungs often filled with fluid.

I treat this condition similar to congestive heart failure. Unfortunately, dogs and cats with Dilated Cardiomyopathy do not live long.

Tumors In The Lungs:

Hacking coughs in old dogs and cats are also common when tumors of the lungs are present. These are always sad cases to deal with. When lung tumors are advance, pets may cough up blood as well as phlegm. Primary lung tumors are exceedingly rare in cats and dogs. They are generally secondary tumors that have moved to the lungs from another location. Sometimes, if the disease is advanced, abnormal lung sounds or silent areas are present. X-rays of these animals’ lungs often show a shower of small tumors throughout the lung fields.

The most common tumor type is adenocarcinomas. Although I may refer these pets on to a veterinary oncologist there is really no effective chemotherapy for dog or cats with lung tumors. I try to make their remaining life as pleasant as possible with cough suppressants, steroids and bronchodilators such as theophylline.

Laryngeal Paralysis:

This is a relatively rare condition in which the structures of the throat (larynx) become paralyzed allowing food and water to enter the lungs causing pneumonia. Large breeds of dogs (particularly Labrador Retrievers, Irish Setters and Springer Spaniels) are affected. These dogs loose the ability to bark. They have reduced exercise tolerance and occasional fainting spells. They produce a roaring sound when they inhale. Mild cases can be managed with corticosteroids and cough suppressants such as butorphanol or codeine. The dogs need to be kept cool in the summer. Severe cases require surgery to widen the pet’s airway.

Distemper:

I have not seen a case of distemper in dogs since the 1960’s. Good vaccines have eliminated the disease from middle and upper class neighborhoods throughout the United States. When I was a kennel boy in South Texas, distemper was very common. The first sign of this disease was often a dry hacking cough. Many dogs became listless and ran fevers of 103-105F. A thick, yellow discharge from nose and eyes was common. Most dogs recovered from distemper during a two-week period. Some dogs developed fatal neurological and intestinal disease. Because a virus causes distemper, we were limited to treating these dogs with antibiotics for secondary infections, fluids, nutrients and good supportive care.

Lungworms:

The chief signs of lungworm infections in cats and dogs are coughing and a rise in the number of white blood cells called eosinophiles. I have never diagnosed a case of lungworms because they are quite rare in my urban environment. But I will tell you a little about them. Dogs become infected with a lungworm, Filaroides osleri, while cats become infected with Aelurostrongylus abstrusus. Adults of these parasites live in nodules in the windpipe where they pass living larva, which are coughed up. Some are spit out and others reswallowed and pass out in the stool.

Pups become infected by eating the saliva or feces of an infected dog. Cats obtain these parasites by eating birds or small rodents that have eaten an infected snail or slug. These worms are treated with fenbendazole (Panacur) at 25mg/pound body weight daily for 7-14 days. Most are also given prednisolone to decrease inflammation and coughing. I have never used fenbendazole in cats and would not before I checked into its safety..