Dogs cough for a variety of reasons. Just like people, they can cough to clear their airways of debris or mucous, but a persistent cough should be checked out by a vet. All dogs cough sometimes but only a veterinarian can help you rule out some of these causes to pinpoint why your particular dog is coughing and give you a plan for treatment. Whenever I see a coughing patient, I think through these possibilities and then apply what I know about the particular dog to help me decide what tests might be appropriate to find what the trouble is.
The following are some of the reasons for persistent coughing (not in order of importance):
1. Degenerative Disorders
Degenerative processes occur when structures degrade over time and their ability to function deteriorates.
Examples of degenerative processes that could lead to a cough include: scarring in the lung tissue, either from aging or exposure to an agent that caused or contributed to scar formation, or cardiac disease (like congestive heart failure) which will certainly cause a cough.
Diagnostic testing to decide if degenerative issues are the cause may include a thorough exam and probably radiographs (x-rays). Any underlying disease must be identified and treated. Sometimes the only treatment involves managing the symptoms with cough suppressants or steroids, but trying to manage symptoms without making sure there is no underlying disease could be dangerous.
These processes are less likely in puppies or young dogs. If you have a middle-aged to older dog with a chronic cough, degenerative disorders may be the cause.
2. Anomalous Disorders
Anomalous disorders (typically birth defects or structural abnormalities) occur when anatomical structures do not develop normally. Such disorders can occur from birth as a congenital defect, like cardiac malformations or structural deformities in the thoracic cavity and can cause a cough.
Other examples of this type of abnormality are breed associated, like tracheal collapse (an abnormality frequently noted in small breed dogs where the tracheal narrows and partially blocks the airway) and Brachycephalic airway syndrome (a multifaceted airway issue in smashed face breeds like English bulldogs and Pugs). These may not be noticed until later in life when they start to cause coughing. Because there is such a wide range of causes, it is important to see a vet make sure that a surgery is not indicated. Birth defects can often be completely repaired surgically, if found early, so do not delay. A pet that has never coughed in her life and is now a coughing senior is less likely to suffer from an anomalous defect, but some anomalies can worsen with age and then are both anomalous and degenerative issues.
3. Neoplasia (Cancer)
Cancer of the lung will cause chronic coughing. The lungs get a lot of blood supply because their job is to oxygenate all of the blood, so any type of cancer that sheds cells into the blood can spread to the lungs. Coughing is not the only sign of cancer, but if your dog does have a chronic cough and is an older dog, cancer must be on the list of possible causes and a vet consulted to be sure that your pet is comfortable and you know what to expect. Advances in treatment for pets with cancer have changed the prognosis for some types of cancers, so getting an accurate diagnosis is worth your time.
4. Infectious Diseases
Infections can and do often cause a cough. Bacteria, viruses and fungal infections are all on the list for a coughing dog. Kennel Cough is caused by a bacterium that can easily be spread between dogs.
Think about possible exposures for your dog. If there is a history of your dog spending time with other dogs, like boarding, grooming or playing at a dog park, he could have been exposed to bacteria and viruses. Fungal infections are not as common as the other infectious causes in many parts of the country, but should be on the list, especially if your dog has a fever, spends a lot of time outdoors or likes to dig in soil. Antibiotics are only appropriate in the case of bacterial infections, whereas antifungals or antivirals have specific applications also.
It is imperative that you and your vet find out what you are treating to get the best outcome for your dog. Any age and type of dog can suffer from infections.
5. Inflammatory Disease
Inflammation is a process that is characterized by the production of chemicals by the body in response to a trigger. Sometimes the trigger is an infection, but sometimes, the inflammatory process is prompted by other causes, like allergy or auto-immune disease.
Inflammatory coughing can be caused by things like asthma and allergic bronchitis. Treatment will be aimed at stopping the formation of the chemicals and slowing their damaging effects. Any age of dog can experience inflammatory coughing and some of the causes can be life threatening, so getting an exam and diagnosis is imperative. Depending on the underlying issue, inflammation can be a short term and curable process or a more long-term and incurable (but manageable) process.
Many people do not realize that parasites can cause coughing. Not only are there lungworms that live in the lung tissues, but heartworms are known to invade the heart and lungs. Even the intestinal parasites can have a part of their life cycle that causes them to migrate through the lungs. Most parasite issues can be easily prevented with regular parasite prevention programs.
The best de-wormers and all heart worm preventives are available only by prescription, so you will need to see a vet to manage this possibility. But the benefits to having your dog protected by these products go far beyond coughing.
7. Traumatic Injury
Many times dogs that suffer trauma to the chest will cough. I often see coughing during the healing phases following hit-by-car cases. It does not take a severe and obvious blow to bruise the lungs and cause a cough. If your dog is allowed to run loose or has been missing, you might not even know that he had a traumatic injury. Your vet can help you find out. Treatment can be aimed at pain relief and stabilization while the bruising resolves and your vet can make sure no other injuries have occurred from the trauma.
Knowledge is power when your pet is sick. The more you can find out about why your dog is coughing, the better equipped you are to manage it. Coughing is not going to be something you can manage on your own, since the causes can be varied, but a veterinarian can help you narrow the list and start on the right path to treatment.