When a pet coughs it can mean a problem with two different body systems: the heart or the lungs and respiratory tract. Each set of organs causes problems for different reasons but both can potentially be serious.
When there is an abnormal substance in the lungs or trachea, nerve receptors are triggered and a cough is stimulated. Substances can include smoke, dust, pollen, fluid, mucus, and even small objects, with the purpose of the cough being to expel the offending material from the respiratory tract. Something simple like a seasonal allergy can lead to sporadic coughing, though this is not as common as many people think. The biggest reason for coughing in pets tends to be infections, from something as simple as “kennel cough” to pneumonia and even severe fungal diseases. In many small dogs there is a tendency for a condition we call “collapsing trachea”, where the tracheal rings are weak and tend to collapse inward, stimulating a cough as the sides touch.
Something becoming stuck in the trachea or even in the lungs is far less common than most people realize. In my experience, when a pet starts to cough or gag most people jump to the conclusion that something has gone down into their airway and become lodged. However, in fifteen years of practice, I can count on one hand the number of times I have actually seen this happen, despite having pets come in for coughing almost every day of my career. If something truly is stuck in the throat it will usually show as severe retching, coughing, and discomfort, not periodic coughs. When you go to your vet, prepare for the cause of the symptoms to be something other than a stuck object. Even so, there are certainly cases where this may happen, so it should be considered, even if it’s low on most doctors’ list of possibilities.
If coughing is due to a heart condition it actually ties into the principle of something being in the lungs that shouldn’t be there. In certain types of heart disease affecting the left side of the heart, blood is prevented from flowing properly and backs up in the blood vessels. When the blood pressure rises in these vessels they will leak fluid into the surrounding tissues. If this happens in the vessels of the lungs, fluid escapes into the airways, eventually reaching the point of triggering a cough. Congestive heart failure causes coughing as a later symptom, with different diseases leading to such disease. Heartworm disease results in coughing because of the inflammation in the lungs from the presence of the worms, as well as damage to the heart and subsequent heart failure.
Lastly, there are parasites that spend part of their life cycle moving through the lungs. This can include lung worms that form cysts in the lung tissue, as well as migration of certain intestinal parasites. Most of the time these parasites can be diagnosed with a fecal exam and treatment is normally easy.
If your pet shows signs of persistent or severe coughing, you certainly should take him or her to your vet. Expect to have chest x-rays performed, as this is the primary tool we use to see the lungs and heart, though other tests may also be necessary. It is important to do the appropriate diagnostics in order to tell which organ system is involved, enabling us to determine the proper course of treatment.
You can learn about other signs of illness in pets by reading the rest of our Common Symptoms blog series.