Why Is My Dog Coughing?
Why Do Dogs Cough?
In all species, coughing is a reflex activity the purpose of which is to clear irritant or foreign materials or infectious agents from the respiratory tract. Receptors present in the walls of the airways detect the presence of such material, and initiate forceful, reflex contractions of the diaphragm and abdominal muscles, while increasing outflow pressure through the larynx, resulting in the forced expulsion of mucus and debris from the lungs and airways.
Coughing is a normal protective bodily function, but when it is persistent or severe, or is accompanied by signs of systemic illness such as fever, inappetence, or loss of exercise tolerance, it may be an indicator of a serious problem.
What Are The Causes of Coughing In Dogs?
The causes of a persistent cough can most simply be divided into two types: primary respiratory and cardiac (heart-related) coughs. In some scenarios the two types may coexist, which can obviously make them more difficult to manage.
Infectious Respiratory Disease In Dogs
The most common type of respiratory seen in veterinary clinics is infectious tracheobronchitis, commonly known as 'kennel cough'. Affected dogs have a persistent or paroxysmal loud, harsh cough, which may or may not be followed by the production of frothy mucus. Owners often mistakenly think that the poor dog has something stuck in his/her throat, or that the dog is choking. In fact, the harsh nature of the cough is due to inflammation of the walls of the trachea and bronchial tree, usually without any significant impairment to breathing. Kennel cough in dogs does not usually cause any generalized signs of illness except in very young, very old, or otherwise debilitated animals.
There are several infectious organisms associated with infectious tracheobronchitis, with one called Bordetella bronchiseptica responsible for the majority of cases. Vaccines are available against this disease, and you should certainly consider including this in your dog's vaccination regime if he/she is regularly in contact with other dogs, regardless whether he is kenneled or not.
Your veterinarian may elect to use a course of antibiotics depending on the severity your dog's cough, and cough suppressants such as codeine are sometimes also used, as the cough can be so severe as to prevent your pet (and yourself!) from sleeping, however a cough suppressant should never be used without your vet's advice, as they can sometimes exacerbate the underlying infection by preventing clearance of bacteria from the airway. Encouraging your dog to inhale steam vapor by bringing him to the bathroom and running the shower, or giving a spoon of honey are two natural and safe remedies you can attempt at home.
Infection of the lower airways (bronchitis) or substance of the lungs (pneumonia) tends to produce more severe signs of illness, and most dogs will be depressed due to septicemia or fever. Coughing in these cases is usually softer than that heard with kennel cough, and you may notice a foul smell from your dog's breath. Bacterial and fungal infections are commonly associated with infections at these lower levels of the respiratory tree, and they will generally require more aggressive treatment by your veterinarian.
Parasites such as Oslerus osleri, lungworm, and heartworm can cause coughing through different mechanisms. Parasitic infestation is worth bearing in mind as a possible cause if your dog has not recently received a deworming dose.
Non-Infectious Respiratory Problems
As we all know, dust, smoke and other irritants can cause coughing. Again, this is a normal phenomenon, but chronic exposure can cause secondary changes in your dog's airways, leading to excessive mucus production, thickening of airway walls, loss of normal elasticity, and hypersensitivity. Allergic pneumonitis is a condition which can cause severe respiratory compromise in dogs, and needs to be managed by allergen identification and removal if possible, as well as with prednisolone (a steroid) or other medications to suppress the immune response.
Chronic bronchitis is a common condition of older dogs (most commonly small breeds such as Terriers), which causes a productive cough with wheezing. It is seen much more often in homes in which the pet is exposed to cigarette smoke. Again, treatment usually requires the use of steroid medication, and bronchodilators can also be useful in some cases.
Tracheal collapse is an upper airway condition which can sound much like kennel cough in that the coughing dog will likely be very well, with a harsh loud cough. It is caused by a weakness in the wall of the main airway (the trachea), and is often made worse by excitement, environmental irritants, or pulling on a lead. This is an anatomical abnormality see in small and toy breeds such as the Yorkshire terrier, and treatment in some cases requires the implantation of a stent within your dog's airway. Weight loss can be very beneficial in mild cases in obese patients.
Tumors within the chest can cause coughing if they impinge on the airways or cause fluid accumulation. The lungs are a common place for secondary tumors to arise from primary masses at other sites in the body.
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Coughing As A Result Of Heart Disease In Dogs
Cardiac coughing in dogs is usually caused by disease of either the heart muscle (cardiomyopathy) or the valves of the heart, which promote the normal flow of blood through the heart, preventing backflow and congestion. Dogs with a cardiac cough will often show other signs of poor circulation, such as exercise intolerance, fainting, or lethargy. Congestive heart failure is the result of blood pooling in the venous system and leakage of fluid into the lungs and body cavities, and as well as coughing, some dogs in congestive heart failure will have a swollen fluid-filled belly.
There are well known breed predispositions to these heart diseases; for example, Doberman Pinschers and Cocker Spaniels are prone to developing Dilated Cardiomyopathy (DCM), while smaller breeds, particularly Cavalier King Charles Spaniels are much more at risk of developing valvular disease.
Both classes of heart disease cause secondary changes in the chambers of the heart leading to heart enlargement. As well as the soft cough caused by fluid congestion in the lungs, this heart enlargement also causes a concurrent harsh cough as the larger chambers, especially the left atrium, compress and irritate the large airways, meaning the type of cough can vary in dogs with heart failure.
With advances in medical and surgical treatments heart disease in dogs has become a very treatable condition in many cases, and your veterinarian will discuss the most appropriate treatments for your pet.
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Diagnosing The Cause Of Your Dog's Cough
As I've already stated above, unless your dog is very well in spite of his cough he should be brought to your veterinarian for examination. In some cases, your vet may be happy to make a diagnosis and prescribe treatment based only on his physical examination findings, but in some cases, for example in an older small breed dog with signs of both heart disease and chronic bronchitis, further testing is probably sensible to determine the best course of treatment.
Complete blood work does not usually provide a diagnosis, but can be important in ensuring any medications prescribed are not going to be harmful to your dog. For example, many older dogs with cardiac disease will also have some degree of kidney insufficiency, which requires great care in choosing the type and dose of medication used.
X-Rays of your dog's chest provide a great deal of useful information on the condition of the lungs and airways, as well as assessing the size, shape and position of the heart. Ultrasonography is a great non-invasive technique for examining soft tissue structures in the chest, but especially the heart, and allows a real time view of the movement and contractility of the cardiac chambers. Bronchoscopy is the insertion of a fibre optic cable down the airways. It needs to be performed under general anesthesia, which can obviously carry some risk, but it is the most useful way to examine the inside of the airways, and allows samples to be collected for bacterial and parasitic examinations, and can also help identify tumors within the lungs and bronchi.
What To Do If Your Dog Is Coughing
In most cases, a dog that has a persistent cough needs to be examined by a veterinarian. If you have a healthy young adult dog that has just recently started coughing, and is not showing other signs of illness, then you may be able to nurse him through it using steam vapor and home remedies as shown above. If you are in any way unsure about what to do, please ring your local surgery for advice.
Let me know in the comments below if there is any further advice you would like to see (non-urgent questions only).