What is chronic bronchitis?
Chronic bronchitis is a long-term inflammatory condition that affects the pulmonary or respiratory system. It is characterized by progressive and irreversible changes to the lung tissue caused by chronic inflammation. It causes a frequent cough that lasts more than 2 months. This condition may also be known as chronic obstructive pulmonary disease (COPD).
What causes chronic bronchitis?
No definitive underlying causes of chronic bronchitis have been determined. However, long term airway inflammation may result from exposure to inhaled irritants such as tobacco smoke, air pollutants or allergens. Dental disease or recurrent infections of the respiratory system may also be underlying causes of chronic bronchitis.
Are there other health factors that can make chronic bronchitis worse?
Yes, obesity is a complicating factor and will worsen symptoms of bronchitis. Dental disease increases the risk of bronchitis, because bacteria can travel from the mouth into the lungs and cause a serious secondary infection. Dogs with chronic bronchitis may also have other concurrent respiratory abnormalities such as tracheal collapse or bronchiectasis (dilated lower airways).
What part of the respiratory system is involved in chronic bronchitis?
The respiratory system is divided into two parts: the upper respiratory tract consists of the nose, nasal sinuses, throat, and trachea (windpipe), while the lower respiratory tract consists of the “small airways” (bronchi and bronchioles) and alveoli (small air sacs deep in the lung tissue where oxygen exchange occurs). Chronic bronchitis involves the lower respiratory tract. Initially it affects the small airways, although in advanced cases it will progress and affect the alveoli.
How does chronic bronchitis affect the dog’s lungs?
In its early stages, chronic bronchitis causes inflammation in the small airways. Persistent inflammation causes blockage of the small airways and ultimately results in reactive changes in the lungs, including dilation of portions of the small airways (bronchiectasis) or scarring in the lungs (pulmonary fibrosis). This condition develops slowly and progressively.
Does it affect all breeds and ages of dogs?
Chronic bronchitis most often affects middle-aged and older dogs. It occurs in all breeds of dogs but may be more common in small-breed and toy-breed dogs, such as West Highland white terriers and cocker spaniels.
What are the signs of chronic bronchitis?
In its early stages, the main symptom of chronic bronchitis is constant coughing or coughing that persists for longer than a month. The cough is usually “dry” or harsh, and gagging is common after coughing.
As the disease progresses, the dog may have difficulty breathing, decreased exercise tolerance (tires easily), or even faint with overexertion. Breathing may become noisy, and the dog may wheeze when exhaling. In later stages, the gums may develop a bluish tinge due to a lack of oxygen.
When at rest, the dog’s breathing rate is faster than normal. With some practice, you can count your dog’s breathing rate (number of breaths per minute) at home. Dogs with chronic bronchitis rarely have a fever and usually their appetite remains normal.
Could these symptoms be caused by something else?
Chronic coughing may also be a symptom of heart disease, infection of the lungs, or some types of cancer.
How is chronic bronchitis diagnosed?
Your veterinarian may suspect chronic bronchitis based on your pet’s history and the results of a physical examination. When they listen to the chest with a stethoscope, your veterinarian may hear “crackles” (harsh crackling or popping sounds) when the dog breathes in and out. With chronic bronchitis, the heart rate is usually normal or lower than normal and there is often a pronounced sinus arrhythmia (an irregular heart rate associated with the breathing cycle).
It is important for your veterinarian to take a thorough medical history, documenting the onset of the problem and its progression, any changes in the dog’s home environment, and any other signs of illness in the dog. A series of tests may be required to confirm the diagnosis and to exclude other diseases that could be causing the symptoms.
- Complete blood count (CBC) and biochemistry profile. These tests assess your dog’s general health, and specific blood or fecal tests may be recommended to rule out parasitic diseases such as heartworm or lungworm.
- Chest X-rays. X-rays often show characteristic changes in the lungs and may help rule out other types of heart or lung disease. Magnetic resonance imaging (MRI) or computed tomography (CT) may also be used, but generally only at referral hospital settings.
- Cytology using bronchoscopy. A bronchoscope (a thin tube with a light and camera) is used to directly examine the inner surfaces of the airways in an anesthetized dog, looking for changes associated with chronic bronchitis. It also allows your veterinarian to collect samples of the cells lining the bronchi and bronchioles, which can be microscopically examined and cultured (kept in a special environment that allows any bacteria present to multiply and be identified).
- Bronchoscopy and bronchoalveolar lavage (BAL). In this procedure, also known as lung wash, the pet is usually placed under sedation or anesthesia, and a thin, flexible, sterile catheter is passed into the lower part of the lungs. A small amount of sterile fluid is flushed forcefully into the area and then promptly suctioned back out. The recovered fluid contains mucus and a small number of cells that can be cultured for microorganisms and examined under the microscope.
What is the treatment for chronic bronchitis?
Most dogs with chronic bronchitis can be treated as outpatients. If the dog is experiencing severe respiratory distress, hospitalization may be required for oxygen therapy and/or intravenous medication to stabilize the condition.
Specific medications that may be prescribed include bronchodilators to dilate the airways and help clear secretions, cough suppressants, antibiotics if there is evidence of a secondary bacterial infection, and/or corticosteroids to decrease inflammation. There have also been some anecdotal reports of veterinarians using maropitant (Cerenia®), a drug normally used for vomiting, as a cough suppressant. Some of these medications can be provided as inhalers. You can help reduce the chance of relapses by helping your pet avoid irritants such as smoke or airborne allergens.
Newer therapies for chronic bronchitis being investigated include stem cell therapy and desensitization with allergen-specific immunotherapy (“allergy shots”). Your veterinarian may prescribe supportive treatments such as supplements that have antioxidant, anti-inflammatory, or immune stimulant functions.
It is important to maintain good oral health in a dog with chronic bronchitis. Daily toothbrushing is extremely beneficial. Regular dental descaling, cleaning, and polishing under general anesthesia is strongly recommended to minimize the chance that bacteria from the mouth will cause a secondary infection in the inflamed respiratory tract.
What is the success rate for treatment of chronic bronchitis?
This condition is non-reversible and is often slowly progressive. Appropriate treatment will slow the progression of disease and will relieve distressing symptoms. With proper management, most dogs with chronic bronchitis enjoy a normal life expectancy and an excellent quality of life. Relapses may occur when the seasons change or if air quality is poor. Adjustments to medication dosages may be necessary at these times. Consult your veterinarian for specific advice.
