Chronic Bronchitis in Dogs

Overview of Canine Chronic Bronchitis

Chronic bronchitis is a persistent inflammation of one or more bronchi, which are tubes that pass air to the lungs from the trachea. The cause of chronic bronchitis in most cases is unknown.

Chronic bronchitis can affect both dogs and cats but is most common in adult small/toy or medium-sized dog breeds. Chronic infective tracheobronchitis is more common in dogs less than one year of age. Younger animals are more likely to be affected with pulmonary (lung) infection or malformation. There is no sex predilection.

What to Watch For

Signs of chronic bronchitis in dogs may include:

• Coughing
• Tachypnea (fast breathing)
• Shortness of breath
• Intermittent gagging (often misinterpreted as “vomiting”)
• Wheezing
• Anorexia
• Depression
• Fever

The cough is worsened by exercise and may be exacerbated at variable times of the day. Severely affected dogs become cyanotic (blue-tinge to gums and tongue) with exertion and may faint after coughing.

Diagnosis of Chronic Bronchitis in Dogs

Diagnostic tests are needed to recognize chronic bronchitis. Tests may include:

• Complete medical history and physical examination including careful auscultation of the heart and lungs. Auscultation of the lungs is often abnormal. Auscultation of the heart is usually normal. Coughing can be elicited upon palpation (the technique of examining parts of the body by touching and feeling them) of the trachea (windpipe) or during excitement. Obesity is common.
• Your dog’s medical history may include questions regarding the following: previous illness, therapy and response to therapy, appetite, weight loss, activity or exercise intolerance, cough and environmental exposure to dusts, smoke, and vapors.
• Radiography (chest X-rays)
• Airway examination
• Cytology and culture

Other diagnostic tests may include:

• Electrocardiogram
• CBC (complete blood count)
• Arterial blood gas

Treatment of Chronic Bronchitis in Dogs

Chronic bronchitis can be a severe and progressive condition that causes difficulty breathing. Therapy of chronic bronchitis is guided by the cytology and culture of the tracheobronchial secretions (sputum), by the extent of radiographic changes (e.g. pneumonia) and by response to therapy. Chronic, intermittent antibiotic or corticosteroid therapy, combined with the use of bronchodilators, cough medicine and supportive care of the respiratory system, form the basis for chronic therapy.

Rarely is a cure obtained; however, with diligent home care, significant improvement of clinical signs does occur in many dogs.

Home Care and Prevention

There is no specific home care that can treat this disease. However, you should follow up with your veterinarian for examinations and radiographs and administer all veterinary prescribed medication as directed.

Provide exercise only as your dog can tolerate. Do not allow your dog to get short or breath with activity. If a restraint collar is worn, replace it with a harness. You may want to provide a vaporizer or nebulizer so your pet can inhale humidified air. Also, treatment of dental disease and oral cavity infections is recommended.

Prevention is not easy, although you can take steps to minimize the problem. Obesity should be controlled. Weight reduction over a two to three month period is recommended for obese pets. You should also minimize enviromental irritants. Decrease airway irritation. Avoid environmental stresses including house dust, vapors, chemical fumes and tobacco smoke.

In-depth Information on Chronic Bronchitis in Dogs

Chronic bronchitis refers to a persistent inflammatory change in the bronchial tree that may involve lobar bronchi or the smaller airways. Chronic bronchial inflammation or irritation, regardless of cause, seems to promote the predictable responses of increased tracheobronchial secretions, cough and progressive architectural changes in the bronchial tree, which alter airflow.

• Small airway obstruction, often with mucus, leads to an increased work of breathing, which can be compounded by dynamic, expiratory collapse of the large airways (the large airways close or collapse when breathing out). Lobar bronchi and the intrathoracic trachea may totally collapse during forced expiration or with coughing. Mucus and bronchial secretions stimulate a cough.
• Mucus plugs may further obstruct air flow and airway collapse. These changes can predispose the dog to recurrent respiratory infections. These changes cause nonreversible and often result in progressive changes.
• Visual examination of the bronchial tree, for example by fiberoptic bronchoscopy, demonstrates red and granular mucosa (lining), mucus hypersecretion and discharge that may occlude smaller bronchi. Bronchiectasis, pneumonia, chronic bronchitis and large airway disease are evident in some dogs.
• Causes of bronchitis are frequently not determined but may include chronic or recurrent viral or bacterial infection that may suggest an abnormality of local immunity, lingering infection, ciliary dyskinesis, which is a congenital abnormality of respiratory cilia which is rare, and environmental pollutants, including passive exposure to cigarette smoke and hypersensitivity reactions.
• Environmental pollutants are speculated to be causes of chronic airway irritation and injury and there may be a relationship of chronic respiratory diseases to poor oral health, but this is unproven.

Other medical problems can lead to symptoms similar to those encountered in chronic bronchitis. Diagnostic testing such as radiographs (X-rays) and bronchoalveolar lavage (BAL]) will often diagnose chronic bronchitis. Further diagnostic testing may be needed to determine secondary factors such as active inflammation or to eliminate other causes of similar symptoms such as heart disease.

Diseases that can appear similar to those with chronic bronchitis include:

• Aspiration (the act of inhaling) from chronic esophageal disease
• Bronchopneumonia (bacterial or fungal)
• Congestive heart failure
• Foreign body
• Heartworm disease
• Inflammatory lung disease
• Lung worm infection
• Pneumonia (inflammation/infection of the lungs)
• Pulmonary fibrosis (formation of fibrous tissue in the lungs)
• Pulmonary neoplasia (lung tumors)
• Tracheal (windpipe) collapse

In-depth Information on Diagnosis

Certain diagnostic tests are needed to confirm the diagnosis of chronic bronchitis in dogs and exclude other diseases that may cause similar symptoms. Tests may include:

• A complete medical history and physical examination
• Radiography (chest X-rays). The thoracic radiograph is abnormal in most cases. Typical findings include increased interstitial density.
• An examination of the trachea and bronchi (tracheobronchial examination) including cytology and culture. Sputum (mucous secretions from the lungs, bronchi and trachea) may be obtained using different techniques. A tracheal wash, also called a trans-tracheal wash (TTW), is a procedure in which a fluid sample is obtained and analyzed. This test is involves placing a small needle into the trachea of a lightly sedated patient. Bronchoalveolar lavage is another method to obtain fluid samples.
• Evaluation of collected sputum specimens. The sputum sample is cultured for bacteria and sensitivity testing is done. Cytology is also recommended to determine the cell time present (active infection, evidence of allergy, parasites, or cancer cells).
• Bronchoscopy. This procedure consists of placing a small flexible fiberoptic tube into the airway that allows for direct visualization of the upper and lower airways. This test can establish the diagnosis and rule out other diseases, such as inflammatory disease, lungworms, fungal infections and cancer.

Other laboratory tests may be helpful in assessing your pet’s heart and lungs and eliminating the possibility of other diseases. These tests may include:

• A complete blood count (CBC) to determine general health and check for secondary conditions. The CBC in dogs with chronic bronchitis is usually normal. Abnormal changes in the CBC can be noted with pneumonia, respiratory parasites, heartworm disease or other secondary diseases.
• Biochemistry. Serum blood tests may be recommended to determine your pet’s general health and check for secondary conditions.
• Heartworm test to determine presence of heartworm antibodies
• Fecal test to evaluate for lungworms
• Electrocardiogram (ECG) to determine the rhythm and look for abnormalities of the heart
• Arterial blood gas tests. These tests may be used as a method for sampling arterial blood to determine oxygen levels. This is a sensitive test for verifying the presence of significant lung disease. Many veterinary hospitals do not have the equipment to run this test, but blood can be analyzed easily at a local human hospital.

In-depth Information on Treatment

Treatment of chronic bronchitis must be individualized based on the severity of the condition, the cause, secondary diseases or conditions and other factors that must be analyzed by your veterinarian. Therapy of idiopathic chronic bronchitis is frustrating because the underlying cause of inflammation is rarely determined or controlled. Rarely is a cure obtained; however, with diligent home care – that includes avoidance of risk factors and weight loss – and medical therapy, significant improvement of clinical signs does occur in many dogs. Patients with advanced changes including bronchiectasis (chronic dilation of the bronchi and bronchioles with secondary infection) or lobar atelectasis generally respond poorly to medical therapy. Complete suppression of the cough is rare.

Therapy of chronic bronchitis is guided by the cytology and culture of the tracheobronchial secretions (sputum), by the extent of radiographic changes and by response to therapy. Chronic, intermittent antibiotic or corticosteroid therapy, combined with the use of bronchodilators, antitussives and supportive care of the respiratory system, form the basis for medical therapy.

• Antitussive therapy. The use of cough suppressants varies on a case-by case basis. In dogs with non-bacterial bronchitis, breaking the cough cycle is an essential part of treatment. Cough suppressants are contraindicated with pneumonia. Examples of cough suppressants used include hydrocodone (Tussionex® or Hycodan®) or butorphanol (Torbutrol®).
• Bronchodilator therapy. Bronchodilators may increase the vigor of contraction of the respiratory muscles, which may be useful in dogs with chronic dyspnea (difficult breathing). Theophylline and its various salts are most commonly chosen. Long-acting theophylline (Theo-Dur®) if often used twice daily. Some dogs cannot tolerate the adverse effects of xanthines, which include anxiety, restlessness, tachycardia, polyuria and emesis.
• Antibacterial therapy. This should be used in dogs with primary bacterial tracheobronchitis or a complicating bacterial infection. Drug choice is ideally chosen based on the results of the culture and sensitivity. In most dogs, however, antibiotic treatment causes little improvement, presumably due to a nonbacterial cause or lack of suitable culture and sensitivity testing. Antibiotic choices may include: amoxicillin-clavulanic acid (Clavamox®); trimethoprim-sulfonamide; cephalothin or cephalexin; enrofloxacin (Baytril®); or tetracycline for a minimum of three weeks. Other antibiotics may be chosen when Bordetella bronchiseptica is cultured. Gentamicin may be used via nebulization (a treatment in which an antibiotic is converted to a spray form in which your pet breaths in). This treatment is often administered twice daily for five days.
• Anti-inflammatory therapy. Using prednisolone or prednisone is most effective for control of most cases of bronchitis and is the most efficacious treatment of bronchitis that has eosinophils on cytology. Drugs used include prednisone often give twice daily then tapered to lowest effective dose (often given every day or every other day).

Follow-up Care for Dogs with Chronic Bronchitis

Optimal treatment for your dog requires a combination of home and professional veterinary care. Follow-up can be critical and may include the following:

• Administer prescribed medications as directed and be certain to contact your veterinarian if you are experiencing problems treating your dog.
• Treatment with bronchodilators, cough suppressants and antibiotics are additional measures that can be taken to reduce the need for continuous or high dosages of corticosteroids. Some dogs develop secondary infection and prednisone therapy may need to be discontinued. The response to treatment varies with some pets making near-recoveries and others requiring relatively high doses and varying combinations of medication throughout their life.
• Obesity can accentuate respiratory problems because diaphragmatic function is impaired, small airways close earlier than normal and ventilation may be impeded. Therefore, recommend weight reduction over a two to three month period using dietary restriction or a special diet.
• If your dog wears a restraint collar, replace it with a harness to decrease airway irritation.
• Avoid exposing your dog to environmental stresses including house dust, vapors, chemical fumes and tobacco smoke.
• Inhalation of humidified air, via a vaporizer or nebulizer, may liquefy secretions, hydrate the airways and reduce your pet’s cough. Exercise your pet lightly following these procedures and to encourage cough.
• Treatment of dental disease and oral cavity infections is prudent in dogs with chronic bronchitis. At the time of the dentistry, tracheal wash can be obtained during induction of anesthesia, thereby permitting examination of tracheobronchial secretions.
• Serum concentrations of theophylline, obtained after one week of therapy, can be used to guide dosage.
• Serial blood gas determinations and bronchoalveolar lavage cytology can be used to monitor your pet’s therapy and the clinical course of the disease.