Disorders and Diseases of the Bronchi, Chest, and Lungs
Common diseases of the bronchi include canine infectious tracheobronchitis (kennel cough), allergic bronchitis, canine chronic bronchitis and Oslerus osleri infection. Infection with microorganisms that cause kennel cough, irritation from air pollution or allergies can trigger a bout of coughing that is associated with inflammation of the bronchi. This condition is called acute bronchitis. An affected dog has a harsh, dry cough but otherwise appears well. Diagnosis is based on the dog's medical history and the clinical signs. Diagnostic tests are seldom necessary for simple acute bronchitis. Treatment is the same as for in infectious cough. A cough that persists for more than eight weeks has become chronic. Such coughing is rarely caused by infection, although infection may precede its development. It is actually due to a persistent inflammation of the bronchi, a condition called chronic obstructive pulmonary disease (COPD). COPD usually affects middle-aged and older dogs. Although an exact cause is rarely discovered, pollutants and allergens are usually implicated. The disorder is fairly common in west Highland White terriers, a breed that has a known risk of developing allergic skin conditions. Coughing may be triggered by exercise or excitement and is worst at night. The coughing is dry and harsh and may end with gagging and retching of foamy saliva, which is often mistaken for vomiting. In all other respects, an affected dog appears normal.
X-rays of a dog with COPD reveal thickening of the bronchi and possibly emphysema (rupture of the air sacs in the lungs), although mild emphysema is not visible on X-rays. Bronchoscopy and bronchial washes may be performed to check for any infected debris in the airways. Initial management may include a short course of corticosteroid drugs to reduce inflammation. If these produce a dramatic improvement, the dose is reduced, with the vet aiming at low-dose alternate-day treatment. Bronchodilators are used to ease the dog's breathing, while cough medicines containing codeine are given to reduce the tickle of the cough.
While causes for respiratory diseases can be remote from the respiratory system, most contagious (infectious) pneumonias or upper respiratory infections result from direct attack on the respiratory tissue. Pneumonia, also called pneumonitis, is inflammation of the lungs due to bacterial, viral, or fungal infections. Pneumonia often occurs as a secondary infection that has spread from the upper respiratory tract. It is uncommon in healthy dogs, occurring most frequently in very young and very old animals, or those with impaired immune system. In addition, individuals with chronic bronchitis or a collapsing trachea are more susceptible than normal. Inhalation of smoke or noxious chemicals may also lead to pneumonia. Aspiration pneumonia occurs when food or fluid gets into the lungs as a result of an impairment of the dog's swallowing mechanism or during general anesthesia. A dog pneumonia is depressed, feverish, and breathes fast. There is often a moist-sounding bubbly cough. If the pneumonia is severe, the affected dog may sit or stand with its head extended to make its breathing easier.
Diagnosis is made by chest X-ray and blood tests. Treatment with antibiotics begins immediately and continues for at least three weeks, until X-rays show that the lungs are beginning to heal. Some dogs need to be hospitalized in an oxygen-enriched kennel. Nonsteroidal anti-inflammatory drugs (NSAIDs) may be used to relieve discomfort. Cough suppressants, however, are never given because coughing is beneficial in pneumonia as it helps to clear blocked air passages and mucus.
Interstitial lung diseases is a diverse group of diseases that affect the lung tissue. They are characterized by an initial inflammation of pulmonary alveoli that extends to the interstitium ((the tissue and space around the air sacs of the lungs) and beyond leading to idiopathic pulmonary fibrosis. Interstitial lung diseases are classified by their etiology (known or unknown causes), and radiological-pathological features. Idiopathic pulmonary fibrosis commonly affects the Westhighland White Terrier and Cairn Terrier. Clinical signs develop over months or years. Initially, rapid and labored breathing is noted along with exercise intolerance, progressing to coughing. Affected dogs are otherwise healthy and have a normal appetite. A combination of therapeutic agents will help to relieve the signs, but the condition is progressive and will lead to respiratory failure eventually. Survival time from diagnosis is between 6 and 12 months, but some dogs can survive for up to 3 years.1
The common fungal diseases that can involve the lungs are blastomycosis, histoplasmosis, and coccidioidomycosis. IN most cases the organisms enter the body through the respiratory tract. The infection may be transient and successfully eliminated without the animal showing clinical signs, or it may progress to cause disease involving the lungs alone or spread to other organs.
A number of parasites can cause lung disease. Toxocara canis causes transient pneumonia in young animals, typically those younger than a few months. Dirofilaria immitis causes heartworm disease and can result in severe pulmonary disease marked by inflammation and formation of clots. Oslerus osleri causes tracheobronchitis marked by chronic nonproductive cough and wheezing.2 Capillaria aerophila is a parasitic nematode affecting the respiratory systems of domestic carnivores and occasionally of humans. The adult lungworms live embedded in the epithelia of the bronchioles, bronchi, and trachea of the host causing chronic bronchitis (pulmonary capillariosis). Animals may display minimal respiratory signs or inflammation, sneezing, wheezing, and chronic dry cough; when bacterial complications occur, the cough may become moist and productive, leading to bronchopneumonia and respiratory failure and death.3 Paragonimus kellicotti flatworm infects the bronchi and lungs causing inflammation; signs are similar to those seen in allergic bronchitis.
Pleurisy, also called pleuritis, is inflammation of the chest (pleural) cavity. The condition usually occurs in conjunction with pneumonia. An affected dog breathes shallowly, has a fever, and shows signs of pain if it is touched on the chest. Treatment includes drugs to eliminate the infection and provide pain control.
An accumulation of any fluid between the pleura (the two membranes that cover the lungs and the chest cavity) is known as pleural effusion. Trauma, tumors and spontaneous bleeding disorders may all cause blood to build up in the chest causing hemothorax. Much more commonly, transudate (a serum-like fluid) may accumulate in the area as a consequence of heart failure. Fluid may also build up as a result of liver or kidney disease, or tumors that have spread to the lungs from elsewhere in the body. In some situations, pleurisy produces pus that collects in the chest cavity. Whatever the fluid involved, an affected dog finds it increasingly difficult to breathe, and may stand with its head and neck extended, taking short, rapid, labored breaths. The lips and gums may turn blue (a sign called cyanosis). X-rays reveal a characteristic "ground glass" appearance due to the presence of fluid around the lungs. Urgent treatment is needed. Using either a catheter or a needle, the vet will drain the fluid from around the lungs. The procedure is also usually diagnostic, because the type of fluid that has accumulated in the chest cavity will indicate to the vet the cause of the fluid buildup.