Laryngitis, Tracheitis, and Bronchitis in Animals

LARYNGITIS, TRACHEITIS, BRONCHITIS By Dr. Hussein AlNaji

Inflammation of the air passages usually involves all levels, and no attempt is made here to 2 differentiate between inflammations of various parts of the tract. They are all characterized by one or more of cough, noisy inspiration, and some degree of inspiratory embarrassment. ETIOLOGY Cattle 1. Infectious bovine rhinotracheitis (bovine herpesvirus-1), calf diphtheria (necrotic laryngitis), Histophilus somnus. Tracheal stenosis in feedlot cattle, honker cattle, etiology unknown 2. 3. Necrotic laryngitis in calves1. 4. Syngamus laryngeus infests the larynx of cattle in the tropics. 5. Trauma, including balling gun induced injury

3 Sheep. 1. Chronic infection with Actinomyces pyogenes Horses. 1. Equine herpesvirus 1, 2 or 5 (EVR), equine viral arteritis (EVA), equine viral influenza (EVI), strangles (S. equi) 2. Idiopathic ulceration of the mucosa covering the arytenoid cartilages. 3. Lymphoid hyperplasia of the pharynx of horses.

PATHOGENESIS 1. Irritation of the mucosa causes frequent coughing, and swelling causes partial obstruction of the air passages, with resulting inspiratory dyspnea. 2. Necrotic laryngitis in calves is associated with marked changes in pulmonary function, modifies tracheal dynamics, and disturbs the growth process by increasing the energetic cost of breathing.

CLINICAL FINDINGS 5 1. Coughing and inspiratory dyspnea with laryngeal roaring or stridor are the common clinical signs. 2. In the early stages of acute infections, the cough is usually dry and nonproductive and is easily induced by grasping the trachea or larynx, or by exposure to cold air or dusty atmospheres. 3. In acute laryngitis, the soft tissues around the larynx are usually enlarged and painful on palpation. 4. In chronic infections, the cough may be less frequent and distressing and is usually dry and harsh. 5. Tracheal stenosis in cattle is characterized by extensive edema and hemorrhage of the dorsal wall of the trachea, resulting in coughing (honking), dyspnea, and respiratory

TREATMENT 6 a. Most of the common viral infections of larynx, trachea, and major bronchi will resolve spontaneously if the affected animals are rested, not worked, and not exposed to inclement weather and dusty feeds. b. The bacterial infections treated with 1. Treated with antimicrobials. Calves with calf diphtheria should be treated with a broadspectrum antimicrobial daily for 3 to 5 day. 2. NSAIDs such as flunixin meglumide may be used in an attempt to reduce the laryngeal edema. 3. Animals with severe lesions and marked inspiratory dyspnea may require a tracheotomy. 4. Tracheolaryngostomy of calves with chronic laryngeal obstruction because of necrobacillosis.

7 PULMONARY CONGESTION AND EDEMA Pulmonary congestion is caused by an increase in the amount of blood in the lungs because of engorgement of the pulmonary vascular bed. It is sometimes accompanied by pulmonary edema, and the temporal relationship between the two can be difficult to determine.

ETIOLOGY 8 Pulmonary congestion A.Primary Pulmonary Congestion 1. Early stages of most cases of pneumonia . 2. Inhalation of smoke and fumes. 3. Anaphylactic reactions. 4. Recumbency, especially in large animals. 5. Racehorses with acute severe exercise-induced pulmonary hemorrhage. A.Secondary Pulmonary Congestion. 1. Congestive heart failure (cardiogenic pulmonary edema), including ruptured chordae tendineae of the mitral valve, ionophore toxicosis, and left-sided heart failure.

9 Pulmonary edema occurs because of imbalances in the Starling forces across the pulmonary capillary. From a clinical perspective, the common proximate causes of pulmonary edema are injury to the endothelium of the pulmonary capillary with subsequent leakage of protein-rich fluid into the interstitial spaces, elevated blood pressure in the alveolar capillaries, or, less commonly, low plasma oncotic pressure. 1. Acute anaphylaxis. 2. Acute pneumonia Pasteurella haemolytica . 3. Congestive heart failure and acute heart failure (e.g., the myocardial form of enzootic muscular dystrophy in inherited myocardiopathy of Hereford calves); ruptured mitral valve or chordae tendonae.

10 4. Inhalation of smoke or manure gas. 5. Transient upper airway obstruction in the horse (negative-pressure pulmonary edema). 6. After general anesthesia in horses. 7. Yew (Taxus sp.) intoxication. 8. Exercise-induced pulmonary edema in racehorses 9. Specific diseases, including: East Coast fever in cattle; the pulmonary form of African horse sickness; poisoning with organophosphates, plant poisonings by oleander,. 10. Doxycycline intoxication of calves 11. Clostridium perfringens type D epsilon toxin in calves and sheep.

11 PATHOGENESIS In pulmonary congestion, ventilation is reduced, and oxygenation of the blood is impaired. Oxygenation is reduced by the decreased rate of blood flow through the pulmonary vascular bed. Hypoxemic anoxia develops and is the cause of most of the clinical signs that appear. Hypoxemia occurs in pulmonary edema because of ventilation-perfusion abnormalities, diffusion abnormalities (although this is usually a minor contributor to the hypoxemia), and hypoventilation caused by the physical obstruction.

CLINICAL SIGNS 12 1. The depth of respiration is increased to the point of extreme dyspnea with the head extended, the nostrils flared, and mouth breathing. 2. Breathing movements are greatly exaggerated. 3. A typical stance is usually adopted, with the front legs spread wide apart, the elbows abducted, and the head hung low. 4. The respiratory rate is usually increased, especially if there is hyperthermia, which occurs in acute anaphylaxis and after violent exercise and in the early stages of pneumonia. 5. The heart rate is usually elevated (up to 100/min), and the nasal mucosa is bright red or cyanotic in terminal cases.

6. In acute pulmonary congestion, there are harsh breath sounds, but no crackles are 13 present on auscultation. 7. When pulmonary edema develops, loud breath sounds and crackles are audible over the ventral aspects of the lungs. 8. Coughing is usually present, but the cough is soft and moist and is not painful. CLINICAL PATHOLOGY Laboratory examinations are of value only in differentiating the causes of congestion or edema. NECROPSY FINDINGS In acute pulmonary congestion the lungs are dark red in color. Excessive quantities of venous blood exude from the cut surface. Similar but less marked changes occur in milder forms of congestion but are only seen in those animals that die of intercurrent disease

TREATMENT 14 The principles of treatment of pulmonary congestion and edema are one or more of the following: 1. reduction of pulmonary capillary pressure (by reduction either of pulmonary venous or pulmonary arterial pressure), can be reduced in animals with left-sided heart failure by reduction of cardiac preload with used furosemide , improvement in cardiac pump function by used digoxin , or a combination of these factors 2. Alleviation of pulmonary microvascular damage is more difficult. Administration of antiinflammatory drugs, including NSAIDs or glucocorticoids. 3. Correction of low plasma oncotic pressure can be increased by intravenous infusion of plasma (10-40 mL/ kg) or synthetic colloids such as hetastarch. Administration of crystalloid solutions.

ATELECTASIS 15 Atelectasis is collapse of the alveoli as a result of failure of the alveoli to inflate or because of compression of the alveoli. Atelectasis is therefore classified as obstruction (resorption), compression, or contraction. a. Obstruction atelectasis occurs secondary to obstruction of the airways, with subsequent resorption of alveolar gases and collapse of the alveoli. This disease is usually caused by obstruction of small bronchioles by fluid and exudate. It is common in animals with pneumonia or aspiration of a foreign body.

16 b. Compression atelectasis occurs when intrathoracic (intrapleural) pressure exceeds alveolar pressure, thereby deflating alveoli. This occurs when there is excessive pleural fluid or the animal has a pneumothorax. It also occurs in the dependent lung or portions of lung in recumbent animals and is evident on computed tomographic or radiographic examination of the lungs of foals c. Contraction atelectasis occurs when there is compression of parts of the lung by fibrotic changes in the pleura. D. Patchy atelectasis occurs in the absence of surfactant, such as can occur in newborns. Failure of the lung to inflate, or development of atelectasis of the lungs of the newborn, usually those born prematurely, tory distress, tachypnea, tachycardia, and cyanosis.

PULMONARY EMPHYSEMA 17 Pulmonary emphysema is distension of the lung caused by overdistension of alveoli with rupture of alveolar walls with or without escape of air into the interstitial spaces. ETIOLOGY Cattle 1. Acute interstitial pneumonia 2. Parasitic pneumonia with pulmonary edema in acute anaphylaxis 3. Perforation of the lung by foreign body as in traumatic reticuloperitonitis. 4. Poisoning by the plants 5. Pulmonary abscess

18 Horses 1. Bronchiolitis as a result of viral infection of the respiratory tract in young horses. All Species 1. Secondary to bronchopneumonia. 2. Poisoning by oleander, Bryophyllum pinnatum, and moldy sweet potatoes 3. Acute chemical injury as in inhalation of welding fumes . 4. Chlorine gas poisoning.

19 PATHOGENESIS Emphysema occurs because of destruction of the connective tissues of the lung, including the supporting and elastic tissue of the pulmonary parenchyma. Tissue damage resulting in emphysema in humans is caused by the action of proteases in the lung. Whether this occurs in the farm animal species is unknown but is a consideration.

CLINICAL FINDING 20 1. Diffuse pulmonary emphysema causes severe expiratory dyspnea with a grunt on expiration and loud crackling lung sounds on auscultation over the emphysematous lungs. 2. In severe cases in cattle, the emphysema is commonly interstitial, and dissection of the mediastinum and fascial planes results in subcutaneous emphysema over the withers. 3. In severe cases in cattle, open-mouth breathing is common. In cattle and pigs, the presence of pulmonary emphysema in pulmonary disease is often not detectable clinically. TREATMENT The treatment of pulmonary emphysema will depend on the species affected, the cause of the emphysema, and the stage of the disease

DIFFERENTIAL DIAGNOSIS 21 1. Acute emphysema in cattle is often accompanied by pulmonary edema with the presence of consolidation and crackles in the ventral parts of the lungs. It may be similar to acute pulmonary congestion and edema caused by anaphylaxis, but forced expiration is not a characteristic of these latter conditions. 2. Acute pneumonia in cattle or horses is characterized by fever and localization of abnormal respiratory sounds, which are not as marked nor as widely distributed as those of emphysema. 3. Chronic pneumonia is characterized by dyspnea, chronic toxemia, crackles and wheezes, and poor response to therapy. 4. Pneumothorax is accompanied by forced inspiration and an absence of normal breath sounds.

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