Merck Manual

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Professional Version

Clinical Signs of Respiratory Disease in Animals


Caroline C. Tonozzi

, DVM, DACVECC, Mission Veterinary Partners

Reviewed/Revised Apr 2021 | Modified Nov 2022

Nasal discharge may be serous, catarrhal, purulent, or hemorrhagic, depending on the extent of mucosal or turbinate damage. It indicates increased production of normal secretions, sometimes supplemented by neutrophils (purulent) or blood (hemorrhage). It probably also indicates decreased “grooming” of the nostrils with the tongue when animals are ill. Epistaxis (bleeding from the nose) is often caused by vascular rupture, such as in mycotic infection of the guttural pouch or exercise-induced pulmonary hemorrhage in horses Exercise-Induced Pulmonary Hemorrhage in Horses Exercise-induced pulmonary hemorrhage (EIPH) is defined as detection of blood in the airways of horses after strenuous exercise. Epistaxis is rarely detected; however, identification of blood... read more Exercise-Induced Pulmonary Hemorrhage in Horses , or by intranasal fungal infection or neoplasia, systemic coagulopathy, vasculitis, thrombocytopenia (immune-mediated or a result of rickettsial infection), hyperviscosity syndrome, hypertension, or nasal trauma. Hemoptysis (the coughing up of blood) occurs after rupture of pulmonary aneurysms in the lungs of cattle with chronic lung abscesses. Bleeding may also result from polyps, neoplasms, granulomas, trauma, thrombocytopenia Platelet Disorders in Animals Disorders of platelets can be divided into acquired or congenital thrombocytopenias and acquired or congenital functional disorders (thrombocytopathias), with acquired thrombocytopenia being... read more , and bracken fern Bracken Fern Poisoning in Animals Bracken fern, growing from large, dense, woody rhizomes, forms deciduous, stipitate, erect to spreading fronds with nonanastomosing veins. The pinnae are stalked, opposite or subopposite (inset)... read more Bracken Fern Poisoning in Animals or sweet clover toxicity Sweet Clover Poisoning in Animals Melilotus spp (sweet clover). In the 1920s, cattle in North America developed a fatal hemorrhagic disease. Various causes, including pathogenic organisms and nutritional deficiencies... read more Sweet Clover Poisoning in Animals .

Tachypnea (an increase in rate and depth of breathing) may be a sign of disease; however, it also occurs in healthy animals such as after vigorous exercise. Infectious respiratory diseases that cause sepsis and inflammation may further compromise the host, eg, pneumonia in cattle due to Mannheimia haemolytica. Respiratory lesion localization may occur when the animal is observed to have more notable signs on either inhalation or exhalation. Labored inhalation (ie, stridor or stertor) is seen with upper airway obstruction or if the obstruction is above the thoracic inlet (eg, laryngeal paralysis, cervical tracheal collapse). Labored expiration is seen with obstructive diseases distal to the thoracic inlet (eg, diffuse bronchitis, principal bronchial collapse, or pulmonary edema). Fixed airway obstructions (eg, tracheal neoplasia Neoplasia of the Respiratory System in Dogs and Cats Nasal lymphoma involving the left nasal cavity. There is breach of the left orbital wall with tumor extension into the left orbital region. The left eye is deviated craniolaterally. The tumor... read more Neoplasia of the Respiratory System in Dogs and Cats , foreign body, or stenosis) or a combination of upper and lower airway diseases (eg, pleural effusion with congestive heart failure) result in marked respiratory distress or respiratory failure. Other responses include coughing, clear nasal exudate, and shallow breathing with grunting; are often associated with the pain due to pleuritis.

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