Respiratory System
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Respiratory System IntroductionThe respiratory system begins at the nose and ends at the distal alveoli. It is comprised of the upper and lower airways. The upper airway includes the nose, sinuses, and pharynx. The nose provides olfaction and temperature regulation in hyperthermic patients. The nasal turbinates initially humidify and warm air, and filter particulate matter. The lower airways include the trachea, bronchi, bronchioles, and alveoli. The primary function of the respiratory system is to deliver oxygen to the lungs to be exchanged with carbon dioxide.
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Aspiration Pneumonia in Large AnimalsFor discussion of aspiration pneumonia in small animals, see Respiratory Diseases of Small Animals.
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Diaphragmatic HerniaDiaphragmatic hernia is protrusion of abdominal organs or tissue through a congenital opening or traumatic rupture in the diaphragm. This may cause respiratory signs or may be subclinical. Thoracic radiography is highly diagnostic, and treatment centers on stabilization and surgical repair.
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Fungal PneumoniaFungal infections occur more commonly in dogs than cats and even less frequently in large animals. Clinical signs include chronic cough, acute respiratory distress, and lethargy. Diagnosis can be made by serologic testing or detection of fungal antigens in urine (for Histoplasma and Blastomyces). Treatment includes systemic antifungal medication, oxygen, and sometimes anti-inflammatory medications.
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Laryngeal DisordersLaryngeal disorders are characterized by stertorous breathing and can often lead to death if untreated. The mainstay of treatment is steroids or NSAIDs. Presumptive diagnosis is largely based on clinical signs.
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Lungworm InfectionLungworm infection, also known as verminous bronchitis or verminous pneumonia, is an inflammatory disease of the lower respiratory tract caused by a variety of nematodes. Coughing and dyspnea are the most common clinical signs, which can be exacerbated by concomitant bacterial or viral infections. The Baermann technique is used to detect first-stage larvae in fecal samples. In some countries, an ELISA test is available to detect antibodies against Dictyocaulus viviparus; however, interpretation is hampered by persistent titers. Treatment and control of bovine lungworm is achieved primarily via strategic use of anthelmintics, although an orally administered vaccine is available in some countries.
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PharyngitisPharyngitis is an inflammatory condition of the oro- or nasopharynx. It develops secondary to viral or bacterial infections of the upper respiratory tract. Clinical signs of pharyngitis include upper respiratory tract noise, nasal discharge, coughing, and occasionally dysphagia. The diagnosis of pharyngitis is confirmed with upper airway endoscopy. Treatment of pharyngitis includes administration of antimicrobials and anti-inflammatories and restriction of exercise.
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Pulmonary EmphysemaPulmonary emphysema is one of the two conditions under the umbrella term chronic obstructive pulmonary disease (COPD), with the other being chronic bronchitis. Pulmonary emphysema is identified by marked overdistention of alveoli along with destruction of supporting alveolar and interstitial structures. Computed tomography is currently the best way to diagnose the disease, and treatment includes a combination of bronchodilators and anti-inflammatory medications. Because it causes permanent damage, prevention is key.
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Infectious Respiratory System Diseases in CattleSinusitis in cattle typically involves the frontal or maxillary sinus. Frontal sinusitis is usually associated with dehorning, and maxillary sinusitis is usually associated with infected upper teeth. Common clinical signs include nasal discharge and an apparent decrease in airflow through nasal passages. Diagnosis is made by percussion of the face and skull radiographs. Treatment is drainage of the affected sinus via trephination and lavage.
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Bovine Respiratory Disease ComplexBovine respiratory disease (BRD), shipping fever pneumonia, or undifferentiated fever is a respiratory disease of cattle of multifactorial etiology with Mannheimia haemolytica and, less commonly, Pasteurella multocida, Histophilus somni ( All.see page Histophilosis), or Mycoplasma bovis being the important bacterial agents involved. Viral pathogens may also be involved, such as bovine herpesvirus 1, parainfluenza-3 virus, and bovine respiratory syncytial virus.
- Overview of Bovine Respiratory Disease Complex
- Viral Infections Associated with Bovine Respiratory Disease Complex in Cattle
- Bacterial Pneumonia in Cattle with Bovine Respiratory Disease Complex
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Non-Infectious Respiratory System Diseases in CattleAllergic rhinitis is an uncommon disease of cattle that, when chronic, may lead to granuloma formation. The etiology is an allergic reaction to pollen or fungal spores. Clinical signs are seasonal, occurring in warm, moist conditions; they include rhinorrhea, sneezing, and a sudden onset of dyspnea. In the chronic stage, multiple granulomas may form on the mucosal surface of the nasal cavity. Cytologic examination of nasal discharge samples may reveal eosinophils.
- Allergic Rhinitis and Enzootic Nasal Granuloma in Cattle
- Tracheal Stenosis Syndrome of Feeder Cattle
- Pulmonary Emphysema, Edema, and Interstitial Pneumonia in Cattle
- Anaphylaxis in Cattle
- Hypersensitivity Pneumonitis in Cattle
- Diffuse Fibrosing Alveolitis in Cattle
- Acute Respiratory Distress Syndrome of Feedlot Cattle
- 4-Ipomeanol Toxicosis (Moldy Sweet Potato) and Perilla Ketone Toxicosis (Purple Mint Toxicosis) in Cattle
- Respiratory Disease in Cattle due to Exposure to Toxic Gases
- Vena Caval Thrombosis and Metastatic Pneumonia in Cattle
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Respiratory Diseases of HorsesViral respiratory infections are common in horses; the most notable are equine herpesvirus infection, equine influenza, and equine viral arteritis. The clinical manifestations are similar and include pyrexia, serous nasal discharge, submandibular lymphadenopathy, anorexia, and cough. In addition to respiratory disease, equine herpesvirus type 1 (EHV-1) can cause abortion and neurologic disease, and equine herpesvirus type 5 (EHV-5) is a newly recognized cause of multinodular pulmonary fibrosis. Equine viral arteritis produces respiratory disease, vasculitis, and abortion. Equine herpesvirus type 2 (EHV-2), equine rhinitis virus, and reovirus are ubiquitous viral respiratory pathogens, and infection results in minimal clinical disease. Adenovirus pneumonia is most often seen in association with severe combined immunodeficiency in Arabian foals. Hendra virus ( All.see page Hendra Virus Infection) is a zoonotic disease of horses identified in Australia; it is rapidly fatal in horses, and close contact is necessary for disease transmission.
- Overview of Respiratory Diseases of Horses
- Equine Herpesvirus Infection
- Equine Influenza
- Equine Viral Arteritis
- Hendra Virus Infection in Horses
- Pleuropneumonia in Horses
- Rhodococcus equi Pneumonia in Foals
- Acute Bronchointerstitial Pneumonia in Foals
- Strangles in Horses
- Recurrent Airway Obstruction in Horses
- Inflammatory Airway Disease in Horses
- Exercise-Induced Pulmonary Hemorrhage in Horses
- Laryngeal Hemiplegia in Horses
- Pharyngeal Lymphoid Hyperplasia in Horses
- Dorsal Displacement of the Soft Palate in Horses
- Epiglottic Entrapment in Horses
- Subepiglottic Cyst in Horses
- Fourth Branchial Arch Defect in Horses
- Diseases of the Nasal Passages in Horses
- Diseases of the Paranasal Sinuses in Horses
- Guttural Pouch Disease in Horses
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Respiratory Diseases of PigsRespiratory diseases of pigs can be classified into two broad categories based on the extent and duration of overt disease: those that affect large numbers of pigs and may be serious but of limited duration, and those that persist in a large number of pigs for indefinite periods. Diseases in the first category can be costly, but the losses are limited rather than ongoing. They include swine influenza, classical swine fever, the pneumonic forms of pseudorabies, porcine circovirus-associated disease, and porcine reproductive and respiratory syndrome (PRRS). The causal viruses may persist in a herd, but outbreaks of overt disease tend to be self-limiting.
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Respiratory Diseases of Sheep and GoatsLarvae of the sheep nasal botfly (Oestrus ovis) develop in the nasal sinuses of sheep. Signs of infestation include nasal discharge and sneezing. Rarely, more serious disease develops. Antiparasitic treatment with ivermectin is effective.
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Respiratory Diseases of Small AnimalsA varying flora of indigenous commensal organisms (including Pasteurella multocida, Bordetella bronchiseptica, streptococci, staphylococci, pseudomonads, and coliform bacteria) normally reside in the nasal passages, nasopharynx, and upper trachea, and at least intermittently in the lungs of dogs and cats, without causing clinical signs. Opportunistic infections by these bacteria may occur when respiratory defense mechanisms are compromised by infection with a primary pathogen (eg, distemper, parainfluenza virus, or canine type 2 adenovirus in dogs, and rhinotracheitis virus or calicivirus in cats), other insults (eg, inhalation of smoke or noxious gases), or diseases such as congestive heart failure and pulmonary neoplasia.
- Overview of Respiratory Diseases of Dogs and Cats
- Allergic Pneumonitis in Dogs and Cats
- Canine Influenza (Flu)
- Canine Nasal Mites
- Feline Bronchial Asthma
- Feline Respiratory Disease Complex
- Kennel Cough
- Lung Flukes in Dogs and Cats
- Lung Nematodes in Small Animals
- Neoplasia of the Respiratory System in Dogs and Cats
- Pneumonia in Dogs and Cats
- Pulmonary Thromboembolism in Dogs and Cats
- Rhinitis and Sinusitis in Dogs and Cats
- Tonsillitis in Dogs and Cats
