Large Animal Upper Airway Conditions

Large Animal Upper Airway Conditions

• Learning objectives include identifying and contrasting clinical signs associated with specific disorders of the upper respiratory tract in large animals. Diagnosis of the case should utilise appropriate tests for the specific upper respiratory disorders. Treatment recommendations should also be described, along with the role of infectious agents. Finally the means of preventing upper respiratory tract disorders in large animals should be discussed.

• The examination of the nasal passages involves determining nasal discharge characteristics including odour, as well as assessing for diminished airflow, open-mouth breathing, facial deformation (chronic), sneezing, snorting, head shaking and systemic involvement.

• A quick look up the nose requires an examination through endoscopy

• Sinus anatomy shows communications between sinuses. Drainage occurs from the nasomaxillary opening.

• Nasal discharge source can be determined through an endoscopic exam. The nasomaxillary opening and the most caudal aspect of the middle nasal meatus are important locations for the source.

• Sinusitis can be diagnosed presumptively as secondary, then a detailed oral exam (sedated, speculum), radiographs, and upper airway scope should be conducted.

• Sinusitis treatment includes addressing the primary cause (e.g. extracting teeth, removing masses/cysts). Treatment for severe/chronic infections involves flushing the sinus and using trephination holes. Antibiotics (systemic and local) may be used depending on the findings. Note the possible need for cultures to identify the bacteria/fungi in the nasal discharge or directly from the sinus.

• Nasal diseases including rhinitis (often bilateral), viral etiologies (e.g. Equine Herpes Virus-1 and-4, Equine Viral Arteritis, Equine Influenza, Equine Rhinitis Viruses, and Equine Adenovirus), and masses (e.g. granulomas, neoplasia, polyps, abscesses).

• Nasal granulomas can have bacterial causes (e.g. actinomyces, actinobacillus, nocardia), and fungal causes (e.g. rhinosporidium, aspergillus, conidiobolus, cryptococcus, and coccidiodes) as well as several other species.

• Nasal neoplasias include adenoma, squamous cell carcinoma, and adenocarcinoma. Adenocarcinoma in sheep can be secondary to a virus.

• Nasal masses can be diagnosed using direct exams, radiography, rhinoscopy, and biopsy. Techniques for cytology, histology (necrosis often common), culture, PCR (bacterial and fungal), and PCR for retroviruses (sheep/goat, enzootic nasal tumour virus).

• Nasal mass therapy starts with surgical debulking and may involve systemic treatment. Specific treatments include topical antifungals, antibiotics, and chemotherapy based on the diagnosis.

• Ethmoid hematoma in horses can present in a number of ways with periodic epistaxis, usually unilateral, and is often not severe. A slowly expanding mass of ethmoid choncae may be present. The cause of the condition is often unknown. Diagnosis is through endoscopy or radiographs; a suspected case warrants biopsy and histopathological examination; treatments involve surgical or chemical ablation.

• Larynx conditions include normal-ish larynx appearance, variation of normal Pharyngeal Lymphoid Hyperplasia, and Larynx anatomy.

• Dorsal Displacement of the Soft Palate (DDSP) presents with exercise intolerance, noise during exercise, and/or coughing. The caudal border of the soft palate displaces dorsally to cover the epiglottis, with a persistent or intermittent character. Diagnosis is with a presumptive test characterising respiratory noise during exercise; definitive diagnosis requires endoscopy during work, and care must be taken for the sedation, as it can exacerbate the condition. Treatments involve various surgical strategies withguarded prognosis for performance.

• Epiglottic Entrapment (EE) in racehorses may present with poor performance and/or noisy breathing during exercise, but is usually not apparent at rest. In this case the loose ventral mucosa moves up over the dorsal surface of the epiglottis, and the cause of this is often unknown. The condition is often intermittent or persistent, and may be linked to epiglottitis (subepiglottal cysts), chronic upper respiratory tract (URT) inflammation, and/or an underlying DDSP. Diagnosis uses endoscopy, possibly during work.

• Laryngeal hemiplegia ("roaring") affect taller breeds and often presents with poor performance, noise during exercise, and, rarely, pronounced inspiratory dyspnoea at rest (if bilateral). Arytenoid cartilage is often not properly abducted during inspiration and often there is a narrowing of the airway. Causes can include injury to the vagus or recurrent laryngeal nerve, which can also be idiopathic. Grading using palpation is common. In this case the arytenoid cartilage is examined for its position, and if it is not in position for abduction.

• Retropharyngeal abscesses occur in horses and cattle with different causes. Horses may experience pharyngeal trauma from coarse stemmy hay or iatrogenic causes like a nasogastric tube, and may be infected by strangles. Cattle can have these abscesses from iatrogenic problems including balling gun/dose syringe use or a coarse feed; Diagnosis via Speculum, Radiography, and Endoscopy. Treatment by lancing through oral cavity and using systemic antibiotics directed at the species of bacteria.

• Other conditions include GP mycosis, and Atrophic Rhinitis (AR). GP mycosis presents with periodic unilateral or bilateral epistaxis and causes erosion into artery or nerve dysfunction. Diagnosis uses endoscopy to examine the presence of gray/white/yellow/black fibrinonecrotic plaques, blood clots and localisation over arteries (internal/external carotid and maxillary branch). Treatment involves either topical antifungals or surgical intervention (e.g. obstructing carotid artery to induce thrombus). AR, primarily in young pigs, includes sneezing, snorting, and nasal discharge; epistaxis, tear staining, nasal and facial deformation, and economic reduction of growth. It is caused by toxigenic bacteria that affect the nasopharynx. Diagnosis using bacteriological and PCR tests. Treatment uses antibiotics parenterally, or in feed. Prevention involves vaccinations.