References
How to approach the bird with respiratory signs
Abstract
Respiratory disease is common in avian species. Rapid diagnosis and treatment are essential as birds tend to hide clinical signs of illness until disease is advanced and cases can deteriorate rapidly. Risk factors are frequently related to diet and environment, and include hypovitaminosis A and inhaled irritants. Birds presenting with respiratory signs should initially be stabilised with oxygen supplementation and supportive care before further diagnostics are pursued. Work up of these cases includes blood sampling for biochemistry and haematology, imaging including radiography and rigid endoscopy, and culture and polymerase chain reaction testing of respiratory secretions. Chlamydia and aspergillosis are common diagnoses encountered in practice. Treatment includes systemic antimicrobials, non-steroidal anti-inflammatory drugs and inhaled medications administered via nebulisation. Correction of underlying risk factors is also essential for a successful outcome. This article gives an overview of avian respiratory disease and describes a systematic approach to the investigation and treatment of these cases, achievable in general practice.
Birds have a unique respiratory anatomy, with some clinically important features. The upper respiratory tract comprises the nasal passages that connect to a large air-filled infraorbital sinus. The infraorbital sinus is particularly well developed in psittacines and extends rostroventral to the eye (König et al, 2016). Air flows from the nasal cavity through the choana, a slit in the roof of the mouth, and through the glottis, which is positioned at the base of the tongue. The trachea comprises complete rings of cartilage. The syrinx is used for vocalisation and is positioned just cranial to the tracheal bifurcation. The lungs are composed of semi-rigid parabronchi, which have a unidirectional flow of air, allowing a very efficient cross current for gas exchange (O’Malley, 2005). The air sacs are poorly vascularised and act as bellows to push air over the lungs during both inspiration and expiration. They are not involved in gas exchange. Birds lack a diaphragm and both inspiration and expiration are active processes involving outward movement of the ribs and sternum. For this reason, it is important not to place too much pressure around the thorax during handling as ventilation can be significantly compromised (O’Malley, 2005).
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