Avian Air Sacculitis Study Guide

Overview and Clinical Importance

Air sacculitis (also spelled airsacculitis or aerosacculitis) is a common inflammatory condition of the avian air sacs caused by various microbial pathogens, primarily bacteria and fungi. This condition is clinically significant because birds possess a unique respiratory system with nine air sacs that are essential for respiration, thermoregulation, and vocalization. Unlike mammalian lungs that expand and contract, avian lungs are rigid and non-expansile; instead, air sacs function as bellows to drive unidirectional airflow through the parabronchi where gas exchange occurs.

Air sacculitis represents a significant category on the NAVLE because it affects virtually all avian species and can have substantial economic impact on poultry operations. The condition typically affects birds between 6 and 12 weeks of age and often occurs secondary to primary respiratory infections or immunosuppression. Understanding the unique anatomy of the avian respiratory system is essential for diagnosing and treating this condition.

Avian Respiratory Anatomy Review

The avian respiratory system is fundamentally different from the mammalian system and is considered the most efficient gas exchanger among air-breathing vertebrates. Key anatomical features include: