Department of Zoology, University of Johannesburg, Auckland Park Campus, Kingsway Avenue, Johannesburg, 2006, South Africa.
Biol Rev Camb Philos Soc. 2023 Dec;98(6):2152-2187. doi: 10.1111/brv.13000. Epub 2023 Jul 24.
In commercial poultry farming, respiratory diseases cause high morbidities and mortalities, begetting colossal economic losses. Without empirical evidence, early observations led to the supposition that birds in general, and poultry in particular, have weak innate and adaptive pulmonary defences and are therefore highly susceptible to injury by pathogens. Recent findings have, however, shown that birds possess notably efficient pulmonary defences that include: (i) a structurally complex three-tiered airway arrangement with aerodynamically intricate air-flow dynamics that provide efficient filtration of inhaled air; (ii) a specialised airway mucosal lining that comprises air-filtering (ciliated) cells and various resident phagocytic cells such as surface and tissue macrophages, dendritic cells and lymphocytes; (iii) an exceptionally efficient mucociliary escalator system that efficiently removes trapped foreign agents; (iv) phagocytotic atrial and infundibular epithelial cells; (v) phagocytically competent surface macrophages that destroy pathogens and injurious particulates; (vi) pulmonary intravascular macrophages that protect the lung from the vascular side; and (vii) proficiently phagocytic pulmonary extravasated erythrocytes. Additionally, the avian respiratory system rapidly translocates phagocytic cells onto the respiratory surface, ostensibly from the subepithelial space and the circulatory system: the mobilised cells complement the surface macrophages in destroying foreign agents. Further studies are needed to determine whether the posited weak defence of the avian respiratory system is a global avian feature or is exclusive to poultry. This review argues that any inadequacies of pulmonary defences in poultry may have derived from exacting genetic manipulation(s) for traits such as rapid weight gain from efficient conversion of food into meat and eggs and the harsh environmental conditions and severe husbandry operations in modern poultry farming. To reduce pulmonary diseases and their severity, greater effort must be directed at establishment of optimal poultry housing conditions and use of more humane husbandry practices.
在商业家禽养殖中，呼吸道疾病导致高发病率和死亡率，造成巨大的经济损失。没有经验证据，早期的观察导致了这样的假设，即一般鸟类，特别是家禽，具有较弱的先天和适应性肺防御能力，因此极易受到病原体的伤害。然而，最近的发现表明，鸟类具有显著有效的肺防御能力，包括：（i）具有复杂的三层气道结构，气流动力学复杂，可有效过滤吸入的空气；（ii）具有特殊的气道黏膜衬里，包括空气过滤（纤毛）细胞和各种固有吞噬细胞，如表面和组织巨噬细胞、树突状细胞和淋巴细胞；（iii）一种非常有效的黏液纤毛上升系统，可有效清除捕获的外来物质；（iv）吞噬性心房和漏斗状上皮细胞；（v）吞噬功能强大的表面巨噬细胞，可破坏病原体和有害颗粒；（vi）肺血管内巨噬细胞可保护肺部免受血管侧的侵害；（vii）具有吞噬功能的肺外溢红细胞。此外，禽类呼吸系统迅速将吞噬细胞转移到呼吸表面，显然是从上皮下空间和循环系统转移而来：动员的细胞与表面巨噬细胞一起破坏外来物质。需要进一步研究以确定禽类呼吸系统假定的防御薄弱是否是全球性的禽类特征，还是仅存在于家禽中。本综述认为，家禽中肺防御的任何不足可能是由于对某些特征的严格基因操作所致，例如从食物到肉和蛋的高效转化，从而快速增加体重，以及现代家禽养殖中的恶劣环境条件和严格的饲养操作。为了减少呼吸道疾病及其严重程度，必须更加努力地建立最佳家禽饲养条件，并采用更加人道的饲养方法。
