Abstract

Among the possible infectious agents that affect poultry, diseases of the respiratory tract are considered the main health problem, causing both an increase in the number of carcass condemnations and a decrease in the productivity of the flocks [1]. This situation can be partially justified by the avian anatomical characteristics and the propensity to the diseases [2,3]. If the avian evolutionary adaptation makes respiratory efficiency superior to that of mammals, this particularity also facilitates the occurrence of pathologies [4]. The narrow duct that communicates the nasal sinuses in birds, for example, makes it difficult to drain secretions. Likewise, the mucociliary apparatus - characteristic of the respiratory tract histology - is absent in the air sacs, so these structures are more predisposed and susceptible to infections [5]. Respiratory diseases are also the most common health problem among humans. Viral respiratory tract infections are the leading cause of disease and mortality in children under five years of age, who generally have six to eight infections per year [6,7].