What factors cause or predispose to respiratory disease in poultry?

What factors cause or predispose to respiratory disease in poultryRespiratory physiology of poultry is unique. Unlike human respiratory anatomy the avian lungs do not expand or contract on breathing. The direction of the flow of gases is unidirectional in the lungs making it more efficient in gas exchange.  The air sacs associated with the poultry respiration form a very important component for air storage during inhalation or exhalation.  The air sacs also regulate body temperature by diverting air flow to pneumatic bones for effective heat exchange.

All etiologies for respiratory disease in poultry have an aerosol mediated entry point. The contact of these agents with the capillary system associated with the lungs is brief as they are diverted to the air sac for temporary storage. Air sacculitis forms a major finding for respiratory related mortalities on post mortem examinations. Keeping these facts in mind we can list factors affecting respiratory disease as;

Environmental stress affecting breathing of the birds

a) Heat/cold stress

b) Handling stress

Immunisation failures

a) Vaccine component failure

b) Immunodeficiency

Inflammatory agents affecting respiratory system

a) Microbial etiology in bio-aerosols

b) Irritant gases and particulates

Nutritional deficiencies

a) Hypovitaminosis ( A & B 12)

b) Amino acid deficiencies