Atherosclerosis refers to the accumulation of plaque (fatty deposits) in the chicken's arteries. These deposits are made up of cholesterol, fatty substances, cellular waste products, calcium and fibrin. As the plaque builds up, the wall of the blood vessel thickens and narrow the channel within the artery. This obstructs blood flow and reduces the supply of oxygen-rich blood to tissues of vital organs in the chicken's body.
The most frequently affected site in birds is the aorta at the heart’s base. Other sites of importance include the brachiocephalic trunk, pulmonary artery, dorsal aorta, heart valves, and mural arteries. In all cases, atherosclerotic lesions are more pronounced at the level of, or just before, the branching of smaller arteries. Clinical conditions associated with atherosclerosis in chickens include vascular occlusion, rupture, and thrombosis.
Risk factors for the development of atherosclerosis in chickens include:
- Poor Diet: Consumption of a high-cholesterol diet, a diet low in polyunsaturated fatty acids (PUFA) and high in saturated fatty acids, or a high-fat diet enriched in linoleic acid.
- Viral induced: Infection with the Marek's disease virus, which is known to cause atherosclerotic-like lesions in the arteries.
Clinical Signs of Atherosclerosis in Chickens
Signs of atherosclerosis don't appear until the arteries are severely narrowed which leads to a poor oxygen-rich blood supply. They also depend on which arteries are affected and how much blood flow is blocked.
Signs of atherosclerosis may initially appear intermittently, such as when the chicken is experiencing physical or emotional stress where the body requires more oxygen. Signs may include:
- Exercise intolerance: The chicken tires easily and demonstrates heavy panting and darkening of face and comb color. It returns to a normal color after the chicken rests or calms down.
- Behavioral changes: Chickens may act out of character--suddenly becoming more 'aggressive' towards humans (roosters) or more shy and anti-social.
- Reduced activity: The chicken may become less interested in normal activities and appear more lethargic or subdued.
- Weight loss: Affected chickens may lose their appetite and interest in certain foods or feed altogether.
- Ascites: The chicken's abdomen may become enlarged due to accumulation of fluid.
Unless you are observant of each individual flock member, the first indication of the disease will likely be a mysterious sudden death.