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Atherosclerosis

Atherosclerosis is the buildup of plaque (fatty deposits) within the arteries. This plaque is composed of cholesterol, fats, cellular waste products, calcium, and fibrin. As it accumulates, the artery walls thicken and the inner passageway narrows, restricting blood flow. This reduces the delivery of oxygen-rich blood to the tissues and vital organs of the chicken’s body.

In birds, the most commonly affected area is the aorta at the base of the heart. Other important sites include the brachiocephalic trunk, pulmonary artery, dorsal aorta, heart valves, and mural arteries. Lesions tend to be most pronounced at or just before arterial branch points. Atherosclerosis can lead to serious complications, including ischemic stroke and congestive heart failure.

Risk factors for atherosclerosis in chickens include:
  • Poor Diet: Diets high in cholesterol, high in saturated fats, low in polyunsaturated fatty acids (PUFAs), or enriched with certain fats like linoleic acid.
  • Viral causes: Infection with Marek's disease virus can produce atherosclerosis-like lesions in the arteries.

Clinical Clinical signs of atherosclerosis in chickens


Symptoms often do not appear until the arteries are significantly narrowed and oxygen supply is compromised. Signs can vary depending on which arteries are affected and may appear intermittently, especially during times of physical or emotional stress when oxygen demand increases.
  • Exercise intolerance: The chicken tires easily, may pant heavily, and can develop a darkened face or comb that returns to normal after resting.
  • Behavioral changes: Chickens may act out of character—roosters may become more aggressive, while others may become withdrawn or less social.
  • Reduced activity: A noticeable decrease in activity level, with increased lethargy.
  • Weight loss: Loss of appetite which results in weight loss.
  • Ascites: Enlargement of the abdomen due to fluid accumulation.
Unless you closely monitor each bird, the first sign of atherosclerosis may unfortunately be sudden, unexplained death.

Treatment of atherosclerosis

Atherosclerosis treatment consists of diet modification and improving peripheral perfusion.
  • Peripheral vasodilators: Isoxsuprine, angiotensin-converting enzyme (ACE) inhibitors (enalapril and benazepril).
  • Pentoxifylline: May help improve peripheral perfusion.
  • Statins: For lowering plasma total cholesterol concentrations.
  • Omega-3 fatty acids: May help improve lipid metabolism, reduce inflammation and reduce the risk of atherosclerosis.

Clinical Signs

Behavioral changes
Weight loss
Muscle wasting
Decreased appetite
Lethargy
Exercise intolerance
Difficulty breathing
Darkening of the comb
Ascites
Weakness
Ataxia
Falling off perch
Seizures
Progressive paresis
Disorientation
Sudden death

Diagnosis

  • History
  • Radiographs - may identify cardiomegaly associated with atherosclerosis and severe vascular mineralization.
  • changes in serum cholesterol and lipoprotein levels
  • CBC
  • Echocardiography
  • CT
  • Necropsy

Reported Cases

  • Case 1: Arteriosclerosis in a Parrot A 40-year-old female African grey parrot exhibited weakness due to anorexia for several days. Physical examination revealed that the bird was weak, cachectic and had abdominal effusion. There was 15 ml of clear fluid in the thoracic cavity and 25 ml of clear fluid in the abdominal cavity. The aorta and left and right pulmonary arteries were firm, gritty, and had a nodular appearance. The right thyroid was enlarged, 6 mm in diameter. The left thyroid was 3 mm in diameter. Hypoalbuminemia (total protein 1.2 gm/dl, albumin 0.5 gm/dl, and globulin 0.7 gm/dl) was observed in blood chemistry profile. The lesions of the aorta and pulmonary arteries consisted of fragmentation of elastic and collagen fibers with cholesterol deposition and proliferation of spindle cells in the media. There was chondroid metaplasia, mineralization and proliferation of smooth muscle cells in the subintimal tissue and intima, which caused narrowing of the lumen. Ref

  • Case 2: Presumed atherosclerosis in a Eagle A 19-year-old male golden eagle presented for an abnormal heart rhythm on auscultation. An electrocardiogram was performed on the patient and demonstrated frequent supraventricular premature complexes. While an echocardiogram on the same patient revealed marked systolic dysfunction of the severely enlarged left ventricle as well as severely enlarged left atrium. No clinical evidence of left-sided congestive heart failure was noted. Treatment with isoxsuprine and atenolol was initiated. After 2 weeks, no significant changes were appreciable on repeat examination. The medical therapy was modified to isoxsuprine, sotalol, and pimobendan. Following 4 weeks of the new treatment plan, chamber sizes of the left ventricle and atrium were reduced, and the cardiac rhythm had converted to a normal rhythm. A computed tomography angiography (CTA) was conducted and identified substantial narrowing of the internal diameter of the right brachiocephalic artery. Fifteen months after initial diagnosis, the patient continued to maintain a normal sinus rhythm, normal cardiac size, and appropriate systolic function of the left ventricle despite no changes observed in the right brachiocephalic arterial diameter on repeat CTA. This case report demonstrates the therapeutic potential of sotalol at 1 mg/kg PO BID for the treatment of supraventricular premature complexes and a diagnostic utility of CTA for the case of suspected atherosclerosis. Ref

  • Case 3: Atherosclerosis in a Budgie A 16-year-old male grey-cheeked parakeet was presented for dyspnea and decreased activity. The bird's diet was primarily table food, with a large proportion of animal products. Radiographs revealed a linear mineralized structure in the plane of the aorta and an enlarged hepatocardiac silhouette. Left atrial and left ventricular enlargement and a left ventricular systolic dysfunction were diagnosed by echocardiography. The bird's condition progressively declined, and it died 5 days after presentation. A postmortem examination revealed marked atherosclerosis of the aorta, great vessels of the heart, and coronary arteries with myocardial degeneration, pulmonary congestion, and ascites. Ref

  • Case 4: Atherosclerosis in a Parrot A 20-year-old female African Grey parrot was evaluated to determine the cause of lethargy, hyporexia, weight loss, and persistent ascites of 21 days' duration. Physical examination revealed a markedly distended abdomen and systolic heart murmur. Thoracic radiography revealed cardiomegaly and hepatomegaly. Doppler echocardiography revealed severe eccentric and concentric hypertrophy of the right ventricle with systolic dysfunction, moderate regurgitation through the right atrioventricular valve, a substantial increase in estimated systolic pulmonary arterial pressure, hepatic venous congestion, and coelomic effusion. A clinical diagnosis of chronic cor pulmonale was established. The parrot was initially stabilized by use of coelomocentesis. During the next month, the parrot was treated by administration of furosemide, hydrochlorothiazide, spironolactone, benazepril, and pimobendan. The parrot appeared to be responding well to treatment but was found dead in its cage 35 days following initial examination. Postmortem examination revealed substantial atherosclerosis of the large pulmonary arteries, with lesions extending into the medium-size arteries. Pulmonary atherosclerosis was suspected as a cause of the severe pulmonary hypertension. Ref

  • Case 5: Atherosclerosis in a Parrot A 35-year-old yellow-naped Amazon parrot was presented for gradually increasing inappetence, ataxia, weakness, and lethargy. Radiographic and ultrasonographic findings were strongly suggestive of atherosclerosis. Isoxsuprine, a peripheral vasodilator demonstrated to be of benefit in humans with intermittent limb pain, weakness, and lameness secondary to occlusive vascular disease, was selected for treatment. The bird's clinical signs resolved during treatment but recurred after varying periods of time when the medication was stopped intermittently. Nearly 3 years after the initial examination, the parrot was doing well on isoxsuprine therapy, with normal prehension of food with its feet and no recurrence of clinical signs. Ref

Treatment

NameSummary
Supportive careIsolate the bird from the flock and place in a safe, comfortable, warm location (your own chicken "intensive care unit") with easy access to water and food. Limit stress. Call your veterinarian.
Weight control Restrict how much feed and fat the chicken receives in their diet to encourage weight loss in overweight birds and/or prevent them from becoming obese.
Omega-3 fatty acids and Vitamin EAdded to the dietO Cojean et al., 2020; A Sekikawa et al., 2019; C Petzinger et al 2013; N Ozer et al
Isoxsuprine5-10 mg/kg PO q24hFitzgerald, Brenna Colleen et al., 2018; Simone-Freilicher, Elisabeth., 2007
AtorvastatinSupplementing the diet with 20 mg/kg of atorvastatin suppressed lipogenesis, enhanced antioxidant response, and improved gut and cardio-pulmonary function in cornish chicks subjected to hypobaric hypoxia.S Abaszadeh et al., 2023

Support

Prevention

  • Feed a low fat, low cholesterol diet with plenty of omega-3 fatty acids, particularly long chain EPA and DHA sources.
  • Vaccinate chicks for Marek's disease
  • Encourage exercis
  • Don't feed chickens table scraps.

Prognosis

Poor

Scientific References

Age Range

Usually seen in adult chickens.

Risk Factors

  • Infection with Chlamydophila psittaci
  • Unhealthy diet. Foods that are high in saturated and trans fats, cholesterol, sodium (salt), and sugar.
  • Feeding chickens a steady diet of table food and/or eggs.
  • Infection with Marek's Disease virus (MDV)
  • Heavier breeds and/or obesity
  • Increased age
  • Lack of exercise

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