Merck Manual

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Spontaneous Cardiomyopathy of Turkeys

(Round Heart Disease)

By

Billy M. Hargis

, DVM, PhD, DACPV, Department of Poultry Science, Dale Bumpers College of Agricultural, Food and Life Sciences, University of Arkansas and the Arkansas Agricultural Experiment Station, UA Division of Agriculture

Last review/revision Feb 2023

Spontaneous cardiomyopathy of turkeys generally occurs in poults < 4 weeks old and results in sudden death. The etiology is unknown, and there is no treatment. The incidence of this condition has decreased dramatically since 1980.

Spontaneous cardiomyopathy of young turkeys is characterized by sudden death due to cardiac arrest and is not related to other cardiomyopathies of poultry. Historically, it was an important problem; however, the incidence of this disease has greatly diminished since the 1980s, possibly as a result of genetic selection processes at the primary breeder level. Turkey-industry veterinarians polled indicate that spontaneous cardiomyopathy is now only occasionally observed, and the incidence is much lower within affected flocks (generally < 0.5%) than it was before 1980.

Etiology and Pathophysiology of Spontaneous Cardiomyopathy of Turkeys

The exact etiology of spontaneous cardiomyopathy in turkeys is unknown, due to minimal funded research. However, one study in which furazolidone was administered to produce dilated cardiomyopathy in turkeys indicated altered membrane transport resulting in myocardial failure.(1 References Spontaneous cardiomyopathy of turkeys generally occurs in poults Spontaneous cardiomyopathy of young turkeys is characterized by sudden death due to cardiac arrest and is not related to other... read more ) CK activity, glycolysis, glycogen concentration, myofibril function, the activity of Krebs cycle enzymes, fatty acid oxidation, and the concentration of soluble proteins were all decreased. The calcium-transport ATPase activity of the sarcoplasmic reticulum increased. This pattern of biochemical changes suggests that ischemia plays a role in the pathogenesis of spontaneous cardiomyopathy in turkeys.

Some outbreaks of spontaneous cardiomyopathy have been associated with an environment low in oxygen with increased CO2. This can occur during incubation of the eggs and often during transport (hatchery to brood farm) often in cold weather. Poults on the bottom tier within transport trucks have been suggested by veterinarians to be at increased risk. At the brooder farm, stratification of the air in poorly ventilated facilities that lack (or improperly operate) circulation fans may produce similar environmental conditions (decreased oxygen, increased CO2) particularly in cold weather.

Clinical Findings

Although most turkey deaths due to spontaneous cardiomyopathy occur during the brooding period, the ratio of heart weight to body weight of affected birds is higher than normal throughout the growing period. The chronic cardiac insufficiency decreases the growth rate, leading to attacks on affected birds by their healthy cohorts. In affected turkeys that survive to market age, body weights are lower by an average of 3 pounds (1.4 kg).

Most deaths from spontaneous cardiomyopathy occur during the first 4 weeks of life, with mortality peaking at 2–3 weeks. Affected poults die suddenly, but some may have ruffled feathers, drooping wings, and a generally unthrifty appearance and may show dyspnea before death. After 3 weeks of age, mortality is sporadic.

Characteristically, the affected poult in the first 4 weeks of life has a greatly enlarged heart that is due to dilatation of both ventricles, congested lungs, and a swollen liver. Ascites, generalized and pulmonary edema, and hydropericardium may be present. In older poults, enlarged hearts are due to marked hypertrophy of the ventricles, in addition to dilatation. Histologically, lesions of abnormal hearts are nonspecific and include congestion, damage to the myofibrils of the cardiocytes, and focal infiltration by lymphocytes.

Diagnosis of Spontaneous Cardiomyopathy of Turkeys

  • History

  • Gross findings at necropsy

Generally, diagnosis of spontaneous cardiomyopathy in turkeys is based on history and gross findings at necropsy. Although an ECG can be performed, it is of little practical use.

Treatment and Prevention of Spontaneous Cardiomyopathy of Turkeys

No treatment for spontaneous cardiomyopathy is available. Increased incidence of this condition in turkeys has most frequently been associated with hypoxia during incubation, transportation, or brooding. Enhanced ventilation during these periods appears to be critical to disease prevention.

Turkey-industry veterinarians have occasionally noted an association between high amounts of copper in feed or drinking water and increased incidence of spontaneous cardiomyopathy. Given that overheating has also been postulated to increase the incidence of this disease, good brooding practices with attention to optimal environment, feeding and husbandry practices specific for raising turkeys may decrease mortality.

Key Points

  • Spontaneous cardiomyopathy in turkeys results in cardiac failure, as in other species.

  • The condition affects young growing turkeys and results in substantially decreased market weight or sudden death.

  • The etiology is unknown, and there is no treatment. Prevention is aimed at ensuring normal ambient oxygen levels for eggs and hatchlings.

References

  • Staley NA, Noren GR, Bandt CM, Sharp HL. Furazolidone-induced cardiomyopathy in turkeys. Association with a relative alpha1-antitrypsin deficiency. Am J Pathol. 1978;91(3):531–544.

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