Alteration by immunosuppression of early mortality in a naturally occurring cardiomyopathy

Turkeys from a highly inbred flock, which shows a 100 per cent incidence of naturally occurring cardiomyopathy, were treated daily for 3 weeks following hatching with cortisone acetate, or for 4 days following hatching with parenteral cyclophosphamide, or underwent surgical removal of the bursa of Fabricius at hatching. Mortality was significantly reduced during the first 10 days of age when each of the treated groups was compared with its own control group. By 5 weeks of age, the mortality rates in the bursectomized and cyclophosphamide-treated birds were not significantly different than their control groups. Five-week mortality in the cortisone acetate-treated group, however, was significantly lower than in its control group. Long-term morbidity, as reflected by the incidence of cardiac dilatation and hypertrophy in all birds during or killed through one year of age, was lower in the cortisone acetate-treated birds and significantly reduced in the bursectomized birds. These data suggest that the humoral immune system may function in the pathogenesis of this naturally occurring cardiomyopathy in the turkey.