TURKEY ROUND HEART DISEASE: 
A MODEL CARDIOMYOPATHY 
E. F. Jankus,* N. A. Staley" and G. R. Noren*" 
Turkey Round Heart Disease (RH) is characterized 
by cardiomegaly in the growing poult. An experimental 
breeding flock has been established with progeny hav- 
ing a grossly identified incidence of RH of up to 26 
percent. Breeding trials suggest that the disease has a 
familial mode of inheritance. In all birds examined his- 
tologically, a wide spectrum of focal myocarditis is evi- 
dent within the first week after hatching, and increases 
in severity to two weeks of age. Some birds that survive 
this acute phase develop biventricular dilatation at two 
to three weeks of age. The RH male to female death 
ratio during the chronic phase is approximately two to 
one. Left ventricular endocardial fibroelastosis becomes 
prominent after one month of life, and progresses in se- 
verity thereafter. The clinical diagnosis of RH after the 
acute phase is based upon electrocardiographic (ECG) 
evidence of a shift in the frontal plane axis of the QRS 
complex. Approximately 30% of five week old RH tur- 
keys have cardiac murmurs consistent with mitral in- 
sufficiency. ECG evidence of spontaneous RH recovery 
is associated with conversion to a normal QRS axis, but 
with significantly lower spatial vector strength. Recov- 
ery during the chronic phase occurs in about one-half 
of the RH birds previously diagnosed. Hemodynami- 
cally, both the ECG identified RH and recovered birds 
are hypotensive, and have increased cardiac filling pres- 
sures. Features of turkey RH are consistent with J. P. 
Goodwin's [LANCET 1 (1970) 731] classification of 
a congestive cardiomyopathy. 
INTRODUCTION 
Round Heart Disease (RH) in turkeys has 
been described by several authors.^-^ It has 
been defined as having acute and chronic 
phases.* The acute phase occurs during the first 
two weeks of life and is characterized by pan- 
carditis, focal interstitial myocarditis, and high 
mortality. A wide spectrum of cardiac dilatation, 
ventricular hypertrophy and left ventricu- 
lar endocardial fibroelastosis (EFE) character- 
izes the chronic phase, while death during this 
phase is associated with congestive heart fail- 
* College of Veterinary Medicine, University of Minnesota, St. 
Paul, Minnesota. 
♦* Veterans Administration Hospital, Minneapolis, Minnesota. 
**• Hennepin County General Hospital, Minneapolis, Minnesota. 
ure. The criteria for electrocardiographic 
(ECG) identification of RH turkeys have been 
reported.*' 
This report will present data of breeding 
trials on the mode of inheritance of turkey RH 
and the clinical course of the disease during the 
chronic phase, 
METHODS 
Breeding Trials 
Two blood lines, Flocks 1 and 2, of small 
broad breasted white turkeys with known past 
experience of RH were used for breeding exper- 
iments (1971). All hens were artificially 
inseminated. "Pooled" semen from toms of the 
respective flocks was used for insemination of the 
pen mated hens. From Flock 2 sixteen hens and 
six toms were selected for pedigreeing. Eggs 
from all groups were set at weekly intervals, 
and fertility was determined by candling on the 
fourteenth day of incubation. Hatchability was 
calculated on the basis of number of fertile 
eggs. Hatched poults were fed a commercial 
"starter" ration until five weeks of age. At this 
time those poults not saved for breeder replace- 
ment were sacrificed. The presence or absence 
of RH in the replacement poults was deter- 
mined by ECG. 
Clinical Course of Turkey RH 
During the Chronic Phase 
A second group of turkeys, independent of 
those previously mentioned, was obtained from 
a commercial producer having an RH problem. 
From this source nine control and eighteen RH 
turkeys were selected at four weeks on the basis 
of ECG criteria previously reported.^ These 
poults were fed the same commercial starter ra- 
tion used for the breeding trial flocks to six 
53 
