12 BULLETIN" 939, U. S. DEPARTMENT OF AGRICULTURE. 
from gapeworm can be greatly reduced, inasmuch as infection of the 
runs by the brood hens is not often likely to occur because of the 
rarity of gapeworms among adult chickens. As the eggs and larvss 
of gapeworms have been kept alive in the laboratory for more than 
eight months at a temperature ranging from 70° to 95° F., and for 
more than a year at a temperature of about 50° F. (writer's observa- 
tions), it is advisable not to allow young chickens to run on once- 
contaminated ground until after a considerable period of time has 
elapsed, not less than a year at least, since its exposure to contamina- 
tion. Consequently it is important in locating new runs for young 
chickens on farms where gapes has been prevalent to select a spot that 
is known to have been but little, if at all, frequented by turkeys within 
at least a year. Naturally also it would be unwise to select a spot 
where chickens with gapes had been the year before, even if in the 
meantime there had been no chance of contamination by turkeys. As 
a rule, in order easily to secure immunity from gapeworm losses 
among chickens, it may be found necessary to abandon the keeping of 
turkeys on farms where chickens are raised, because of the difficulty 
of controlling the turkeys so as to prevent contamination of the 
chicken runs. In fact the simplest way of preventing gapes among 
chickens seems to be to exclude turkeys from farms where chickens 
are raised. 
CONCLUSIONS. 
The turkey is probably the natural host of the gapeworm. 
Adult turkeys as well as young turkeys commonly harbor gape- 
worms though they may show no symptoms of infestation. 
The turkey is apparently the chief agent in the spread of gape- 
worms to new localities and is apparently the principal source of 
infection to the soil on poultry farms where gapes is prevalent. 
Gapes among chickens appears to be more prevalent on farms 
where turkeys frequent the chicken runs than on farms where there 
are no turkeys. 
Available evidence indicates that gapes has a tendency to dis- 
appear from farms following the removal of turkeys. 
Chickens, unlike turkeys, are readily susceptible to infection with 
gapeworms only while they are young. They become less susceptible 
to infection as they grow older. 
Adult chickens, at least in some localities, rarely harbor gape- 
worms and hence in such localities are seldom likely to spread 
infection. 
In those instances in which gapeworms develop in adult chickens 
or chickens approaching maturity the parasites are likely to live only 
a short time. 
