INFECTIOUS ENTERO-HEPATITIS OF TURKEYS 121 
gella, a vibratory membrane and one posterior flagellum. The nu- 
cleus is placed anteriorly. One or more food vacuoles may be ob- 
served. The average length of this form is about 10 microns. 
Pathogenicity. Young turkeys are especially susceptible, al- 
though there appears to be no period of immunity to primary in- 
fection during the life of the bird. The greatest losses occur during 
the first two or three months of life. Practically all of the exposed 
poults contract the disease at this time. Young chickens are only 
slightly susceptible but may serve as carriers of the organism. 
Source of infection. The disease is principally spread through 
exposure to infested ground. Once the causative agent has been 
brought on the premises, it is apt to continue its activity year 
after year. Whether this is wholly due to the resistance of the 
encysted stage of the parasite, to climatic or other external influ- 
ences or whether it is perpetuated in the intestinal tract of compara- 
tively resistant turkeys or chickens is open to speculation. From 
the fact that mature turkeys may show symptoms of entero-hepatitis 
during all seasons of the year, it is reasonable to assume that they 
constantly harbor the organism in a saprophytic form and only de- 
velop the disease as a result of adverse conditions or weakened con- 
stitution from other causes. Curtice states that chickens though 
rarely infected may serve as carriers. In any case, the disease is 
contracted by the poults ranging on ground infested by the droppings 
of carriers of the parasite. The parasite passes from the intestine in 
the encysted or resistant stage. In this form when not exposed to 
the direct rays of the sun or to considerable drying it may retain its 
vitality for a long period, possibly one to two years. Earth worms 
may play some part as mechanical carriers of cysts which have sur- 
vived in the soil under favorable conditions. When these encysted 
forms are taken into the alimentary tract by poults in feeding, they 
undergo changes which renew their activity. The tough resistant 
covering is discarded and forms developed from the central granular 
mass or nucleus penetrate.the mucosa of the intestine, especially the 
ceca and may be carried by the blood stream to the liver. The para- 
sites multiply rapidly in the intestine and are passed out in enormous 
numbers in the droppings. By this means, other susceptible birds 
in the flock are directly infected through coming in contact with the 
contaminated material in feeding. 
Symptoms. The symptoms of entero-hepatitis become apparent 
within a period of four weeks after exposure. Young birds show 
less resistance and develop manifestations earlier than grown ones. 
