572 HORSE, SWINE AND POULTRY DISEASES 



enlarged and filled with fecal matter sometimes giving it a dark 

 blue-black appearance, at other times it may be filled with a yellow- 

 ish slimy mass, which when ejected adheres to the feathers in the 

 vicinity of the anus. There is no sign of disease in any other part 

 of the digestive tract; the liver, however, is seriously affected, being 

 about twice its normal size, dark in color and filled throughout with 

 yellow spots varying in shape and size. But few of these spots have 

 a definite outline, and the color varies from a mottled yellow to a 

 dark brown, which merges into the surrounding tissue; they are 

 flat, and sometimes depressed below the surface of the liver. Some 

 of the larger ones, however, are raised like blisters. These spots are 

 composed of dead liver tissue, and are the disease centers where the 

 parasites may be found. The liver is not always affected, as birds 

 nave been dissected in which there were no other lesions except in 

 the free ends of the caeca. 



Cause of the Disease. As before stated, this disease is caused 

 by protozoa, animal parasites which are from one to four times as 

 large as blood corpuscles. They can only be detected by the aid of 

 a microscope, and slides properly prepared for it. They are more or 

 less circular in form, and have a nucleated granular spot usually 

 near the center. Because of their minuteness, and growth in the 

 mucous membranes of the digestive tract, they are easily carried by 

 the excreta to food which, upon becoming contaminated, transmits 

 them to other fowls. This is the usual means of infection. 



While they are no doubt carried by the circulatory system to all 

 parts of the body, it is to be inferred that the caeca and liver are 

 the principal seats of disease, but the blackening of the head 

 which occurs at times is probably due to growths of the parasites 

 causing thrombosis, a damming of the blood, which would indicate 

 that they do grow elsewhere than in the liver and caeca. 



Symptoms. The most pronounced symptom is diarrhoea which, 

 once begun, is constant. The discharges are frequent, thin, watery 

 and generally of a yellowish color. This, however, sometimes occure 

 from other intestinal disorders, such as tapeworms, or bacterial irri- 

 tation, and therefore cannot alone signify that they are afflicted 

 with this particular malady. If the affection first occurs in the 

 caeca, diarrhoea will appear earlier than if it were in the liver, for 

 the disease in the liver must progress to such a stage as to interfere 

 with the gall ducts discharging the contents of the gall bladder into 

 the intestines, thus interfering with digestion and causing diarrhoea; 

 the next symptom is a drooping of the tail, followed by a drooping 

 of the wings, after which death soon ensues. 



If a blackening of the head occurs, by an engorgement of blood, 

 it takes place about the time when the tail droops and usually con- 

 tinues until death. The affected birds have fickle appetites and 

 mope about; in chronic cases they become emaciated, whereas in 

 the acute form, when both liver and caeca are affected, they die be- 

 fore there is any appreciable wasting away. 



Young turkeys are much more susceptible than are the older 

 ones, or they may be more delicate and cannot withstand the in- 



