CHAPTER IX 

 CONTAGIOUS DISEASES 



There is a group of contagious diseases which are accom- 

 panied by diarrhea. Among these diseases we find blackhead, 

 chicken-cholera, and white diarrhea. 



BLACKHEAD 



Blackhead is scientifically known as enterohepatitis, because 

 it afi'ects the intestines and liver. 



It is .called blackhead because the head is supposed to turn 

 blue or bluish black. This is not always the case. 



Blackhead affects turkeys and, more rarely, chickens. 

 Among turkeys it causes great losses, and in some parts of the 

 country poultrymen find turkey raising very difficult. No 

 such reports have been made on this disease for chickens. 



Blackhead affects young turkeys more than the older birds, 

 though adult birds quite frequently are afflicted with it. 



Cause. — ^The disease is due to a single-celled animal organ- 

 ism or parasite. It is necessary to magnify the germ several 

 hundred times by aid of a microscope in order to see it. This 

 germ was first discovered by Theobald Smith who gave it the 

 name Ameba meleagridis. 



The germs are found in the diseased areas of the liver and 

 bowel, and can be seen in a slide prepared from this portion 

 and examined under the microscope. 



Thousands of these germs are given off from the area of dis- 

 ease in the intestine. Water or food may become soiled or 

 polluted with droppings from the afflicted bird. Other birds 

 become affected by eating or consuming this polluted food. 



The germs on entering the digestive tract locate themselves 

 in the blind pouches or ceca. The ceca are 5 to 7 inches long, 

 and are located at the termination of the small intestines, 

 13 225 



