158 Agricultural Bacteriology. 



Post-mortem examination. The liver is usually very 

 much enlarged and softened; the intestinal organs are 

 congested, but the changes are not such as make it easy 

 to diagnose the disease. 



Manner of infection. The bacteria are found in the 

 blood at the time of death. If any part of the carcass 

 is consumed by well birds, they are certain to become in- 

 fected. The only known manner of infection is by the 

 food or water. The material that drops from the beak 

 of the sick fowl may serve to contaminate the drinking 

 water. The extensive lesions of the intestines allow 

 blood to be mixed with the manure, and the contamina- 

 tion of the food with this material is a cause of rapid 

 spread of the trouble. 



The disease may begin in a flock by the introduction 

 of a bird ill with the chronic type of the disease. Doves 

 and wild birds are also supposed to be agents concerned 

 in the spread of cholera. The improper disposal of dead 

 birds, as by throwing them into a stream may cause in- 

 fection of flocks at a distance. 



Prevention. Nothing can be done for the already in- 

 fected bird. All efforts must be concentrated in pre- 

 venting the spread of the trouble, by the prompt dis- 

 posal of all dead birds, the killing of any that show 

 signs of illness, thorough disinfection of the roosting 

 houses, and the feeding and watering troughs. If pos- 

 sible the flock should be moved onto fresh, uncontamin- 

 ated grounds. The germ is easily killed by drying, sun- 

 light, and disinfectants. It has been shown by experi- 

 ment that it is safe to bring new stock onto land after a 

 period of two weeks, if care has been taken in the disin- 

 fection of the house and other contaminated objects. 



