FOWL 'CHOLERA 585 



the infected blood or with cultures of the organism. Some 

 of the domesticated animals are susceptible to intravenous 

 injections of highly virulent cultures of the organism. The 

 disease is not produced in dogs, cats or hogs from eating the 

 infected meat of fowls. The virulence of the organism may 

 be increased by repeatedly passing it through chickens, 

 guinea pigs, pigeons or sparrows. The organism may be 

 attenuated by subjecting it to sunlight, drying and exposure 

 to the air. The attenuation may be sufficient to prevent 

 further spread of the disease. 



Natural Infection. Natural infection may take place in 

 numerous ways: (a) The droppings of fowls contaminate 

 the feed and water given other fowls and the infection is 

 thus introduced immediately into the digestive tract. 



(6) In most cases the flock is infected through newly 

 acquired cholera-sick birds, or birds returned from shows 

 or exhibitions where they have been in contact with the 

 infection. 



(c) Pigeons and sparrows play an important part in the 

 dissemination of cholera, by carrying the infection from 

 flock to flock. This accounts for isolated outbreaks of the 

 disease where no exchange of birds has taken place. 



(d) The infection is frequently carried on clothing, shoes 

 and other objects. 



(e) It may be spread by carelessness in disinfecting cars 

 in which cases have been transported. This has proved to 

 be the source of infection in a number of instances. 



(/) Eggs have been the carriers of the infection in some 

 few cases reported. 



The infection in most cases is taken directly in the 

 digestive tract with the food or drink. The bacilli pene- 

 trate the mucous membrane and enter the lymph spaces of 

 the walls of the intestines. They are soon taken into the 

 circulation where they multiply very rapidly. In some 

 cases when the infection is introduced into wounds it is 

 taken into the circulation more promptly, and consequently 

 the course of the disease is more rapid. Death results in 

 these cases no doubt from the large amount of toxins formed. 



