78 FOWL CHOLERA 



its presence seems to have been determined by scientific 

 investigation in but a very few of these. Salmon investigated 

 it in South Carolina in 1879-80, and Higgins in 1898 reported 

 it from Canada. Salmon gave special attention to vaccination 

 and the effect of disinfectants in destroying the virus. 



Perroncito was among the first to describe the specific 

 cause of the disease. This was followed by the contributions 

 of Pasteur, who, in 1880, cultivated the bacterium in chicken 

 broth and showed that its virulence might be reduced to such 

 an extent that it could safely be used for vaccination. This 

 is the first case in which a virulent organism was successfully 

 modified in a laboratory and made to act as a vaccine. It was 

 the forerunner to the preparation of vaccines for a number of 

 diseases, more particularly for anthrax, black quarter, and 

 rabies. 



§ 65. Geographical distribution. Fowl cholera seems 

 to be widely distributed in Europe and it has been found in a 

 few localities in the United States and in Canada. 



§ 66. Etiology. Fowl cholera is caused by a specific 

 bacterium which is not di.stinguishable morphologically or in 

 its cultural manifestations from the other members of the 

 group of bacteria of which Bad. septicaerniae hemorrhagicac is 

 the type. In this group are the bacteria of rabbit septicae- 

 miae, swune plague, and Wildseuche. It is a small slightly 

 elongated organism with rounded ends. In stained prepara- 

 tions from the tissues it exhibits a pronounced polar stain. 



§ 67. Symptoms. The symptoms described for this 

 disease in Europe differ somewhat from those reported by 

 Salmon. The period of incubation is placed by European 

 writers at from 18 to 48 hours. In the case of 40 fowls inocu- 

 lated by Salmon, it varied from 4 to 20 days the average 

 period being 8 days. The duration of the disease also varies. 

 Usually the sick birds stop eating or the appetite is lessened, 

 though occasionally they continue to eat almost to the time of 

 death. The earliest indication of the disease, is a yellow- 

 coloration of the urates. In health, these are a pure white 

 though they are frequently tinted with yellow as the result of 

 disorders other than cholera. 



