582 HORSE, SWINE AND POULTRY DISEASES 



has received the name Bacillus bipolaris septicus (syn. B. choleras 

 gallinarum, S. avicida, Pasturella avium). The organism is path- 

 ogenic to practically all poultry, also to mice. For rabbits and 

 guinea pigs, though not often fatal when inoculated subcutaneously, 

 it produces abscesses.* It is not highly resistant, being rendered 

 non-virulent by light, and it is killed by a temperature of 80-85 

 C in ten minutes. It resists freezing, however, for fourteen days, 

 although prolonged cold weakens the virulence. It appears to be 

 killed by weak germicides, such as 1 per cent carbolic acid. It is 

 not motile. 



In the diseased bird, the organism can be found in the blood 

 and in nearly all the organs. From these it can be removed by bac- 

 teriological methods and examined miscroscopically and in cultures. 

 Such an examination is of value in the diagnosis of the disease. 



The Origin of the Disease and Its Manner of Transmission. 

 Just how the disease gains its entrance to a flock is not known. It 

 is known, however, that the causative organism is found occasion- 

 ally in the intestinal canal of apparently healthy poultry. It is also 

 present at times in the intestines of certain wild birds, especially 

 pigeons. Therefore, while it cannot be doubted that many epi- 

 demics owe their origin to the importation of germs from neighbor- 

 ing farms, to infected birds obtained in, or returning from, poultry 

 shows, or to infected pigeons or other wild birds which have cas- 

 ually visited the location of cholera epidemics, it is true that some 

 epidemics do appear to arise spontaneously; and this circumstance 

 can be explained only on the grounds that the germs of cholera, 

 which live for some time harmlessly in the intestinal tract of poul- 

 try, may, upon occasion, suddenly acquire a greater virulence, which 

 for a time increases as the organisms are passed on through succes- 

 sive birds. The virulence may again subside during the last of the 

 epidemic, and the organism return to the inocuous condition of a 

 harmless parasite in the intestinal tract of the fowls. Such possible 

 rises and falls in the virulence of an organism during the course of 

 an epidemic are not yet well understood by investigators. It is pos- 

 sible that certain species of wild birds, such as pigeons (which are 

 very susceptible to cholera) may serve to heighten the virulence of 

 organisms which at first have only a feeble pathogenic power for 

 other poultry. 



Thus, although little is ever ascertained regarding the origin 

 of a given epidemic, more data are available to show in what way, 

 when the disease has once entered a flock, it spreads from one bird 

 to another. It is well known that the excreta from the intestines 

 of sick birds are loaded with the causative organisms, which are 

 disseminated about the poultry houses and yards. Experiments 

 have shown that the disease may be produced in fowls when this 

 material has access to the blood of birds through open wounds in 

 the comb, wattles or feet. Even the membranes of the mouth may 

 be penetrated; but above all, infection comes about through the in- 

 gestion, along with food or water, of material containing the dis- 



*Babbits may die when infected with very virulent cultures. 



