Symptoms 93 



fested by opened mouth, inspiration as well as expiration being 

 associated with moist rales. As the weakness progresses they 

 lie with closed eyes and in a stupor in one place. If they at- 

 tempt to rise they soon collapse and finally die with manifesta- 

 tions of convulsions or coma. 



In the chronic form of the disease progressive anemia de- 

 velops after the disappearance of the acute symptoms, or from 

 the onset of the disease, attended by emaciation ; finally a per- 

 sistent diarrhea occurs. Sometimes one or more joints of the 

 wings or feet swell; later the swelling bursts, whereupon a 

 caseous purulent mass containing bacilli is discharged from 

 the joints. The arthritis interferes to a great extent with the 

 movements of the already weakened birds. 



The duration of the disease is from 1 to 3 days in the 

 majority of acute cases with the exception of the peracute 

 cases. It may, however, exceptionally extend from 7 to 12 

 days. In these cases the symptoms are less severe from the 

 onset, and the exhaustion appears later. The course of the 

 chronic form extends over several weeks. 



The prognosis is very unfavorable. Frequently entire flocks 

 of chickens succumb to the infection, while in other cases a cer- 

 tain percentage of the birds escape probably owing to a slighter 

 intensity of the infection. However, in exceptional cases re- 

 coveries may take place. 



Diagnosis. Chicken cholera in its course and symptoms 

 greatly resembles chicken pest. The latter comes into con- 

 sideration particularly when it affects chickens exclusively. 

 From this as well as from other septicemic affections of fowls, 

 and also from acute poisonings which are frequently suspected 

 by the owners, the disease can be differentiated with certainty 

 by an autopsy and bacteriological examination (see also 

 chicken pest.) Intestinal worms (for instance, the trichosoma 

 coUare) may also produce cholera-like symptoms. 



Chronic cases, particularly those which are associated with 

 arthritis, may be mistaken for tuberculosis and gout. A dif- 

 ferentiation is here also only possible by microscopical exam- 

 ination of the exudates from the joints, as well as by autopsies. 



On autopsy the presence of intestinal inflammation, the 

 fibrinous exudate contained in the serous cavities, and the 

 hemorrhages are strongly suggestive of fowl cholera, but to 

 establish a definite diagnosis even in such cases a bacteriological 

 examination of the blood and the inflammatory products is 

 necessary. 



The microscopical examination consists in the preparation of cover-glass smears 

 iii which usually large masses of bipolar rods can be easily recognized by the aid 

 of the previously mentioned staining methods (see page 79). Pigeons are best 

 suited for test inoculations, especially since they are not susceptible to chicken 

 pest. For this purpose the point of a knife is dipped into blood or exudate and then 

 used for scarifying the skin, or a small quantity of the material is injected, sub- 

 eutaneously or it may be introduced into the breast muscles. The inoculation 

 usually results in a short time in the death of the test animals and when the in- 



