270 VETERINARY BACTERIOLOGY 



of the rabbit. Mohler and Buckley produced a fatal infection in 

 young house-rats, while other authors report the rat as immune. 

 The same is true of the dog, though this animal is relatively resist- 

 ant. Chickens are immune. Sheep are readily infected. The 

 hog succumbs to intravenous injection, as well as through feeding. 



Type of Disease and Lesions Produced. In man the infection 

 is marked by a severe enteritis and enlargement of the lymph- 

 follicles and Peyer's patches, and by small hemorrhages. The 

 mortality in infections is low probably less than 5 per cent. 



The infection in cattle, as observed by Mohler and Buckley, 

 was characterized by degeneration of the heart muscle (frequently 

 fatty) and hemorrhages therein; in the liver parenchymatous 

 degeneration was accompanied by localized hemorrhagic extravasa- 

 tions; the spleen was enlarged and hemorrhagic and the lesions 

 of acute enteritis, with necrosis of the epithelium, were evident. 



Immunity. The so-called " toxin "of the B. enteritidis is prob- 

 ably an unusually soluble and potent endotoxin. It differs from 

 true toxins in being exceptionally heat resistant. Meat which 

 has been quite thoroughly cooked is sometimes found capable of 

 giving rise to toxic symptoms when ingested. The bacteria-free 

 nitrates from bouillon cultures and cultures in which the organisms 

 have been killed by heat will kill guinea-pigs when injected in 

 suitable quantities. It is probable that this endotoxin is respon- 

 sible for the quick development of symptoms in those who are 

 poisoned by eating infected food. Specific agglutinins are devel- 

 oped in the blood of infected individuals, as are also coagglutinins 

 for other members of the intestinal group. Some differences in 

 agglutinability of the different strains isolated have been noted. 

 It has been proposed that meat may be tested for the presence of 

 B. enteritidis by expressing the juice and determining its agglutin- 

 ating power. This has not been proved practicable. It is prob- 

 able that the bacilli already present in the meat would in some cases 

 fix all the agglutinins present, if stored for any length of time. 

 Practicable methods of prophylactic or curative immunization 

 have not been demonstrated. 



Bacteriologic Diagnosis. The organism may be demonstrated 

 by plate cultures from infected flesh. In man the disease may be 

 diagnosed by the agglutination test, although with difficulty, for, 



