INFECTIOUS DISEASES OF MICE 409 



vated at 50°C. for 30 minutes, and is antigenic, producing an antitoxin 

 which neutralizes its action (225, 227). Antisera specific for the various 

 strains may be produced in rabbits. Organic gold preparations are bac- 

 tericidal for these organisms in vitro and are highly active in preventing 

 experimental infection (71). 



Epidemic Pneumonia in Mice 



Pneumonic lesions in mice may be found in several of the bacterial dis- 

 eases already described and in certain of the virus diseases. In addition, 

 apparently distinct epidemic respiratory infections associated with at 

 least three other bacteria have been reported. In each instance pneumonic 

 involvement has been a prominent part of the clinical and pathological 

 picture. A brief description of these epidemics follows. 



Infection associated with Brucella bronchiseptica. — In 1920, Keegan 

 (118) reported an epidemic which occurred in an animal room containing 

 150 mice and 86 guinea pigs. The disease appeared first in the mice as a 

 prolonged illness causing death in a few of the animals. It was char- 

 acterized by a profuse purulent conjunctivitis with swelling of the eyelids 

 and desquamation and depilation of the surrounding skin, roughening of the 

 fur, nasal discharge, and occasionally death. A few weeks later the condi- 

 tion increased in severity, with the additional signs of rapid, labored breath- 

 ing and weight loss. Mice killed at this time showed a firm, greyish-white, 

 lobular consolidation of one or more lobes without pleuritis. The bronchi 

 were dilated and filled with thick purulent exudate. Microscopic sections 

 revealed purulent bronchitis and bronchopneumonia. The bronchi were 

 filled with polymorphonuclear exudate; the mucosa was thickened or 

 desquamated in some areas and mononuclear infiltration was present in the 

 walls and about the bronchi and blood vessels. Alveolar lesions consisted 

 of areas of polymorphonuclear exudate and partial or complete atelectasis. 

 During the latter part of the epidemic some of the animals succumbed 

 rapidly instead of after a prolonged course. At autopsy, hemorrhagic 

 lesions were present in the lungs, which presented a microscopic picture vary- 

 ing from marked capillary engorgement and serous alveolar exudation to 

 frank hemorrhage. Fifty of the 150 mice developed signs of illness. The 

 mortality was low but the incidence high since many mice, apparentlv 

 normal, showed pulmonary lesions when killed. Infection in the guinea 

 pigs developed late in the course of the epidemic, appearing first in those 

 cages closest to the mice. 



