398 BIOLOGY OF THE LABORATORY MOUSE 



Mouse septicemia (Erysipelothrix). "Mouse septicemia" is the name 

 given to an infection tirst reported in 1880 by Koch (132) in mice which 

 had been injected subcutaneously with putrefying blood. Although infre- 

 quent, the disease has been encountered both sporadically and epidemically 

 (94, 173, 153, 305, 17, 204, 61) and has been the subject of experimental 

 investigation (82, 139, 300). The etiological agent is Erysipelothrix 

 muriseptica. 



The most complete description of the natural disease is given by Way- 

 son (305), who studied an epidemic in migrating California meadow mice 

 (Microtus Calif ornicus estuarensis) and house mice {Mus musculiis). The 

 infected animals "... sat about with roached backs, roughened pelage, 

 labored breathing, and with eyelids glued together with purulent exudate, 

 and were easily caught by hand." 



The gross pathology was that of a septicemia with purulent conjunc- 

 tivitis and congestion of the subcutaneous vessels producing a deep reddish- 

 pink color in the subcutaneous tissues, particularly about the lymph nodes. 

 Dark red patches of pneumonic infiltration were present in the lungs, with a 

 small amount of effusion in the pleural cavity. The spleen was enlarged 

 and, together with the lymph nodes and liver, was congested and showed 

 occasional tiny white areas of necrosis. Scattered subserous petechiae 

 were noted in the intestinal walls. Organisms were present in large numbers 

 in the blood and viscera. Wayson considered that the infection was spread 

 by cannibalism and by excreta. 



The disease may also occur in stock laboratory mice. In performing 

 routine examinations on dead mice from a normal stock, Balfour- Jones (17) 

 noted purulent conjunctivitis, a peculiar gelatinous appearance of the 

 abdominal organs, enlargement of the spleen, and small discrete greyish- 

 white areas about i to 2 mm. in diameter in the liver. The lesions appeared 

 as pits on the surface of the liver, and microscopically consisted of round 

 areas of necrosis surrounded by an outer zone of leukocytes. During a 

 4-month period, 59 of 393 mice showed the above picture — chiefly mice 

 weighing between 12 and 15 grams. The organism isolated reproduced 

 the disease and was identified as an Erysipelothrix strain. 



Experimentally, the disease may be reproduced by parenteral injection, 

 by oral, dermal, and conjunctival routes, and by inhalation. A septicemia 

 results from parenteral injection, fatal in 2 to 5 days. By other routes the 

 infection progresses more slowly. The first sign of illness is conjunctivitis, 

 at first serous, then purulent, gluing the eyelids together. Lassitude 

 follows; the animal sits with arched back and becomes anorexic and con- 



