INFECTIOUS DISEASES OF MICE 391 



since the introduction of test material might be sufficient to light up the 

 latent Salmonella infection, with erroneous and misleading results. 



There are no satisfactory methods at the present time for the eradica- 

 tion of the disease from an infected colony. In some cases the entire herd 

 must be destroyed and a new stock obtained; in others, a Salmonella-iree 

 stock may be obtained by quarantining the entire colony, dividing it into 

 small units of 5 or 6 mice, destroying all the mice in any unit in which a 

 death occurs from mouse typhoid, and finally destroying units in which 

 fecal carriers are present as determined by repeated cultures. The second 

 procedure is expensive and in many cases impracticable because of the labor 

 involved. Once a stock is obtained free from infection, it can be maintained 

 by adherence to general preventive measures which will be outlined later 

 in the chapter. 



Septicemic Diseases of Mice: Pasteurellosis, Pseudotuberculosis, 



Mouse Septicemia 



Mice are highly susceptible to at least three types of septicemic dis- 

 eases, namely, pasteurellosis. pseudotuberculosis iCorynehacteriiim) and 

 "mouse septicemia" (Erysipelolhri.x). Spontaneous epidemics, however, 

 are uncommon, although sporadic deaths are not infrequently encountered. 

 In general, the diseases run an acute course and thus may not produce 

 characteristic morbid changes, so that the diagnosis must usually be made 

 by isolation and identification of the etiological agent. The three t>3)es will 

 be discussed separately, in conjunction with diseases related by virtue of 

 their character or the nature of the infecting agent. 



Pasteurellosis. — Diseases due to Pasteiirella organisms are primarily 

 endemic in wild animals and include the so-called "hemorrhagic septicemia" 

 group, pseudotuberculosis of rodents, and plague. All three types may 

 occur in mice, but only the first is of much importance. 



Hemorrhagic septicemia in mice. — Of all the septicemic diseases of 

 animals, one tj-pe may be differentiated, since it is characterized by septi- 

 cemia, capillary hemorrhage, serous, fibrinous, or sanguineous exudation, 

 and the presence of short bipolar-staining organisms. The disease is found 

 in a wide variety of animal species and occurs in spontaneous epidemics in 

 mice (285, 278, 94, 93, 19). 



Detailed clinical and pathological descriptions of the spontaneous dis- 

 ease in mice are lacking. The illness usually is acute, death occurring a few 

 hours after the onset of signs which are nonspecific — apathy, ruffled coat, 

 anorexia, conjunctivitis, rapid respiration, etc. The disease is contagious, 



