4i6 BIOLOGY OF THE LABORATORY MOUSE 



Kutschera (136) observed a spontaneous epidemic in white mice due to 

 a streptococcus, although a staphylococcus was present as well in many 

 animals. The affected animals appeared ill, their eyelids were adherent, 

 hair roughened, and breathing rapid. At autopsy the spleen was enlarged 

 to three or four times normal size and studded with yellowish, pin-head 

 sized abscesses. Of 30 mice studied bacteriologically, most showed a 

 double infection with streptococci and staphylococci. Organisms were 

 seen in smears of the liver, kidney, spleen, heart, and bone marrow. Experi- 

 mental inoculations of normal mice with organ suspensions of infected 

 animals produced death in i to 2 days, the findings resembling those of the 

 spontaneous disease without abscesses. Subcutaneous inoculation with a 

 pure culture of the streptococcus resulted in death in 3 days. A local 

 abscess was formed at the injection site, about which the tissues were 

 hemorrhagic; punctiform hemorrhages were present in the peritoneum, 

 intestines, and testicles, and the spleen was swollen. Similar experimental 

 infections with streptococci have been obtained by other workers (139, 300). 



Although such epidemics are rare, apparently normal mice may harbor 

 streptococci (341). Cultures of the blood of 35 white mice were positive 

 for streptococci in two instances. After injection with sterile milk, adren- 

 alin, or plague vaccine, 6 of 35 mice showed streptococci by blood culture. 

 The strains obtained were not identical in their cultural reactions and only 

 one produced hemolysis, although all were gram-positive cocci, growing in 

 long chains. 



Infection with Bacillus Piliformis 



A highly fatal bacterial disease in Japanese waltzing mice has been 

 reported by Tyzzer (295). The disease spread among this inbred stock in 

 epidemic fashion, affected a few hybrids of the first and second filial genera- 

 tions (Fi and Fo), but did not involve the common laboratory mice. It 

 presumably originated from the common mouse during cross-breeding 

 experiments, although the organism was not found in stained sections of the 

 intestines of many laboratory and wild mice. 



Signs of infection appeared 24 to 48 hours before death and consisted 

 of roughened fur, ataxia, and watery or slimy diarrhea. In young animals 

 the disease was more acute, with diarrhea the prominent feature. Diagnosis 

 could be made in some animals by removing the fur from the abdomen and 

 viewing the lesions on the ventral surface of the liver through the transparent 

 abdominal wall. The time of death varied from 6 to 44 days after exposure, 

 with an average of 10 to 20 days. 



