606 BACTERIOLOGY OF MILK 



In addition, the viruses of certain infections specific for man may 

 be transmitted in milk. These organisms gain entrance to the milk 

 directly from human sources, incidental to the various handlings 

 which it undergoes, and they may persist in unheated milk in suffi- 

 cient numbers to infect the consumers. Typhoid, diphtheria, scarlet- 

 fever, epidemic sore throat and pseudodiphtheria infection, dysentery 

 (bacillary), various types of epidemic diarrhea and even Asiatic 

 cholera are the more important diseases thus transmitted. 



Except in very rare instances, specific pathogenic bacteria other 

 than the bovine tubercle bacillus and Micrococcus melitensis. have 

 not been isolated directly from milk. The evidence of the transmis- 

 sion of pathogenic bacteria through infected milk rests largely upon 

 statistical data. It is very conclusive, however, and many severe 

 epidemics of typhoid fever and other infections have been satisfac- 

 torily traced to carriers or mild cases of the same disease among those 

 who have undoubtedly handled the milk. 



Conradi, 1 however, appears to have isolated the typhoid bacillus from 

 infected milk which was shown to be responsible for a small outbreak 

 of typhoid fever, and Bruck 2 and others have shown that typhoid 

 bacilli and similar pathogenic bacteria may persist and even multiply 

 in the presence of the various microorganisms commonly present in 

 ordinarily good grades of milk. 



The virus of foot and mouth disease and the bovine tubercle bacillus 

 have been detected in butter and cheese prepared from milk containing 

 these viruses. 



The origin and relation of streptococci to milk-borne epidemics of 

 septic sore throat and tonsillitis have been subjects of controversy. 

 There appear to be two theories: one theory maintains that the 

 streptococci are of bovine origin and presumably derived from the 

 udders of cows which are suffering from mastitis or garget. The 

 other theory assumes that these streptococci are usually of human 

 origin and have gained entrance to the milk at some stage of its post- 

 bovine history. Theobald Smith 3 and Brown have made an extensive 

 study of this subject and their conclusions are of particular interest 

 in this connection. They state that "there is at present no satis- 

 factory evidence that bovine streptococci associated with mastitis 

 or garget are the agent of tonsillitis in man. Whenever cases of 



1 Centralbl. f. Bakt., Orig., 1906, xl, 31. 



2 Deutsch. med. Wchnschr., 1903, xxix, 460. 



3 Jour. Med. Research, 1911, xxxi, 501. 



