CHAPTER VI 



INFLUENCE OF DISEASE UPQN MILK 



MAN is susceptible to several of the specific infectious 

 diseases of cattle viz: tuberculosis, aphthous fever or 

 foot and mouth disease, cowpox, anthrax, rabies, and 

 actinomycosis. Furthermore, mastitis, calf cholera, acute 

 croupous and hemorrhagic enteritis (paracoli infection), 

 septic metritis, and many suppurative conditions in cattle 

 are caused by bacteria which are pathogenic for man. In 

 certain non-bacterial affections, such as gastro-intestinal 

 catarrh, the milk sometimes becomes unpalatable and, 

 when ingested, may cause irritation of the gastro-intes- 

 tinal tract, especially in children. 



The study of the conditions under which disease-pro- 

 ducing organisms enter the milk and the effect of disease 

 upon the milk secretion is one of the important divisions 

 of milk hygiene. Bacteria or virus may be carried by the 

 blood to the udder and be eliminated with the milk, or 

 they may be excreted through one of the other normal 

 open channels or discharged from wounds and enter the 

 milk after it is drawn from the udder. The first method 

 is called direct infection and the latter secondary infec- 

 tion. There is no doubt that bacteria circulating in the 

 blood may pass over into the milk when the tissue sepa- 

 rating the udder alveoli and tubules from the capillaries 

 is broken down by disease. Some investigators are of 

 the opinion that this may also occur when the udder tissue 

 is intact, but this view is disputed by others. When 

 bacteria invade the udder through the teat canal, as 



72 



