96 PRINCIPLES AND PRACTICE OF MILK HYGIENE 



APHTHOUS FEVER OR FOOT AND MOUTH DISEASE 



In the milder forms of foot and mouth disease the 

 milk secretion may not be affected, but in the more severe 

 cases the milk flow is reduced one-half and the milk is con- 

 siderably changed in composition and appearance. The 

 alterations are similar to those observed in inflammation 

 of the udder. The albumin, globulin and salts are in- 

 creased in quantity, while the sugar, casein, and usually 

 the fat are decreased, although sometimes the fat is in- 

 creased. The milk becomes thin, and after it stands 

 for a while a layer of slimy, dirty cream forms at the 

 top of the fluid and considerable sediment is deposited 

 at the bottom of the vessel. When examined microscopic- 

 ally, the sediment is found to be rich in cells epithelial 

 cells, leucocytes, and red-blood cells. The milk coagu- 

 lates when boiled, reacts positively to the alcohol test and 

 contains a large amount of catalase. 



Nocard has shown that the milk of affected cows does 

 not contain the virus of foot and mouth disease when it 

 is drawn from the udder in a manner which pre- 

 vents external contamination,. But when vesicles or 

 ulcers are present on the teats or udder it is not possible 

 to draw milk in the ordinary way without it becoming 

 contaminated with the virus. Merely a trace of the serum 

 from the vesicles is sufficient to render 50 to 100 quarts 

 of milk infectious. Practical experience indicates that 

 the milk of affected cows is frequently infectious. Fur- 

 thermore, the extraordinary facility with which the virus 

 is disseminated makes it extremely probable that all of 

 the milk of a herd in which the disease exists may be 

 infected secondarily. 



The disease may be transmitted to man through milk, 



