THE RELATION OF COW’S MILK TO THE ZOO-PARASITIC 
DISEASES OF MAN. 
By Ch. Wardell Stiles, Pli. D., 
Chief, Division of Zoology, Hygienic Laboratory, Public Health and Marine- 
Hospital Service. 
Summary. — Theoretically, it is possible that certain infections with animal 
parasites may be contracted through the milk supply, but such possibility does 
not present any danger which is even remotely comparable with the danger of 
contracting typhoid through the milk. No animal parasite is known for which 
milk is a necessary transmitting medium or a necessary habitat in any particu- 
lar stage of the life cycle. Accordingly, the danger of contracting zoo-parasitic 
diseases through the milk supply is in general more theoretical than real, and 
can be prevented by the most elementary methods of cleanliness. 
There is no animal parasite known for man for which cow's milk is 
either the necessary medium of transmission or the necessary habitat 
during any portion of its life cycle. The question of the relation of 
cow’s milk to the zoo-parasitic diseases of man reduces itself therefore 
to the question as to what animal parasites of man are most likely to 
gain access to the milk accidentally during a stage of their life cycle 
which would render their transmission to man possible. 
In reference to this question the broad statement may be made that 
such possible cases would in general be due to the following causes : 
(a) Fraudulent practices on the part of persons in the milk trade 
in diluting the milk with water. 
( b ) The use of contaminated water either in such cases or in wash- 
ing the utensils with which the milk comes into contact. 
(c) Improper disposal of fecal matter. 
(d) Careless personal habits on the part of milk dealers, servants, 
etc., whereby the milk might, by coming into contact with their hands, 
become infected with stages in the life cycle of the parasites which 
would render transmission possible. 
(e) Carelessness whereby fecal material from various animals 
(particularly of dogs, rats, and mice) might gain access to the milk; 
and 
(/) Permitting cats or dogs to have access to the milk or to the 
dishes used for milk. 
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