THE RELATION OF COW'S MILK TO THE ZOO-PARASITIC DISEASES OF MAN. BY CH. WARDELL STILES, Ph. D., Chief, Division of Zoology, Hygienic Laboratory, Public Health and MarineHospital 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 particular 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 washing 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 (f) Permitting cats or dogs to have access to the milk or to the dishes used for milk. From the foregoing it will be seen that the entire question under discussion is one of simple, elementary cleanliness, honesty, and propriety; that when due regard is had for these three factors the danger of infection by animal parasites, through the milk supply, is eliminated; but that such danger increases in proportion as these factors are ignored. There is no evidence on record that any one of the foregoing possibilities has ever played an important rôle in producing any large number of cases of infection. Still it may be well worth while to refer to these possibilities briefly as contributing arguments in favor of a clean milk supply. (a and b) Water-born parasites.-If contaminated water is used in washing milk cans or in fraudulently diluting milk it stands to reason that the contamination in question may be transmitted to the milk and through the latter it may be transmitted to the consumer. In this manner any obligatory or faculative water-born zoo-parasitic infection (such as amebic dysentery, coccidiosis, possibly some forms of distomatosis, cysticercosis, hydatid diseases, eel worms, etc.), might be transmitted through the milk. The dangers involved are not sufficient to cause any sensation or alarm, but they are sufficiently real to present contributing arguments in favor of protecting milk from foul and contaminated water. (c) Improper disposal of fecal material.-When fecal material is not properly disposed of, the danger is present that the infection which it contains may be spread in various ways, as by flies, to the food, and thus it may gain access to man. The danger involved in reference to the animal parasites is not, in general, so great as it is in reference to the bacterial infections-such as typhoid, cholera, etc.; for in case of the zooparasites the transmission in most of the instances in which it is theoretically possible could take place only when the organisms had reached a certain stage in their life cycle. For instance, a typhoid or a cholera stool would, a priori, be more dangerous when fresh than when one to several weeks old, and its danger would decrease with age; from a case of amebic dysentery, hook-worm disease, or eel-worm infection, danger from a perfectly fresh stool would in general be nil; gradually the stool would become infectious corresponding to the rapidity of the development of the infecting stage of the parasites in question; this infectiousness would increase to a maximum, according to conditions of heat and moisture, and then the infectivity would gradually decrease. If stools in an infective condition are visited by flies or are washed into a water supply or are scattered in dust form, they can, according to the various conditions, form the basis of various zoo-parasitic infections, and should particles of such stools be accidentally carried to milk, the milk could |