Anthrax, actinomycosis (lumpy jaw), rabies, and malta fever are diseases the organisms of which have been found in the milk of affected animals. In case of the first three, while the possibility exists of the infection of human beings by milk, it is improbable that such infection does normally occur. Malta fever is becoming an important disease in portions of southern Europe. It is produced in man by the use of milk of goats suffering from the disease.
The organism causing contagious abortion in cattle is known to be present in the milk of the infected animal at the time of its withdrawal from the udder. It is not probable that the organism is of any sanitary significance as far as man is concerned. It has been shown that the organism is able to produce a disease in guinea pigs on artificial inoculation that is very similar, so far as the lesions are concerned, to tuberculosis. It is also probable that the by-products of creameries and cheese factories may serve to spread the disease from one herd to another.
Inflammation of the udder (garget) is a frequent trouble in every herd. It is marked by the swelling of one or more quarters, by the appearance of fever and changes in the appearance and composition of the milk. The inflammation may be caused by cold or injury, or by the invasion of the udder with pus-forming bacteria. In the first case the trouble is not likely to persist for any length of time, and does not spread to other members of the herd. The milk may be more or less stringy, and may show a slimy flocculent sediment. It cannot be asserted that such milk is harmful to man but it should be rejected on general sanitary grounds, and because it cannot always be differentiated from that coming from an udder in which the inflammation is produced by bacteria.
Inflammation caused by the invasion of the udder with specific bacteria is usually of greater severity, the entire gland often becoming involved. The secretion of milk may cease and the function of the diseased quarters may never be restored. The milk in the less severe cases may not be abnormal in appearance, but with increasing severity, the nature of the milk changes, until it may be a watery liquid. The milk of any animal suffering from any form of garget should be rejected, as it may cause trouble, especially in children. There is some reason to believe that organisms coming from cases of garget have been responsible for the extensive outbreaks of septic sore throat that have occurred in some parts of the country.
The milk of animals suffering from indigestion, diarrhea, abscesses on any part of the body, as from those which have retained the afterbirth should be likewise rejected. In short only the milk of healthy animals should be used for human food; that from any animal suffering from any disease or which is receiving medical treatment should not be so used.
Typhoid fever. The most important disease germ, distributed through the medium of milk, that is unable to produce a diseased condition in the cow is the organism of typhoid fever. This malady is an intestinal affliction of man, and the germ causing the same is found abundantly in the dejecta, both solid and liquid, as well as in the blood in certain stages of the disease. While the causal organism does not leave the body through the expired air, it is found abundantly in both the urine and feces. Therefore, the dejecta, and any articles that may be soiled with the same become a positive menace.
Many different methods of transmitting the contagion exist, such as water, food infected in various ways, contact with infected persons, and through the medium of milk. Milk is not so frequently the cause of dissemination as the other factors, but where milk supplies become contaminated, epidemics of considerable magnitude are wont to occur. The danger from milk is also aggravated by the fact that the typhoid bacillus is capable of withstanding considerable amounts of acid, and consequently finds, even in raw milk containing the normal lactic acid bacteria, conditions favorable for its growth. In a considerable percentage of cases, the disease is not sufficiently severe to cause the patient to take to his bed. These so-called "walking typhoid" cases are particularly dangerous, because they serve to spread the disease organism more widely.
A very considerable proportion of the people that recover from typhoid fever still continue to harbor the typhoid bacillus in their urinary and gall bladders. This condition may obtain for years, and since such individuals are in perfect health and are ignorant of their own condition, and since they give off the organisms more or less constantly, they are often the cause of extensive milk borne epidemics. Such persons are known as "typhoid carriers" and constitute one of the gravest problems the public official has to contend with in his struggle to prevent the spread of typhoid fever.
Where outbreaks are caused by milk, they can readily be traced by means of the milk route, as there are always a sufficient number of susceptible persons, so that outbreaks of epidemic proportions develop. In the Stamford, Conn., outbreak in 1895, 386 cases developed on one milk route. In this case it was shown that the carrying cans were thoroughly washed, but were later rinsed out with cold water from a polluted shallow well.
The mode of infection of milk varies, but in general, the original pollution is occasioned by the use of infected water in washing the utensils, or a case of "walking typhoid" or bacillus carrier, who directly infects the milk. In case of sickness in rural families, some member of the household may serve in the dual capacity of nurse and milkmaid, thus establishing the necessary connection. Busey and Kober report twenty-one outbreaks, in which dairy employees also acted in the capacity of nurses. The fact that the urine of a convalescent may retain the typhoid germ in large numbers for some weeks renders the danger from this source in reality greater than from feces, as, naturally, much less care is exercised in the disposition of the urine.