| Town Shippons. | Country Shippons. | Total. | ||||
| Total. 228 | Infected. 12 | Per cent. 5.2 | Total. 67 | Infected. 9 | Per cent. 13.4 | 295 |
Such results are very significant, and indicate the importance of all large corporations obtaining the service of systematic and periodic bacteriological examination of the milk supply. Nor are the results surprising, for when we remember the habits of the tubercle bacillus we cannot conceive a more favourable nurture ground than the typical byre. "Nothing worse than the insanitary conditions of the life of the average dairy cow," says Sir George Brown, late of the Board of Agriculture, "can be imagined." It will be obvious that the above facts make it incumbent upon responsible authorities to see that not a stone is left unturned to enforce cleanliness in all dairy work, isolation of diseased cows, and strict treatment of all infected milk.
Typhoid Fever. Jaccoud in France and Hart in England have shown that enteric fever (typhoid) is not infrequently spread by milk. An epidemic affecting 386 persons in Stamford, Conn., U.S.A., was traced to milk, 97 per cent. of the cases coming from one single milk supply. Dr. McNail recently recorded an outbreak of twenty-two cases of enteric, due to a polluted milk supply.
Within the last twelve months much attention has been drawn to a milk source of typhoid infection by the epidemic of typhoid at Bristol. Dr. D. S. Davies has pointed out that a brook received the sewage of thirty-seven houses, the overflow of a cesspool serving twenty-two more, the washings from fields over which the drainage of several others was distributed, and the direct sewage from at least one other, and then flowed directly through a certain farm. The water of this stream supplied the farm pump, and the water itself, it is scarcely necessary to add, was highly charged with putrescent organic matter and micro-organisms. This water was used for washing the milk-cans from this particular farm, otherwise the dairy arrangements were efficient. Part of the milk was distributed to fifty-seven houses in Clifton; in forty-one of them cases of typhoid occurred. Another part of the milk was sold over the counter; twenty households so obtaining it were attacked with typhoid fever, and a number of further infections and complications arose. This evidence would appear to support the fact that milk may act in the same way, though not in such a high degree, as water in the conveyance of typhoid fever.
It may be pointed out that specific typhoid is not a disease of animals; consequently no danger need be apprehended from milk if it is properly cared for after it comes from the cow. Typhoid milk is almost invariably due to the addition of typhoid-infected water, either by way of adulteration or in the process of washing out the milk-cans. Cases have, however, been recorded in which there has been direct transmission to the milk from a person convalescing from the disease, and also indirect transmission by a milker serving also in the capacity of nurse to a patient in his own family.
Though the typhoid bacillus appears not to have the power of multiplying in milk, it has the faculty of existing and thriving in milk, even when it has curdled or soured, for a considerable time, and may thus infect milk products like butter and cheese. But infection by milk products may be eliminated as of too rare occurrence to deserve attention. The bacillus does not coagulate the milk like its ally the Bacillus coli communis, which is a much more frequent and less injurious inhabitant of milk.
Cholera. The cholera bacillus, as we have already pointed out, is unable to live in an acid medium. Hence its life in milk is a limited one, and generally depends on some alkaline change in the milk. Heim found that cholera bacilli would live in raw milk from one to four days, depending upon the temperature. D. D. Cunningham, from the results of a large number of investigations in India, concludes that the rapidly developing acid fermentations normally or usually setting in, connected with the rapid multiplication of other common bacteria and moulds, tend to arrest the multiplication of cholera bacilli, and eventually to destroy their vitality. Boiling milk appears, on the contrary, to increase the suitability of milk as a nidus for cholera bacilli, partly by its germicidal effect upon the acid-producing microbes, and partly because it removes from the milk the enormous numbers of common bacteria, which in raw milk cause such keen competition that the cholera bacillus finds existence impossible.
Professor W. J. Simpson, lately the Medical Officer of Health for Calcutta, has placed on record an interesting series of cholera cases on board the Ardenclutha, in the port of Calcutta, which arose from drinking milk which had been polluted with one quarter of its volume of cholera-infected water. This water came from a tank into which some cholera dejecta had passed. Of the ten men who drank the milk four died, five were severely ill, and one, who drank but very little of the milk, was only slightly ill. There was no illness whatever amongst those who did not drink the milk.
Diphtheria. Recent observations on the infectivity of diphtheria in milk by Schottelius have established the fact that milk is a good medium for the bacillus of diphtheria, but that it rarely acts as a vehicle for transmitting the disease. Klein has emphasised the possibility of this means of infection. In the first place, it is obvious that the milk may become infected from a human source—from pollution with diphtheritic discharges or dried "fomites." Secondly, from a variety of different quarters evidence has been forthcoming to throw some suspicion upon the cow itself as the agent. Klein states that "a new eruptive disease on the teats and udder of the cow," consisting of papules, vesicles, and induration, may be set up by the subcutaneous inoculation of a pure culture of the Bacillus diphtheriæ. In these eruptions a bacillus similar to the B. diphtheriæ was demonstrated. On a priori grounds this evidence substantiates a belief that diphtheria, in some form or other, may be a disease of cows. Other observers have not been able to confirm these observations, and the whole matter of cow diphtheria must remain for the present sub judice.
As long ago as 1879 W. H. Power traced an epidemic of diphtheria in North London to the milk supply. In 1887 the same authority studied another outbreak, and other observers have produced further evidence in favour of the conveyance of this disease by milk. Air infection of milk by the Bacillus diphtheriæ probably occurs only very rarely, on account of the fact that the organism is readily killed by desiccation, and yet such is necessary before it can be airborne. The most frequent mode of infection of milk with this disease is from the throats, hands, bodies, or clothing of dairy workers suffering from a mild or acute form of the disease.