The evidence that flies carry and spread the deadly germs of cholera is most conclusive. The germs may be carried on the body where they will live but a short time, or they may be carried in the alimentary canal where they will live for a much longer period and are finally deposited in the fly-specks where they retain their virulence for some time. Flies that had been allowed to contaminate themselves with cholera germs were allowed access to milk and meat. In both cases hundreds of colonies of the germs could later be recovered from the food. As with the typhoid germs milk seems to be a particularly good medium for the development of the cholera germs. In several of the experiments that have been made along this line the milk has been readily infected by the flies visiting it.
Of course an outbreak of cholera is of rare occurrence in our country, but unfortunately this is not so in regard to some other intestinal diseases such as diarrhea and enteritis which annually cause the death of many children, especially bottle-fed babies. Those who have made close studies of the way in which these diseases are disseminated are convinced that the flies are one of the most important factors in their spread.
It has long been observed that flies are particularly fond of sputum and will feed on it on the sidewalk, in the gutter, the cuspidor or wherever opportunity offers. It is well known, too, that the sputum of a consumptive contains myriads of virulent tubercular germs. A fly feeding and crawling over such material must necessarily get some of it on its body, and as it dries and the insect flies about the germs will be distributed through the air, possibly over our food. It has been shown that the excretion from a fly that has fed on tubercular sputum contains tubercular bacilli that may remain virulent for at least fifteen days. Thus we see again the danger that may lurk in the too familiar "fly-specks."
Although it is generally supposed that the flea is solely responsible for the spread of the bubonic plague and no doubt is the principal distributing agent, the fact must not be overlooked that the house-fly may also be of considerable importance in this connection. Carefully planned experiments have shown that flies that have become infected by being fed on plague-infected material may carry the germs for several days and that they may die of the disease. During plague epidemics flies may become infected by visiting the sores on human or rat victims or by feeding on dead rats or on the excreta of sick patients, and an infected fly is always a menace should it visit our food or open wounds or sores. Anthrax bacilli are carried about and deposited by flies showing the possibility of the disease being spread in this way.
Some believe that leprosy, smallpox and many other diseases are carried by the house-fly, so it is little wonder that it is fast losing its standing as a household companion and that we are beginning to regard it not only as a nuisance but as a source of danger which should no longer be tolerated in any community.
Of course only a small per cent of the flies that visit our food in the dairies or market places or kitchens actually carry dangerous diseases, but they are all bred in filth and it is not possible without careful experiments or laboratory analysis to determine whether any of the germs among the millions that are on their bodies are dangerous or not. The chances that they may be are too great. The only safe way is to banish them all or to see that all of our food is protected from them.
FIGHTING FLIES
Screens and sticky fly-paper have their places and give some little relief in a well-kept house. But of what use is it to protect your food after it has entered your home if in the stores, in the market place, in the dairy barn, or dairy wagon, in the grocers' and butchers' cart, it has been exposed to contamination by hundreds of flies that have visited it.
The problem is a larger one than keeping the house free from flies; larger but not more difficult, for the remedy is simple, effective, practicable and inexpensive. Destroy their breeding-places and you will have no flies. As the flies breed principally in manure the first remedial measure is to see that all manure is removed from the barn-yard at least once a week and spread over the fields to dry, for the flies cannot breed in the dry manure. If it is not practicable to remove it this often the manure should be kept in a bin that is closed so tight that no flies can get into it to lay their eggs. Sometimes the manure may be treated with some substance such as kerosene, crude oil, chlorid of lime, tobacco water or mixture of two or more of these and thus rendered unsuitable for the flies to breed in, but in general practice none of them has been found very satisfactory for the treatment is either not thorough enough or is too expensive of time and material.