# Popular Science Monthly/Volume 58/January 1901/Flies and Typhoid Fever

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* FLIES AND TYPHOID FEVER.
By Dr. L. O. HOWARD,
U. S. DEPARTMENT OF AGRICULTURE.
AFTER the outbreak of the late war with Spain in the early summer of 1898, typhoid fever soon became prevalent in concentration camps in different parts of the country. In many cases—in fact in fully one-half of the total number—the fever was not recognized as typhoid for some time, but towards the close of the summer it was practically decided that the fever which prevailed was not malarial, but enteric. During that summer the medical journals and the newspapers contained a number of communications from contract surgeons and others advancing the theory that flies were largely responsible for the spread of the disease, owing to the fact that in many of these camps the sinks or latrines were placed near the kitchens and dining tents, and that the enormous quantity of excrement in the sinks was not properly cared for. One of the most forcible writers on this topic was Dr. H. A. Veeder, whose paper, entitled 'Flies as Spreaders of Disease in Camps' published in the 'New York Medical Record' of September 17, 1898, brought together a series of observations and strong arguments in favor of his conclusion that flies are prolific conveyors of typhoid under improper camp conditions.
This idea was not a new one. Following the proof of the agency of flies in the transmission of Asiatic cholera by Tizzoni and Cattani, Sawtchanko, Simmonds, Uffelmann, Flugge and Macrae, it was shown by Celli as early as 1888 that flies fed on the pure cultures of Bacillus typhi abdominalis are able to transmit virulent bacilli in their excrement. Dr. George M. Kober, of Washington, in his lectures before the Medical College of Georgetown University, had for some years been insisting upon the agency of flies in the transmission of typhoid, and in the report of the health officer of the District of Columbia for the year ending June 30, 1895, referred to the probable transferrence of typhoid germs from the privies and other receptacles for typhoid stools to the food supply of the house by the agency of flies.
Moreover, the Surgeon-General of the Army, Dr. George M. Sternberg, was fully alive to the great importance of the isolation and disinfection of excrement, as evidenced in his prize essay on 'Disinfection and Personal Prophylaxis in Infectious Diseases,' published by the American Public Health Association in 1885, and in the first circular issued from his office in the spring of 1898 (April) careful ​instructions were given regarding the preparation of sinks and their care, with a direct indication of the danger of transfer of typhoid fever by flies. These instructions were not followed, and the result was that over 21 per cent, of the troops in the national encampments in this country during the summer of 1898 had typhoid fever, and over 80 per cent, of the total number of deaths during that year were from this one cause.
This condition of affairs was not confined to the United States. An epidemic occurred in the camp of the Eighth Cavalry at Puerto Principe, Cuba, in which two hundred and fifty cases of the fever occurred. The disease was imported by the regiment into its Cuban camp, and Dr. Walter Reed, U. S. A., upon investigation, reported to the Surgeon-General that the epidemic "was clearly not due to water infection, but was transferred from the infected stools of the patients to the food by means of flies, the conditions being especially favorable for this manner of dissemination. . . . "
In all the published accounts, and in all literature of closely allied subjects, the expression used in connection with the insects has been
simply the word 'flies.' Nothing could be more unsatisfactory to the entomologist than such a general word as this, except it were taken for granted that the house-fly (Musca domestica) was always meant. It has not apparently been realized that there are many species of flies which are attracted to intestinal discharges, nor does it seem to have been realized that, while certain of these species may visit, and do visit, food supplies in dining rooms, kitchens and elsewhere, many others are not likely to be attracted.
In 1895, the writer made a study of the house-fly, not from this ​standpoint, but from a desire to learn the principal source from which our houses are supplied with this eternal nuisance, with a view to being able to suggest remedial measures. Experimental work in this direction was continued for some years. In the course of this work he early decided that an overwhelming majority of the house-flies found in domiciles breed in horse manure. This substance is its favored larval food, and experimental work showed that by the semi-weekly treatment of the horse manure in one large stable, the house-fly supply of the neighborhood was very greatly reduced. In confined breeding cages he had been unable to breed house-flies in any other substance than horse dung, and consequently when the camp typhoid question and the agency of flies became a matter of such general comment in 1898, he saw the desirability of a careful study of the insects which frequent or breed in human excrement, in order to give exact data from which reliable statements
could be made and upon which reliable conclusions could be based. This work was begun and carried on through the summer of 1899 and to some extent in the summer of 1900, with results which will be briefly summarized in the following paragraphs. The exact details, somewhat too technical, altogether too long and certainly too unpleasant for publication in a journal of this character, will be published in the Proceedings of the Washington Academy of Sciences.
In all seventy-seven distinct species of flies, belonging to twenty-one different families, were found by actual observation, either by rearing or by captures, to be coprophagous; thirty-six species were found to breed in human fæces under more or less normal conditions, while forty-one were captured upon such material. All have been studied with more or less care, and their other habits ascertained. The most ​abundant of the flies reared were Helicobia quadriselosa, Sepsis violacea, Nemopoda minuta, Limosina albipennis, Limosina fontinalis, Sphærocera subsultans and Scatophaga furcata, while the most abundant forms captured were Phormia terranovæ and Borborus equinus. In a second class, not including the most abundant forms reared and captured, but including species which were rather abundantly found, were Sarcophaga sarraceniæ, Sarcophaga assidua, Sarcophaga trivialis, Musca domestica (the common house-fly), Morellia micans, Muscina stabulans, Myospila meditabunda, Ophyra leucostoma, Phorbia cinerella, and Spharocera pusilla, of the reared series, and Pseudopyrellia cornicina and Limosina crassimana among the captured series. All the others of the seventy-seven species were either scarce or not abundant.
The results so far stated and the observations made in the investigation as a whole have a distinct entomological interest, as showing the exact food habits of a large number of species, many of the observations
being novel contributions to the previous knowledge of these forms. But the principal bearings of the work are only brought out when we consider which of these forms are likely, from their habits, actually to convey disease germs from the substance in which they have bred or which they have frequented to substances upon which people feed. Therefore, collections of the Dipterous insects (flies) occurring in kitchens, pantries and dining rooms were made, with the assistance of correspondents and observers in different parts of the country, through the summer of 1899, and also in the summer and autumn of 1900. Such collections were made in the States of Massachusetts, New York, Pennsylvania, District of Columbia, Florida, Georgia, Louisiana, Nebraska and California. Nearly all of the flies thus captured were caught upon sheets of the ordinary sticky fly-paper, which, while ruining them as cabinet specimens, did not disfigure them beyond the point of specific recognition.
​In all 23,087 flies were examined. They were caught in rooms in which food supplies are ordinarily exposed, and may safely he said to have been attracted by the presence of these food supplies. Of these 23,087 flies, 22,808 were Musca domestica; that is to say, 98.8 per cent, of the whole number captured belonged to the species known as the common house-fly. The remainder, consisting of 1.2 per cent, of the whole, comprised various species, the most significant ones being Homaloymia canicularis (the species ordinarily known as the 'little house-fly'), of which 81 specimens were captured; the stable-fly (Muscina stabulans), 37 specimens; Phora femorata, 33; Lucilia cæsar (screw-worm fly), 8; Drosophila amelophila, 15; Sarcophaga trivialis, 10; and Calliphora erythrocephala (the common blow-fly), 7.
Musca domestica is, therefore, the species of greatest importance from
the food-infesting standpoint; Homaloymia canicularis is important and Muscina stabulans is of somewhat lesser importance. Drosophila amelophila, although not occurring in the former list of abundant species, does rarely breed in excreta and is an important form; it would have been much more abundant in the records of house captures had more of these been made in the autumn, after fruit makes its appearance upon the dining tables and sideboards, since this species is the commonest of the little fruit-flies which are seen flying about ripe fruit in the fall of the year. The Calliphora and the Lucilia are of slight importance, not only on account of their rarity in houses, but because they are not, strictly speaking, true excrement insects. They ​are rather carrion species. Other forms were taken, but either their household occurrence was probably accidental or from their habits they have no significance in the disease-transfer function.
It appears plainly that the most abundant species breeding in or attracted to dejecta do not occur in kitchens and dining rooms, but it is none the less obvious that while the common house-fly, under ordinary city and town conditions as they exist at the present day, and more especially in such cities and towns, or in such portions of cities as are well cared for and inhabited by a cleanly and respectable population, may not be considered an imminent source of danger, it is, nevertheless, under other conditions a factor of the greatest importance in the spreading of enteric fever.
The house-fly undoubtedly prefers horse manure as a breeding place. We have shown that it is not one of the most abundant species of flies breeding in or attached to human fæces, but, in the course of the observations made in the summer of 1899, we have definitely proved
the following facts relative to the house-fly, and in the statement of these facts it must be remembered that every specimen has been carefully examined by an expert dipterologist, so that there can be no mistake:
(1.) In the army camps the latrines are not properly cared for and where their contents are left exposed, Musca domestica will, and does, breed in these contents in large numbers, and is attracted to them without necessary oviposition.
Such observations were not made by the writer at the concentration camps of 1898, but were made at the summer camps of the District of Columbia Militia, during the summers of 1899 and 1900.
The contrast between the conditions here observed and those which existed at the great army camp at the Presidio, San Francisco, California, as observed by the writer through the courtesy of Surgeon General Sternberg and Colonel W. H. Forwood, surgeon in charge of the Department of California, in the late autumn of 1899, was most ​striking. At the Presidio camp, the chance for the transfer of typhoid by flies had by intelligent care been reduced to zero. This, however, Mas, of course, a more or less permanent camp and opportunities were better, but indicated in a beautiful way what might be done and what should be done even in a temporary camp.
(2) In towns where the box privy nuisance is still in existence the house-fly is attracted to such places to a certain extent, though not as abundantly as other flies, which, however, are not found in houses. Observations to this effect were made by the writer and his assistants in many parts of the United States.
(3.) In the filthy regions of a city, where sanitary supervision is lax, and where in low alleys and corners and vacant lots deposits are made by dirty people, the house-fly is attracted to the stools, may breed in them, and is thus a constant source of danger. The writer has seen a deposit made over night in South Washington in an alleyway swarming
with flies, in the bright sunlight of a June morning, temperature 92° F., and within thirty feet of this substance were the open doors and windows of the kitchens of two houses occupied by poor people, these two houses being only elements in a long row.
The conclusions which the writer has reached after two years of this experimental work are:
(1) Of the seventy-seven species of flies found under such conditions that their bodies, especially their feet and their proboscides, may become covered with virulent typhoid germs, only eight are likely to carry them to objects from which they can enter the alimentary canal of man.
(2) Of these eight species, two, namely, Lucilia cæsar and Calliphora erythrocephala. can very rarely carry such germs, though they may carry the germs of putrefaction and cause blood-poisoning, in alighting upon abrasions of the skin or open wounds.
​(3) Four of these specimens, namely, Homaloymia canicularis, Muscina stabulans, Phora femorata and Sarcophaga trivialis, possess some degree of importance, but their comparative scarcity in houses renders them by no means of prime importance.
(4) The common little fruit-fly, Drosophila ampelophila, is a dangerous species.
(5) The house-fly is a constant source of danger, and wherever the least carelessness in the disposal of or the disinfection of dejecta exists, it becomes an imminent source of danger.
When we consider the prevalence of typhoid fever and the fact that virulent typhoid bacilli may occur in the excrement of an individual for some time before the disease is recognized in him, and that virulent germs may be found in the excrement for a long time after the apparent recovery of a patient, the wonder is not that typhoid is so prevalent, but that it does not prevail to a much greater extent Fig. 10. Muscina stabulans—Enlarged.
Box privies should be abolished in every community, or they should be disinfected daily. The depositing of excrement in the open within the town or city limits should be considered a punishable misdemeanor in cities which have not already such regulations, and the law should be enforced more vigorously in towns in which it is already prohibited. Such offenses are generally committed after dark, and it is often difficult, or even impossible, to trace the offender; therefore, the regulations should be carried even further, and should require the first responsible person who notices the deposit to immediately inform the police, so that it may be removed or covered up. Dead animals are so reported, but human excrement is much more dangerous. Boards of health in all communities should look after the proper treatment or disposal of horse manure, primarily in order to reduce the number of houseflies to a minimum, and all regulations regarding the disposal of garbage and foul matter should be made more stringent and should he more stringently enforced.
* ↑ Conclusions reached after a study of typhoid fever among American soldiers in 1898, by Dr. Victor C. Vaughan, a member of the Army Typhoid Commission, read before the annual meeting of the American Medical Association at Atlantic City, N. J., June 6, 1900. 'Philadelphia Medical Journal,' June 9, 1900, pages 1315 to 1325.
* ↑ 'Sanitary Lessons of the War,' by George M. Sternberg, Surgeon-General, U. S. A., read at the meeting of the American Medical Association, at Columbus, O., June 6 to 9, 1899. 'Phila. Med. Jour.,' June 10 and 17, 1899.
* ↑ The determination work in the Diptera was all done by the writer's assistant, Mr. D. W. Coquillett, who is an authority on this group of insects.