Part 24 (1/2)
_Chicken pox._
Chicken pox is the mildest of eruptive diseases. It has no relation to smallpox, so that the theory sometimes held, that an attack of chicken pox prevents any attack of smallpox later, is a mistake. Instances are on record where a person has had both diseases almost at the same time.
The appearance of the eruption is the characteristic feature of this disease, and it is so well distinguished that there is no danger of failing to recognize it. It is not common in grown people, and while it should not arouse suspicion in children, it is so uncommon in adults that a suspected case is probably a mild case of smallpox, and should always be quarantined as such.
With children, the accompanying cold and fever is often very mild, so that the appearance of the rash is the first and only symptom of the disease. The eruption is a progressive thing, each day's crop coming to full bloom and dying out as the next day's crop develops. This is, by the way, a distinguis.h.i.+ng characteristic of this disease, differentiating it from smallpox where the pustules are more persistent and where the breaking out is more general. The pustules are sometimes extremely irritating, and it is very hard to keep children from scratching, the results of which may leave deep scars and so should be avoided. An antiseptic ointment should be used as with scarlet fever and measles, carbolized vaseline being suitable, although sometimes a strong solution of soda is subst.i.tuted. It is not common to disinfect in chicken pox to the same extent as in the other diseases, the contagion being apparently in the air rather than in clothing and short lived. In New York State, in 1908, no deaths are recorded from chicken pox, and it is because of this lack of fatal results that the disease is regarded so indifferently and no particular pains taken to prevent its spread.
CHAPTER XIX
_PARASITICAL DISEASES (MALARIA, YELLOW FEVER, HOOKWORM, BUBONIC PLAGUE, AND PELLAGRA)_
_Malaria._
From time immemorial, malaria (or fever-and-ague) has been one of the great plagues of humanity. No advance outpost of civilization but has suffered, more or less severely, from this disease. d.i.c.kens, in one of his novels, describes graphically the disease as it existed in the early American settlements, and vividly portrays its ravages, both mental and physical, among the pioneer settlers. Certain sections of the world have been especially noted for the prevalence of this disease, making extensive regions practically uninhabitable. The vicinity of Rome, with its swampy marshes and low-lying areas, has been one of these plague spots. The jungles and swamps of the equator and the coastline of Africa and South America and the valley lands of the Mississippi River have all been noted as most dangerous districts for human beings to live in. Even in civilized communities the ravages of the disease have, under conditions most conducive to malaria, been fearful, so that only most urgent requirements of mining, manufacturing, or similar material processes have prevented the obliteration of entire communities.
The cause of the heavy death roll resulting from a bold defiance of the reputation of these localities--a defiance bravely adopted by hardy pioneers, by agents of trading companies, and by representatives of governments--has been, up to the last ten years, a.s.signed to the water-laden condition of low-lying ground. Swamps and stagnant pools, moisture-laden air, and a hot climate have been universally considered to be the cause of the fever, and the transmission of the disease has been supposed to be due to the pa.s.sage through the moist air of the germs of the disease, although the exact form and behavior of these germs was unknown. Certain specifics have been proved by experience to have some value. For instance, it has been found that planting a row of trees between the house and a pool from which malaria might come has been of aid in warding off the disease. In a number of cases a thick row of eucalyptus trees, so a.s.sociated in the popular mind with this purpose that they are known as the malaria tree, have been planted as a tight hedge with apparently very useful results. Drainage or filling up the low lands has always been found to reduce the prevalence of the disease.
Many years ago the use of quinine in large doses was found to be a specific, and the writer well remembers, on the occasion of his visit to a malarial region, buying quinine at the grocery store by the ounce in the same way that one would buy spices or tea, the dose being a teaspoonful. Why quinine should prevent the daily or periodical chills characteristic of the disease was not known, or why a row of eucalyptus trees interfered with the development of the disease was not known, and people generally were content to rest with the knowledge of these facts only.
_Mosquitoes and malaria._
[Ill.u.s.tration: FIG. 78.--Resting positions for ordinary mosquito (left) and malarial mosquito (right).]
In the year 1900, however, English scientists, working in the Roman Campagna, demonstrated conclusively that which had been vaguely suggested before, namely, that the cause of malaria is a parasite composed of little more than an unformed ma.s.s of protoplasm, not floating in the air at all, but transmitted only by the bite of a mosquito. By a series of most interesting experiments, conducted by them and by other scientists in other parts of the world, it has been definitely proved that when a mosquito bites an individual suffering from malaria, the mosquito draws up into his body, along with the blood of the bitten person, some of the malarial parasites. In the body of the mosquito, the parasite develops, requiring for a full-grown specimen about seven days; then, if the mosquito bites another person, the parasite is injected into the skin of the victim, and in the course of about a week a good case of malaria ensues.
Fortunately, only a small proportion of the number of mosquitoes in the world are capable of nouris.h.i.+ng the malaria parasite. Under ordinary conditions about 5 per cent of all mosquitoes found are malarial, and a particular name has been given to those capable of transmitting the disease. The ordinary mosquito is known as the ”culex,” while the malarial kind is known as ”anopheles.” Figure 78 shows the characteristic att.i.tude of the two kinds by which the one can be distinguished from the other when resting on a wall or ceiling. As will be noticed in the drawing, the culex carries his body parallel to the wall with his hind legs crossed over his back. The harmful mosquito, the female anopheles, always hangs on by her front legs and has her body at an angle of about forty-five degrees to the surface to which she clings, her hind legs hanging down. The wings of the harmless mosquito are usually mottled, while the wings of the malarial mosquito are of an even color. The details of the behavior of the parasite on its long journey from the original malarial patient through the body of the mosquito and into the body of the person bitten is full of interest to the scientist, who must, however, be provided with a good microscope to follow such minute bodies; but the methods of avoiding the disease are more pertinent to our present purpose.
While quinine is still recognized as the particular antidote for the malarial poison, efficient as we know now because it is poisonous to the parasite and not because it has any particular effect on the person, of late years more and more stress is being laid on the elimination of the mosquito. Naturally, if the mosquito can be destroyed and the transmission of the disease thus prevented, there will be no further need of quinine. The general impression that swampy land is favorable to the development of malaria is correct, but not because the damp air is itself pernicious. The significance of the damp ground lies solely in the fact that mosquitoes in one stage of their existence require water for their development. They breed only in water and always deposit their eggs in water, on the surface of which the eggs float in very small layers. The eggs hatch into larvae or wrigglers, which also must remain in water for development, and it is not until the third stage, that of the full-grown mosquito, that the animal leaves the water which was his birthplace. Obviously, therefore, if there is no water there can be no mosquitoes.
_Elimination of mosquitoes._
Another pertinent fact discovered by scientific research is that the development of the malarial mosquito is confined to the vicinity of stagnant pools, because in fresh water, where fish are to be found, the eggs and larvae of the mosquito are a most acceptable fish food. One of the most practical ways, therefore, of getting rid of possible mosquitoes is to make sure that the pond always contains a number of fish. Woods Hutchinson gives the following interesting description of the way this fact was discovered:--
”It was early noted that mosquitoes would not breed freely in open rivers or in large ponds or lakes, but why this should be the case was a puzzle. One day an enthusiastic mosquito student brought home a number of eggs of different species, which he had collected from the neighboring marshes, and put them into his laboratory aquarium for the sake of watching them develop and identifying their species. The next morning, when he went to look at them, they had totally disappeared.
Thinking that perhaps the laboratory cat had taken them, and overlooking a most contented twinkle in the corner of the eyes of the minnows that inhabited the aquarium, he went out and collected another series. This time the minnows were ready for him, and before his astonished eyes promptly pounced on the raft of eggs and swallowed them whole. Here was the answer at once: mosquitoes would not develop freely where fish had free access; and this fact is an important weapon in the crusade for their extermination. If the pond be large enough, all that is necessary is simply to stock it with any of the local fish,--minnows, killies, perch, dace, ba.s.s,--and presto! the mosquitoes practically disappear.”
[Ill.u.s.tration: FIG. 79.--Top view is of larva of Anopheles. Bottom view is of larva of Culex.]
Another factor in the development of the mosquito from the egg to full-grown mosquitohood is that in the larvae stage air must be supplied, curiously enough, through the tail which projects slightly above the surface of the water as the larvae hang head downwards (see Fig. 79). If the surface of the water is covered with some impervious material, the mosquito larvae will be suffocated, and it has been found that oil lends itself most readily to this desirable purpose, applied at the rate of one ounce per fifteen square feet of water surface. The oil spreads out over the surface in a very thin film, but persistent enough to keep off the air supply from the mosquito larvae. This method, about which much has been written and said, is perhaps the one most commonly employed, and its results have been most satisfactory. In the vicinity of the city of Newark, New Jersey, for instance, is an area of about 3500 acres, 8 miles long and about 3 miles wide, practically all marshland. In 1903 ditches were dug throughout this marsh in such a way that the surface water was drained off, drying the ground so that hay can now be cut where formerly rubber boots were necessary to get onto the ground at all. The consequence has been that the mosquitoes have practically disappeared from this region, formerly frightfully infested, and the cost of the 70 miles of small ditches dug has been amply repaid by the freedom from malaria as well as from the nuisance of the ordinary mosquito.
Other campaigns have been waged, using kerosene or crude petroleum for the coating of ponds or pools. Wherever clear water exists the kerosene treatment is probably best. Where marshland is found, through which the kerosene penetrates with difficulty, drainage is a more useful method.
The size of the pools required for the development of the mosquito is very small. Thousands of mosquitoes may be formed in the amount of water contained in an old tomato can, and barrels half full of rain water or pools of water in the vicinity of an old pump or in the barnyard will afford golden opportunities for mosquitoes looking for a place to lay their eggs. While the ordinary culex requires from one to two weeks only for the complete transition from egg to mosquito, so that a pool filled with rain water and not dried up within that period will be sufficient to develop a brood, the malarial mosquito requires much longer--two or three months--for the full completion of her development. It is, therefore, a simple problem for an individual householder to search out the pools which remain filled with water for a period of two months, and either stock them with fish, drain them entirely, or coat them with kerosene. No hesitation need be felt about the result of this treatment.
It will positively eliminate all malaria in the vicinity if the work is thoroughly done.
_Limitation of mosquito infection._
The distance that the malarial mosquito can fly is of interest as indicating the distance which one must go from a house, hunting for available pools. All mosquitoes are unable to fly against the wind, so that, as already noted, one side of a swamp may be comparatively free from malaria, while the other side may be overrun with it, merely on account of the direction of the prevailing winds. Some mosquitoes that breed in salt marshes may be carried for miles, so that a land breeze will bring millions of the pests to seash.o.r.e cottages which, with a sea breeze, are quite free from them. The anopheles has a habit of clinging to weeds, shrubs, and bushes when the wind blows, so that it is seldom carried more than about two hundred yards from the place where it is hatched. If all pools of water, therefore, within this radius are disposed of, the elimination of malaria will logically follow.