Rural Hygiene

by Henry N. Ogden

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. Dickens, 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, assigned 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 passage 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 associated 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.

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 mass 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 nourishing 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 attitude 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 larvæ 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.