MALARIA.

Malaria, or Ague, is a generic name given to a disease caused by the invasion of the body by the plasmodium malariæ, discovered by Laveran in 1880. It occurs in two chief types, remittent fever and intermittent fever. For many generations it has been regarded as due to a marshy condition of the soil, associated with decaying vegetable matter, and a moderately high temperature. It is now clear that these conditions are necessary, only because they are necessary for the life of the mosquito. The well-known danger of being out of doors at night in a malarious country is explained by the nocturnal habits of the mosquito. The higher salubrity of the upper stories of houses is explained by the fact that the mosquito does not rise high from the ground; and of high-lying localities by their greater dryness. The value of the mosquito net, of smoke, and of fire as protections from malaria are due to their keeping mosquitos at a distance. The mosquito clings to the puddle or swamp where she was born, and where she will deposit her eggs. Hence the special danger of the immediate vicinity of such collections of water. Thus the prevention of malaria resolves itself chiefly into means for preventing the development of certain species of Anopheles (page [282]). The conditions necessary for the multiplication of these are (1), an atmospheric temperature from 75° to 104° F.; (2) collections of fresh or slightly brackish water; and (3) the presence in these of low forms of animal and vegetable life. We have already described the cycle of life of the plasmodium malariæ (page [282]). Man is the chief, if not the only source, from which the mosquito derives this parasite. In native communities the young children, even when apparently not ill with malaria, nearly always harbour these parasites in their blood corpuscles. Hence the importance of Europeans having their dwellings as remote as possible from native houses. Mosquitos do not travel far.

Instances of the prevalence of malaria in the absence of mosquitos are not substantiated. The outbreaks of malaria where the soil has been disturbed after long lying uncultivated, probably mean the formation of puddles favourable to the breeding of the larvæ of mosquitos.

The necessary preventive measures are classified by Manson as:

The suppression of mosquitos involves the draining or filling in of swamps and ponds, the cleansing and canalisation of sluggish streams, and the afforestation of hills to prevent floods. Cultivation of rice and other plants entailing the prolonged flooding of land should be restricted to fields remote from dwellings. Subsoil drainage is helpful. The “painting” of stagnant waters with petroleum, which should be renewed every week or two, frees water for a considerable time from the larvæ of mosquitos. Eucalyptus and other balsamic trees may help to dry up pools, &c.

The prevention of infection of mosquitos is secured by insisting on all malarial patients using mosquito nets. This prevents the access of mosquitos. At the same time patients should vigorously and persistently take quinine, which kills the malarial parasites in the blood, and thus diminishes and finally removes the danger to other persons produced by the intermediation of the mosquito.

The prevention of mosquito bites is secured by rendering the house mosquito-proof by filling in all openings by fine wire gauze, and by having mosquito curtains to all beds; also by fumigating the rooms occasionally with the dried flowers of the chrysanthemum, by strict cleanliness of rooms, and by flushing them with sunlight. The proof of the mosquito theory as to the causation of malaria has been recently supplied by two test experiments. (a) In the first, a number of mosquitos which had been fed on the blood of malarious patients were sent to London from Rome. These were allowed to bite Dr. Manson’s son, who had never previously had malaria. A few days later he had a characteristic attack of fever. Malarial parasites were found in his blood. He recovered in a week’s time after free dosage with quinine, and the parasites disappeared from his blood. He suffered from a slight relapse about a year later. (b) On a fever-haunted spot in the Roman Campagna a wooden hut was built, and Drs. Sambon and Low, and three others took up their abode here during the malarious season, the only precautions taken being the use of mosquito nets and wire screens in doors and windows. They went about the country daily, but were always home before sunset. They all remained at the end of the season free from malaria.

[CHAPTER XLV.]
TUBERCULOSIS.

Consumption and other Tubercular Diseases.

Consumption (also called phthisis or phthisis pulmonalis) in the year 1899 caused a recorded death-rate of 1,336, and tubercular diseases of other parts of the body a death-rate of 575 per million of the population. In the same year the chief infectious diseases, including small-pox, measles, scarlet fever, whooping cough, typhus, and enteric fever, and diphtheria, were together responsible for a death-rate of 1,248 per million. In the five years, 1861-65, the mean death-rate from consumption was 2,527 per million, so that a reduction of nearly 50 per cent. has apparently occurred. Notwithstanding this great decline, consumption and other consumptive diseases, which may together be classed under the name tuberculosis, still cause more deaths than all the acute infectious diseases put together. Its importance is emphasised by the fact that between the ages of 20 and 45, one-third of all the deaths of males, and between one-third and one-fourth of all the deaths of females occurring at these ages are due to consumption of the lungs.

Formerly great stress was laid on the hereditary character of consumption. It would appear, however, that what is inherited is simply an increased vulnerability of tissues. Judging by the analogy of other animals it may be said that infants are rarely, if ever, born tuberculous. Bang examined 6,000 head of cattle with the tuberculin test (see page [311]), and found that in calves under 6 months old only 10·7 per cent. reacted, i.e. showed evidence of tuberculosis, between 6 and 12 months old 18·7 per cent., 1 to 2 years 23·2 per cent., and over this age 31·3 per cent. reacted; from which it may be inferred that the infection is nearly always received after birth.

The real cause of tuberculosis was shewn by Koch, in 1881, to be the tubercle bacillus. This is a minute bacillus, the length of which is from a quarter to half the size of a blood corpuscle. These bacilli, obtained from tuberculous growths in the body, Koch was able to cultivate on glycerine agar at blood-heat outside the body. By sub-culturing he obtained pure cultures, and after growing the bacilli for as long as fifty-four days, he inoculated various animals, producing tuberculosis in every case, while in similar check experiments in which all the conditions were the same, barring the absence of bacilli, no tuberculosis resulted.

The tubercle bacilli are easily distinguished from most other bacilli by the fact that after being stained by aniline dyes, such as carbol-fuchsin, the colouration is not removed when the preparation is soaked in dilute acid. By this means the presence of tubercle bacilli in the sputum (expectoration) of a phthisical patient is easily discovered, and a valuable means of early recognition of the disease secured. This is most important, as in its early stages consumption is an easily curable disease. Tubercle bacilli are discharged from the lungs in consumption of the lungs, from the bowels in consumption of the bowels, and so on. Hence the essential necessity for disinfecting these discharges. Such discharges while in a moist condition have, unless they are actually swallowed, little or no capacity for evil. It is when they become dry that they become dangerous. Thus the expectoration of a consumptive patient spat on to the floor or deposited in a pocket handkerchief is, so long as it remains moist, perfectly innocuous. What is evaporated from the wet surface is simply steam, harmless as the steam escaping from the domestic tea-kettle. But when it becomes dry, then comes danger. Dust is formed, which contains the living tubercle bacilli, and with the mere shaking of the handkerchief or the disturbance of the dust on the floor these are inhaled, and often cause consumption. The person thus infected may be a new patient. Often also it is the consumptive patient who is thus re-infected. Consumptive patients tend to recover. But if the patient’s disease is daily recruited by fresh doses of the tubercle bacilli inhaled with the dust of previous expectoration, fresh centres of disease are produced, and thus the patient is unwittingly helping to cause his own death.

The infectious character of tuberculosis has been long suspected. In the 18th century, in Naples, there were enactments insisting on the isolation of consumptive patients and disinfection of their furniture, books, etc. We now know, however, that these were counsels of panic, and that for practical purposes the infection may be regarded as confined to the sputum. The expired breath is free from infection except during coughing. That the sputum is infectious can be easily proved by feeding guinea-pigs or the domestic fowl on it. These rapidly become affected by generalised tuberculosis. The simple character of the precautions against infection which are required may be gathered from the following copy of a card which is given to consumptive patients in Brighton:—

Precautions for Consumptive Persons.

Consumption is, to a limited extent, an infectious disease. It is spread chiefly by inhaling the expectoration (spit) of patients which has been allowed to become dry and float about the room as dust.

Do not spit except into receptacles, the contents of which are to be destroyed before they become dry. If this simple precaution is taken, there is practically no danger of infection. The breath of consumptive persons is free from infection.

The following detailed rules will be found useful, both to the consumptive and to his friends:—

1.—Expectoration indoors should be received into small paper bags and afterwards burnt.

2.—Expectoration out of doors should be received into a suitable bottle, to be afterwards washed out with boiling water; or into a small paper handkerchief, which is afterwards burnt.

3.—If ordinary handkerchiefs are ever used for expectoration, they should be put into boiling water before they have time to become dry; or into a solution of a disinfectant, as directed by the doctor.

4.—Wet cleansing of rooms, particularly of bedrooms occupied by sick persons, should be substituted for “dusting” and sweeping.

5.—Sunlight and fresh air are the greatest enemies of infection. Every patient should sleep with his bedroom window open top and bottom, a screen being arranged, if necessary, to prevent direct draught; and, if possible, occupy a separate bedroom. The patient need not fear going out of doors in any weather, if warmly clad.

N.B.—The patient himself is the greatest gainer by the above precautions, as his recovery is retarded and frequently prevented by renewed infection derived from his own expectoration.

6.—Persons in good health have little reason to fear the infection of consumption. Over-fatigue, intemperance, bad air, dusty occupations, and dirty rooms favour consumption.

The most common source of infection is undoubtedly the dried expectoration. Infection may, however, probably be derived from infected food, as milk or meat.

The danger from meat is much less than that from milk, because the former is more generally cooked than the latter, and because the diseased portions of the former would be at least partially removed before it was sold. The conditions under which the meat derived from tuberculous cattle should be destroyed are given on page [24]. The abolition of private slaughter-houses, the general establishment of public abattoirs, and efficient meat inspection would do much towards aiding in eliminating tuberculous cattle from herds; because it would no longer be found remunerative to keep tuberculous cows until they become seriously diseased.

The danger from infected milk is probably very great. This has been repeatedly proved experimentally for bovine tuberculosis by experimenting on calves and pigs. A cow may suffer from tuberculosis of its udder, and yet go on freely secreting milk. The milk from such an udder readily produces tuberculosis in calves or pigs drinking it; but if another animal be fed during the same period with boiled milk obtained from the same udder, it remains well.

The presence of tuberculosis in cattle can be determined with almost complete certainty by the tuberculin test. A glycerine extract of pure cultivations of tubercle bacilli (filtered so as to be free from bacilli) was found by Koch to contain substances which, when injected into guinea-pigs suffering from tuberculosis, produced a febrile reaction, and appeared likely to cure the disease. So far as man and larger animals are concerned the hope of cure by this means has not been realised; but as a means of diagnosis, i.e. detection of tuberculosis, injection of a small quantity of tuberculin under the skin, has been found most valuable. If the cow thus injected is suffering from the slightest tuberculosis, it becomes feverish for a few days; if it is healthy no “febrile reaction” occurs. By using this test tuberculous cattle can be detected, they can then be kept in separate sheds, the former sheds cleansed and disinfected; the milk of these cattle kept separate from that of the rest of the herd, and boiled before being drunk, or the infected cattle sent to the butcher. If the disease is strictly localised the carcases can be utilised for food, after careful destruction of all diseased portions. If these means were generally adopted, tuberculosis might gradually be eliminated from the cattle of the entire country, and a serious source of loss to farmers, as well as of danger to children drinking the infected milk, removed. The presence of tubercle bacilli in cow’s milk is detected by microscopic examination and by injection of small quantities of the suspected milk into guinea-pigs. The proportion of infected samples found when examinations of milk supplies have been made in different towns has varied from 10 to over 50 per cent.

It is probable that tuberculosis is conveyed by cow’s milk only when the tuberculous disease affects the udder. But inasmuch as the udder of a tuberculous animal may become tuberculous very rapidly and without being detected for a considerable time, it is evident that no tuberculous animal of any kind should be allowed to remain in any cowshed where milch cows are kept.

Recently (July, 1901) Koch has thrown doubt on the identity of bovine and human tuberculosis, which was previously accepted, because (unlike some other observers) he has been unable to produce in 19 cattle, on which he experimented, tuberculosis by mixing with their food expectoration of consumptive persons, or inoculating under their skins similar material. Even if these negative results should subsequently be confirmed, the converse proposition does not follow, that bovine tuberculosis cannot be communicated to man; and apart from this possibility milk containing the bacilli of bovine tuberculosis cannot be regarded as wholesome.

The boiling of milk destroys tubercle bacilli. So does a temperature considerably below 212° F. In Denmark, where butter and cheese are manufactured on a large scale, and the raw milk is collected in central dairies, a law was passed in 1898, obliging every proprietor of a dairy to heat all skimmed milk, or butter milk, to a temperature of 85° C. (185° F.) before returning it to the farms. Pasteurization, i.e. the heating of milk in a special apparatus to a temperature of 70° C. (158° F.), and keeping it at this temperature for 30 minutes kills tubercle bacilli. If it is rapidly cooled, the nutritive value and taste of the milk are not spoilt. It is safer, however, to go beyond this point, and the use of an apparatus like the Aylmer or Sentinel Sterilizer can be recommended. More recent experiments have made it doubtful whether tubercle bacilli in milk are always killed in milk at a temperature of 70° C., the pellicle formed on milk when it is heated appearing to shield the bacilli from the effect of the heat. Hence it is desirable that “no sterilizer should be looked upon as thoroughly efficient for the purpose in which a temperature of at least 85° C. (185° F.) is not attained.”

The following test may be used to determine whether milk has been efficiently pasteurized:—

Natural milk contains a ferment or enzyme, which is destroyed at a temperature of 176° F. This enzyme splits up hydrogen peroxide (H₂O₂) into water and oxygen, but this effect is not produced in milk heated above 176° F. Take one drop of a dilute aqueous solution of hydrogen peroxide, add it to one teaspoonful of the milk. Next add two drops of a watery solution of paraphenyldiamine. A dark indigo colour is produced with uncooked milk, no change of colour if the milk has been pasteurized. The same test can be used for determining whether butter has been made with pasteurized milk.

Infection is not the sole determining cause of tuberculosis. Certain conditions of environment may determine whether the infection will succeed in “taking root” or not. Of these the following are important:

The nutrition of the individual if defective favours infection. Probably one chief reason why consumption has declined nearly 50 per cent. in the last 50 years is the better, more varied and more abundant food of the population.

Improved housing of the population has greatly helped in the same direction. Tubercular diseases increase with density of population, and are most prevalent in overcrowded tenements. Probably overcrowding chiefly acts by favouring direct infection, but it must also lower the health and power of resistance of the individual against infection.

The drying of the subsoil has been regarded as a chief cause of the reduction of consumption (page [226]). It is probable, however, that the wet soil merely predisposed to consumption, because it was commonly associated with cold and wet houses, which would favour catarrhs, and open the way for the infection of consumption.

The dryness of the house is a most important matter. If a damp soil means also a damp house it must favour consumption and other chest affections. Damp air, like water, rapidly abstracts heat from the body. Compare, for instance, the discomfort of sitting clad in water at a temperature of 65° F. with the comfort of sitting clad in a dry room at the same temperature! The domestic fowl is naturally immune to anthrax; but by being kept for a few hours with its feet in cold water, it can be rendered susceptible to inoculation with this disease.

The effects of breathing foul air are clearly shewn by the varying death-rate from phthisis in different occupations. Thus, if the comparative mortality figures of agriculturists be represented as 100, that of a commercial clerk = 176, of a draper = 200, of a tailor = 211, of a printer = 244, of a bookbinder = 246.

The effects of breathing dust-laden air are even more marked. Thus, if the comparative mortality figures from phthisis of agriculturists = 100, that of a coal-miner = 166, of a mason = 215, of a chimney-sweep = 249, of a file-maker = 373, of a cutler = 407, of a potter = 453. The last figure probably also shows the influence of alcoholism, which greatly favours tuberculosis.

Means for Preventing Tuberculosis.—The means for preventing tuberculosis from infected milk and meat have been already indicated. They comprise—

(a) Means of eradicating tuberculosis from cattle;

(b) Means of preventing harm from tubercle bacilli in milk or meat;

Under the first head improved conditions of housing of cattle, greater air-space, improved ventilation, a larger proportion of out-door life are important. The use of the tuberculin test, the separation of healthy from diseased cattle; the disinfection of sheds occupied by infected cattle are also essential.

Under the second head come efficient sterilization of suspected food (see p. 13), and the rejection of diseased meat. (See p. 24).

The most important measure against tuberculosis is the prevention of infection from patients with consumption. Under this head are comprised the following steps:—

A. Means of ascertaining the existence of the disease—

B. Direct preventive measures—

C. Education of the public and of patients as to the importance of the preceding measures.

The gratuitous examination of suspected sputum is now being undertaken in certain towns. The earlier the infectious condition of expectoration is detected, the sooner can the necessary precautions be taken.

The notification to the medical officer of health of all cases of consumption I have repeatedly advocated. This is already carried out for the chief acute infectious diseases, and although the difficulties of acting on the information received in regard to a chronic disease like consumption are considerable, they can be overcome with tact and discretion. Voluntary notification is already practised in Brighton, Manchester, and a few other towns. Notification gives increased and more exact opportunities of preventing phthisis by—1. Enabling disinfection and cleansing of affected rooms to be effected; 2. Enabling instructions to be given to the patient and his relatives as to the exact precautions required; and by 3. Facilitating the removal of the insanitary conditions of home and work which may have caused the case or favoured its untoward progress.

The following scheme of measures of disinfection was prepared by Drs. Niven and Newman and myself for the National Association for the Prevention of Consumption, and is issued by them in pamphlet form:—

In preventing a consumptive person from spreading the disease, two sets of preventive measures are required:—1st, The removal or destruction of the infective matter already disseminated by the patient’s discharges, especially by his phlegm; and, 2nd, the prevention of future dissemination. For the latter purpose the main object is not to permit any discharge to become dry before being destroyed. Before the consumptive person has learned the personal precautions which must be taken, and up to the time when he has been trained to carry them out carefully, he has probably distributed a considerable amount of infective matter. This is especially liable to accumulate in a dangerous form at home, where the space is small, and light and ventilation are defective. Infective particles will be found in greater abundance on and near the floors, on ledges, and in room-hangings. But the personal clothing and bedclothes will also have become infected. Hence it is necessary to disinfect the floor, walls, and ceiling of the rooms occupied by the patient, as well as the furniture, carpet, bedclothes, &c.

When this has been done, if the personal precautions advised are carried out by the consumptive, further disinfection should not be needed.

It is, however, difficult to make sure that personal precautions are fully carried out, and rooms should therefore be subsequently cleaned at least once in six months, the floors being scrubbed with soft soap, the furniture washed, the walls cleaned down with dough, and the ceiling whitewashed.

Confined workshops in which a consumptive has worked for some time should be cleansed, and a notice in reference to spitting should be suspended in all workshops. The latter precaution should also be observed in all public-houses and common lodging houses, both of which require special attention to cleansing.

Disinfection of rooms which have been occupied by consumptive patients may be secured in various ways, but the following are the practical rules which must underlie any methods adopted:—

1. Gaseous Disinfection of Rooms, or “Fumigation,” as it is termed, by whatever method it is practised, is inefficient in such cases.

2. In order to remove and destroy the dried infective discharges, the Disinfectant must be applied directly to the infected surfaces of the room.

3. The Disinfectant may be applied by washing, brushing, or spraying.

4. Amongst other chemical solutions used for this purpose a solution of Chloride of Lime (1 to 2 per cent.) has proved satisfactory and efficient.

5. In view of the well-established fact that it is the dust from dried discharges which is chiefly infective, emphasis must be laid upon the importance of thorough and wet cleansing of infected rooms.

6. Bedding, carpets, curtains, wearing apparel, and all similar articles belonging to or used by the patient, which cannot be thoroughly washed, should be disinfected in an efficient steam disinfector.

7. After all necessary measures of Disinfection have been carried out, the essential principle governing the subsequent control of a case of consumption is that all discharges, of whatever kind (especially expectoration from the lungs), should under no circumstances be allowed to become dry.

Besides measures of disinfection and cleanliness, the patient must be placed under the best conditions for overcoming the disease. The same measures tend to prevent infection. Thus abundant food, an open-air life, sleeping with bedroom windows widely open, avoidance of dust, abundance of sunshine, are all important. The importance of sunlight in the prevention of consumption can scarcely be exaggerated. Koch found that tubercle bacilli were killed in from a few minutes to some hours, according to the thickness of the layer in which they were exposed to the sunlight. He found that even ordinary daylight produced the same effect, if it lasted long enough; cultures of tubercle bacilli dying in from five to seven days if exposed at the window in compact masses. These experimental facts emphasise the importance of abundant open space about dwelling-houses (see p. 203), the provision of a large window-area (see pages 202 and 216), of staircase ventilation, and lighting, &c.

Scrofula means a tubercular affection of the lymphatic glands. It occurs most commonly in the neck. The infection is usually received from some neighbouring mucous surface, as from the throat, being derived from dried expectoration or diseased milk. The same indications as for the prevention of phthisis hold good for scrofula.

[CHAPTER XLVI.]
NOTIFICATION AND ISOLATION.

We are confident from the actual discovery of the micro-organisms causing certain infective diseases, that the other diseases of an analogous nature are similarly caused by living contagia. On this supposition, action is taken for the prevention of these diseases. This action comes under a number of different heads, which may be classified as follows:—

1. Means for the early recognition of the infectious character of a disease. The bacteriological aids to recognition in diphtheria (page [299]), enteric fever (page [301]), and phthisis (page 310) have been already mentioned. It is important to call in medical aid when any suspicious symptoms arise, even when these symptoms do not appear to be urgent. If an infectious disease is not recognised in its early stage, it may be easily overlooked, and the patient cause a serious epidemic. The following hints for teachers are in Brighton sent with each circular letter as to excluding infected children from school. The list is not exhaustive, but may aid in drawing attention to suspicious symptoms. The only safe rule when in doubt is to act as though a case is infectious until a skilled opinion can be obtained.