"All plants and animals possess parasites, and thousands of different species of parasites have been closely studied by science; we therefore know much about their general ways of life. As a rule, a particular species of parasite can live only in the particular species of animal in which, by the evolution of ages, it has acquired the power of living. It is therefore not enough for the parasites of an individual animal—say a man—to be able to multiply within that individual, but they must also make arrangements, so to speak, for their progeny to enter into and infect other individuals of the same species. They cannot live for ever in one individual; they must spread in some way or other to other individuals."The shifts made by parasites to meet this requirement of their nature are many and various, and constitute one of the wonders of nature. Some scatter their spores and eggs broadcast in the soil, water, or air, as it were in the hope that some of them will alight by accident on a plant or animal suitable for their future growth. Many parasites employ, in various ways, a second species of animal as a go-between. Thus, some tapeworms, and the worms which cause trichinosis, spend a part of their lives in the flesh of swine, and transfer themselves to human beings when the latter eat this flesh. To complete the cycle, the parasites return to swine from human offal; so that they propagate alternately from men to swine, and from swine to men. The blood-parasites which cause the deadly tsetse-fly disease among cattle in South Africa are transferred from one ox to another on the proboscis of the ox-biting or tsetse-fly. The progeny of the flukes of sheep enter a kind of snail, which spreads the parasites upon grass. The progeny of the guinea-worm of man enter a water-flea. The progeny of the parasites which cause Texas cattle-fever, and which are very like the malarial parasites, live in cattle-ticks, andare transferred by the young of these ticks into healthy cattle." (Ross,Malarial Fever, 1902.)
"All plants and animals possess parasites, and thousands of different species of parasites have been closely studied by science; we therefore know much about their general ways of life. As a rule, a particular species of parasite can live only in the particular species of animal in which, by the evolution of ages, it has acquired the power of living. It is therefore not enough for the parasites of an individual animal—say a man—to be able to multiply within that individual, but they must also make arrangements, so to speak, for their progeny to enter into and infect other individuals of the same species. They cannot live for ever in one individual; they must spread in some way or other to other individuals.
"The shifts made by parasites to meet this requirement of their nature are many and various, and constitute one of the wonders of nature. Some scatter their spores and eggs broadcast in the soil, water, or air, as it were in the hope that some of them will alight by accident on a plant or animal suitable for their future growth. Many parasites employ, in various ways, a second species of animal as a go-between. Thus, some tapeworms, and the worms which cause trichinosis, spend a part of their lives in the flesh of swine, and transfer themselves to human beings when the latter eat this flesh. To complete the cycle, the parasites return to swine from human offal; so that they propagate alternately from men to swine, and from swine to men. The blood-parasites which cause the deadly tsetse-fly disease among cattle in South Africa are transferred from one ox to another on the proboscis of the ox-biting or tsetse-fly. The progeny of the flukes of sheep enter a kind of snail, which spreads the parasites upon grass. The progeny of the guinea-worm of man enter a water-flea. The progeny of the parasites which cause Texas cattle-fever, and which are very like the malarial parasites, live in cattle-ticks, andare transferred by the young of these ticks into healthy cattle." (Ross,Malarial Fever, 1902.)
Theplasmodium malariæwas discovered by Laveran in 1880, in the blood of malarial patients. For many years his work stopped there, because it was impossible to find theplasmodiumin animals: "the difficulties surrounding the subject were so great that this discovery seemed to be almost hopeless." In 1894, Sir Patrick Manson—who had proved mosquitoes to be the intermediate host in the case of the parasitic nematodefilaria—suggested, as a working theory of malaria, that the plasmodium was carried by mosquitoes. This belief, not itself new, he made current coin. He observed that there is a flagellate form of the plasmodium, which only comes into existence after the blood has left the body: and he suggested that the flagella might develop in the mosquito as an intermediate host, a halfway-house between man and man. Then, in 1895, Ross set to work in India, keeping and feeding vast numbers of mosquitoes on malarial blood; and for two years without any conclusive result. About this time came MacCallum's observations, at the Johns Hopkins University, on a parasitic organism,halteridium, closely allied to the plasmodium malariæ; he showed that the flagella of the halteridium are organs of impregnation, having observed that the non-flagellated form, which he regarded as the female, after receiving one of the flagella, changed shape, and became motile. In August 1897, Ross found bodies, containing pigment like that of the malarial parasite, in the outer coat of the stomach of one kind of mosquito, the grey or dapple-wingedmosquito,Anopheles maculipennis, that had been fed on malarial blood. In February 1898, he was put on special duty under the Sanitary Commissioner with the Government of India, to study malaria, and started work again in Calcutta:—
"Arriving there at a non-fever season, he took up the study of what may be called 'bird malaria.' In birds, two parasites have become well known—(1) the halteridium, (2) the proteosoma of Labbé. Both have flagellated forms, and both are closely allied to the plasmodium malariæ. Using grey mosquitoes and proteosoma-infected birds, Ross showed by a large number of observations that it was only from blood containing the proteosoma that pigmented cells in the grey mosquito could be got; therefore that this cell is derived from the proteosoma, and is an evolutionary stage of that parasite. Next, Ross proceeded to find out its exact location, and found that it lay among the muscular fibres of the wall of the mosquito's stomach. It grows large (40-70 micro-millimetres) and protrudes from the external surface of the stomach, which under the microscope appears as if covered with minute warts." (Manson, at Edinburgh meeting of British Medical Association, 1898.)
These pigmented spherical cells give issue to innumerable swarms of spindle-shaped bodies, "germinal rods"; and in infected mosquitoes Ross found these rods, in the glands that communicate with the proboscis. Thus the evidence was complete, that the plasmodium malariæ, like many other parasites, has a special intermediate host for its intermediate stage of development; and that this host is the dapple-winged mosquito. It is impossible to over-estimate the infinite delicacy and difficulty of Ross's work; for instance, in his "Abstract of Recent Experiments with Grey Mosquitoes," he says that "out of 245 grey mosquitoes fed on birdswith proteosoma, 178, or 72 per cent., contained pigmented cells; out of 249 fed on blood containing halteridium, immature proteosoma, &c., not one contained a single pigmented cell." Another time (April 1898) he counted these pigment-cells under the microscope:—
"Ten mosquitoes fed on the sparrow with numerous proteosoma contained 1009 pigmented cells, or an average of 101 each. Ten mosquitoes fed on the sparrow with moderate proteosoma contained 292 pigmented cells, or an average of 29 each. The mosquitoes fed on the sparrow with no proteosoma contained no pigmented cells."
Finally, he completed the circle of development by infecting healthy sparrows by causing mosquitoes to bite them.
In 1899, there went out a German Commission to German East Africa, a Royal Society's Commission to British Central Africa, and an expedition from the Liverpool School of Tropical Medicine; in 1900, another German Commission, this time to the East Indies, and another expedition from the Liverpool School; by July 1901, the Liverpool School was organising its seventh expedition. Italy, of course, has given infinite study to the disease:—
"It has been decided that, in addition to the stations of observation and experiment in the provinces of Rome, Milan, Cremona, Mantua, Gercara, Foggia, Lecce, others shall be established in the provinces of Udine, Verona, Vicenza, Padua, Ravenna, Pisa, Basilicata, and Syracuse. Besides epidemiological researches, applications on a large scale will be made of preventive measures for the protection of the agricultural population against the scourge. Another extensive experiment on the prophylaxisof malaria will be made on the Emilian littoral. Moreover, in all the malarious regions of the Italian peninsula the provincial and communal administrations and many private persons will co-operate in the application of preventive measures. From all this it may be gathered that during the summer and autumn the war against malaria will be carried on in Italy with great vigour and thoroughness." (British Medical Journal, 6th July 1901.)
In India, the work started in 1900 by the Royal Society Commissioners, and by the Nagpur Conference, has been widely extended; especially by such researches as those of Major Buchanan, I.M.S., Superintendent of the Central Jail, Nagpur. The following paragraph, from the report of the Sanitary Commissioner with the Government of India, refers to Major Buchanan's published work,Malarial Fevers and Malarial Parasites in India:—
"A remarkable note is struck at the outset, in the acknowledgment made, by the author, of the capable assistance rendered in these researches by several of his Burmese prisoners, whom he trained to the use of the microscope, and who soon became expert in detecting and distinguishing the various kinds of parasites.... Besides a systematic clinical account of the different forms of fever and the associated parasites, which is the first attempt of the kind in India, there are a summary of the facts showing the relation of the seasonal prevalence ofAnophelesto the incidence of attacks; experiments exhibiting the protective effects of mosquito-curtains; inoculation-experiments; researches on the blood-parasites of birds; and many other points.... Nor can we pause to notice the many attempts now being made by health officers and others to pursue the methods of prophylaxis indicated; these efforts are necessarily in the tentative stage, but, so far,and especially where carried out in connection with small communities and institutions, they are giving promise of gratifying success."
The famous experiment made by Dr. Sambon and Dr. Low in 1900, must be recalled here:—
"Dr. Luigi Sambon and Dr. G. C. Low, both connected with the London School of Tropical Medicine, volunteered to live from June till October, that is to say, through what may be called the height of the malaria season, in a part of the Campagna near Ostia, which is so infested by the disease that no one who spends a night there under ordinary conditions escapes the effect of the poison. Dr. Sambon, Dr. Low, Signor Terzi, and their servants, have now exposed themselves to the pestilential influence of this valley of the shadow of death for over two months. They live in a mosquito-proof hut; they take no quinine or other drug which might be regarded as prophylactic. Not one of the experimenting party has the least sign of infection.[38]..."What for practical purposes may be regarded as an experiment of the same kind is being conducted in West Africa. Dr. Elliot, a member of the Liverpool expedition sent to Nigeria some time ago to investigate the subject of malarial fever, has recently returned to this country. He reports that the members of the expedition have been perfectly well, although they have spent four months in some of the most malarious spots. They lived practically amongst marshes and other places hitherto supposed to be the most deadly. They have not kept the fever off by the use of quinine, and they attribute their immunity to the careful use of mosquito-nets at night." (British Medical Journal, 22nd September 1900.)
"Dr. Luigi Sambon and Dr. G. C. Low, both connected with the London School of Tropical Medicine, volunteered to live from June till October, that is to say, through what may be called the height of the malaria season, in a part of the Campagna near Ostia, which is so infested by the disease that no one who spends a night there under ordinary conditions escapes the effect of the poison. Dr. Sambon, Dr. Low, Signor Terzi, and their servants, have now exposed themselves to the pestilential influence of this valley of the shadow of death for over two months. They live in a mosquito-proof hut; they take no quinine or other drug which might be regarded as prophylactic. Not one of the experimenting party has the least sign of infection.[38]...
"What for practical purposes may be regarded as an experiment of the same kind is being conducted in West Africa. Dr. Elliot, a member of the Liverpool expedition sent to Nigeria some time ago to investigate the subject of malarial fever, has recently returned to this country. He reports that the members of the expedition have been perfectly well, although they have spent four months in some of the most malarious spots. They lived practically amongst marshes and other places hitherto supposed to be the most deadly. They have not kept the fever off by the use of quinine, and they attribute their immunity to the careful use of mosquito-nets at night." (British Medical Journal, 22nd September 1900.)
A similar "experiment," of the utmost importance, was made in 1900 by Professor Grassi. It concerned the workmen and their families along the Battipaglia-Reggio railway, 104 in all, including 33 children. The great majority of them had suffered from malaria in the preceding year; and only 11, including 4 children, had never suffered from it. Pending the arrival of the malarial season, quinine was given to all who needed it. The firstAnopheleswith its salivary glands infected was found on 14th June. Twelve days later came a case of malaria outside the "zone of experiment," in a person who had never had malaria before. The twelve days correspond to the incubation-period after infection.Anopheleshaving come, and the malarial season with him, the experiment was begun. The houses were carefully protected with wire netting, chimneys and all; thesiestawas taken under wire netting; the workmen, if they were out in the evening or at night, wore veils and gloves; andAnopheleswas to be killed wherever he was found. Quinine was altogether given up and forbidden, except for three workmen who had escaped or evaded its usebefore June, and had, indeed, never before been treated with quinine; one of them, moreover, had been sleeping outside the zone of experiment in July. Except these three, all the 104 and their doctors remained absolutely free from malaria up to 16th September, the date of Professor Grassi's report:—
"Rightly to estimate the value of these facts, it is necessary briefly to describe the surroundings of the protected area. Towards the north, coming from Battipaglia, three railway cottages are situated, at a distance of 1, 2, and 3 kilometres respectively. The 25 inhabitants of these cottages, although they were put under the tonic and quinine treatment in the non-malarial season, all without exception were taken ill with malarial fevers, in many cases obstinate."
Experiments of voluntary exposure to bite from an infected mosquito were made at or about this time, in London, New York, Italy, and India. The London "consignment" of mosquitoes had been allowed to bite a malaria-patient in Rome. The experiment had to be very carefully planned:—
"To have sent mosquitoes infected with malignant tertian parasites might have endangered the life of the subject of the experiment; and quartan-infected insects might have conferred a type of disease which, though not endangering life, is extremely difficult to eradicate. The cases, therefore, on which the experimental insects were fed had to be examples of pure benign tertian—a type of case not readily met with in Rome during the height of the malarial season; the absolute purity of the infection could be ascertained only by repeated and careful microscopic examination of the blood of the patient." (British Medical Journal, 29th September 1900.)
The mosquitoes were forwarded, through the British Embassy in Rome, to the London School of Tropical Medicine. The two brave gentlemen who let themselves be bitten by some thirty of the mosquitoes were in due time attacked by malaria, and the tertian forms of the parasite were found in their blood. Nine months later, one of them had a relapse, and the parasite was again found in his blood.
It is not possible to sum up the wealth of work on malaria published in 1900-1901. Good accounts of it are in the Transactions of the Section of Tropical Diseases, at the Annual Meeting of the British Medical Association (Cheltenham, 1901), and in the Thompson Yates Laboratories Reports, vol. iii., pt. 2, 1901. Everything had to be studied: not only the nature and action of theplasmodiumin all its phases, but also the whole natural history and habits of theAnophelesof different countries; and, above all, the incidence of the disease on natives and on Europeans in China, India, and Africa. All that can be done here is to try to indicate the principal lines followed in the present world-wide campaign against malaria. The following paragraphs are taken mostly from the accounts given by Dr. Christophers and Dr. Annett, in the Thompson Yates Laboratories Report, 1901:—
1.Elimination of the Infection at its Source.This is the method employed with success by Professor Koch in New Guinea, viz., to search out all cases of malaria (the concealed ones in particular), and to render them harmless by curing them with quinine. At Stephansort, by thus hunting up all infected cases, and as it were, sterilising them by the systematic administration of quinine, he was able to achieve a great reduction of the disease in the next malarial season, even underadverse conditions. He says, in his report to the German Government: "The results of our experiment, which has lasted nearly six months, have been so uniform and unequivocal that they cannot be regarded as accidental. We may assume that it is directly owing to the measures we have adopted that malaria here has, in a comparatively short time, almost disappeared."
This method, of course, is applicable only in small communities; and, within these limits, it may become one of the most valuable of all methods, being, like the quality of mercy, a blessing both to him who gives and to him who taketh. But it cannot be practised on a vast scale. This difficulty is well put by Sir William MacGregor, K.C.M.G., Governor of Lagos, West Africa:—
"In all probability, the day will come before long, when newly-appointed officers for places like Lagos will have to undergo a test as to whether they can tolerate quinine or not. A man that cannot, or a man that will not, take quinine, should not be sent to or remain in a malarial country, as he will be doing so at the risk of his own life,and to the danger of others.... The great difficulty is how to extend this treatment beyond the service, more particularly to the uneducated masses of the natives. It is simply impossible to protect the whole population by quinine administered as a prophylactic. In the first place, the great mass of natives would not take the medicine; and, in the second place, the Government could not afford to pay for the 70 tons of quinine a year that would be required to give even a daily grain dose to each of 3,000,000 of people."
2.Segregation of Europeans from Natives.This method is strongly advocated by the members of the Nigeria Expedition of the Liverpool School (1900). The distance of removal to half a mile is consideredsufficient: "Considerable evidence has now been accumulated to prove that the distance which is traversed by a mosquito is never very great, and extremely rarely reaches so much as half a mile." The arguments in favour of this method of "segregation" are of so great interest that they must be put here at some length. The drawback is that the method cannot be followed everywhere to its logical issue without some risk of giving offence, of seeming to abandon the native, of damaging commerce, and so forth. But, short of this, much might be done for the protection of Europeans in Africa:—
"This method is a corollary of the discovery that native children in Africa practically all contain the malaria parasite, and are the source from which Europeans derive malaria. Koch showed in New Guinea that in most places infection was very prevalent in native children, so much so that in some villages 100 per cent. of those examined contained parasites. He also showed that, as the children increased in age, immunity was produced, so that in the case of adults a marked immunity was present, and malarial infection was absent. The Malaria Commission showed, independently, that a condition of universal infection existed among the children of tropical Africa, associated with an immunity of the adults. This infection in children had many remarkable characteristics. The children were in apparent health, but often contained large numbers of parasites, and a small proportion only of the children failed to show some degree of infection.... The Liverpool School Expedition found a similar condition of affairs in all parts of Nigeria visited by them."With a knowledge of the ubiquity of native malaria, the method of infection of Europeans becomes abundantly clear. The reputed unhealthiness or healthiness of stations is seen at once to be dependent on the proximityor non-proximity of native huts. The attack of malaria after a tour up-country, the malaria at military stations like Prah-su, the abundance of malaria on railways, are all explicable when the extraordinary condition of universal native infection is appreciated. It is evident that, could Europeans avoid the close proximity of native huts, they would do away with a very obvious and great source of infection.... When it is understood that each of these huts certainly contains many children with parasites in their blood, and also scores or hundreds ofAnophelesto carry the infection, then the frequency with which Europeans suffer from malaria is scarcely to be wondered at.... The accompanying plan is that of a new railway settlement on the Sierra Leone Railway. Miles of land free from huts exist along the line, but the close neighbourhood of native huts has been selected. At the time of building of these quarters, it lay in the power of the engineers to have a malaria-free settlement; instead of which, by the non-observance of a simple fact, the station is most malarious: in this particular instance, much ingenuity has been shown in providing each set of European quarters with plenty of malarial infection. In towns only is there any difficulty in carrying out the principle of segregation. In two instances, however, this has been carried out in towns, with the result that the segregated communities of Europeans are notoriously the most healthy on the West Coast. Even when no scheme of complete segregation can be carried out, the principle should always be borne in mind, and, whenever opportunity offers, huts should be removed, and European houses built in the open.... It is almost universally the rule in West Africa to find European houses built round by native quarters, a practice which long experience in India has taught Europeans to avoid carefully. At Old Calabar, many of the factories are almost surrounded, except in front, by native habitations; similarly, at Egwanga, the small native town is built by the side and back of one of the factories. Also at the Niger Company's factory at Lokoja, the native houses are very close upto the Company's boundary railings. Akassa engineers' quarters may be, again, mentioned as an example where the engineering artisans, chiefly natives of Lagos, Accra, and Sierra Leone, are housed with their families alongside the European house. A large proportion of these native children were found by us to contain malarial parasites. Similarly also at Asaba, the proximity of the barracks of the Hausa soldiers, who have their wives and children with them, is a dangerous menace to the officers at the Force House."Examples of the opposite condition of affairs might also be given. For instance, at Old Calabar, the Government offices and Consulate, Vice-Consulate, and medical house, are comparatively free from malarial fever; it having been established that the natives shall not build on the European side of the creek separating the two slopes on which the native town and European quarters are built. This creek is at a distance of about half a mile from the houses mentioned."
"This method is a corollary of the discovery that native children in Africa practically all contain the malaria parasite, and are the source from which Europeans derive malaria. Koch showed in New Guinea that in most places infection was very prevalent in native children, so much so that in some villages 100 per cent. of those examined contained parasites. He also showed that, as the children increased in age, immunity was produced, so that in the case of adults a marked immunity was present, and malarial infection was absent. The Malaria Commission showed, independently, that a condition of universal infection existed among the children of tropical Africa, associated with an immunity of the adults. This infection in children had many remarkable characteristics. The children were in apparent health, but often contained large numbers of parasites, and a small proportion only of the children failed to show some degree of infection.... The Liverpool School Expedition found a similar condition of a
"With a knowledge of the ubiquity of native malaria, the method of infection of Europeans becomes abundantly clear. The reputed unhealthiness or healthiness of stations is seen at once to be dependent on the proximityor non-proximity of native huts. The attack of malaria after a tour up-country, the malaria at military stations like Prah-su, the abundance of malaria on railways, are all explicable when the extraordinary condition of universal native infection is appreciated. It is evident that, could Europeans avoid the close proximity of native huts, they would do away with a very obvious and great source of infection.... When it is understood that each of these huts certainly contains many children with parasites in their blood, and also scores or hundreds ofAnophelesto carry the infection, then the frequency with which Europeans suffer from malaria is scarcely to be wondered at.... The accompanying plan is that of a new railway settlement on the Sierra Leone Railway. Miles of land free from huts exist along the line, but the close neighbourhood of native huts has been selected. At the time of building of these quarters, it lay in the power of the engineers to have a malaria-free settlement; instead of which, by the non-observance of a simple fact, the station is most malarious: in this particular instance, much ingenuity has been shown in providing each set of European quarters with plenty of malarial infection. In towns only is there any difficulty in carrying out the principle of segregation. In two instances, however, this has been carried out in towns, with the result that the segregated communities of Europeans are notoriously the most healthy on the West Coast. Even when no scheme of complete segregation can be carried out, the principle should always be borne in mind, and, whenever opportunity offers, huts should be removed, and European houses built in the open.... It is almost universally the rule in West Africa to find European houses built round by native quarters, a practice which long experience in India has taught Europeans to avoid carefully. At Old Calabar, many of the factories are almost surrounded, except in front, by native habitations; similarly, at Egwanga, the small native town is built by the side and back of one of the factories. Also at the Niger Company's factory at Lokoja, the native houses are very close upto the Company's boundary railings. Akassa engineers' quarters may be, again, mentioned as an example where the engineering artisans, chiefly natives of Lagos, Accra, and Sierra Leone, are housed with their families alongside the European house. A large proportion of these native children were found by us to contain malarial parasites. Similarly also at Asaba, the proximity of the barracks of the Hausa soldiers, who have their wives and children with them, is a dangerous menace to the officers at the Force House.
"Examples of the opposite condition of affairs might also be given. For instance, at Old Calabar, the Government offices and Consulate, Vice-Consulate, and medical house, are comparatively free from malarial fever; it having been established that the natives shall not build on the European side of the creek separating the two slopes on which the native town and European quarters are built. This creek is at a distance of about half a mile from the houses mentioned."
It is plain, from these and other instances given by the members of the Nigeria Expedition, that a modified sort of "segregation" can be effected in many places, without any injury either to native feelings, or to politics, or to commerce; and that by such segregation the risk of malaria among Europeans in Africa would be diminished.
3.Protection against Anopheles.Manson, in hisTropical Diseases(1905), says, "The question is often asked, Is there any other way by which malaria can be contracted than through a mosquito-bite? For many reasons, I believe not. It is difficult to prove a negative; but, so far, there is no observation capable of bearing investigation that would lead us to suppose that malaria can be acquired, under natural conditions, except by mosquito-bite," All authorities are agreedthat, practically, the fight against malaria and the fight againstAnophelesare one and the same thing; and the experiments by Sambon, Low, and Grassi, show what can be done, in this war against the mosquito, by way of defence. But what is practicable in Italy might not be generally practicable on the West African coast; as Sir William MacGregor says of Lagos:—
"It is not likely that in a place like Lagos as good results can be obtained from the use of mosquito-proof netting as in Italy. One great objection to it here is the serious and highly disagreeable way it checks ventilation. This is a difficulty that cannot be fully brought home to one in a cold climate. But, in a low-lying, hot, and moist locality like Lagos, it comes to be a choice of evils, to sit inside the netting stewed and suffocated, or to be worried and poisoned by mosquitoes outside. The netting is hardly a feasible remedy as regards native houses. It is not possible to protect even European quarters completely by it. Few officers or others are so occupied that they could spend the day in a mosquito-proof room. Certain it is that any man that suffers from the singular delusion that mosquitoes bite only during the night, would have a speedy cure by spending a few days, or even a few hours, in Lagos. Operations here (September 1901) are being limited to supplying one mosquito-proof room to the quarters of each officer. In this he will be able to spend the evening free from mosquitoes if he chooses to do so. The European wards of the hospital are similarly protected."
The European in Africa, as Ross says, is generally neglectful of his health; and the "unhealthiness" of the African coast is to some extent due to the life that men lead there:—
"Let us compare the habits of a European in a business-house in Calcutta with the habits of a European inWest Africa. In Calcutta he sleeps under a punkah or mosquito-net, or both; he dresses and breakfasts under a punkah; in the evening he takes vigorous exercise, and he dines under a punkah. He wears the lightest possible clothing, he lives in a solid, cool, airy house, and he obtains very good food; once in five or six years, he returns to Europe for leave.... In Africa, the houses are frequently very bad; in Freetown, for instance, they are the same as the houses of natives, and are mingled with them. The Anglo-African seems to imagine that he can live in the tropics in the same manner as he lives in England. He seldom uses a punkah, except perhaps for an hour at dinner-time, and, not seldom, he neglects even the mosquito-net. The food is often, or generally, execrable. Owing to the frequent absence of gymkhanas and clubs, the exile obtains little suitable exercise."
But whatever risks the old resident may choose to take, the newcomer can at least use a proper and efficient mosquito-net at night, and avoid sleeping in a native house, and protect himself in these and the like ways against malaria.
4.The keeping down of Anopheles.The breeding places ofAnophelesare ponds, swamps, and puddles, roadside ditches, tanks, and cisterns, old disused canoes, and the like collections of stagnant water: also the smaller receptacles that are more generally occupied byCulex, such as broken bottles, old tins, pots, and calabashes, and barrels, whatever will hold water—all the débris and broken rubbish round huts or houses. In all these places,Anopheles'eggs or larvæ are found; and, with practice, it is easy to detect them. Of course, it is not easy to wage war against the adult mosquito: the work is,Venienti occurrere morbo, to organise gangs of workmen, or of prison labour, and"mosquito brigades"; to clear the ground of cartloads of old biscuit-tins, broken gin-bottles, and other dust-heap things, in and around the place; to cover-in the cisterns, rain-barrels, and wells; to clean pools and duck-ponds of weed, and stock them with minnows; to put a film of kerosene to the puddles, or sweep them out, or fill them up and turf them over; everywhere, to drain, and level, and clean-up the surface soil; and everywhere, by these and the like methods, to break the cycle of the life of theplasmodium malariæ:—
"Draining and cultivation where the land will repay the expenditure, permanent and complete flooding where it will not, and such flooding is possible; proper paving of unhealthy towns, and the filling-in of stagnant, swampy pools; these—in other words, all measures calculated to keep down mosquitoes—are the more important things to be striven for in attempting the sanitation of malarious districts. In England, in Holland, in France, in Algeria, in America, and in many other places, enormous tracts of country, which formerly were useless and pestilential, have been rendered healthy and productive by such means." (Manson.)
And, short of such great enterprises as Government works of drainage, much has already been done, in many African towns, and in India, by the work of a few men and women: not only by practical sanitary improvements, but by insistent teaching and lecturing. For the admirable results recently obtained in Ismailia, Algeria, Formosa, and the Malay States, see theMedical Annual, 1905 and 1906.[39]
Before leaving the subject of malaria, it must be added that the discovery and study of the parasite which causes it have cleared up the mystery of the specific action of quinine upon the disease. It operates simply by its germicidal effect upon the microbe. But, beyond this, we have now a clue which we never had before to guide us to the most advantageous manner of administering the drug.
The specific organism of malaria may become active again and again in the blood, causing relapses twenty years or more after the original infection. The specific organism of yellow fever expends itself at once, in one acute attack; and, if the patient recovers, he is thenceforth more or less immune against infection. That the inoculation of the disease, by the application of a single mosquito recently contaminated, is calculated to produce a mild or abortive attack less dangerous than the average attack among the non-acclimatised, was known to Finlay, and was confirmed in 1899 by the Army Commission of the United States.
Of the mortality of the disease, Sir Patrick Manson, in 1900, wrote as follows:—
"It is better for women and children than for men; better for old residents than for newcomers; worst of all for the intemperate. According to a table of 293 carefully observed cases given by Sternberg, the mean mortality in the whole 293 cases was 27.7 per cent. This may be taken as a fairly representative mortality in yellow fever among the unacclimatised, something between 25 and 30 per cent., although in some epidemics it has risen as high as 50 or even 80 per cent. of those attacked.... Someof these epidemic visitations bring a heavy death-bill; thus, in New Orleans, in 1853, 7970 people died of yellow fever; in 1867, 3093; in Rio, in 1850, it claimed 4160 victims; in 1852, 1943; and in 1886, 1397. In Havana, the annual mortality from this cause ranges from 500 to 1600 or over."
The earlier attempts to reproduce the disease, by inoculation with its products, failed altogether:—
"In 1816, Dr. Chervin, of Point-à-Pitre (Antilles), drank repeatedly large quantities of black vomit without feeling the least disturbance. Some years before, other North American colleagues, Doctors Potter, Firth, Catteral, and Parker, did everything possible to inoculate themselves with yellow fever. After having uselessly attempted experiments on animals, they experimented on themselves, inoculating the black matter at the very moment in which the moribund patient rejected it, placing this matter in their eyes, or in wounds made in their arms, injecting it more than twenty times in various parts of their body ... in short, devising every sort of daring means for experimentally transmitting yellow fever. All these experiments were without result, and in the United States during many years it was believed that this terrible malady was non-contagious." (British Medical Journal, 3rd July, 1897.)
The history of the subject, from 1812 to 1880, is given by Dr. Finlay of Havana, in theNew York Medical Record(9th February 1901). In 1880, two very important reports on the disease were published; one by a Havana Commission of the National Board of Health of the United States, the other by the United States Navy Department. They tended to show that yellow fever is a "germ-disease"; that it is not wind-borne; and that there may be some change, outside the body of the patient, whereby the virulence of theactive principle of the disease is heightened. From these reports, Dr. Finlay advanced his doctrine that the mosquito receives and transmits the germs of the disease:—
"It was upon the above line of reasoning (in these reports), that I conceived the idea that the yellow-fever germ must be conveyed from the patient to the non-immunes by inoculation, a process which could be performed in nature only through the agency of some stinging insect whose biological conditions must be identical with those which were known to favour the transmissibility of the disease."
In 1881 he inoculated himself and six soldiers with infected mosquitoes, and obtained, as he had calculated, mild attacks and subsequent immunity. During the years 1881-1900 he inoculated by this method 104 persons:—
"In these inoculations, be it remembered, my principal object was rather to avoid than to seek the development of a severe attack; in point of fact, only seventeen showed any appreciable pathogenic effects after their inoculation. I felt sure, however, that severe or fatal result might follow an inoculation either with several mosquitoes contaminated from severe cases of the disease, or from a single insect applied several days or weeks after its contamination, having come to this last conclusion in view of the facts connected with theAnne Marie, and the epidemic of Saint Nazaire."
Dr. Finlay's discovery that the mosquito can convey yellow fever, and that the germ of the disease is more virulent after a prolonged sojourning in the mosquito, was proved beyond all question by the work of 1889-1901. But, so far as immunisation is concerned, fewpeople would submit themselves to be bitten by an infected mosquito, even with perfect assurance that the germs contained in it were of a low degree of virulence: the urgent need, therefore, was for an immunising serum. In 1896, at Flores, Sanarelli discovered thebacillus icteroides; and by October 1897, he had prepared an immunising serum which was able to give a considerable amount of protection to animals.[40]Next year (Annales de l'Institut Pasteur, May 1898) came the news that he had advanced against yellow fever with its own weapons—Premières expériences sur l'emploi du sérum curatif et préventif de la fièvre jaune. Of the first 8 cases (Rio de Janeiro), 4 recovered. Then came the 22 cases at San Carlos do Pinhal, in Saint-Paul au Brésil (January 1898), with 16 recoveries, and only 6 deaths. And it is to be noted that he submitted his method of treatment to the utmost test that was possible; he chose the bad cases, and the country where the fever was most fatal:—
"Chaque cas était choisi de commun accord entre nous, dans le but de mettre bien en évidence l'action thérapeutique du sérum,mettant toujours de côté tous les cas qui se présentaient avec des symptômes vagues ou attenuès ou en forme légère ou fruste. On ne conservait donc que des cas oû, d'après la violence des phénomènes d'invasion, on devait considérer comme très peu probable une crise spontanée de la maladie...."
Furthermore, Sanarelli was able to show the preventive value of the serum. At the end of February 1898, yellow fever broke out in the jail at San Carlos:—
"La première victime fut un condamné, qui vivait avec tous les autres dans une salle oû les conditions hygiéniques étaient assez mauvaises. Le lendemain, la sentinelle, qui était en rapport continuel avec la salle des condamnés, tombait malade. Quelques jours après, un autre condamné suivait le sort du premier, et bientôt un quatrième cas, mortel aussi, finit par signaler la prison comme un nouveau foyer d'infection qui venait s'allumer au centre d'un quartier de la ville encore resté indemne."Si on avait abandonné la chose à elle-même, on aurait vu se produire le même spectacle qu'avaient fourni, dans les conditions identiques, pendant les dernières épidémies, les prisons de Rio-Claro, de Limeira, et d'autres villes de l'État de Saint-Paul."
"La première victime fut un condamné, qui vivait avec tous les autres dans une salle oû les conditions hygiéniques étaient assez mauvaises. Le lendemain, la sentinelle, qui était en rapport continuel avec la salle des condamnés, tombait malade. Quelques jours après, un autre condamné suivait le sort du premier, et bientôt un quatrième cas, mortel aussi, finit par signaler la prison comme un nouveau foyer d'infection qui venait s'allumer au centre d'un quartier de la ville encore resté indemne.
"Si on avait abandonné la chose à elle-même, on aurait vu se produire le même spectacle qu'avaient fourni, dans les conditions identiques, pendant les dernières épidémies, les prisons de Rio-Claro, de Limeira, et d'autres villes de l'État de Saint-Paul."
Every prisoner, except one who had already had the fever, was therefore given the preventive treatment. At once the outbreak stopped; no more cases occurred, though only a weak serum was used, though the state of the prison and its occupants was unhealthy, though the fever, two months later, was still raging round the prison, in the town.
In October 1900, the United States Commission on Yellow Fever published a preliminary report on 11 cases of mosquito-inoculation. Of these, the majority gave a negative result, and were found susceptible to infection, at a later date, from the blood of a yellow-fever patient. Two gave a positive result. In the course of these experiments, Dr. Lazear, a member of the Commission, died of the disease. In February 1901, and again in July, the Commission published further reports, emphasising the fact that the mosquito conveys the disease, and denying that the disease can be conveyed in clothing, bedding, and so forth:—
"Our observations appear to demonstrate that the parasite of this disease must undergo a definite cycle ofdevelopment in the body of the mosquito before the latter is capable of conveying infection. This period would seem to be not less than twelve days."We also consider the question of house infection, and are able to show that this infection is due to the presence of mosquitoes that have previously bitten yellow-fever patients; and that the danger of contracting the disease may be avoided in the case of non-immune individuals who sleep in this building, by the use of a wire screen."We also demonstrate, by observations made at this camp (Fort Lazear), that clothes and bedding contaminated by contact with yellow-fever cases, or by the excreta of these cases, is absolutely without effect in conveying the disease."
"Our observations appear to demonstrate that the parasite of this disease must undergo a definite cycle ofdevelopment in the body of the mosquito before the latter is capable of conveying infection. This period would seem to be not less than twelve days.
"We also consider the question of house infection, and are able to show that this infection is due to the presence of mosquitoes that have previously bitten yellow-fever patients; and that the danger of contracting the disease may be avoided in the case of non-immune individuals who sleep in this building, by the use of a wire screen.
"We also demonstrate, by observations made at this camp (Fort Lazear), that clothes and bedding contaminated by contact with yellow-fever cases, or by the excreta of these cases, is absolutely without effect in conveying the disease."
In February 1901, Dr. H. E. Durham published an abstract of aninterimreport of the Liverpool School Yellow Fever Commission. He and Dr. Walter Myers, the two Commissioners, had both of them been attacked by the disease, and Dr. Myers had died of it. The report gives evidence that the disease is due to a bacillus which is not thebacillus icteroides; and it does not wholly favour the earlier report (1900) of the American Commission. A later Commission to New Orleans, September 1901 to January 1902, reported an extensive series of investigations, which seem rather to support the belief that thebacillus icteroidesis the cause of the disease. Later still, this belief is again denied; and, as in rabies, so in yellow fever, the good work has gone on without waiting for the identity of this or that micro-organism.
Immunisation, by the direct use of an infected mosquito, may be compared with the old custom ofinoculation against smallpox. The use of Sanarelli's serum-treatment has not gone far. There remains for consideration the method of keeping down infection by keeping downCulex.
Three reports, in 1901-1902, come from Dr. Guitéras (Havana), Surgeon-Major Gorgas, chief sanitary officer (Havana), and the Commission at New Orleans. Dr. Guitéras reports that 6 cases of yellow fever (inoculation) were treated in a large "mosquito-proof" building, which also contained cases of other diseases. No prophylaxis was enforced, save the exclusion of mosquitoes; non-immunes visited the yellow fever cases, non-immunes nursed them, and most of the attendants and labourers about the place were non-immunes; but not a single case of infection occurred. The New Orleans Commission reports that, of 200 cisterns, &c., examined in the city for the presence of larvæ, the larva ofCulex(Stegomyia) predominated in more than 60 per cent.
The report of Surgeon-Major Gorgas is very pleasant reading. For two centuries, Cuba had been cursed with yellow fever; then, after the war with Spain, America took it over:—
"The army took charge of the health department of Havana, when deaths (from all causes) were occurring at the rate of 21,252 per year. It gives it up, with deaths occurring at the rate of 5720 per year. It took charge, with smallpox endemic for years. It gives it up, with not a case having occurred in the city for over eighteen months. It took charge, with yellow fever endemic for two centuries—the relentless foe of every foreigner who came within Havana's borders, which he could not escape, and from whose attack he well knew every fourth man must die. The army has stamped out this disease in its greatest stronghold."
Make fair allowance for the wide variation, from year to year, of the number of yellow fever cases in any town within the geographical belt of the disease; admit that a town may, in the course of nature, have many hundred cases in one year, and only half a dozen in another year. Again, make fair allowance for all other good influences of the American occupation of Cuba, beside those that were concerned with the stamping out ofCulex; admit that the general death-rate of Havana, in the last February of Spanish rule (1898), was 82.32 per thousand, and in February 1901, was 19.32. Still, there is an example here, in the 1901 work in Havana, for the world to follow, wherever yellow fever exists. The following abstract of Surgeon-Major Gorgas' results was published in thePractitioner, May 1902, by Professor Hewlett, one of the foremost of English bacteriologists:—
"Commencing in February 1901, orders were issued that every suspected case of yellow fever should be screened with wire gauze at the public expense, so as to render the room or rooms mosquito-proof. All mosquitoes in the infected house and in contiguous houses were destroyed. After the middle of February, 100 men were employed in carrying out the destruction of the mosquito-larvæ in their breeding places, putting oil in the cesspools of all houses, clearing the streams, draining pools, and oiling the larger bodies of water. Up to June, quarantine was enforced, together with disinfection of the house and fomites. After that, however, rigid quarantine of the patient was stopped, and disinfection of fabrics and clothing ceased. It was merely required that the patient should be reported, his house placarded and screened, and a guard placed over each case to report how general sick-room sanitation was carried out, to see that the screen-door communicating with the screened part of the house was kept properly closed, and to see that communicationwith the sick-room was not too free, four or five non-immunes only being allowed in.By the end of September, the last focus of the disease had been got rid of, and since then, up to the beginning of January, there has not been a single case.Whereas, for the years since 1889, from 1st April to 1st December, yellow fever caused an average of 410.54 deaths, with a maximum of 1175 for 1896, and a minimum of 79 for 1899,it caused in 1901 5 deaths only. In the months of October and November, when the disease has hitherto been exceedingly rife in Havana, there has not been a single case. For the first time in 150 years, Havana has been free from yellow fever."
Sir Patrick Manson, lecturing in America, last year, on tropical diseases, summed up the work as follows:—
"Time will not permit—what to you is probably quite unnecessary—the recapitulation of the story of the labours of Reed and his coadjutors. I cannot pass on, however, to what I have to say in connection with this work without a word of admiration for the insight, the energy, the skill, the courage, and withal the modesty and simplicity of the leader of that remarkable band of workers. If any man deserved a monument to his memory, it was Reed. If any band of men deserve recognition at the hands of their countrymen, it is Reed's colleagues."The principal outcome of the labours of these men has been the demonstration, first, that the ultra-microscopic germ of yellow fever is present in the blood of the patient during the first three days of the disease. Second, that the first step in the passage of the germ from the sick to the sound is made, under natural conditions, in the stegomyia mosquito. And third, that after about twelve days and upwards in stegomyia, the yellow fever germ, when implanted by the said mosquito into another human host, is capable of reproduction, so that at the end of a further period of about three days it has established itself throughout the blood, is causing the violent reaction,the clinical manifestations of which we call yellow fever, and is once more in a condition to re-enter the mosquito."These are great etiological facts. They are of supreme practical and scientific value. Acting on them, the United States sanitary authorities expelled yellow fever from Havana. Acting on them, they should be able in the future to protect the United States themselves from such terrible visitations as in the past have swept through some of your cities."
"Time will not permit—what to you is probably quite unnecessary—the recapitulation of the story of the labours of Reed and his coadjutors. I cannot pass on, however, to what I have to say in connection with this work without a word of admiration for the insight, the energy, the skill, the courage, and withal the modesty and simplicity of the leader of that remarkable band of workers. If any man deserved a monument to his memory, it was Reed. If any band of men deserve recognition at the hands of their countrymen, it is Reed's colleagues.
"The principal outcome of the labours of these men has been the demonstration, first, that the ultra-microscopic germ of yellow fever is present in the blood of the patient during the first three days of the disease. Second, that the first step in the passage of the germ from the sick to the sound is made, under natural conditions, in the stegomyia mosquito. And third, that after about twelve days and upwards in stegomyia, the yellow fever germ, when implanted by the said mosquito into another human host, is capable of reproduction, so that at the end of a further period of about three days it has established itself throughout the blood, is causing the violent reaction,the clinical manifestations of which we call yellow fever, and is once more in a condition to re-enter the mosquito.
"These are great etiological facts. They are of supreme practical and scientific value. Acting on them, the United States sanitary authorities expelled yellow fever from Havana. Acting on them, they should be able in the future to protect the United States themselves from such terrible visitations as in the past have swept through some of your cities."
These same lectures contain an admirable account of the life-history ofFilaria. It is not necessary here to describe the loathsome deformities which occur in the later stages of filariasis. These deformities (elephantiasis, Barbadoes leg), which may attain colossal size, are due to the blocking of the lymphatic vessels with filarial worms. Cases of the disease are hardly ever seen in this country; but it is very frequent in some parts of the tropics.In the endemic areas, says Manson,10 per cent. is not an uncommon proportion of the population to be found affected with filariasis. Thirty and even 50 per cent. may be affected. In many of the Pacific Islands—the Samoa group for instance—I believe that even this proportion is exceeded.
ThatCulex(fatigans) can carry the parasite, has been proved past all doubt. Neither does anybody doubt, that the keeping down of this mosquito would keep down filariasis. A report of great interest, from Barbadoes, was published in theBritish Medical Journalfor 14th June 1902. It is written by Dr. Low, whose experiment on himself in the Campagna has already been noted in this chapter. Dr. Low reports that there is no indigenous malaria in the island, and that neitherhe nor Mr. Lefroy could find a singleAnopheleslarva, though they hunted diligently in the swamps and other likely places. But filariasis is terribly common, and so isCulex fatigans. Dr. Low examined the night-blood of 600 cases of all kinds in the General Hospital, the Central Almshouse, and elsewhere, and found the filaria-embryos in no less than 76 = 12.66 per cent. He caught and dissected a hundred mosquitoes (Culex fatigans) from the wards and corridors of the General Hospital, and found that no less than 23 of them were infected. If it were not forCulex, and for men's indifference and apathy, filariasis could be kept down all over the island:—