Colonial Prospect
THE FIGHT FOR HEALTH
By SIR PHILIP MANSON-BAHR THAT present health problems which fall upon the shoulders of the Colonial Governments are immense, intricate and
burdensome no one can deny. In the tropics unceasing war is being waged, not only against the diseases which are peculiar to warm climates, but also against that whole array of scourges which afflict mankind. There tuberculosis, for example, assumes a deadli- ness unknown elsewhere. There, too, malaria takes first place as captain of the men of death. Until recently this was considered the commonest disease in the world, constituting the chief bar to pro- gress and development ; but now it can be claimed that it has been to a great extent arrested and that ultimate victory is in sight. Let us consider how this transformation has been achieved.
When some fifty years ago the mosquito-transmission of malaria had been proved beyond doubt, its eradication at that time appeared comparatively simple. It spelt, in fact, the destruction of mosquitoes wherever malaria was rife, though it soon had to be accepted that this was an impossible task. As the result of intensive studies by entomologists in many lands it became evident that for some biological reasons only a comparatively small number of anopheline mosquitoes arc capable of transmitting malaria from man to man, and that each of these favours certain breeding places and maintains peculiar feeding habits, so that by concentrating attacks upon them, within the limits of their own peculiar haunts, some success might be obtained. This method was aptly termed "species sanitation."
The operative procedures entailed in carrying out these measures differed widely in different countries. In Malaya, for example, some species have been to a great extent eliminated by altering the environ- ment of .their breeding waters. Some arc partial to shade and concealment ; others court the sunlight, and so on. At the present time anti-malarial campaigns have been completely revolutionised by the application of D.D.T., an insecticide which has proved itself to be the most efficient weapon yet discovered.
Throughout the whole of equatorial Africa, Anopheles garribiae, a common as well as the most dangerous carrier of malaria, flourishes in almost every collection of water, however polluted or foul. Until two years ago the possibility of eradication of this small insect from such an immense area appeared fantastic, but now with the example of the successful campaigns in Sudan and Upper Egypt before us, and with the introduction of other insecticides, such as gammexane, malaria is rapidly becoming a rarity in what was formerly known as the white man's grave. Malaria, indeed, is receding wherever the spraying of mosquito breeding-grounds is being undertaken. It has just been announced that in this year the island of Cyprus has been freed from the menace after a brief D.D.T. campaign ably directed by Dr. Horace Shelley, Dr. M. Aziz and Professor George Macdonald, which has served as a model for the world.
In British Guiana Dr. George Giglioli, O.B.E., has been almost equally successful in an even more remarkable feat, for there he had to deal with vast alluvial plains with rice and cane-fields, swamps and waterways stretching for hundreds of miles. The brunt of this attack was directed against the two most dangerous species— Anopheles darlingi and A. aquasalis—by spraying huts and dwelling houses which they frequented with D.D.T. In spite of the fact that both these dangerous species have entirely different breeding habits —one breeds in fresh water, the other in brackish—within the space of two years they have been brought to the verge of extinction and concurrently malaria has practically disappeared.
When we turn to trypanosomiasis, or sleeping sickness, there is also a stirring tale to tell. The trypanosome is a small tadpole-like creature which lives in the blood and is transmitted by vicious and bloodthirsty tsetse flies. These insects are confined to Equatorial Africa, and wherever they abound they spell death to man and his domestic animals. It is estimated that of the sixty-five millions of natives of tropical Africa no less than two millions arc infected with the deadly trypanosome. On account of this only two-fifths of the enormous territory of Tanganyika arc suitable for settlement and
development ; the rest is one vast fly-belt. Some twenty-one species of tsetse are known to science, of which some six arc adapted to the conveyance of the germ of sleeping sickness ; and it has now been discovered that for each species of fly certain plant associations and climatic conditions arc essential in order that it may flourish.
The fight against sleeping sickness has been long and protracted. Whole populations have been transplanted from danger areas, and the ingenuity of many devoted entomologists has been taxed to the utmost to discover methods of controlling the fly. Vast schemes for destroying their breeding places have been put into execution. D.D.T. " smoke" spread by aeroplanes has indeed achieved some local and temporary success. Powerful curative drugs, such as antrypol and tryparsamide, have been discovered and freely used ; but the battle is not yet won. The epic of the Anchau corridor has now been told. The market town of Anchau in North Nigeria in the Emirate of Zahaia has always constituted a hot-bed of sleeping sick- ness and, owing to its filthy and insanitary state, a danger to the community. To free this area from sleeping sickness 70o square miles of country had to be cleared of bush, and, within the space of ten years, the native population had been resettled in a new town with model wells and market-places. Cattle, pigs and poultry have been introduced, and flourish' there. The cesspit which constituted old Anchau has now been transformed into a settlement aptly termed Takalafiya or "Walk in Health." For this magnificent achievement Dr. H. M. Lester, Dr. T. A. M. Nash and Dr. Kenneth Morris must be given full and generous credit.
The story of the conquest of yellow fever, or " yellow jack " as it was known to our forefathers, has been one of constant and heroic endeavour in which British scientists have played a leading part and one in which valuable British lives have been sacrificed. A hundred years ago yellow fever in epidemic form swept across the West Indies and the South American continent, and from time to time broke out also in West and Central Africa. The germ cause has been found to be an ultramicroscopic virus which is present in the blood in the first three days of the fever and is disseminated from thc sick to the healthy by a gaily marked " tiger mosquito "—Aedes aegypti. Fortunately this is a domestic insect abounding in the haunts of man, especially in large towns, whence it can be easily ousted by D.D.T. This has now been done in many parts of South America and West Africa, so that with its disappearance yellow fever has been banished from the main centres of population.
With the development of irrigation and cultivation bilharziasis is spreading throughout the Continent of Africa. The. bilharzia (so- called after its discoverer, Bilharz—and familiarly nicknamed "Bill Harris" by our troops) is a worm, just under half an inch in length which lives securely within blood vessels. Here the female produces a great number of hard-shelled eggs which are shed outside the body in the excreta and, when passed in water, give rise to a motile ciliated creature which burrows into the liver of certain freshwater snails which abound in F t reams, ponds, rivers, reservoirs and other collec- tions of water. In this organ an elaborate reproduction takes place, the final phase of which is the cercaria, a small thread-like creature with a bifid tail which swims actively in water for about two days. This, now 11 juvenile bilharzia worm, is attracted to man and, by burrowing through the skin, enters the body and settles down within the portal vein. It is obvious that in the extermination of these peculiar snails, which constitute the host of the bilharzia parasite, lies the only hope of curtailing its ravages. This is a gigantic task which entails the draining of streams, ponds and waterways in an unceasing destruction of these molluscs with sulphate of copper.
This brief inadequate account is a story of the manner in which the defeat of the main tropical diseases has been, or is being, brought about. It is probably true that, perhaps with the exception of leprosy, we now possess efficient drugs which are antidotes for them all. This is the lynch-pin upon which the health, prosperity and happiness of millions of our fellow subjects depend. For this happy solution a tribute should be paid to members of our Colonial Medical Service, who, unread and unsung, sometimes subjected to unjust and uninformed criticism, have laboured on, often amidst =con- genial surroundings, such as can hardly be realised by those who slumber by their firesides at home.
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