Conclusions

30.1	Mosquito reduction

1. 1.From a malarial standpoint, the Malay Peninsula can be divided into several zones which may conveniently be distinguished as, the Mangrove Zone, the Coastal Plain, the Coastal Hills, the Inland Plain, and the Inland Hills.
2. 2.These zones may be malarial naturally, or may become so through the operations of man.
3. 3.The part of the Mangrove Zone covered daily by the tide contains no Anopheles and is non-malarial. When the forest is felled and the tidal flow obstructed, it may become intensely malarial from the appearance of A. ludlowi, which has been proved to be a natural carrier of malaria and is probably the most important carrier in the Mangrove Zones.
4. 4.The part of the Mangrove Zone covered only by the spring tides is naturally malarial from the presence of A. umbrosus, which has been proved to be a natural carrier of malaria. Clearing the forest allows A. ludlowi to enter this portion of the zone also.
5. 5.Both A. ludlowi and A. umbrosus are eliminated by clean weeded drains and good drainage; and many examples of how good agriculture abolished these mosquitoes and their malaria from the Mangrove Zone can be given.
6. 6.The Coastal Plain is malarial from the presence of A. umbrosus in its virgin jungle.
7. 7.Hundreds of square miles of flat land in the Coastal Plain of Malaya have been freed from malaria by simply draining and felling the jungle, and cultivating the land.
8. 8.The disappearance of malaria from the Coastal Plain coincides with the disappearance of A. umbrosus, which breeds in pools in undrained jungle, but cannot breed in open earth drains when kept free from weeds, and with a current of water. There are probably other reasons connected with the quality of the water in well-drained land.
9. 9.Ten years ago the cost of these rural anti-malaria measures in Malaya was about £3 sterling an acre, being £2 to drain, and £1 to fell the heavy virgin jungle. This expenditure is, at the same time, the first step in agriculture, and the land has then acquired a considerably increased value. Today the cost of draining and felling is about 70% higher. When an estate is newly opened, it is possible for the Medical Officer to select non-malarial sites, and then the cost of controlling malaria is, of course—nil.
10. 10.In the low Coastal Hills next to the Coastal Plain, malaria is prevalent when the ravines are under jungle owing to the presence of A. umbrosus in large numbers.
11. 11.Clearing and draining of these ravines frees them from A. umbrosus, but does not free the land from malaria.
12. 12.Malaria persists in the Coastal Hills after the ravines have been cleared and drained, and after A. umbrosus has disappeared, from the appearance of A. maculatus.
13. 13.A. maculatus does not live in ravines covered by heavy jungle; but appears only after the shade has been removed. The cleaner the water, and the better drained the ravine, the more suitable the ravine becomes for A. maculatus.
14. 14.The utmost care and cleanliness from an agricultural point of view continued over a period of years, fails to eliminate A. maculatus and its malaria.
15. 15.A. maculatus can be completely abolished from ravines by subsoil drainage, or spraying with suitable oils: and its malaria disappears with it.
16. 16.The Inland Plains are poorly represented in Malaya. They are healthy like the Coastal Plains when opened; but A. aconitus, if present in streams of running water, must be controlled.
17. 17.The Inland Hills are non-malarial when under virgin jungle, because A. umbrosus does not exist in the ravines. They differ in this respect from the Coastal Hills.
18. 18.The Inland Hills become intensely malarial when the ravines are opened, because A. maculatus appears. In this respect they are like the Coastal Hills.
19. 19.Subsoil drainage and oiling, which control A. maculatus in the Coastal Hills, are equally suitable in the Inland Hills. In the future, it will probably be found more economical in many places to allow the ravines to revert to jungle. In opening land in this zone in the future, malaria can be avoided by refraining from felling the jungle in the ravines. This will cost nothing.

30.2	Rice fields

1. 20.Rice fields on the Coastal Plain are practically free from malaria. The Anopheles found are A. rossi, A. kochi, A. sinensis, A. barbirostris , and maybe A. fuliginosus.
2. 21.Rice fields in narrow valleys are usually, in my experience, malarial. The Anopheles found are A. rossi, A. kochi, A. sinensis, A. barbirostris, A. fuliginosus, and A. aconitus; [the latter] has been proved a natural carrier of malaria.
3. 22.Further research will almost certainly show how the malaria of rice fields in valleys can be controlled by altering the composition of the water—by polluting it; which will be a great boon not only to the Malays, who cultivate the rice, but to others, by increasing the food production of the country.

30.3

Quinine

1. 23.Quinine given regularly reduces the sick rate and death rate of those exposed to malaria.
2. 24.Doses of less than 6 grains daily are of little value where malaria is intense—say where the spleen rate is over 60%.
3. 25.Where malaria is intense, and the population consists of immigrants, take 10-grain doses on six days out of the seven, and 20-grain doses when suffering from pyrexia or not at work on account of ill-health, between 20 and 30% of those taking the drug will be found with parasites in their peripheral blood.
4. 26.The use of quinine can, therefore, never result in the abolition of malaria, nor make any material reduction in the liability to infection in an intensely malarial locality.
5. 27.In twenty years’ experience I have seen quinine given systematically for long periods in many intensely malarial places; but in no place have I seen any material reduction in liability to infection due to quinine alone; most newcomers have become infected, and have died or become immune.
6. 28.Quinine systematically given probably assists the infected to acquire a natural immunity. Where there is no reinfection, ten to twenty grains in solution for three months is an almost certain cure for the people of most races—Malayalees appear to be an exception. Rest in bed on four successive Sundays assists quinine to stop relapses. In women there is a special necessity for quinine at menstrual periods. Abortion and the very fatal malarial anaemia of pregnancy can often be prevented by the continuous use of quinine in doses of from ten to twenty grains daily throughout pregnancy. Abortion is produced not by the quinine, but by the malaria.

30.4

Screening

1. 29.The attempt to discover a satisfactory screened coolie line ended in an inconclusive experiment, as I was unable to supervise it to its termination.
2. 30.Screened bungalows for Europeans have proved of great value.
3. 31.Screened hospitals give a real protection in patients; mosquito curtains in hospitals for Asiatics are practically valueless, and are more expensive than screening.

30.5	The labour problem

Much is said about the difficulty there will be in the future of obtaining labour for F.M.S. It is stated that the F.M.S. will never be able to attract from India all the coolies required, and that the estates will have to depend on Chinese labourers.

I confess I am an optimist on this subject, and have no fear for the future, if a wise medical policy be adopted by this country. For a number of years now, I have watched many estates; and as a result have come to these conclusions.

1. 32.Until the recent difficulties with shortage of rice and adverse Indian [currency] exchange [rate], few healthy estates have failed to obtain all the coolies required; some years there may be shortage, but in most years more are recruited than are required. This applies not only to old estates, but also to new estates like “EE,” which in its third year imported more labour from India than any other estate in the F.M.S. The chief difficulty of healthy estates is the prevention of crimping; that is, having their coolies enticed away by unhealthy estates.
2. 33.Unhealthy estates are perfectly well known to the coolies both here and in India, and are generally avoided; not only have these estates difficulty in obtaining labour, but the annual loss of labour through death, discharge, etc., is 30 to 50% greater than on the healthy estates.
3. 34.Chinese labour, being originally non-immune to malaria, suffers almost as much as Indian labour, when living permanently on the estate like Indian labour. It is only when the Chinese labourer can leave the estate when ill, that he survives to resume his work another day; he gradually acquires a natural immunity.
4. 35.Chinese know which estates are unhealthy; and the wages paid on unhealthy estates to Chinese are much higher than those paid to Tamils on healthy estates.
5. 36.Healthy estates are not without interest in all others becoming healthy, since the unhealthy estates, by their attraction of higher wages, unsettle the coolies of the healthy estates and often attract their skilled tappers.
6. 37.Were all estates healthy, more Indian labour would be attracted; it would be more efficient; and there would be more inducement for the coolies to make the F.M.S. their home.
7. 38.Were the country inhabited by the Malays, and more particularly the rice fields of valleys, made healthy, the Malay infantile death rate would be greatly reduced, and an abundant healthy Malay population supported by their rice fields would come into being. Java is a wonderful example of how a Malay race can expand.

In this way, even apart from the Chinese, this naturally rich country would obtain the labour force without which its development is impossible, “and I believe,” as I wrote ten years ago, “that the labour problem is nothing but the malaria problem, and that the solution of the malaria problem will also be the solution of the labour problem. No estate can ever have an assured labour force where the women wail, ‘We cannot have children here, and the children we bring with us die.’ Such is the cry on the unhealthy estates: ‘It is vain to contend with the instinct of her who weeps for her children and will not be comforted.’ It is because I believe we do now know how to save the children that I am an optimist for Malaya.”

This volume has shown how malaria has been driven from great tracts of country, and how the development of the country under the British has been a boon, not only to the native, but to the foreigner also. Already irrigation and drainage have not only assured them of their crops, and given them wealth beyond anything they had known, but have given them freedom from their most deadly disease over wide areas. It remains but to extend these benefits. And although some details have still to be learned, I think that working on Ross’s discovery, and on the method advocated by him, we may confidently hope to drive the disease completely from the land.