British Malaya: malaria control in Klang district

On assuming duty as District Surgeon of Klang, Federated Malay States, early in January 1901, I found that a very large percentage of the patients in my hospital suffered from malaria. Not only was the town of Klang full of malaria, but the whole coast-line was suffering from a “wave” of the disease. The little town of Jugra, twenty miles south of Klang was so unhealthy that a proposal to remove it bodily was being discussed. As a student of the London School of Tropical Medicine, I was familiar with the malaria parasite, and I was also aware of Ross’ discovery that Anopheles carried malaria. It appeared to me that ward after ward might be built to accommodate the increasing number of patients without any very substantial advantage to the community; for only a small fraction of the sick would ever come to hospital; or, if they came, could be accommodated in the hospital, however much it was likely to be extended. It was clear to me, that, even at the risk of being accused of neglecting my patients and “wasting my time on research,” it was my duty to spend some of my time in studying the disease outside of the wards, and to make some attempt to prevent people from getting the disease.

It was necessary first of all to obtain an accurate knowledge of where the malaria cases came from, and statistics were carefully prepared. The breeding places of Anopheles were next sought out, and marked out on a plan. Then came the really difficult question, what method was to be adopted to stamp out the disease. Medical opinion was strongly divided then, as it was to be for many years after. Fortunately I made what was to prove in the end, the right choice. The position will be realized from the following paragraphs extracted from an earlier work of my own:1

At this time, Ross’ brilliant discovery had been fully confirmed by the Italians and others. Manson’s dramatic proof at Ostia and at London left no doubt of what could be done under certain conditions. Ross himself had favoured mosquito reduction, and was actively engaged in West Africa in putting this method to the test. The Italians were rather in favour of mechanical prophylaxis by mosquito netting, and by the use of quinine, and Koch had already reported a success in a small community by the regular use of this drug.

At this time nothing was known about the species of Anophelines, and the valuable reports of the Commissioners of the Malaria Committee of the Royal Society bearing on the importance of species were not published until the year after the works at Klang had been begun.

At Klang the work of eradicating malaria seemed well nigh hopeless. No hot or cold season even temporarily stopped the mosquito pest, and every well, ditch, and swamp teemed with larvae.

The active co-operation of the native community could not be expected, and active resistance, especially from the Chinese, was certain if any attempt were made to enforce the use of quinine. The enforcement of mosquito nets was, of course, impossible, since this would have meant constant house visitation at night. Compulsory screening of the whole of all the houses was impossible, for financial reasons. The large acreage of swamp, the heavy rainfall, and the amount of supervision required, apart altogether from its cost and temporary efficacy, prohibited the use of petroleum.

Again, with an area so extensive, subsoil water so high as to form permanent swamps, and aquatic vegetation so dense, the sweeping out or dealing with the individual collections of water in any continuous manner was impossible. As Surgeon of a district fully 100 miles long, I felt that the time I could devote to any anti-malaria measures would be limited, and I also felt that no other member of the community was at all likely, either to be willing or able, to give more time than myself to the supervision of measures which would only keep down mosquitoes as long as they were constantly applied. And, to be quite candid, knowing that the burden would fall on myself, I did not quite appreciate the idea of having constantly to stand in the sun supervising coolies, and insisting on that thoroughness on which alone success would depend.

Considering all these elements of the problem, I rejected as impossible Koch’s quinine method, and the Italian mechanical prophylaxis, and decided to recommend Ross’ method of mosquito reduction. To suit the local conditions I determined that any expenditure should be on works of a permanent nature. By draining and filling there would be a large and permanent reduction of the breeding places of mosquitoes, and presumably malaria would be correspondingly reduced.

A proposal was made to Government that Klang town should be drained, to test the new mosquito theory; and the money was at once voted. Work was begun at once by the Sanitary Board, and within a couple of years malaria had ceased to be of any practical consequence.

On the 15^th September 1901, this new port was opened, and a considerable official population was removed from Klang to it. Almost immediately malaria became so severe that work could not be carried on properly either by the shipping, the Harbour Department, or the railway; and two months later the High Commissioner ordered the closure of the port until it could be made healthier. In the meantime a local commission had been appointed, and it recommended that instead of closing the port an attempt should be made to make it healthier by carrying out certain sanitary measures recommended strongly by me in the previous April. As the site of the town was below high-tide level—in fact, the houses were built in a mangrove swamp, the trees of which were often within 50 feet of the houses—embankments were constructed to keep out the sea; and tide-valves were affixed to the ends of the drains, so that while water could escape at low tide, no seawater could enter. In addition to drainage, all pools were oiled; and quinine was offered to and taken by many of the people. In a short time the work of the port was proceeding as if such a thing as malaria had never existed.

As a result of the drainage of these two places, the number of cases of malaria admitted to hospital fell very rapidly, which was in marked contrast to the surrounding district. There was also a remarkable diminution in the number of deaths, as shown in Table 2.1.

When the diminution in the number of deaths from other diseases than malaria was first observed, I was puzzled. It was possible to suppose that the improvement in health was not due to malaria having been driven off; but that there had disappeared some unrecognised malign influence which had in some way affected everyone, and made many succumb easily to all diseases, including malaria, and that the removal of this had enabled everyone to resist malaria and all other diseases more successfully, I could think, however, of no general cause which could have so acted; food, climate, water, everything were identical. Then the explanation flashed on me.

In my hospital work, a long series of blood examinations from patients who made no complaint of malaria had shown me that many people harbour the malaria parasite without having high temperatures; that even when their temperatures are high, they may be quite unconscious of the fact; but that such people suffer from abscess, diarrhoea, dysentery, etc., because their weakened health makes them easy victims to the attacks of such disease germs. This being so, then the elimination of malaria from a community would not only prevent deaths that were recognisably due to malaria, but it would also prevent the deaths of many who succumbed to diseases that were really unrecognised sequelae of malaria (a microscopic examination of the blood would have shown the true connection); and that unrecognised malaria itself was in fact the “unrecognised malign influence” which had disappeared.

The drainage and filling of swamps in the towns of Klang and Port Swettenham had cost respectively about $30,000 and $50,000,2 and the areas dealt with had amounted to only about 300 and 100 acres, respectively. Certainly, at that cost per acre it would be impossible to free the surrounding districts from malaria. But a study of the adjoining district of Kuala Selangor led me to think that “the stamping out of malaria, or at least reducing it to a negligible quantity, is a much more hopeful affair than has been hitherto anticipated.”

From the study of that district, I felt justified in urging the better drainage of the Kapar portion of the Klang district; and after inquiry the Government voted the sum of $110,000 for the Kapar Drainage Scheme. Thirty-seven miles of main drains about 20 ft. wide were cut or improved, and this enabled planters to drain 24,000 acres.

To me this great agricultural development was a great experiment in the prevention of malaria. It was a unique opportunity, and I determined to spare nothing in an attempt to understand it. Accordingly I began a systematic examination of the blood of children on different estates; and also charted the different species of Anopheles found in different parts of my districts. After I had carried out this work as a hobby for a considerable time, giving planters all the assistance I could in order to improve the health of their labour forces, I was asked to become medical adviser to a large number of them. This enabled me to improve my transport, and being in the confidence of the planters, to count on their cooperation and help in the work I was attempting.

To cut a long3 story short, I have traced from year to year the steady disappearance of malaria from 500 square miles of country.

A definite connection was traced between malaria and its carrier, A. umbrosus, which bred in stagnant pools in the jungle; and it was proved that the abolition of these pools occurred when land was drained and cultivated. I made observations on the parasite and spleen rates, so we have considerable data. It was also shown that the spleen rate diminished the further we passed from the jungle pool; that the death rate was intimately connected with the spleen rate; and that about half a mile from the breeding place, malaria had disappeared. We had thus made the important discovery that in low-lying alluvial clay soil with a high ground water—the great stronghold of malaria—we had complete control over the disease. So complete was our control that the simplest possible rules could be laid down for practical men. They were, either (1) remove your habitations to a distance of half a mile from the jungle pools, or (2) fell jungle and drain jungle pools for a similar distance. These two simple measures have been extensively used, with the result that the true spleen rate of many estates is zero (any children with enlarged spleens being new arrivals from malarious places); and the death rates are from 5 to 20 per 1000, including all women, children, and dependants; while the total admission rates from all diseases are down to 100 per 1000, and malarial admission rates are under 20 (these, again, mainly due to new arrivals who have come from malarious parts of the peninsula).

Figure 2.2: Chart showing variation of death rate with spleen rate in Klang District

By attention to these rules new estates of thousands of acres have been opened without ever suffering from malaria. But we have one unfortunate estate which reversed the process ; it put coolies near to the jungle, with the result that the force wasted away from 600 coolies to about 300. The spleen rate rose from 3.7 to 58. The daily sick in hospital rose from 2 to 30; the outpatients, from 8 to 90; and owing to this sickness the labour was insufficient to tap the trees, and the manager failed to get his estimate by 30,000 lbs. of rubber, a loss of some £7000. I could not account for the outbreak. As far as I knew, and I thought I knew the estate, no coolie lines were within half a mile of the jungle, and the manager assured me this was so. But at length, having failed completely to find a breeding place near the lines, I set out to examine the boundaries of the estate, and found they bent in near to some new lines. A redistribution of labour had mixed up all the coolies, and so I had been unable to trace the outbreak to its origin at first. The moral is that a medical officer should not merely think he knows an estate, but by actually visiting every part of it, know it from personal examination.

Finally, there is an interesting instance when a spleen rate dropped from 50 to 5. The jungle, from which the malaria came, apparently remained unaltered. I was, however, convinced something had happened to the jungle, and stated my conviction to the manager. He then reminded me that it had been drained, though not felled, by the neighbouring estate in connection with their water supply. This obviously was the explanation, and furnished another instance of the connection of malaria with jungle pools on low, at coastal lands, and its disappearance on the drainage of these pools.

The malaria problem now seemed to be solved in the Federated Malay States: we might expect the disease to disappear of itself with the extension of cultivation. But in 1909 I had to abandon this idea in so far as it related to many of the hilly districts in the Federated Malay States. It was perfectly true that one or two estates where the land was hilly were perfectly healthy; these indeed obscured the problem. But ninety nine out of a hundred hill estates remained as intensely malarious as they had been when first opened. We had succeeded in eradicating malaria from the place where we least expected success—in the low-lying coast land with a stiff clay soil and high ground water; we had failed completely where we least expected failure—in our beautiful hill land, where swamps were conspicuous only by their absence, and the only water was the crystal spring and brook. In hill land the admission rates to hospital often ran to 3000 per mille per annum of the population, and the death rates, which averaged 150, often leapt to 400 and 500 when many new arrivals came to an estate. The European staff suffered as much as the coolies, and the highest Government officials were not exempt. Public works no less than private enterprise were time and again almost brought to a standstill. Quinine, tried in every shape and form, completely failed to eradicate the disease, although it lowered both the admission rate and the death rate.

The reason for the persistence of malaria in hill land proved ultimately to be ascribable to the different habits of the carrier by which in these regions it is conveyed. The carrier is A. maculatus (in those days we knew it as Anopheles or Nyssorhynchus willmori), which breeds in clear springs and crystal brooks, and cannot be eradicated by weeding the edges of the stream. In spite of quite a strong current it can hang on to rocks and pebbles in a stream where not a blade of grass or other aquatic vegetation is to be found; although it is no less at home when a stream is full of grass, provided there is a sufficient flow to keep the water fresh. I came to the conclusion, therefore, that unless we could alter the composition of th water in these hill streams in such a was to make it uncongenial to all malaria-carrying mosquitoes, the only way we could get rid of the insect (and malaria) here would be by putting the streams underground in pipes.

Having seen estate after estate become healthy on the low coast land, as we got rid of A. umbrosus, I was convinced that the right way to deal with the hill-land malaria was to strike directly at the mosquito larva, rather than to put people inside screened houses. I proposed that the population of an estate should be concentrated on one or more sanitary areas, and that all water for a certain distance round the areas should be carried off underground in ordinary agricultural pipe drains, such as we are familiar with in Europe.

I suggested such a scheme for Seafield Estate, where I was satisfied the work would be done with the thoroughness necessary for success. Few men, whether they be medical men or laymen, had striven harder to overcome the pestilence than Mr H. R. Quartley, Manager of Seafield Estate. It was because of the thoroughness with which quinine had been given to the coolies on Seafield Estate over a period of several years, that I was convinced quinine alone could never do all that Koch and the Italians claimed for it. And it was because the streams on Seafield had been scrupulously clean-weeded over a period of four years with the definite object of eliminating A. maculatus, that I felt entitled to say that no treatment on such lines of these streams would eliminate the mosquito. This mosquito had been proved up to the hilt to be the chief offender. Its larva we could find in the streams; the adult insect could be caught in the coolie lines, and on dissection 20 to 25 percent were found to have malaria parasites in their stomachs or salivary glands. Unless we could abolish malaria, we could never establish a healthy labour force sufficient to cultivate the estate; and on Mr Quartley laying all these facts before his directors, they agreed to spend £3000 sterling on an attempt to make the estate healthy.

When we had reached the conclusion that subsoil drainage was necessary if malaria was to be overcome, the practical application of this measure presented many problems. Panama, where it had been employed for a hundred yards round buildings, in conjunction with oiling and screening, gave no help; and, as I have since learned, it is not essential to the successful result there.

It was important to know the area requiring to be done. This obviously was related not so much to the distance an odd mosquito might fly or be blown from its breeding place, as to the distance at which there would not be a sufficient number of mosquitoes to furnish the complete and complicated chain of the parasites life from man through the mosquito to man. This on the flat land was shown to be about 40 chains (half a mile) from the jungle breeding pool. These measurements were made from jungle which generally existed as a menace to health only on one side of the coolie lines, for, as a rule, there was a wide stretch of opened land on other sides. In other words, the mosquitoes on at land came from only one direction.

Our proposal for hill lands was to create a mosquito-free circle, into which, presumably, mosquitoes would pour from all points of the compass. Would 40 chains be enough under these circumstances? It seemed to me to be well worth trying less than 40 chains, for two reasons. The first was that, on the hill land, mosquitoes would not really fly in from all directions, for part of the boundary of the circle would be high dry land not breeding mosquitoes. Mosquitoes would in reality be breeding only in the ravines, and the mosquito attack on the coolie lines might be likened to a series of columns (the number depending on the number of ravines) advancing on a centre.

The second reason was that 90 percent of the Anopheles caught on the lines of Seafield were A. maculatus (or willmori), and only 10 percent A. umbrosus. A. maculatus is a small and rather delicate mosquito, and it is reasonable to regard its malaria-carrying flight as less than that of A. umbrosus, the carrier on whom the flat land measurements were based. It was plain, too, that, purely as a business proposal, it was advisable to work from within outwards, for the area of the work and the expense of the work increases as the square of the radius. To double the radius of the circle was at least to quadruple the expense. Taking all these things into consideration, I was content to begin with about a 30 chain radius. By not draining the quarry ravine on Seafield Estate, we actually were free on one side only for 27 chains.

The pipes in Panama were covered with stone, and then a grass covering was allowed to grow over them; both of value in preventing storm-water scouring out the pipes. Neither of these methods was at first available for Seafield. To have put down stones on the pipes would have multiplied enormously the expense of the work, for little stone is to be found on the estate. It appeared to me that we could do without stone; as has proved to be the case, except in a few places.

Figure 2.3: Bukit Ijok estate, Federated Malay States. Subsoil drainage to tap springs on the side of a steep ravine.

I also regarded the use of grass as prohibited; for if, from any unforeseen reason, the piping were to prove a failure, the grass once established in the ravines, would add greatly to the cost of weeding. I was anxious to avoid this; and only approved of grass being grown when satisfied the subsoil drainage would ultimately be effective. How valuable grass is can be seen from the comparative ease with which the anti-malarial work in Kuala Lumpur has been carried out. Before beginning the Kuala Lumpur work the engineer to the Malaria Advisory Board visited Seafield and carefully studied what had been done there; particularly he benefited by the various ingenious methods devised on Seafield to prevent damage from storms without using grass. At Kuala Lumpur the Board’s problem was simplified by its being able to use turf and grass to any extent it wished. The excellent results later obtained in Kuala Lumpur owed much to the pioneer work on Seafield, where greater natural difficulties had to be overcome, even apart from the fact that the work was a first attempt.

After a careful survey at Seafield, the late Mr Irvine, Assoc.M.Inst.C.E., drew up a drainage scheme in 1910. The actual work was begun in June 1911, under the supervision of Mr John Bach, Assoc.M.Inst.C.E., and at the end of April 1912 drainage had been carried out to a distance that varied from 25 to 28 chains from the coolie lines. There was a definite, but insufficient, improvement in the health; and in September 1913 the area was extended to give 40 chains in all directions, except one where a deep swamp presented special difficulty to any kind of drainage. It was also found that in the very wet weather of December 1913, the pipes in three of the ravines could not carry away the water with sufficient rapidity to keep the ravines dry; but by June 1914, larger pipes had been laid down. It is now expected the ravines will remain completely dry and free from Anopheles in any weather; and I am confident the long wished-for result will be obtained.

On some hill estates we got rid of malaria very easily; the coolie lines were simply rebuilt on at land at a distance of about 40 chains, or half a mile, from the hills. On one estate a block of 70 acres of low-lying swamp was opened at my suggestion; coolie lines were removed to it from a site on the hills, and the new site proved to be the healthiest on the estate. It was so low-lying and swampy that it had been rejected by the planter; but to the sanitarian it proved to be the chief cornerstone, and after two years trial is now being made the headquarters of the estate labour force.

On two estates where the lines were situated with hills behind and a long stretch of at land in front, it was an easy matter to pipe-drain the hills where alone A. maculatus was breeding, and the results were most gratifying. On North Hummock Estate, where this was done, the daily sick rate dropped from 13.5 percent in November 1911 to 2.2 percent in December 1912, and the spleen rate from 11 out of 12 (91 percent) to 2 out of 14 (14 percent), with a corresponding improvement in the general appearance and health of the whole labour force. It will be realized that here we have had to deal with an invasion of Anopheles only from one half of the circle, and not from all round as on Seafield. On Bukit Ijoh Estate a similar result followed some difficult drainage carried out most efficiently by Mr N. Fish, the engineer of the estate.

I have already spoken about the relationship that exists between spleen rates and death rates, and given a chart to illustrate it (see Figure 2.2). Although prepared from observations made in 1909, later experience has only confirmed its lessons. Of the fatal effect of malaria on a population, it is evidence which cannot be misread; and it also helps us to see in what direction we must push sanitary work, if we are to get the maximum amount of good for the money at our disposal.