The malaria of the Coastal Plain and Anopheles umbrosus

The land to which I allude is the alluvial land between high-tide level and the nearest lower or Coastal Hills. In the course of our inquiry, it will be found convenient to consider malaria as it is found in the different zones of land existing in the Peninsula. The zone nearest the sea I propose to call the Mangrove Zone. Next will come the Coastal Plains; then the Coastal Hills. Still farther inland we come to areas of flat or relatively flat land which may be conveniently called the Inland Plains. Finally we come to the main range of hills forming the backbone of the Peninsula which I propose to call the Inland Hills. When opened up and inhabited, each of these areas presents special problems. It must not, however, be forgotten that in nature all are clothed in primeval forest; and that when inhabited they are in an unnatural, indeed a highly artificial, state. The Coastal Plain, in nature, is an alluvial flat composed of a heavy clay covered by dense, almost impenetrable, jungle. The ground water is almost permanently above the surface level; during the wetter months it may be waist deep. In some places the clay is covered with a coarse peat, formed from slowly decaying vegetable matter. Its depth varies from a few inches to many feet.

Many mosquitoes have their home in this jungle; but practically the only anopheline is Anopheles umbrosus, which I found to be an efficient natural carrier of malaria. I use the word practically, for only on one occasion have I found another Anopheles in this virgin jungle. It was A. aurirostris. There may, of course, be others yet to be discovered.

A. umbrosus, as we saw (Chapter 2), may be present in enormous numbers. Generally speaking, it is so abundant in houses situated near to this jungle, that it may be obtained without difficulty; for, being a large black mosquito, it is easily seen. Sometimes, however, it disappears temporarily even from places where it is the rule to find it in abundance.

As we pass away from the jungle, the number of the mosquitoes decreases, and at half a mile (or 40 chains) the number has so decreased that malaria, as indicated by the spleen rate, has disappeared, although occasionally cases of malaria do occur. For many years this mosquito has been under observation, and its association with malaria studied. The sum of these observations is that malaria, in certain portions of the district, namely the flat land, is exclusively carried by A. umbrosus, which breeds in pools in undrained jungle; and when the jungle is felled and the pools drained, this mosquito is exterminated completely; and with its extermination malaria disappears. It has been found, too, that the spleen rate in the children decreases with the distance they live from the breeding places of the mosquito; and that the death rate of an estate varies as the spleen rate. Finally these facts have enabled me to forecast with considerable accuracy the probable health or unhealthiness of a proposed site for coolie lines, and to give advice which has borne fruit. A theory which will provide a sound working rule is one of considerable value.

In order to make good these statements, I must now refer to the individual estates, the positions of which will be seen from the maps. In these are seen the parts under cultivation and the parts still (1909) undrained jungle. Coolie lines or houses are shown by the number, which is the spleen rate for the lines or group of lines at that part of the estate.

This was opened in 1906, and the coolies were housed within 100 yards of the jungle (see Figure 8.1). In 1907 malaria was very prevalent among them, and it became necessary to administer quinine daily. Rapid progress, however, was made in opening up the land; and within a year there was an extraordinary improvement in the health of the estate. The most striking evidence is to be found in the reports of the Indian Immigration Department, from which the figures in Table 8.1 are taken.

These figures demonstrate the economic importance of malaria. The whole success and, in fact, the very existence of tropical agriculture depends on a healthy and contented labour force. The severe prevalence of malaria in 1907 led not only to a high death rate, but to the unnecessary loss, in other ways, of about 150 coolies. Coolies will not remain on an unhealthy estate; therefore, 34 deserted, 125 gave the legal month’s notice and left. Instead of having a fine labour force of close on 300 coolies, the estate had to begin the year with considerably fewer than it had the previous year.

In 1907 the manager, and a friend who had lived with him for some time, both suffered severely from malaria. On 23^rd July 1907, only 167 out of 245 coolies were working, and of those not at work 10 had high temperatures. Three months later, after much loss of labour, I found on one occasion 8% of the labour force with fever, with oedematous feet, and the other sequelae of malaria.

The present manager has been on the estate for nearly two years. He has been off work for one day only and that not as a result of malaria, a disease from which he has not suffered. On 10^th January 1910 I examined all the children on the estate,9 and out of the fifty-one examined, I found one with enlarged spleen, who, inquiry elicited, had come from an estate in another district, the death rate of which in 1908 was 108‰, and which I knew suffered severely from malaria. The child had malaria when it came to estate “A.”

I regret I have no figure referring to the children in 1907, but I consider the figures I have given demonstrate in the most striking way how malaria has disappeared with the draining and opening up of the land. Undrained jungle is now about half a mile distant from the lines. For its subsequent history see Chapter 21.

I first examined this estate in 1904, when all the nine children were found free from parasites. There was only a small labour force, about sixty in all, and only occasionally was there a case of fever. The jungle was comparatively near; but the land immediately behind the coolie lines was drained. I find, however, that a small labour force often escapes when a larger one is seriously affected. This estate has continued to enjoy good health throughout, and on 10^th January 1910 none of the thirty children on the estate had enlarged spleen, and the conductor, who had been there for one and a half years, told me he had not had fever.

The death rates during 1906, 1907, and 1908 have been 22, 28, and 9‰, respectively. Since I came to know it, this estate has shown continued good health, although in 1907 its neighbour, only half a mile away, had suffered severely from malaria.

These estates illustrate clearly the association of malaria with undrained jungle. In 1909 they were being developed from virgin jungle, of which, of course, only a portion could be opened each year. During this period of development the labour forces were necessarily housed in varying proximity to the jungle; and all four suffered from malaria. It will be noted that at any time the incidence of malaria was greater the nearer a labour force was to the jungle; and that as the years passed it decreased pari passu with the disappearance of the jungle. The years in which the various blocks of land were cleared are marked on the plan (Figure 8.2).

Only part of the story could be told when the first edition of this book was written in 1909. Malaria had not yet disappeared from the upper division of estate “C;” estate “E” was only half-way out of the wood; the labour forces of estates “F” and “G” were still living close to jungle, and still suffering from intense malaria. But development was proceeding rapidly. It was a period of transition, which can best be recalled by reprinting what was written in 1909. Afterwards I will bring the story up to date.

This estate began operations in 1904, when its labour force was placed on land already opened a year or two before by Malays. They were thus placed on drained land from the beginning, and accordingly were healthy. Its death rate shows this, and was as listed in Table 8.4.

An experiment was carried out on this estate in 1906 and 1907, which bore out the extraordinary limitation of the flight of the mosquito, the relation of malaria to undrained jungle, the importance of selecting the best site for the housing of a labour force, and the certainty with which one could predict the health or otherwise of a site on the flat land.

It is an estate of about 3000 acres, and, with the healthy labour force it possessed, such rapid progress was made that within three years of starting 1000 acres were already opened; and it was proposed to open still more. In 1906 much of the work of the coolies was one to two miles distant from their lines, and it was obviously an economy, both to the estate and the coolie, to house him nearer to his work.

I was informed in 1906 that it was proposed to remove most of the force to what would ultimately be the centre of the estate, which at that time was still on the edge of undrained jungle. Knowing from experience that the site would probably be very unhealthy, I strongly advised that only a few coolies should be removed until the land had been further opened up. However, four sets of lines were built, three about 25 chains, i.e., quarter of a mile from jungle; and the other about 100 yards. The removal took place in October 1906, and on 22^nd November there were 120 coolies in the lines marked “Spleen Rate 16,” and 80 in a set of lines near to the jungle at quarter of a mile from the place marked “80” in Figures 8.1 and 8.2.10

Figure 8.2: Map of estate “C” and adjoining parts of estates “E,” “F,” and “G.” See text for details.

The result was disastrous. The coolies were overwhelmed with malaria, and soon had to be removed. I am indebted to the manager, E. H. King-Harman, for the following explanation:

Re abandoning lines: You ask me my reason for abandoning four sets of coolie lines in March 1907. They are as follows: I found that amongst the coolies living near EE drain (place marked “16,” about twenty-five chains from the jungle) I had 28% down ill with fever every day, and amongst those living near to my bungalow, marked “80” about ten chains from jungle, the rate was 33% daily.

On that account I removed that portion of my labour force to the south-western end of the estate, which had previously been healthy, and I abandoned the top lines altogether; but about the beginning of 1909 I put a portion of my labour force back again near EE drain, the jungle being then forty chains away; and I am glad to say the fever rate has been very small, and of very little consequence.

On 22^nd November 1906, there were fifteen children in the lines marked “16,” of whom only one had enlargement of the spleen. On 17^th February 1907, there were twelve children, of whom seven, or 58%, had enlarged spleens. As these were the same children, it shows how malarious the place had become. On 4^th January 1909, there were fifteen children living in the same place, of whom three had enlargement (very small in the case of two), equal to 20%. A portion of the force had only recently been removed to the edge of the drained jungle on block II, so that the figures for the whole division were thirty children, of which five, or 16% had enlarged spleens.

Now on the south-western portion of the estate, that is, the portion of the estate first occupied in 1904, I examined, on 5^th January 1910, the children—in all 109. Of these, four had enlarged spleen, giving a spleen rate of 3.6%. They were recent arrivals. I recognised two sisters as being the only two children who had been found with enlargement on an estate in the neighbourhood; one other had come two months previously from an estate in another district; and one had come from an estate where the spleen rate was 100%. The corrected spleen rate should therefore be nil.

The bungalow to which the manager refers is still in occupation, and malaria is far from unknown to its occupants; while the bungalow on the south-western division has never been infected with malaria.

The medical history of this estate has been practically that of a series of experiments of the most convincing character. If any doubt remained, a glance at the map showing the condition of the estates marked “E,” “F,” and “G,” the coolie lines of which at the present moment vary in distance from jungle which has been drained for about one year only. The lines marked “23” had undrained jungle to within 200 yards about a year ago. Jungle is now about 500 yards distant, and it has been drained for about four months. The lines marked “59” on estate “F” are opposite and within fifty yards of jungle, which, however, has been drained for some months. The percentage of children with abnormal spleens was 59, based on the examination of thirty-two children. Of the thirteen with no enlargement, one has been one and a half years on the estate, three had been only fourteen days, while the others had been less than six months. It is interesting to note that the jungle opposite had been drained for about the same period, and this probably accounted for these children having escaped. Dr. T. S. Macaulay kindly examined the blood of twenty children on this estate, and found parasites in seven, or 31.9%. These children got about 5 grains of quinine daily.

On 6^th December 1906, I examined three children on this estate, and of these two had considerable enlargement of the spleen. The death rate of the estate in 1908 was 41‰.

This estate has been unhealthy since it was opened, as undrained jungle has always been within less than 100 yards of all the coolie lines. On 5^th January 1910, I examined twenty-four children on this estate, and of these fifteen had enlarged spleen, equal to 62%. Of the nine with no enlargement, two had been only fourteen days on it; and one had a high temperature at the time of my examination. Dr. Macaulay examined the blood of eleven of the children on this estate, but did not find parasites. All were on quinine, about 5 grains daily.

On 6^th December 1906, I examined eight children on this estate and found three, or 37%, with enlarged spleen. The death rate given in the Indian Immigration Return is 69, but this does not represent the exact death rate, since estate “M,” which belongs to the same company, had an estate hospital, to which the sick from this estate were sent. Those who died there were not accredited to “G,” but swelled the death rate of estate “M,” to an unnatural degree. I will draw attention to this later.

From these figures it is evident that the opening up of the estates “F” and “G” did not lead to any improvement in their health; and the reason was obviously that the lines were still as near to the jungle as when the estates were first opened. This is in marked contrast to the improvement to be seen where the opening of the estates pushes the jungle away from the lines.

The medical history of this estate can be found from Table 8.6. Now from these figures it is obvious that a marked improvement occurred in the health of this estate in 1906. I give in the manager’s own words the explanation:

In answer to your inquiry with regard to the health of this estate: In 1904 only 160 acres were opened and jungle came comparatively close to the lines. There was so much fever that coolies had to be dosed with quinine daily at muster. Little opening was done during 1905, and the state of health among coolies remained much the same. In 1906 jungle was carried back by opening to a distance of one and a quarter miles on one side and about half a mile on the other, and from that date there has been practically no fever on the estate and the out-turn of coolies daily has improved to a marked extent.

Dated 5/1/10. N. C. S. Bosanquet.

Comment on this is hardly necessary, but I might mention that the lines were distant from the jungle in 1904 about a quarter of a mile. The extra quarter of a mile made all the difference. Being a quarter of a mile away to begin with the estate was not suffering so severely from malaria as would have been the case had the lines been closer, but I think the lesson can hardly be missed.

Opened in 1904, this estate suffered very severely from malaria, more so than the percentage of children infected in 1905 would lead one to suppose. It was so severe that not a child below the age of one year was to be found on the estate; although the adult labour force was then about 250. The manager suffered so severely from the disease that he had to be sent on three months’ leave of absence. In December 1905, I saw no fewer than seventeen coolies, or 6-8% of the whole labour force ill with malaria fever, while diarrhoea and dysentery, the common terminal sequelae of malaria, were far from uncommon. Then, in 1906, opening up having been continued, improvement took place (see Table 8.8). The present manager had been on the estate for over three years and had not had malaria. The jungle is now (1909) rather less than half a mile from the lines.

This estate, begun in 1902, had already a considerable area opened and drained by November 1904, when I first made an examination of the children. Table 8.10 shows the result of blood and spleen examination of children, and the death rate of Estate “L.” Dr. Macaulay, to whom I am indebted for the examinations in 1909, says that of the thirty-nine children, the only one with enlargement of the spleen was a child eight months old, born on the estate. The enlargement was so slight that he could hardly call it pathological. Here again we see the improvement which has followed the abolition of the malaria carrier, for A. umbrosus can no longer be found on this estate.

This estate was first opened in 1898, and I cannot recall the time, since I came to the district in 1901, when it was unhealthy. Such figures as I have show this (Table 8.11).

That the estate is free from malaria is shown by the fact that no European has contracted malaria on it since I came to the district; and there is now, and has been for several years, a European staff of six.

Table 8.12 shows the spleen rates in recent years. The Europeans have continued to be free from malaria.

The lines of both the estates are now a considerable distance from the jungle, the nearest being the mangrove, which is 600 to 1000 yards off.

I have few figures concerning these estates. I remember on one occasion in 1905 visiting a set of lines on “N” and found many cases of fever. It was then within 100 yards of the jungle. Unfortunately, I cannot find my notes of this. The figures in Table 8.13 show that the estates are not by any means unhealthy. The labour force is small on each, being only 280 on “N” and 120 on “O”.

This is one of the largest estates in the country, and stretches over several square miles. Within its boundaries are to be found lines at varying distances from undrained jungle. These show in the most distinct manner what has been evident on all the other estates to which I have previously referred.

It will be seen from a reference to the map, that the lines 82 are close to the jungle. They contained seventeen children, of whom fourteen had enlarged spleens. Farther along, on the edge of the same jungle, are lines containing eleven children, of whom ten have spleens abnormal in size, giving a rate of 90.9%. Two hundred yards from these the lines containing fifteen children showed a spleen rate of 53.3%, while at a distance of 300 yards from the lines marked 82 the spleen rate of twenty-two children was 59.9%.

In marked contrast to these are the 109 children who live at a greater distance from the jungle and whose spleen rate is 8.2. That it should be so high as this is due to some of the lines being near to a small belt of jungle once drained, but whose drains are not upkept. When the lines were put there in 1906 I have notes showing that there were considerable numbers of cases of malaria on the estate, and I recollect that these were unhealthy; but, unfortunately, I have not recorded the exact number of cases found in each of the different sets of lines. There is no doubt, however, that these lines next to the belt of jungle have improved in health to a very considerable extent. In tabular form these facts become more evident (see Table 8.14).

For the subsequent history of estate “P,” see Chapter 16.

The lines on this estate also vary in distance from one hundred yards to a quarter of a mile from the jungle. I found, however, that the coolies had been moving from the lines nearest to the jungle to others farther away. I therefore cannot determine with accuracy the spleen rate of the different lines. The lines a quarter of a mile from jungle have a spleen rate of 28, while that of those within 100 yards is 59.3. The other rates are 55.5, 42.9 and 60, and that for the whole estate is 53.6.

The death rate was 60 per 1000 in 1908. For the later history see Chapter 16.

Within 150 yards of the lines on this estate is a small swamp about half an acre in extent. There is no other swamp within half a mile.

Of nineteen children examined in 1910, 10.5% had enlarged spleen. The death rate of the estate has been 40, 56, and 45 in the years 1906, 1907, and 1908 respectively.

Passing south across the Klang River we come to estate “S” which has been opened for some years. Although extensive in area, the opening has not been such as to decrease the distance of the lines from the nearest jungle. Table 8.15 gives the facts.

There has been a great improvement in the health of this estate during 1909 due to the extensive use of quinine. It is an example of how quinine may appear of greater value in a place where malaria is not very severe than where the disease is intense.

The estate has always been unhealthy, but not intensely malarious, the spleen rate of the whole estate being only 23; still the disease has caused considerable trouble. There are no official figures for 1907, but in that year the manager was invalided to Europe on account of malaria. In the same year a large gang of coolies also left on account of the disease. In 1908 there was great sickness; and I saw many cases of chronic and acute malaria on the estate. In the months of November and December, no fewer than sixteen coolies died from malaria and its complications. The whole labour force was then put on to quinine—ten grains daily, and the death rate at once came down. Of the six deaths in 1909, none was due to malaria either directly or indirectly. The figures are interesting (Table 8.16).

This is the only estate on which quinine is given systematically, the spleen rate of which is below 40. I refer to the subject of the dose of quinine in relation to the intensity of the disease in Section 12.6.

Estate “SSS”, a small clearing in the jungle, follows the usual rule. No coolies can be kept on it, as it is so unhealthy.

Turning back towards the coast, we come to these estates, which are among the oldest in the district, and have large areas opened up. On all, with one exception, the lines are at a distance from jungle, and the health of all is good. It was not, however, always so. I remember, when District Surgeon, that cases of malaria were not infrequently admitted from estate “V”; while in the first half of 1906 I find from my notes that malaria was constantly seen in the lines of estate “X”, which are marked 7, and which were then on the edge of the jungle. I have, however, no figures referring to the children. Table 8.18 shows their present condition.

It is hardly necessary to comment on these figures. But on estate “V”, of the three coolies with enlarged spleens, one came from a set of lines on another estate the spleen rate of which is over 50. In April 1909, Dr. Stanton, of the Institute for Medical Research, examined 160 unselected coolies on this estate, and found only two, or 13%, with malaria parasites in the blood.

Although the estate is classed among those of the flat land, it is not entirely flat. Part of it is hilly. The absence of malaria is due to the valleys between the hills being of such a formation that no proper hill streams are found, and A. maculatus cannot be found either in the drains or in the lines of the estate. Klang Town is also hilly, but here again there are no hill streams in which A. maculatus breeds.11 Hence open drains sufficed to eradicate malaria. An idea was prevalent among medical men at one time that malaria was due to a disturbance of hill soil, the exposure and excavation of red earth, and the quarrying of laterite.

The absence of malaria from estate “V”, where red earth and laterite are abundant, from the town of Klang where the constant quarrying of laterite and the excavation of red earth have gone on for years, from the midst of the town and at the hospital, shows that malaria is not due to the presence or disturbance of these soils. The one constant condition which I have found associated with malaria is the presence of certain species of Anopheles. It is true that, in some of the most malarious places, it is said by the layman that there are no mosquitoes. On one such place, an estate where the spleen rate is 100% and the death rate in 1908 was 30%, the manager, a man of more than ordinary intelligence, assured me that mosquitoes were never seen except on a wet night, and then only in small numbers. My experience was that, whereas the man who helps me to catch mosquitoes usually earns 20 or 30 cents in a couple of hours, being paid at the rate of 3 cents for each anopheline, on this estate he earned 3 dollars and 12 cents in the same time, and at the same rate; having thus caught 104 anophelines. When I went to the lines I found the mosquitoes, mostly A. maculatus, in great abundance. A. maculatus is a small mosquito; it makes little noise and causes little, if any, pain when it bites. This is different from A. umbrosus, which gives a painful bite something like a sharp hot needle.

The next estate is “FF”, and in the lines next to the jungle the rate is 33, while in the more distant lines it is nil. For the whole estate it is 23.7%, and the death rate for 1908 was 5.3%.

Farther on, Estate “GG” has a spleen rate of 2.2% (fifty-nine examined), although the lines are a quarter of a mile from jungle and separated from it by a river. On this estate were eighteen children, of whom ten had enlarged spleen. These came from an estate whose rate is about fifty. By deducting these children the corrected rate of the estate would be 7.3%.12 The death rate of the estate in 1908 was 31. It has been healthy from the beginning as it began on open land.

In marked contrast to this is the next Estate “HH” only half a mile farther on; where all the lines are within a hundred yards of jungle. Of forty-six children 54.3% had enlargement of the spleen, and in 1908 the death rate of the estate was correspondingly high, namely 6%.

Estate “TT” has a spleen rate of only 13 in the fifteen children examined. The lines are about 200 yards from jungle, but are separated from it by a river. Its death rate in 1908 was 47.

These three estates again corroborate the evidence which we have been so steadily accumulating. Estate “JJ” has lines within a quarter of a mile of jungle and the spleen rate of fifty-three children is 26.3%. Its death rate was 39. The figures (Table 8.20) tell their own tale.

The only child found on estate “LL” with enlarged spleen had come from an estate whose spleen rate was between 30 and 40%.

Adjoining estate “KK” are two estates illustrating the same rule. Estate “PP” is a small one, but the manager and his coolies suffer considerably from fever. The two children on it had both enlarged spleens. They all live within a hundred yards of jungle. In due course the jungle was opened up and health improved (see Table 8.19). The three children with enlarged spleen belonged to one family, which had arrived from India only 11/2 months previously.

Estate “OO” has lines in two places. One set of lines is now half a mile from jungle, but until recently the jungle was only a quarter of a mile away. The other set of lines are, and have been, half a mile from jungle for about two years. The result is very striking; for, whereas in the lines which were until recently a quarter of a mile from jungle, 60% of the twenty-eight children examined suffered from splenic enlargement, of the seventeen in the other lines, the spleen rate was nil.

Until recently the lines on Estate “NN” were one third of a mile from jungle. The spleen rate of the thirty-five children is 11.4%; while the lines of Estate “MM” are over 1000 yards from jungle and none of the twelve children have abnormality of the spleen.

1919

The spleen rates for these estates have been as shown in Table 8.19. Estate “MM” has continued healthy. Estate “NN” is now one of the largest in the district; it is divided into two divisions a few miles apart. The girl with enlarged spleen in January 1917 had recently come from India. She had not suffered from fever on the estate, and had worked regularly without missing a day. At the November examination, her spleen could not be palpitated, nor was splenic dullness enlarged to percussion. Of the two with enlarged spleen in November, one was a returned bolter, the other had suffered from fever on the estate a month previously.

Figure 8.3: Map of a part of Kuala Langat District, showing Spleen rates in 1909