The reappearance of malaria

The year 1911 was more than usually malarious, and a breakdown in the quarantine arrangements at Penang had a serious effect on the mortality of the year. But the estate had recruited only eighty-four new coolies, and something more than an annual variation seemed necessary to account for the outbreak, which showed itself not merely in attacks on the adults, but also in its effects on the children, many of whom died suddenly.

For a time I was completely at a loss to account for the epidemic. In ten years I had never seen the reappearance of malaria on a flat land estate; none of the lines, as far as I knew, and I thought I knew the estate thoroughly, were within 40 chains of jungle or swamp; and the manager assured me this was so. I was, therefore, seriously alarmed at the outbreak; it looked as if we could not rely on healthy flat land estates remaining healthy; that malaria, on the flat land estates, might become persistent, as in hill land, from the appearance of some malaria-carrying Anopheles hitherto not recognised. For the whole rubber industry, indeed for the whole country, the outbreak looked most ominous.

Accordingly, I searched every drain, pool, and puddle close to the coolie lines, and among the rubber trees for some new Anopheles; but without discovering any. In the course of my examination, I decided to tour the whole estate, and then I discovered the cause of the outbreak was a very simple one.

Requiring increased line accommodation for his labour force, in May 1910 the manager built new lines about 20 chains from the jungle, without realising that the jungle was so near, for at two points the boundary of the estate bends inwards, instead of running in a straight line as I had assumed it did. The new sites were responsible for the cases of malaria in 1910, which had quickly disappeared; and it was not until September 1911 that the disease became of serious consequence—that is some fourteen months after the lines had been built.

The outbreak would have been confined to the new lines, but, for estate reasons, the labour force had been redistributed; many of the infected coolies had been moved back to the old lines, and the healthy coolies moved to the new lines. In consequence of these changes, when I came to investigate the outbreak, I found malaria cases in the old lines, and the disease appeared to be spread over the whole estate. It was only after I discovered that the new lines were close to the jungle, and made inquiry about any changes in the distribution of the labour force, that the whole story was elucidated.

The remedy was obvious. The new lines were at once abandoned; others were built on the old site, and the health at once improved, as the figures in Table 22.4 show.

In 1918 the only child with enlarged spleen came from a malarious estate in Johore. The morale is plain. An Estate Medical Officer should know by inspection the whole of an estate, and should, if possible, possess a plan of it.

For a year or so after it was opened in 1906, this estate suffered from malaria; but by 1907 it was healthy, and remained so until 1915, as the death rates show. In January 1913, the spleen rate of 120 children was 4%.

The health continued satisfactory until September 1915; towards the end of that month, and until the end of the year, malaria was present to a considerable extent. In view of the complete freedom from malaria in the past, it seemed at the time impossible to believe the whole of the ill-health was due to malaria; especially as only 3 out of 120 children had enlarged spleen. Accordingly, 150 coolies, who were anaemic, were given a course of chenopodium treatment in order to eliminate ankylostomiasis as a contributing factor in the ill-health (about 99% of Indian labourers harbour the worm).

Health improved somewhat in the early months of 1916, these being the least malarious months in the year; but, by July, there was no doubt we had to face the fact that, for some reason or other, malaria had taken a firm hold on the estate. Not only had the acting manager suffered from the disease, but so had his servants. Of seventy-two coolies who had arrived from India between 1^st November 1915 and 31^st July 1916, sixteen had absconded; and of the remaining fifty-four, no fewer than thirty-nine, or 72%, had suffered from malaria since their arrival on the estate. Finally, the spleen rate had jumped from 3/120 (2.5%) in September 1915 to 35/144 (24.3%) in July 1916.

The outbreak was difficult to explain. The lines remained on the sites they had occupied for years; the drainage of the estate had been improved year by year. It was therefore necessary to look outside the estate boundary for the cause; some condition that had come into force within the previous two or three years; something that had presumably created mosquito breeding places, which had not previously existed.

Having this in mind, it occurred to me that, although the railway had not interfered with the estate drainage, it might have done so with that of the native holdings; and, in any case, had probably created a series of borrow pits which would be breeding places for Anopheles. An examination showed this to be the case.

In borrow pits along the railway, the following species of Anopheles were found: A. rossi, A. sinensis, A. umbrosus, and in enormous numbers A. ludlowi. A. umbrosus was a known carrier. Dr. Barbour, who kindly dissected some A. ludlowi, found in the first he examined the salivary glands “stuffed with sporozoites” (13/8/16).

An interview with the Acting General Manager of Railways found him willing to drain the borrow pits; a cable from the directors of the estate gave the manager a free hand to carry out my recommendations. The borrow pits and native holdings had their drains opened up; oil was freely used and health rapidly improved. Today the health is excellent again (see Table 22.5).

In 1919, at the examination, ten of the eleven children with enlarged spleen had been several years on the estate; so it is evident the enlarged spleens are evidence of the outbreak of 1916. In a letter dated November 1919, the manager tells me, “at the present time, conditions of health could not very well be better.”

The adjoining estate suffered in a similar way; and so did others to a lesser degree. The cure was similar. It is unnecessary to give these in details.

The wave of malaria spread inland to a considerable distance and affected estates which one expected might have escaped. A number of conditions exist in this district, which call for careful investigation in the light of our present knowledge of malaria; for this outbreak shows the margin of safety of some of these estates is small.

Figure 22.4: Wicken Fen. The most interesting relic of the true Fen. “Here we find the peace of the fens unbroken … where the reeds grow beautiful along the watersides, guarding from sight the last home of rare and beautiful things, which almost everywhere else have been destroyed by man.”—Camb. Geog.

Figure 22.5: Wingland Marsh, near Sutton Bridge, in Lincolnshire. Reclaimed from the sea, under cultivation. (“Marsh,” in Lincolnshire, means salt-water swamp; “Fen,” a fresh-water swamp.)

Before closing this section I would appeal to the engineers of this and other countries, not to allow history to keep on repeating itself. Some time ago I was reading a book about the Fens of Lincolnshire in England, and therein noted some things not without bearing on this matter:

“The Romans, discovering the remarkable fertility of certain of the dry or drying parts, desired to increase their area, and formed a rude plan for the reclamation by embanking. … They laid down, too, certain causeways across the Fens, a notable example of which extends from Denver in Norfolk, over the Wash to Chark, and from thence to Marsh and Peterborough, a distance of about 30 miles. The Roman embankments, however, along the coast seem to have had the result of increasing the inundation of the low-lying lands of the Level.”

Then came some lines, as a quotation, the source of which is not given: “whilst they dammed the salt water out, they also held back the fresh, no provision having been made for improving and deepening the outfalls of the rivers flowing through the Level into the Wash. The Fenlands in winter were thus not only flooded by the rainfall of the Fens themselves, and by the upland waters which flowed from the interior, and also by the daily flux of the tides which drove in from the German Ocean, holding back the fresh waters, and even mixing with them far inland.”

So there is precedent for coast roads, if not for coast railways, interfering with drainage; but surely work which “leaves a trail of malaria behind is bad engineering.” It is high time to break with the past.

About a mile from Klang on the Langat Road is what is now called Batu Unjor Estate; and on the opposite side of the road, Tremelbye Estate and some native holdings. At the time this part of Tremelbye was under jungle, it was full of A. umbrosus, as I recorded in Section 2.5; and the bungalow of Batu Unjor Estate was malarious.

With the opening of Tremelbye Estate in 1906, A. umbrosus and the malaria disappeared; and Batu Unjor became a healthy estate, described as Estate “X” in the earlier part of this volume.

It continued healthy until 1913, when a ravine in a native holding opposite the lines of Division I. was invaded by A. maculatus. The native owner at first refused to permit the estate to control the mosquitoes, and a sharp outbreak of malaria occurred, showing the maculatus rise in the month of May (Table 22.8).

Dr. Ansley-Young gives me the spleen rates taken quarterly since 1915. The contrast between Division I. which is close to the hill, and Division II. which is out on the flat land, is striking. Dr. Ansley-Young attributes the rise of malaria in 1918 to some breeding places having been overlooked by the oilers; in fact he found A. maculatus breeding close to the lines.

Haron and Klang Lands Estates are, like Klang town and Estate “X,” situated on a small range of hills. They lie about 3 miles from the Klang range, and parallel to it. Most of the range was, until comparatively recently, covered by jungle, and the malaria was caused by A. umbrosus, which was abundantly found in the jungle, coolie lines, and bungalows.

In 1912, on my recommendation, close on 200 acres of jungle were opened up, in two places—which pushed the jungle, if not 40 chains from the lines, at least much farther than it had been.

In view of the extension of A. maculatus to Klang and Estate “X” in 1913, I was anxious lest a similar event should occur on the hill division of this estate. Klang Lands Division is flat land, and the spleen rate at once fell; the hill division, Haron, contains only one ravine, which I searched time and again for A. maculatus without success. Tables 22.10 and 22.11 show the death rates and spleen rates.

The position, therefore, was that, while the health as a whole had greatly improved, and the flat land division had become practically free from malaria, on the hill division the spleen rate refused to fall satisfactorily, and malaria still persisted. It is true jungle swamp existed within 40 chains of the lines, but I was not completely satisfied that it was responsible for all the malaria.

Figure 22.7: Chart of maculatus wave on Haron Estate in 1919

In 1919 I was on leave; and on my return found there had been an outbreak of malaria in the middle months of the year on the hill division with the characteristic curve of A. maculatus malaria. No larvae were, however, found in the ravine in February and March of 1920. But an examination of the children showed the spleen rate was higher than it had ever been: the rate for fourteen children in the lines nearest to the ravine was no less than 57%; against 22% for seventeen children in lines farther off.

I felt pretty certain after this that A. maculatus had been in the ravine in 1919, and would probably return in 1920, on the cessation of the wet weather. Since the cost of oiling would be considerable, it appeared to me more satisfactory to prove definitely the existence of the mosquito before recommending oiling. Towards the end of May malaria began to increase, and A. maculatus was found in the ravine in great abundance. Oiling was begun at once, and I have little doubt will give excellent results; for the manager, Mr. Hammond Smith, has had experience of, and success with, oiling on Pitchakawa, an estate situated at the other end of this same small range.

Some years ago I found A. maculatus in the ravines of Pitchakawa, and oiling was begun. The spleen rates show the results (Table 22.12).

In 1920 all the six children with enlarged spleen had been over five years on the estate, except one who had been three years.

Of twenty-seven children that had been transferred from Klang Lands Divisions about eight months ago, not one had an enlarged spleen. All the children looked well and healthy. Excellent work had been done here.

There had been twenty-nine deaths for the first eight months of 1918, giving a death rate per annum for working coolies of 64.9‰ against 10‰ in 1915. In addition, nineteen children had died. The admission rate to hospital had increased, and additional hospital accommodation had been erected at considerable cost.

On revisiting the main ravine next the lines, which used to be the chief source of A. maculatus, it was evident that the importance of maintaining the anti-malaria work had not been fully realised. A considerable amount of water was still coming from the pipes, which had thus stood the test of six years’ use without taking much harm. But probably half of the water from the ravine was coming down an open channel scoured out by the storm water. In some places, there were probably pipes blocked by silt, but on the whole, from the amount of water discharging from the pipes, it would appear that blocking is comparatively slight.

Oiling was being done with a not very effective hand sprayer; and on my visit, I found the oiling coolie fast asleep in the upper part of the ravine. The war had thrown special work and responsibility on the manager; and, through shortness of staff, insufficient attention had been given to the anti-malaria work.

On my pointing out these things, the drainage and oiling were again made efficient, and the health rapidly improved. Writing in June 1920, the Estate Medical Officer says, “the work on the main ravines is all in good order … leads and road drains are now being made thoroughly and systematically oiled.” He reports the spleen rates as shown in Table 22.15. From these figures it is evident that the health has become practically normal again.

Another example of the reappearance of malaria on a hill estate is given in Section 18.5. Here, the malaria came from the ravines of a newly opened estate which adjoined estate “SC.”