Ronald Ross Nobel Lecture

RESEARCHES   ON   MALARIA 

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18. Darjeeling district (August—September, 1898). Kala-dukh. It was mentioned 

at the end of section 14 that I myself had proposed to Government that kala- 

azar should be included in the programme of my year's special duty; because 

I then hoped that this disease might shed light upon the mosquito theory; but 

now when the theory was established and it was necessary to press on with the 

study of the human malaria, I wished to escape this additional duty, as I dread

- 

ed lest it should involve me in much pathological work which would interfere 

with the principal line of research. I hinted as much to the Director General, 

but was told that he expected me to adhere to the programme. The disease 

was exciting much comment because it was new and was taking some thou

- 

sand lives annually in Assam; but it was forgotten that malaria, though it is 

not new, takes some millions of lives annually in India alone! 

Harold Brown had recently studied a disease which existed at the foot of the 

Darjeeling mountains, and which was called kala-dukh  (black sickness) and 

was evidently closely allied to kala-azar (black fever). Consequently I obtained 

permission to investigate this disorder first, partly because an opportunity 

might be afforded me of making further studies at the same time on malaria 

in my old haunts at Punkabari. Fixing my head quarters at Kurseong in the 

hills on the road to Darjeeling, I made numerous visits to this locality, but was 

dogged by ill-luck. The plague-scare, though waning, was still present; and 

difficulties of transport impeded the work. On the 25th August I arrived at 

Naxalbari, an intensely malarious plantation and village on the plain beyond 

the foot of the hills, and found swarms of small and large dappled-winged 

mosquitoes (probably Anopheles listoni and A. rossi). There was no time to 

make formal experiments, and the people would not have allowed them; but 

I examined some dozens of these mosquitoes caught in the houses of infected 

persons, both for the pigmented cells and the thread-like bodies; but without 

success.* Nearly all my time was however taken up in pathological enquiries 

on kala-dukh - as I feared would be the case. But now it was no longer possible 

to postpone the evil hour without dereliction of duty, and I was obliged to set 

out on the long journey to Assam. 

19.  Assam (September—November, 1898). Kala-azar. I arrived at Nowgong, 

the centre of the epidemic of kala-azar, on the 13th September. It was at once 

obvious that my worst fears were well-founded, and that I would be plunged 

* How unfortunate I was in this respect may be gathered from the papers of Stephens and 

Christophers

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 who later found many of these mosquitoes infected in this very district.

 

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for months into a difficult pathological problem and a long pathological re-

port. But the work was not without interest, and I may be pardoned for touch-

ing upon it briefly. The disease had been first noticed by McNaught in 1882.

A few years later Government sent Giles to investigate it; and Giles, who

probably did not come much in contact with the real disease, seemed to have

been considerably misled, and in a report (which was nevertheless a very able

one) pronounced the malady to be ankylostomiasis

77

. Many of the practi-

tioners in the locality were not satisfied, however, and in 1896 Government

sent Rogers to make a further report. Rogers certainly saw the real disease and

concluded that it was a virulent form of malaria

78

. As it was evidently com-

municable, this implied that he held malarial fever to be communicable - a

thing which no one would believe at that time; but he maintained his opinions

with great courage and success. I was now sent in order, if possible, to decide

the question; and as my researches had shown that contrary to accepted views

malaria must be communicable from the sick to the healthy, Rogers’ position

was justified. But the exact nature of kala-azar still required definition; and, as

I 

was called upon to judge between opposite opinions, I was forced into a

tedious enquiry - though it was my immediate personal impression that the

disease is malaria.

Mixed with the cases of kala-azar there were numerous cases of ordinary

malaria; and I found that the local practitioners could not distinguish which

was which until the cases became exceedingly severe, when they were declared

to be kala-azar. This generally happened only in the later stages of the cases - so

that in fact kala-azar seemed to be simply another name for a very severe and

frequently fatal form of malarial cachexia. As, moreover, many of the pa-

tients had ankylostomes, those who are familiar with the subject will under-

stand that my task was indeed a complex one. The plague-scare not having

penetrated here, I attacked the problem by examining the blood of all the

cases, both of malaria and of kala-azar. My results showed that while the para-

sites were easily found in the early cases, they became more and more scarce as

the disease advanced; until, in the old typical cases of malarial cachexia and

kala-azar 

neither parasites nor pigment were to be found, even in blood taken

from the spleen. I inferred then that kala-azar is probably only malaria, though

it was possible that some secondary infection might account for the gravity of

the cases. I also inferred - what no one would accept before then - that the

spontaneous disappearance of the parasites must be due to the gradual estab-

lishment of immunity; and that the low fever present in these old cases was

due, not to the parasites, but to some secondary intoxication from the greatly

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