Discussion on the prophylaxis of malaria / J.W.W. Stephens [and others].

Date:
1904
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Licence: Public Domain Mark

Credit: Discussion on the prophylaxis of malaria / J.W.W. Stephens [and others]. Source: Wellcome Collection.

    3/30 page 629
    Pe 2 SEVENTY-SECOND ANNUAL MEETING OF THE British Medical Association. Held at Oxford, July 26th, 27th, 28th, and 29th, 1904. PROCEEDINGS OF SECTIONS. SECTION OF TROPICAL DISEASES. Brig.-Surg.-Lieut.-Col. ALEXANDER OromblE, I.M.S. (Ret.), C.B., M.D., President. DISCUSSION ON THE PROPHYLAXIS OF MALARIA. IJ. W. W. Strepxens, B.A., M.D.Camb., Walter Myers Lecturer in Tropical Medicine, Liverpool University. I romk it may help to make our views more precise if, instead of recounting the methods of prophylaxis used and the results achieved in Italy, in British, French, and German tropical possessions, in Japan, I bring before you some scien- tific aspects of the problem which in many of the publica- tions I have read on this subject seem to me to be overlooked. { will assume in this paper that I am dealing with the occur- rence of malaria in our tropical possessions. It is, I believe, not unnecessary even now to point out how malaria is con- tracted. It has been for centuries believed that maiaria is contracted from the vapour of marshes; and now that cer- tain mosquitos are proved to be the cause, it is not uncom- mon to overlook the means whereby the mosquito produces malaria, and still to attribute malaria to the presence of the water in which the mosquito breeds, the ‘shallow pools,” ete. What seems to me to be necessary is that the public should be educated to regard not the pool, not the mosquito, not even the Anopheline, as the source of danger, but the infected Anopheline ; and I would go further: I would have everybody clearly understand how it is that the Anophe- line becomes infected—that is, canconvey malaria. Itresults from the fact—which, I believe, not 1 in 100 laymen in the tropics knows—that malaria is a contagious disease. The source of contagion, unsuspected by the layman, lies in the fact that in the tropics the native population, especially the child population, carries malarial parasites in its blood; that it does so often while presenting not the least outward sign of sickness. It is this apparently healthy but actually highly infected population which is the great source of malaria parasites, and hence of danger, to the European. It is from the native that the malaria-bearing mos- quito gets its parasites, and these it transmits again aiter the lapse of a certain time to the European. I have said that the native population may show no outward sign of sickness. I do not forget, however, that the native also dies from malaria, but if we wish to see malaria in its severest forms, let us visit some up-country miner’s camp or European settlement in the bush. There we shall find those ‘“ malarial wrecks,” the fever-stricken pioneers, ‘‘ down with fever,” as itis called, vomiting inces- santly, with a temperature of 105°, in constant dread of black- water fever, which not uncommonly supervenes. Those who live in the towns not uncommonly forget that itis in these out-stations that malaria exists inits most virulent form. T have dwelt on this condition because it is the lot of these unfortunate Europeans to fill the ‘‘ white man’s grave,” be- cause I think that in schemes for eradicating malaria they are forgotten, because I think that many of these lives can be saved by means which I will specify later, and that we can legitimately do so even at the expense of delaying that general eradication of malaria from the native which will be the work of years, and which will not be achieved in our time. Malaria is indeed a contagious disease. It has been the great discovery of Ross that it isa certain mosquito that conveys the contagion. Let me review briefly the state of our knowledge on this point. We know now that certain mos- quitos of the sub-family -Anophelina, alone can convey the contagion. Now of Anophelines there exist about a hundred species. Which of these, or do all of them in different parts of the world convey malaria? It is surprising that on this point we have but scanty information, : The number of species that we know can convey malaria we may almost count on our ten fingers. They are in Europe —A. maculipennis (mainly); <A. bifurcatus (less concerned) ; P. superpictus; M. pseudopictus (especially in some parts). In Africa A. maculipennis (im Algeria); P. costahs and M. funeste (especially in tropical Africa), and P. Chaudoyei. In india M. listom, M. culicifacies, N. maculipalpis (?. In _North America A. maculipennis. In West Indies Ce. albipes. That is, a dozen species only of which we can say with any certainty they convey malaria out of nearly a hundred existing species. But it may be urged,if one species conveys malaria another will; that is not a scientific argument, and nothing short of actual proof should be allowed to satisfy us. We can go further, and say that we have a certain amount of evidence, gradually increasing, to show that all species do not convey malaria. Let merecall to your mind theresults obtained by Christophers andmyselfin India. We had formed thehypothesis, based upon general observations, that all species of Anophelines were not concerned in the transmission of malaria. We put this hypothesis to the test in two very malarial places in India— Mian Mir (Punjab) and Ennur (Madras). We caught in the same huts, at the same time, in these two far distant places two species of Anophelines—J/, rossii and VM. culicifacies. We determined by actual dissection which of these species con- tained parasites (sporozoits), and found as follows: | . Number Number — Dissected. lufected. Percentage. In Miax Mir: M. culicrfactes | 259 12 | 4.6 M. rossit | 496 | ° fa) In Enxur: : | | M, culicifactes ia 69 6 8.6 M. rossti S02 sel 364 | ° ° So that M. rossii was not carrying malaria under conditions where M. culicifacies was. These observations have been repeated by others and the result is always the srme. M. rossti does not in nature convey malaria. This, while scientifically of great interest, is also of practical value. Shall we spend money and occupy our time in eradicating M. rossi when as far as we know itis not concerned in the transmission of malaria? These mosquitos exist in myriads in Calcutta, Madras, Bombay, and in all large towns. We believe them to be harmless. But this is not an isolated instance. Recently Hirshberg in the United States has got similar results, though in this case by feeding experiments. Two species—A. maculipennis and A. punctipennis—were fed on the same case of malignant tertian malaria under the same conditions, with the following result : No. Infected. A. maculipennis Se nas 48 Ree 8 A. punctipennis oat ms 58 see Vises ° Whether A. punctipennis conveys malaria in nature remains to be seen. Similar results (unpublished) have been obtained in Japan. These results, then, show that certain species of Anophelines do not convey malaria, and on general grounds there is little evidence to connect those species which we know as “wild” mosquitos with the transmission of malaria, Anyhow, it should not suffice to state simply ‘‘the Anopheles was found” without stating what species of Anopheline; but, most important of all, it should be determined by actual dissection whether or no that species does transmit malaria. The practical bearing of these facts is obvious. Ii we can positively state that a certain species of Anopheline does not transmit malaria, it will obviously simplify operations directed against mosquitos. Another point of great interest in connexion with Anophelines is their breeding grounds, Take again the two Indian species mentioned above, MM. rossiz and WM. culicifacies. Christophers and myself showed in India that, broadly speaking, each Anopheline has a breeding ground ofitsown. At any rate, in the case of the above two species they are totally distinct and different in nature, and whereas M. rossii breeds in the shallow pooi or puddle some inches deep only, M. culicifacies does nothing of the kind. It is never found breeding in these dirty puddles; it loves clear, fresh water, of streams, rivers, canals, and other moving water, where it occurs in myriads. Now if our results are true, that M. rossi does not carry malaria, and no doubt has yet been thrown on them, it means that it is unnecessary to '2281
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