Some problems in tropical epidemiology. : An address delivered to the epidemiological society of London / by Patrick Manson.

  • Manson, Patrick, Sir, 1844-1922.
Date:
1901
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Licence: In copyright

Credit: Some problems in tropical epidemiology. : An address delivered to the epidemiological society of London / by Patrick Manson. Source: Wellcome Collection.

Provider: This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.

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    and among the visitors to the island, years before the historical epidemic explosion. These, however, were evi- dently cases in which the infection had been acquired in India, Madagascar, and elsewhere; but although the gametes of malaria must thus for many years prior to 1867 have been imported in abundance into the island, the dis- ease did not spread until after the date I mention. Why ? Because the necessary mosquito host was not present. But about the date mentioned, although there is no direct evidence of the fact, anopheles must have been introduced from without, and gradually spread over the island, subse- quently reaching the neighbouring island of Reunion. The march of the epidemic, so carefully and accurately described by Davidson, tallies exactly with such a hypothesis. Of the many theories which have been promulgated to explain the introduction of malaria into Mauritius, none meets all the circumstances so completely as the one I allude to. Now, if a malaria-nurturing anopheles has been success- fully introduced into Mauritius, with consequences so disastrous to that island, may not a similar calamity befall the Pacific Islands ? May not the absence of anopheles there depend on the circumstance that it has not been introduced from without ? For hygienic reasons, there- fore, as well as for scientific purposes, would it not be well, before it is too late, to ascertain the exact position at the present day of the mosquito fauna of these islands ? If, subsequently, owing to the increasing communications between the Pacific Islands and malarial countries, malaria anopheles and with them malaria be introduced, we shall then know the reason, and in consequence of this know- ledge be better able to cope with, and perhaps to limit the extension of, what for these islands would be a calamity indeed. This is another reason for instituting the investi- gation I suggest. Although it may be found that the freedom from ma- laria which many of the Pacific I.slands still enjoy does not depend on the presence in them of the conditions inimical to the malaria anopheles, my contention may still hold good that local immunity from malarial anopheles often, perhaps genei'ally, depends on the presence in these localities of something which is directly inimical to the insect, and not on the absence of the essential hydraulic and meteorological conditions. I have selected the Pacific Islands as the field for the su‘’’■crested investigation, because these islands are small, OO o *