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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    is the active agent in the diffusion of malaria, and of the discovery that the same insect is the active agent in the diffusion of filariasis, can best be described as immense. In this, as wdth the discovery of every new principle, the first step forward serves but to reveal the vastness of the field that has been entered. When we begin to think of, and to work at, this matter of the mosquito and disease, problem after problem crops up, and many of them on humanitarian, not to mention scientific, grounds urgently call for immediate solution. For example, we already know that certain species of mosquito are efficient definitive hosts of the malarial para- sites, and we also know that other species are not efficient; but, so far, we are not acquainted with all the efficient species, nor with all the inefficient species. AVe already know one species of mosquito which is an efficient inter- mediate host for Filaria nocturna, but we know little or nothing as to the efficiency, or the reverse, of other species. Besides Filaria nocturna, there are at least four other blood- worms which affect the tropical man. As yet we do not know what are their intermediate hosts. AVe do not even know if these intermediate hosts are mosquitoes. Con- sidering that there are, according to Giles, two hundred and .seventy species of mosquito known to zoologists, and pro- bably nearly as many more which are as yet unknown or undescribed, each of which has to be tested as regards its relationship to the various malarial parasites and the various blood-worms, it is evident that in this matter alone there lies a pi’odigious task for the investigator, one demanding years of labour and many workers. Again, we know that the malarial parasite differs in virulence in different localities, and this notwitstanding that the morphological characters of the parasite in these different localities are identical. Does this difference in virulence, and what I might call strain, depend on the passing of the parasite through different species of mos- quito ; on the difference of the cultui’e media, so to speak ? Assuming as probable, although not proved, that the deadly Blackwater Fever of Africa is produced by the malarial parasite, the question forces itself upon us: Does this special virulence result from the passage of the para- site through a special mosquito, Ano])heles funestus, for example, a mosquito widely diffused in malarial Africa, and, I understand, general in the Blackwater Fever zone ? Certain countries with apparently suitable climates, and offering suitable hydraulic conditions, are nevertheless free B