The etiology and epidemiology of plague : a summary of the work of the Plague Commission.

  • India. Plague Commission.
Date:
1908
Catalogue details

Licence: In copyright

Credit: The etiology and epidemiology of plague : a summary of the work of the Plague Commission. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

    29/110 (page 17)
    M. decumanus is more than double that of M. rattus. Before going further we would insist that in Bombay City, just as there are two common species of rats, so there are two epizootics, namely, a M. decumanm epizootic and a M. rattus epizootic, which have to be considered separately. The infection amongst the rats in Bombay must be characterised as being exceedingly severe, 4,381 M. rattus and 13,377 M. decwnanus being shown to be plague infected during the year, a total of nearly 18,000 plague-rats out of a total of 117,000 rats examined. The year, however, may be roughly divided into two seasons, (a) the non-epizootic season, June to November inclusive, and (b) the epi- zootic season, December to May inclusive. During the epizootic season the largest number of infected M. rattus for one week was^ 432, the largest number of M. decumanus for a similar period being 1,334. This was in March. During the non-epizootic season never less than 20 to 30 plague-infected rats were examined during any one week. We see, therefore, that even during the off- plague season acute plague persists amongst the rats, but to a much less extent than in the plague season. The factors which govern this seasonal prevalence will be discussed later on. A study of the sect'on maps, the method of pre])ar'ng which has been described, leads to the conclusion that M. decumanus is chiefly respons ble for the diffusion of the infection throughout the city, as m-ght be expected in consideration of the out-door life and wandering habits of this species. While this is so, it is to be carefully noted that the infection does not spread in any definite manner from one section to another; infection amongst Ihe rats persists during every month of the year in most of the sections. Further, in this connection we have already mentioned that no evi- dence of a general migration of rats from one place to another, when plague breaks out amongst them, could be found. As regards the relation of the decumanus epizootic to the raUu9 epizootic it would appear from a study of the curves which were pre- pared from the figures collected durijag the year, that the former preceded the latter by a mean interval of about ten days. Further, the evidence obtained by the Commission led them to the conclusion that the rfeamanws epizootic was directly accountable for the rattus epizootic. By this statement the general relation between the two epizootics is expressed, but it is not for one moment