Observations on the mechanism of the transmission of plague by fleas / by A.W. Bacot and C.J. Martin.

  • Bacot, Ada W. (Ada White)
Date:
[date of publication not identified]
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Licence: Public Domain Mark

Credit: Observations on the mechanism of the transmission of plague by fleas / by A.W. Bacot and C.J. Martin. Source: Wellcome Collection.

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    Verjbitzki (1904) demonstrated that the puncture in the skin occasioned by the bite of bugs and fleas affords a channel through which plague bacilli can enter, for the application of crushed infected bugs and fleas and their faeces, as well as other plague material to the situation recently bitten, was found to infect an animal; more than one puncture was requisite to obtain infection. The Commission for the Investigation of Plague in India (1907), 2nd Plague Report, discusses the following possible methods by which the flea may transmit plague: 1. By the animals eating the infected fleas. 2. By the proboscis of the flea mechanically conveying the — from the infected to the healthy animal. 3. By the salivary glands of the flea becoming infected, the bacilli being then inoculated along with the saliva: 4, By a regurgitation of the stomach contents through the oeso- phagus and pharynx, the bacilli being then injected with the saliva, or on the pricker, or being rubbed into the wih ee made by the pricker. 5. By a retention of infected blood in the pharynx or about the mouth-parts of the flea, the bacilli multiplying there and then being inoculated into the animal in the same manner as in hypothesis No. 4, 6. By the bacilli contained in the faeces being deposited on the skin, and then being either injected by the pricker or rubbed into wounds made by the pricker. | Methods 1 to 3 are set aside on what seem to us satisfactory grounds, No evidence could be found for 4 or 5. It was, however, shown that infection could be brought about by smearing recent flea-bites with septicaemic blood or a virulent culture of plague, and the conclusion is arrived at that the possibility of infection by the rat rubbing flea-faeces into recent flea-bites is demonstrated, but on the question whether this is the usual method of infection, the Commission did not feel justified in expressing an opinion. The Commission dissected many hundreds of fleas and searched for the presence of plague bacilli in their salivary glands and body cavities, but on no occasion, either by microscopic examination or by culture, were they able to find plague bacilli outside the alimentary canal of the insects. We may say at once that our own observations on this point coincide with those of the Commission, and it appears certain that transmission is not occasioned through infection of the salivary glands of the insect transmitter, as in the case of malana and sleeping sickness.
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