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Epizootic Plague.

The disease amongst animals occupies quite a special department of its own. Until a few years ago, the occurrence of the diseas amongst animals, appears to have attracted but little attention. Indeed, so severe were the past outbreaks of the epidemie that little or no time was available to regard the presence of the disease in animals other than man.

With the advent of more perfect knowledge in regard to the ways of infection, our attention has been directed to the occurrence of diseases in animals, diseases which, when compared with those occurring in man, appear to be similar. The question has therefore arisen—a new one indeed as to the part played by animals in the dissemination of certain diseases amongst the human race. It would be quite impossible, indeed unnecessary, to sketch, even briefly, the con- nections between disease in animals and in man. Summing up the available evidence, we find much in favour of such a connection. Indeed there is good reason to suppose, that in the production of certain widespread and epidemic diseases, animals play an important role, if not the initial factor, in the spread of the disease amongst the genus

us homo.

It must be difficult for a certain class of professional men to get away from the time worn canses of epidemic disease. Indeed, in all text books on plague, one finds the old dogmas of infection, most carefully reproduced, namely, the solution of the problem by a recognition of:—

(a) The communication of the infection from the sick direct. (b.) Indirect means.

(c) Place infection, etc.

AS ASHBURTON THOMPSON says, such a table of causes would amply explain the epidemicity of plague.

The adherents of such a classification of etiology appear to take no cognisance of the advances made by bacteriological research. It would appear from the most recent works on such a subject, that the ways and means afforded to the B. pestis to produce infection, the course of plague infection, and the exact problems un- derlying the spread of the pest, must undergo remodelling upon the lines indicated by the results of modern epidemiology.

As has already been mentioned, the recognition of epizootic plague, as an important factor in nature, is of recent date. At the present day, the epizootic has become one of the most engrossing researches in regard to plague. Sanitary authorities are already recognising that in epizootic plague, they have to deal with probably the greatest disturbing factor in their efforts to stamp out the epidemic. It would be a difficult matter to specialise in regard to the particular species of animal which attracted the attention of past hygienists, as a factor in plague dissemination.

At the present day, however, one cannot take up a book dealing with plague without being struck with the prominent part devoted to rats as disseminators of infection. In fact on the perusal of many such manuscripts one is drawn to the conclusion that rats, and nothing but rats, are responsible for the existence of epidemic plague around us. Going into te question more thoroughly, however, it is difficult to guage exactly the premises upon which a conclusion has been drawn. We have to consider whether rats are the only disseminators of plague- in fact do they disseminate plague epidemics at all-or granting that they are responsible for the occurrence of such-are they solely responsible, or simply partners in the wholesale sewing up of the infection to the human species.

From all works on plague, I have drawn the conclusion that rats—and these vermin alone—are the plague spreaders. This would appear to be too dogmatic a conclusion. Mice associate with rats, are susceptible to plague, domesticate with man where possible, so that it seems probable that under certain circumtances these animals might play as important a role as their neigbours the rats.

Again, the disease is known amongst cats, fowls, pigs, and oxen-all of which animals are more a less occasionally in close contact with man. It therefore seems probable that the existence of an epizootic in plague as a factor or epidemic dissemination, must not be dogmatically restricted to rats but extended to those other animals which occasionally have intimate relationships with the human species.

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