Sessional_Paper_1904 — Page 706

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At the same time the question of the epizootic is a recent one, and in view of its having been applied more particularly to rats, one must enquire as to reasons and the facts upon which such a theory has been founded. It is said that plague is primarily a disease of the rat, that it is commonly communicated to man from the rat, and that man and the rat may be recriprocally infective.

Again epidemics may be present without epizootics and vice versu.

An oc-

Much has been written in regard to the close inter-relationship existing between the epizootic and the epidemic. The evidence at present available would appear to fall short of absolute proof of a direct connection between the two casional and frequent concurrence between the two has been found, but the question whether the epizootic is the cause or an incident of the epidemic is still left unan- swered. The experience of THOMSON in Sydney during 1900 was that plague rats were the sole source from which the infection was communicated to man. The evidence in support of such was however incomplete.

The literature in regard to the relation of rat plague to human plague is defective. SNow's observations note the incidence of plague in rats, but do not suggest any connection between the epizootic and the epidemic. The Indian Plague Commission do not lay any weight on plague infected rats as agents in the dissemination of plague epidemics. BRUCE Low's papers on Bubonic Plague, dated July, 1902, lead me to believe that man and the rat are reciprocally infected. No evidence is forthcoming in regard to the question from a priori grounds.

Many plague workers have much difficulty in perceiving how plague infection could be converged from rat to man.

To explain the transference of the disease from the rat to man, HANKIN (Annal Pasteur, 1898) concluded that plague in man stool in relation to the accessibility to rats and that probably some intermediary insect was necessary to communicate the infection from rat to man. SIMOND ʼn held these observations, and these two investigators may be said to be the only exp nents at present of the epidemiological factor of the part played by rats in the dissemination of the disease. That suctorial insects have much to do with the cause of bubonic plague is by no means obvious. The reports of recent years in regard to epidemic and epizootic plague, do not convince one in regard to the inter-relationship of the two outbreaks.

The cause of this is mainly, in my opinion, the failure to systematically examine both outbreaks. Before anything like a causal connection can be established between two such outbreaks, it would appear necessary to closely examine the severity of the epizootic and then to compare this with the epidemic, particularly in regard to its course, time relations, exact actions, and continuance.

Such has been carried out systematically in Hongkong since the comm 'nce- ment of 1902. Over 300,000 rats have been examined for plague infection. Many of these were caught alive, the existence of acute rat plague, chronic rat plague and latent plague infection has beeu determined. Curves have been pre- pared for each of these years, namely, 1902, 1903 and part of 1904, and the relations of the epizootic have been noted during the interval between epidemics.

In such a way, it has been possible to map out clearly the courses of both out- breaks. For details in regard to these, one is referred to the Histories of the' courses of the epizootics. In dealing with epizootic plague, my attention has been directed more or less directly to rat plague, but the varieties of the disease in animals belonging to other species have not been lost sight of. In fact it has been my object to obtain for examination almost every animal possible, which was sick or died since I arrived in the Colony. By thus stimulating the laymen to the importance of having his dometic pets or other animals examined bacteriologically, I have been able to find plague existent in animals, to a degree, rather suprising to the miods of the ordinary sanitarian.

The following report on epizootic plague is merely the story of my experiences in regard to the disease amongst a number of animals, coupled with brier notice of the existent knowledge in regard to the incidence of the disease in such animals and found affected.

WILLIAM HUNTER.