Sessional_Paper_1904 — Page 693

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The Importance of Food in Plague.

The importance of food in plague appears to have attracte but scant attention. Apart from the researches of WILM, an examination of the literature on plague gives us no idea as to the question whether food is an important factor to be reckoned with in dealing with the prophylaxis of the disease. Soon after my arrival in the Colony, I conducted, along with Professor SIMPSON, certain experiments in regard to the susceptibility of various animals to plague infection. The general result of these experiments was, that the most certain method of producing plague infection in an animal supposed to be resistant was by feeding with plague infected material. Having elicited this fact, I set about an enquiry as to the possibility of the infection in plague being communicated to man by way of the food. I had already satisfied myself as to the existence of profund pathological changes in the stomach and intestines of individuals dead from the disease, and of the presence during the initial phase of plague of marked gastro- intestinal phenomena. The only point which appeared to me to complete the evidence was the possibility of demonstrating the plague bacillus in food stuffs. Accordingly a large number of samples of food was submitted to me for bacterio- logical examination. Thirty-two different specimens were systematically testel, and the results obtained are chronicled in the attached table. It seemed a pity that a larger number was not examined. This, however, was found impossible owing to the existence of numerous other duties connected with the epidemic of plague which was raging at the time. I trust opportunity will be found to investigate the question further. The present results are to be regarded as preliminary. They are of sufficient importance, however, to justify their being recorded and add an important link to the chain of evidence in favour of the gastro-intestinal avenue of infection in plague.

The diet of the Chinese consists mainly of rice with the addition of pork, fish, fowls, etc. These are the staple articles of diet. The notion that mice, rats, dogs, cats are common articles of diet of the Chinese would appear to be erroneous. DYER BALL in his book on "Things Chinese" notes that rats, dogs and cats are occasionally consumed, but only by the lowest class of Chinese. The eating of dead rats would be of great importance in regard to the spread of plague. In Canton dried rats are exposed for sale in the shops. From our experience in Hongkong it is possible to convey plague to swine, fowls and other rats, etc., by feeding them on the dead bodies or individual organs of a plague infected rat.

Further, the coolie or pauper class Chinese supply the large number of cases during an epidemic of plague.

The methods of bacteriological examination, employed by me to isolate the various micro-organisms from the different samples of food are briefly the following:

Small quantities of the particular food to be examined was thoroughly soaked and rubbed up in sterilised physiological saline solution, or in beef tea.

By this means the micro-organisms present were isolate l as far as possible from the solid material. Plate cultivations were made from the solution before and after strong centrifugalisation. Stroke cultures on agar and blood serum tubes were also in- oculated. All the culture were kept at 35° C. The colonies found present were isolated on fresh nutrient media and biological tests and experiments made.

Centrifugalised deposits were also inoculated into animals, e.g., the rat, and positive results obtained. This method is most inconstant in its results owing to the presence of numerous other bacteria.

All the animals experimentel with were previously tested for their condition of health. Some of the samples gave such large numbers of bacteria present, that it was impossible to determine their exact bacteriology.

Again one sample of rice when given to rats, set up plague in those animals. Further, I have infected rice artificially with beef tea cultures of plague, and obtained positive results on feeding rats with the mixture.

Guinea pigs also give similar results.