“ON SHELL!”

Hawera Star, Volume XLVIII, 24 September 1924, Page 7

“ON SHELL!”

HYGIENE AND THE OYSTER

Tile oyster in its relation to public health was discussed recently by Professor J. W. H. Eyre in London, in a lecture given before the Society, of Medical Officers of Health. The food of this mollusc, he said,, consists of microscopic plants and animals, and debris presents in the sea or carried down, by the rivers, as well as the: freeswimming larvae of other bivalves, organic detritus, and other substances of organic origin. Feeding during the summer months is almost continuous, the oyster remaining open, either feeding or breeding, for nineteen hours out of the twenty-four. Says The British Medical Journal (London) in reporting the lecture: “Ouster farms should be situated within easy reach of the shore,-a large volume of sea-water should be available, and a sufficient admixture of river water to ensure the required density. There should also be a clean sea-bottom, subject to the action of the tides, and a constant supply of fresh food. There must be freedom from adjacent sources of pollution, human or mamalian. a point which could only be determined by a. topographical survey of the surrounding country. The greater number of the oyster-beds in England are 'found in the estuaries of rivers, and there are few rivers, speaking generally, which do not carry down to the sea a considerable amount of sewage; organic material received in this form no doubt provides a. good deal of the total sustenance taken in by the oyster. Professor Eyre said that the bacterial content of the matter which reaches the rivers and is ultimately discharged into the sea remains sufficiently virulent to form a potential source of infection to any oyster-beds, and expressed the opinion that, for practical purposes it is* this sewage in which the bacteria remain virulent that constitutes the real danger. Even though the sewage may have been diluted in its/ passage, the oyster itself reverses this process and concentrates the organisms within its own body. If, however, after pollution with any of the specific bacteria, an oyster is transferred, to a bed supplied with water wdiich is not under suspicion from a bacterial point of view, this water, continually entering and leaving the open shell and passing through, the gills of the oyster, will wash away a large number of these micro-organ-isms, and at the end of seven or eight days the objectionable bacteria are completely removed. In examining oysters for sewage pollution, Professor Eyre continued, the analysis is directed primarily to the demonstration of the colon bacillus, which, if planted in unpolluted sea-water, tends to die out in about eight or nine days. The colon bacillus is therefore the best index to sewage contamination, and he indicated a. test which would advise the public health authorities and the oyster farmer of the presence of this organism. It is only within comparatively recent years that the connection between typhoid and other endemic diseases of shell-fish has been realised. In London the total number of typhoid cases remained stationary at about 4000' a year up to 1900. from 1900 to 1914 there was a sharp fall, and since 1914 the number has remained at about 500. The fall coincided with the era of strict supervision of the shellfish industry by the Fishmongers’ Company.”