OYSTERS AND TYPHOID 261 



Lastly, the results of the investigations carried out by Dr 

 Houston for the Eoyal Commission on Sewage, tend to prove that 

 the contamination of oysters by B. coli is widespread and not alto- 

 gether dependent on sewage contamination of the oyster. He 

 examined over 1000 oysters, and nearly all, from whatever laying 

 they were taken, contained B. coli or coliform organisms. This did 

 not hold good as regards deep-sea oysters which were free from this 

 organism (and spores of B. enteritidis sporogenes) as was also deep-sea 

 water. Houston found the number of B. coli in an oyster varied 

 from 10 to 10,000 (in 10-15 c.c.), and the contents of the stomach 

 of the oyster contained more B. coli than the liquor in the shell. 

 Fewer B. coli were found, as a rule, in oysters stored in pure waters, 

 but instances occurred where the number of such bacilli was as 

 great as in oysters from contaminated sources.* 



Such is the bacteriological evidence down to recent date, and 

 whilst some of it may appear to be of a conflicting nature, there are 

 certain conclusions which may be drawn. First, the presence of B. 

 coli in oysters must be judged relatively. Secondly, topographical 

 evidence as to pollution must be taken in conjunction with bacterial 

 evidence. Thirdly, there is the broad general fact that oysters 

 ordinarily grown on oyster-beds contaminated with bacteria may, 

 and do on occasion, contain the virulent specific bacillus of typhoid, 

 which can live both in sea-water and within the shell of the oyster. 

 This being so, the risk of infection of typhoid by oysters is a real 

 one. Yet in actual occurrence many conditions have to be fulfilled. 

 For, in addition to the fact that the oysters must be consumed, as is 

 usual, uncooked, the following conditions must also be present : 



(a) Each infective oyster must contain infected sewage, which 

 presupposes that typhoid excreta from patients suffering from the 

 disease have passed into that particular crude sewage, and have not 

 been disinfected. 



(b) The infective oyster must have fed upon infected sewage, and 

 still contain the virus in its substance. 



(c) There must have been no period of natural cleansing after 

 " fattening." 



(d) The oyster must then be eaten, uncooked or undercooked, 

 by a susceptible person. 



Even to this formidable list of conditions we must add the 

 further remark that, owing to the vitality of the body-cells of the 

 oyster or to the lessened vitality of the bacilli of cholera and typhoid, 

 it is generally the case that the tendency of these organisms is 

 rather to decrease and die out than live and multiply. 



* Royal Commission on Seioage Disposal: Fourth Report on Pollution of Tidal 

 Waters 'and Contamination of Shell-fish, 1904, vols. i. and iii. The latter volume 

 contains a large amount of information as to bacteriological technique, etc. 



