E. COLi: TRANSMISSION 



E. histolytica regarding transmission, infection, preven- 

 tion, etc., are omitted here in order to avoid repetition. 

 Instead, therefore, of following the outline used in dis- 

 cussing E. histolytica, only those phases of the host- 

 parasite relations will be referred to in the case of the 

 other amoebae of man that call for special attention. 



I. ENDAMCHBA COLI 



Epidemiology of transmission. As in the case of E. 

 histolytica, E. coli is no doubt usually transmitted in the 

 cyst stage, although occasionally trophozoites may bring 

 about the colonization of a new host (see p. 65). Ex- 

 periments designed particularly to test the viability of 

 histolytica cysts outside of the body under various condi- 

 tions have contributed also to our knowledge of this 

 subject with respect to cysts of E. coli. Certain of the 

 results of these experiments are included in the account 

 of E. histolytica (see p. 71); these indicate that the 

 same principles obtain in both species and hence a detailed 

 statement regarding the cysts oi E. coli seems unneces- 

 sary. No doubt the cysts oi E. coli reach the digestive 

 tract of man in contaminated food or drink and are 

 carried about by flies and possibly by lower animals such 

 as mice, rats, cats and dogs. The very high incidence of 

 infection with E. coli among the general population, 

 which appears to be at least 50 per cent, indicates that 

 fecal contamination of our food and drink is very prev- 

 alent. All persons in whom E. coli lives are carriers 

 who are more or less constantly passing cysts capable 

 of bringing about the colonization of new hosts. 



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