E. HISTOLYTICA CYSTS I ANIMALS 



elusion reached by these investigators is that flies play 

 a very small role in the transmission of intestinal amoebae. 

 A similar attempt to infect kittens with flies that had 

 fed on fecal matter containing histolytica cysts had pre- 

 viously been made by Wenyon and O'Connor (191 7). 

 Flies were fed by them to two kittens but no infections 

 resulted. 



The data available seem to prove conclusively that flies 

 both in the laboratory and in nature ingest fecal mate- 

 rial containing protozoan cysts; that the cysts are not 

 quickly killed in the flies' intestine ; that living cysts may 

 be deposited in the feces of the fly from 5 minutes to 49 

 hours after feeding; and that these cysts may be de- 

 posited in the food or drink of man where they may re- 

 main viable until ingested by a human host. The con- 

 clusion seems inevitable that flies play an important role 

 in the dissemination of histolytica cysts and that food 

 and drink should be protected from their visits, especially 

 in localities where amoebic dysentery occurs and sanitary 

 conditions are such as to allow flies access to infected 

 fecal matter. It may be pointed out here that the fly 

 does not become infected but is a "passive" carrier, in 

 contrast to the rat described below which is an ''active" 

 carrier. 



The dissemination of cysts by other animals. Under 

 favorable circumstances other insects, such as ants and 

 cockroaches, and even other animals, may serve as dis- 

 tributors of protozoan cysts. Several investigators have 

 incriminated rats and mice. The data furnished by Lynch 

 (1915b) on spontaneous and experimental infections 

 with E. histolytica in rats in South Carolina cannot be 



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