24 PROTOZOAN PARASITISM 



(1925), indicate that such hygienic measures are 

 without avail in preventing the spread of these para- 

 sites and that close personal contact leads to a steady 

 increase in incidence. Hand to mouth transmission 

 and the food handler carrier are undoubtedly promi- 

 nent means of spread of these parasites in places 

 where there is proper disposal of human excreta and 

 protection of water and food from fecal contamina- 

 tion. That being the case, protection against the 

 carrier must be the means of prevention of such trans- 

 mission. 



In places where there is exposure and improper dis- 

 posal of fecal matter, the transfer of cysts by flies 

 and the contamination of food and drink by them are 

 probably means of spreading these parasites, and 

 prevention of such dissemination must mean the con- 

 trol of such conditions. 



Flies may carry live protozoan cysts in their in- 

 testinal tracts, after ingesting them from human 

 excreta, for probably several days, during which time 

 they may contaminate food with them in their own 

 excreta. They may also carry cysts upon their legs, 

 although parasitic protozoa do not survive drying for 

 any considerable period, even in cysts. 



As for those which may be obtained from other 

 animals there is one of importance which is appar- 

 ently so spread, and there is another, the most im- 

 portant intestinal protozoon of man, which may pos- 

 sibly be spread in such a manner. 



The former is Balantidiuni coli, a natural para- 



