TRANSMISSION OF E. HISTOLYTICA! CARRIERS 



out by studies on the transmission of protozoan cysts is 

 that the host is entirely responsible for his own infection. 

 The parasite remains passive and can only reach the 

 intestine of a new host by the activities of the host. The 

 discussion of the methods of protecting individuals and 

 communities from infection is reserved until later (see 

 p. ii6). 



Transmission as a result of association with carriers. 

 The principal reservoirs of E. histolytica are human car- 

 riers who are passing cysts. Observations indicate that 

 the association of such carriers with susceptible hosts 

 result in infections. For example, Kofoid (1923) em- 

 phasizes the spread of the infection in families, and Garin 

 and Lepine (1924) noted that 50 per cent of indigenous 

 cases of amcebiasis near Lyons, France, had associated 

 with colonial troops during the war. The migration of 

 troops to France and their return to the United States 

 furnished an excellent opportunity to study this subject. 

 Stiles (1922) summarized the results of a very extensive 

 study by Boeck and himself (Boeck and Stiles, 1923) in 

 part as follows. 

 Examinations were made of 



13,043 specimens from 8,029 persons in 22 states and 



B.C. 



44 per cent (3,533) were infected with both pro- 

 tozoa and worms. 



39.9 per cent (3,208) were infected with protozoa. 



9.6 per cent (775) were infected with worms. 



4.1 per cent (333) were infected with E. histolytica. 



Positive cases were found in persons from every state 



that sent in a fair number of specimens. These data give 



79 



