210 PROTOZOAN PARASITISM 



ism may dwell in the colon of man as a harmless 

 parasite. 



Walker says that the latency prevalent in bal- 

 antidiosis of man is due chiefly to the fact that the 

 patient, although parasitized, is not ''infected," but 

 in part to the chronicity of the ulcerative process in 

 infected cases. He further states that a person in- 

 fected with Balantidium coli is liable sooner or later 

 to develop balantidial dysentery. 



The state of infection in which there is a chronic 

 or mild and continued process of invasion and ulcera- 

 tion is naturally less known than the comparable 

 case of chronic intestinal amoebiasis, although when 

 symptoms of progressive disease are present they 

 may be more pronounced. Not uncommonly there 

 is a chronic and intractable diarrhoea, and emaciation 

 and anaemia may be conspicuous in the long stand- 

 ing case. Individuals showing symptoms of the in- 

 fection commonly run an intractable course of chronic 

 illness in which periods of dysentery alternate with 

 those of comparative well being or constipation. 



TREATMENT 



Preventive : Since it has been shown that the in- 

 fection of man may come from the pig, and that swine 

 are commonly carriers of Balantidium coli, it neces- 

 sarily follows that those who handle these animals 

 or are in close contact with them must exercise care 

 to avoid contamination of any object which is placed 



