Protozoa of the Digestive and Urogenital Tracts 565 



the ileum occurs occasionally. Both active ciliates and cysts may be ex- 

 pected in stool samples. The incidence of infection seems to vary widely 

 in different parts of the world and is apparently quite low in the United 

 States (163, 180). Host-specificity is evidently less rigid than that of 

 various other intestinal Protozoa. This ciliate apparently occurs in the 

 pig, as well as in man and various other primates, and it has been sug- 

 gested that B. coli may be a natural parasite of the pig. 



Effects on man 



In some cases, the symptoms are insignificant enough to suggest 

 a pseudo-carrier condition. At the other extreme, there may be recurrent 

 attacks of diarrhea, and in severe infections, a chronic dysentery. The 

 stools may contain much mucus and sometimes blood and pus. General 

 symptoms include colic, loss of appetite, occasional nausea, general weak- 

 ness, and fatigability. In long-standing cases, loss of weight may be 

 noticeable. Ulceration of the colon, which may be extensive in acute 

 cases, resembles that produced by E. histolytica. The ciliates penetrate 

 the mucosa where they often occur in groups; in deeper ulcers they may 

 even invade the muscle layers. Perforation of the colon and extension of 

 the infection from the colon to the lower ileum also have been reported. 

 The ciliates have been seen in blood and lymph vessels of the gut and 

 also in adjacent lymph glands, but secondary foci of infection apparently 

 are not established. 



Chemotherapy 



A number of drugs have been tried in balantidiosis, often with 

 unpredictable results. Carbarsone, however, has been effective in a num- 

 ber of cases (163, 180, 181). 



COCCIDIOSIS 



Although other species have been reported in rare instances, Iso- 

 spora homiyiis (Rivolta) Dobell (45a) is the only coccidian known as a 

 frequent parasite of man. The name, Isospora belli, also has been pro- 

 posed for this coccidian (177). Human coccidiosis was formerly considered 

 rare and more than half of the earlier cases had been reported from the 

 Mediterranean area, especially along the easterii shores and in the Balkan 

 countries (108, 115). During World War II, Isospora hoyninis was found 

 to be widely distributed, particularly in tropical areas. Cases have been 

 reported in Indo-China, India, Dutch East Indies, the Philippines, Japan, 

 Hawaii, China, Tonkin-China, southern Russia, Palestine, Argentina, 

 Brazil, Uruguay, Venezuela, Mexico, and Cuba, as well as in the Mediter- 

 ranean region. The incidence of infection in U. S. troops evacuated from 

 Okinawa was about 0.75 per cent (108). 



