THE CILIATES 



373 



to 120|Li. The cytopyge is near the poster- 

 ior end. The macronucleus is sausage- 

 or kidney-shaped, and the micronucleus 

 lies near the center of 1 side. There are 

 2 contractile vacuoles, 1 terminal and the 

 other near the center of the body. There 

 are many food vacuoles containing starch 

 grains, cell fragments, bacteria, erythro- 

 cytes, etc. ; starch is the most important 

 food. The surface is covered by slightly 

 oblique longitudinal rows of cilia. 



Krascheninnikow and Wenrich (1958) 

 studied the morphology and division of 

 B. coli in detail. Auerbach (1953), Sen 

 Gupta and Ray (1955) and Lom (1955) re- 

 ported on cytologic and C3^ochemical 

 studies. 



The cysts are spherical to ovoid and 

 measure 40 to 60 |i in diameter. They 

 are slightly yellowish or greenish, with 

 hyaline cytoplasm. The cyst wall is com- 

 posed of 2 membranes. 



Life Cycle : B. coli reproduces by 

 transverse binary fission (Krascheninni- 

 kow and Wenrich, 1958). Conjugation 

 also takes place (Nelson, 1934; Svensson, 

 1955), and resistant cysts are formed. 



Pathogenesis : In the pig, Balanti- 

 dium coli is ordinarily a commensal in the 

 lumen of the large intestine, where it lives 

 on starcn, other ingesta and bacteria. It 

 does not seem able to penetrate the intact 

 intestinal mucosa by itself. Enormous 

 numbers of Balaiitidiimi may be found in 

 the lumen of the cecum of pigs with normal 

 cecal mucosae. However, once some other 

 organism or condition has initiated a lesion, 

 Balantidium may be a secondary invader 

 and may be found deep in the ulcer. It pro- 

 duces hyaluronidase (Tempelis and Ly- 

 senko, 1957), which might help it to en- 

 large the lesions by attacking the ground 

 substance between the cells, altho it would 

 not help it to initiate the lesions. 



Balantidium is pathogenic in man and 

 other primates. It causes diarrhea or 

 dysentery, and produces undermining 

 lesions similar to those caused by Enta- 

 moeba histolytica. The protozoa may be 

 found down to the muscularis mucosae, 



the ulcers are infiltrated with round cells, 

 and coagulation necrosis and hemorrhagic 

 areas may be present. The protozoa 

 often occur in nests within the tissues or 

 even in the capillaries, lymph ducts and 

 neighboring lymph nodes. The lesions in 

 the pig and other animals are similar. 

 The disease in man has been reviewed by 

 Swartzwelder (1950), Shookhoff (1951) and 

 Arean and Koppisch (1956). 



The infected dog described by Dikmans 

 (1948) died of a severe diarrheal disease, 

 and ulcers were found in the intestine at 

 necropsy. In the case reported by Bailey 

 and Williams (1949), the animal had dysen- 

 tery for several days beginning several 

 days after it ate the intestines of a hog, 

 but it recovered. 



Lesions in the ceca of some naturally 

 infected rats were described by Bogdanovich 

 (1955). 



Bionomics and Epidemiology : Balan- 

 tidium may be transmitted by ingestion of 

 either cysts or trophozoites. The cysts 

 are more resistant to environmental con- 

 ditions. Svensson (1955) found that the 

 trophozoites of different strains of B. coli 

 from the pig differ in their resistance to 

 heat and cooling. Most strains survive 

 heating to 47° C for more than 15 minutes 

 but survive at room temperature for less 

 than 3 days. A cold-resistant strain sur- 

 vived heating for only 5 to 10 minutes, but 

 remained alive at room temperature for 

 5 days or more. B. coli from man is 

 similar to the latter. The cysts may re- 

 main alive for weeks in pig feces if they 

 do not dry out. 



The pig is the usual source of infection 

 for man. Contact with swine has been 

 noted in more than half the human cases 

 reported (Arean and Xoppisch, 1956), and 

 Shookhoof (1951) obtained a history of close 

 contact with pigs in practically all the cases 

 he observed in Puerto Rico. 



Chimpanzees and other primates ap- 

 pear to have their own infection pool. 



Diagnosis : Balantidium can be easily 

 recognized by microscopic examination of 



