CHAPTER XXV 

 THE GENUS BALANTIDIUM 



By 



Robert Hegner 

 The Johns Hopkins University School of Hygiene and PubUc 



Health 



INTRODUCTION 



Species of the genus Balantidium have been reported from man, 

 the chimpanzee, orang, baboon and other Old World and Nev^ 

 World monkeys, domesticated animals (pigs, cattle, sheep, horses, 

 guinea-pigs), a bird, a tortoise, salamanders and frogs, fish, Crus- 

 tacea (sand fleas), insects (cockroaches and Culicoides), snails, 

 annelids, turbellarians and coelenterates. They are particularly 

 abundant in pigs, guinea-pigs and frogs. Many species have been 

 described from these various animals. Specific differences are prin- 

 cipally shape and size of the body, shape and position of the 

 cytostome, and shape and size of the macronucleus. Balantidium 

 is rare in man except in certain localities (e.g., Aguilar, 1925, in 

 Guatemala) and is not frequent in monkeys, but is common in pigs 

 and guinea-pigs. The species from man, monkeys and pigs have 

 for many years been considered to belong to one species (Balan- 

 tidium coli), and recent studies (Scott, 1927) indicate that the 

 species in the guinea-pig is also B. coli. McDonald (1922) believes 

 that a second species, B. suis, occurs in pigs, but it seems probable 

 that he was dealing with exconjugants which have a larger ratio 

 of length to breadth than specimens during growth stages. 



SOURCES OF SUPPLY 



Balantidia are common in pigs. McDonald (1922) reports an 

 incidence of infection of sixty-eight per cent among 200 pigs in 

 California and Nevada, and at least as high an incidence occurs 



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