This is a common ciliate parasite of man, lower primates and hogs. Pathogenesis is similar to that seen in E. histolytica intestinal infections. Extra-intestinal involvement is rare. Human infections are most common where malnutrition occurs, where pigs share habitation with humans, and where fecal contamination of food and water can occur. The parasite appears to be nonpathogenic in pigs.
Asexual reproduction is by transverse fission although conjugation also occurs.
Results of human infection range from asymptomatic to severe with invasion of the mucosal lining followed by hemorrhage and ulceration occurring. Most human cases disappear spontaneously, while some become asymptomatic, resulting in a carrier state. Treatment usually involves oxytetracycline therapy, usually lasting for 10 days. In most situations, B. coli is harmless to pigs and man although diarrhea and dysentery are known. Disease, when it would occur, would be clinically indistinguishable from other causes of hemorrhagic colitis.