"Look Ma, there's a hole in my colon!"
Balantidiasis is a worldwide occuring disease caused by Balantidium coli, a large ciliated protozoan parasite. This astonishingly large critter (50 - 70 micrometer long and wide) lives in the colon of rodents, pigs and humans.
The disease occurs everywhere were humans live in close contact to their snouted friends - pigs - and apparently has been reported in Ireland (who would have thought) and the tropics. Infection happens by ingestion of the parasites' cysts with contaminated food or water. In the hosts' gut the cyst develops to the trophozoit and invades the host's colon and the colonic walls. This then causes diarrhoea, abdominal pain, weight loss and sometimes even perforation of the colon, which obviously is one of the most vicious surgical emergencies, as faeces can flow into the normally sterile abdominal cavity and cause massive sepsis.
Diagnosis is tricky, as the trophozoites die quickly outside the hosts body, so microscopy has to be done quickly on fresh stool.
Treatment is fortunately uncomplicated with Tetracycline, but to avoid catching it in the first place, you'll have to tell your pigs that the living room is just no place for them.
Source: Dion R. Bell, Tropical Medicine, 4th Edition, Blackwell cience, 2000