Ciliates - Parasitic Protozoan
The only ciliate of medical and veterinary importance is Balantidium coli which inhabit the large intestine of man, apes, monkeys and pigs. B. coli have been reported from all parts of the world. It causes invasion of intestinal mucosa, thereby causing diarrhoea, nausea, vomiting. The parasite encysts in the lumen of the host's large intestine and the cysts pass out in the faeces.
Figure: Balantidium coli