Which animal serves as the reservoir host for Balantidium coli infection?

• A. Pig
• B. Dog
• C. Cat
• D. Cattle

Answer: (A)

A reservoir host is an animal that harbors the parasite and sheds infectious forms into the environment, helping to keep the life cycle going and enabling transmission to humans. Balantidium coli mainly lives in the large intestine of pigs, and pigs shed cysts in their feces. Humans often become infected by ingesting these cysts through contaminated water or food, especially in areas with poor sanitation. Because of this strong association with swine, pigs are the typical reservoir. Dogs, cats, and cattle can harbor other parasites, but they are not the usual reservoir for Balantidium coli in humans.