This chapter discusses some enteric protozoa, entenc protozoa, and vector-borne protozoa. They lead to infectious diseases. Balantidium coli is a food- and water-borne infection with pigs being the primary reservoir. It has a widespread distribution worldwide, essentially in any location where pigs are raised. It also has a wide host range; one study identified B. coli in 59 mammalian species just in Japan. Cyclospora cayetanensis is an intestinal parasite that is spread by ingesting food or water that has been contaminated with feces. It has been detected in a few species of wild primates: spider monkeys and howler monkeys in the New World and macaques from Nepal. Giardia lamblia has been described as the most common waterborne human parasite worldwide. It is most often spread through drinking contaminated water, but can also be spread through contact with food, soil, or other objects contaminated with feces.