Once thought to be a harmless yeast, Blastocystis hominis a microscopic single-celled protozoal parasite. It behaves like a tiny animal — hunting and gathering other microbes for food—one reason why having a balanced gut flora is important. Healthy gut floras do not support large amounts of parasites. Many protozoa inhabit your gastrointestinal tract and are harmless; others cause disease.
In 1996, a large outbreak of Cyclospora infection in the United States and Canada was caused by Guatemala-imported raspberries. It is not clear how the fruit became contaminated, but it might have happened when fruit touched the ground or when contaminated water was sprayed over fruit fields by sprinkling systems. People infected with C. cayetanensis excrete oocysts that are not infectious. This is an important clue in diagnosis because other parasitic diseases can be very infectious so more than one person (or pet) in the family will have symptoms at the same time. Cyclospora needs days or weeks after being passed in a bowel movement to become infectious. People most likely get Cyclospora infection by ingesting food or water that was contaminated with stool from an infected person. It is unknown if animals can be infected and pass infection to people.
Cryptosporidium is a five micrometer microscopic intracellular protozoal parasite that was first associated with human gastro-intestinal disease in 1976. With the advent of the acquired immunodeficiency syndrome (AIDS) epidemic, Cryptosporidium infections became increasingly recognized as a cause of diarrheal illness.
Symptoms of Balantidium: Colic, straining to defecate, nausea, vomiting diarrhea, loss of appetite, bloody diarrhea, weakness. Infection can also be without symptoms. The incubation period is usually 3-4 days which means you need to be exposed 3-4 days previous before symptoms appear. This picture was taken from either a fecal sample (which was dyed) or from a colon biopsy.