Entamoeba histolytica (a protozoan parasite in the large intestine)

Amoebiasis (Amoebic dysentery)

Mode of infection: Contamination of food and water by houseflies (carrying the parasite mechanically from the faeces of an infected person to food).

Sign and symptoms: Abdominal pain and cramps, constipation, stools with excess mucous and blood clots.