A parasitic disease is also known as parasitosis, is an infectious disease caused or transmitted by a parasite. There are plenty of parasites that are living in our nature. This parasite enters the human body by way of contaminated food or water when we take inside to our body. These parasites also cause some of the infectious diseases. 70 percent of parasites are microscopic in size. The three main types of parasitic diseases are Protozoa, Plasmodium, and malaria. Most of the parasites do not cause diseases. Trichomoniasis, giardiasis, cryptosporidiosis, toxoplasmosis are some of the common parasitic infections.