A number of unicellular and multicellular organisms belonging to the animal kingdom cause a variety of diseases in humans as well as in animals. These infections are very common in tropical countries. Among the diseases produced by these parasites are amebiasis, giardiasis, malaria, trichomoniasis, leishmaniasis and helminthic infections. A parasite requires a host in which it thrives either symbiotically or as a commensal or as a parasite wherein host is injured and gets disease. The parasitic disease can be called as “cancer” of the tropical countries. Amebiasis is an acute or chronic infection due to an unicellular organism Entamoeba histolytica. The infection exists all over the world and it is a major health problem in developing countries.