Question

When does Entamoeba histilytica become harmful in the large intestine?

Answer 1

entamoeba histolytica causes amoebiasis or amoebic dysentery. 
it is a human parasite that resides in the upper part of the large intestine . it causes amoebic dysentery ie. amoebiasis particularly in children in slum areas. the parasite is unicellular and has one pseudopodium . There is a single nucleus and a number of food vacuoles. This makes the organism more harmful. mode of transmission of this disease is due to the intake of contaminated food and water and copraphagous insects such as house flies and cockroaches . 

this causes abdominal pain, repeated motions with fluid faecal matter with blood and mucus. It can even produce ulcers and can also reach other body organisms.  it feeds on the red blood corpuscles by damaging the wall of large intestine