Entamoeba Histolytica Flashcards
Habitat:
Large intestine mainly cecum and colon in the wall lumen
Is it commensal?
It lives as harmless commensal or as invasive parasite.
Definitive host:
Man
Reservoir
Dog monkey and pig
Infective stage:
Quadrinucleated mature cyst
MOI
Ingestion of (cyst) through:
Contamination of food
Infected food hamdler
Using human excreta as fertilizer
Mechanical transmission by flies and cockroaches
Life cycle:
Ingested cyst hatch in ileum》amoeba with 4n
One trophozoite with 4n emerges, divides three times and each nucleus divides once 》 8 tro
Remain in the colon and encyst
Invade mucosa and invade submucusa and reach systemic circulation》extra-instetinal
3 ways
1.Tro. Remaining in the colon lumen, encyst and pass in stool to repeat the life cycle
2.invade colonic mucosa lead to intestinal Amoebiasis (amoebic dysentery).
3.invading submucosa reach blood (extra intestinal)
Pathogenicity of tro.
It penetrate mucosa of large intestine by:
Contact with host cell causing cell lyses.
Action of pseudopodia
Release of histolytic secretion (proteolytic enzymes) which cause tissue destruction
Ability to phagocyte cells.
Pathological lesions due to Amoebiasis:
Destruction of mucosa with cell infiltration and petichial hemorrhage forming hyperemia and edema, secondary bacterial infection, eosinophilia in tissue but not in the peripheral blood
How ulcer forms:
There is thrombosis in the capillaries and necrosis in the mucosa.
This leads to formation of ulcer
E.his ulcer:
Formed of multiple foci of necrotic mucosa that fuse together forming ulcer
Ulcer shape:
Flasked-shaped (narrow apex and wide base)
Edges: undermined containing trophozoite.
Floor: full of necrotic tissue.
Base: is the muscularis layer of mucosa
Complications of intestinal Amoebiasis:
Haemorrhage
perforation
amoeboma (amoebic granuloma)
stricture (annular fibrosis)
Amoebic appendicitis
Cutaneous Amoebiasis
Extra intestinal Amoebiasis with affection of the liver.
