ENTAMOEBA HISTOLYTICA

Presented By: Daniyal Khan &

Usman Sarwar

Contents Introduction History Structure Transmission Pathology Diagnosis Treatment

Introduction Entamoeba histolytica is an anaerobic

unicellular parasitic protozoan, part of the genus Entamoeba.

The word histolytic literally means "Tissue destroyer“

Infects the human colon and causes acute diarrhea which leads to dysentery.

Domain: EukaryotaPhylum: ArchamoebaeGenus: Entamoeba

History The genus Entamoeba was defined by

Casagrandi and Barbagallo.

E. histolytica is estimated to infect about 50 million people worldwide.

Lösch's organism was renamed Entamoeba histolytica by Fritz Schaudinn in 1903. He later died, in 1906, from a self-inflicted infection when studying this amoeba.

Structure Entamoeba cells are small with a single

nucleus. Immature CYST Mature Cyst Trophozoites.

The trophozoite (feeding-dividing form) is approximately 15-30 μm in diameter and feeds primarily on bacteria.

It divides by simple binary fission to form two smaller daughter cells.

Almost all species form cysts including E.Histolytica, the stage involved in transmission.

Trophozoites are monopodial having a single nucleus and are the invasive and infective form.

Transmission The active (trophozoite) stage exists only in

the host and in fresh loose feces. Cysts survive outside the host in water, in

soils, and on foods, especially under moist conditions.

When cysts are swallowed they cause infections by excysting (releasing the trophozoite) in the digestive tract.

Infection can be asymptomatic or can lead to amoebic dysentery or amoebic liver abscess.

Symptoms can include dysentery, bloody diarrhea, weight loss, fatigue, abdominal pain, and amoeboma.

Pathology Once the Trophozoites are excysted they

colonise the large bowel and feed on bacteria and food particles.

Trophozoites move through the mucus layer where they come in contact with the epithelial cell layer and start the pathological process.

E. histolytica has a lectin that binds to galactose and N-acetylgalactosamine sugars on the surface of the epithelial cells.

The lectin normally is used to bind bacteria for ingestion.

Enzymes such as pore forming proteins, lipases, and cysteine proteases, are used to digest bacteria and cause lysis of the epithelial cells by inducing cellular necrosis and apoptosis.

Amoebapore.

Damage to the epithelial cells attracts immune cells which are then also lysed by the trophozoite.

This releases the hydrolytic enzymes which then cause damage to the tissue.

This destruction manifests itself in the form of an 'ulcer' in the tissue.

Amoeboma is formed in the large bowel which causes lesions in the intestine.

Lytic necrosis (it looks like “flask-shaped” holes in Gastrointestinal tract sections.

This can further lead to the metastatic stages where liver and Brain are damaged by E.Histolytica.

If the infective cells reach the liver they cause LIVER ABSCESS.

Diagnosis1. Microscopic examination of Stool samples. Trophozoites may be seen in a fresh fecal

smear and cysts in an ordinary stool sample.

2. Direct Fecal Smear. DFS and staining. But it does not allow

identification to species level.

3. ELISA and RIA are also used for the diagnosis. The enzyme-linked immunosorbent assay

(ELISA) is a test that uses antibodies and color change to identify a substance.

Radioimmunoassay (RIA) is a very sensitive in vitro assay technique used to measure concentrations of antigens by use of antibodies.

4. Antigen detection – Monoclonal antibody is another useful method.

5. PCR can be done for species identification of ENTAMOEBA.

Treatment There are many kinds of effective drugs: Intestinal infection: Usually

nitroimidazole derivatives are used because they are highly effective against the trophozoite form of the amoeba. But have little effect on the cysts.

Liver abscess: metronidazole and chloroquine. Along with agents which act on the lumen

of the intestine to prevent re-invasion.

Asymptomatic patients: For asymptomatic patients, non endemic areas should be treated by paromomycin.

And other treatments include diloxanide furoate and iodoquinol.

Paromomycin has a higher cure rate.

Paromomycin (Humatin) should be used with caution in patients with colitis, as it is both nephrotoxic and ototoxic.

Thank You