Amebae Inhabiting the Aleimentary Canal

Chapter 11

By Beaver

Introduction:

From the Subphylum Sarcodina Superclass: Rhizopoda Order: Ameobida

General Characteristics:

1. Small , microscopic in size.

2. Have amoeboid motion.

3. Lack contractile vacoules

4. Multiply through binary fission

5. Undergo encystation during unfavorable condition.

6.It has a pseudopodium as the locomotory organ.

• In the genera of Entamoebidae are differentiated by:

= nuclear structure

Genus : Entameobidae

• Spherical nucleus• Distinct nuclear membrane lined with

chromatin granules.• Small karyosomes.• Generally the trophozoite has single

nucleus.• Natural parasites of the alimentary

canal in most vertebrates.

Entamoeba histolytica

Synonyms :

- Amoeba coli

- Amoeba dysenteriae

- Entamoeba dysenteriae

- Entamoeba terragena

- Endameoba histolytica

- Endameoba dysenteria

General Characteristics:

1. Have successive stages: trophozoite, precyst, cyst, metacyst and metacystic trophozoite.

2. Movement results from long finger-like or rounded pseudupodial extensions that progressively in one direction.

3. Nucleus is spherical, with a diameter about one fifth of the entire amoeba.

4. The active (trophozoite) stage exists only in the host and in fresh loose feces

5. cysts survive outside the host in water, soils and on foods, especially under moist conditions on the latter.

6. Mode of entry is through ingestion of contaminated food and water.

7. Ring and dot' appearance: peripheral chromatin and central karyosome

8. 4 visible nuclei

Cyst

Trophozoite stage

Life Cycle Infection occurs by ingestion of cysts (generally

from fecally contaminated food or water) Excystation occurs in the ileum of the small

intestine Trophozoites multiply by binary fission in the

large intestine. Most remain in the lumen of the intestine, however, some may invade the intestinal mucosa, enter the bloodstream and develop in extraintestinal sites. Symptoms

Cyst formation is triggered by the dehydration of gut contents in asymptomatic carriers.

Asymptomatic Amebiasis is a disease caused by a one-

celled parasite called Entamoeba histolytica (ent-a-ME-ba his-to-LI-ti-ka).

If trophozoites penetrate the intestinal wall, serious problems can occur, including liver abcesses, or spread to the lungs and brain, usually resulting in death.

Symptoms/Pathology

Pathogenesis

Vegetative – trophozoite stage

size: 4-12 micrometer

motility: active directional

pseudopodia : fingered shape

rapidly extruded

Inlcusions : Bacteria and other

material no corpuscles

nucleus : invisible

Entamoeba hartmanni

Common names

Entamoeba tenuis Entamoeba minuta Entamoeba minutissima

cyst

Entamoeba coli

Known as:

- Amoeba coli

- Endamoeba hominis

- Loschia coli

- Councilmania lafleuri

small cyst with one visible nucleus. The nucleus shows the peripheral chromatin and a central karyosome

trophozoites (4-11 µm) are similar to E.histolytica trophozoites, present a small karyosome often eccentrical.

Resembles E.histolytica Small race Asymptomatic to humans

is a non-pathogenic species of Entamoeba that frequently exists as a commensal parasite in the human gastrointestinal tract.

trophozoites measure 20-30 µm and have a vescicolous nucleus with a large eccentric karyosome

irregulary distributed peripheral chromatin. The cytoplasm is vacuolated containing

bacteria and yeast

Similar life cycle with E. histolytica

Cyst

trophozoite