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ميحرلا نمحرلا هللا مسب ميحرلا نمحرلا هللا مسب
Umm Al-Qura University
Health Sciences College at Al-Leith
Department of Public Health
Lecture (3)
Lecture (3)
Rhizopodea
Entamoeba histolytica
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Objectives
1/ Know Entamoeba histolytica classification and Geographical distribution.
2/ Study of Entamoeba histolytica External Morphology , Habitat, Life cycle, Mode of Transmission, Pathogenicity.
3/ Show Symptoms of amoebic dysentery disease.
4/ Show Laboratory diagnosis of Entamoeba histolytica.
5/ Know of Treatment and prevention.
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Entamoeba histolytica
Fedor Alexandrewitch describes amoebae associated with severe dysentery in a patient in 1873
He transferred amoebae to a dog by rectal injection, which became ill and
showed ulceration of colon
Patient who died from infection showed similar ulcers upon autopsy
Classification:
Phylum: protozoa
Subphylum: Sarcomastigophora Superclass: Rhizopoda
Class: Lobosea Order: Amoebida
Family: Entamoebidae Genus: Entamoeba
Species: Entamoeba histolytica
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2- Geographical disribution:
Cosmopolitan, but important mainly in the tropics and subtropics.
3- Habitat :
The unencysted parasites occur in the
large intestine
of man.The cysts develop in the intestinal lumen.
4 - Morphology
-:لاكشا ةثلث يف اكيتيلوتسيه ابيماتنلا ليفط دجوي 1- Trophozoite طششانلششا لكشلششا .
2- Precyst لشصوحتملششا لب ششق لكشلششا . 3- cyst لشصوحتملششا لكشلششا .
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Morphological characters:
1- unencysted amoeba, (Trophozoite):
- This is also known as growing stage, feeding stage or active vegetative stage.
- Vary in size from 10 – 60 but majority are around 15 – 30 um.
- contain red blood cells (RBCs).
Trophozoite:
Trophozoite :
2- The encysted amoeba The cysts are round or oval in outline, cyst
containing one, two or four nuclei. The size of the cysts varies between 12 – 15 um.
Cyst :
The fully developed cysts containing for nuclei are ingested by man.
A process of excystation occurs in alimentary canal produces eight amoebae by a process of division an then these individual grow and multiply.
In some cases enter the portal blood stream and so be carried by the portal vien to the liver.
the amoebae invade the mucous membrane of the large intestine and multiply there.
After a period of growth and multiplication in the intestine
encystation
occurs and the cysts are passed out in the faeces.
6- Pathogenicity:
Produce ulceration of the large intestine.
• Trophozoites divide and produce extensive local necrosis in the large intestine. Invasion into the deeper mucosa with extension into the peritoneal cavity may occur.
• This can lead to secondary involvement of other organs, primarily the liver but also the lungs,
brain, and heart.
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In a percentage of infected cases abscess of the liver and rarely of other organs.
6-Symptoms of amoebic dysentery
• abdominal pain.
• fever and chills.
• nausea and vomiting.
• watery diarrhea, which can contain blood, mucus or pus.
• painful passing of stools.
• fatigue.
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8- Laboratory diagnosis
•In intestinal amoebiasis:
• Examination of a fresh dysenteric fecal specimen or rectal scraping for trophozoite stage. (Motile amoebae containing red cells are diagnostic of amoebic dysentery).
•• Examination of formed or semi formed feaces for cyst stage.
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Microscope
Slide
Cover slip Slide
C
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Iodine solution
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Microscope
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9- Treatment
Acute amoebiasis is treated with
1-Metrondiazole followed by iodoquinol, and
asymptomatic carriage amoebiasis can be eradicated with
2- iodoquinol, diloxanide furoate, or paromomycin. And also Metrondiazole,
10- Prevention
1- Introduction of adequate sanitation measures and education about the routes of
transmission.
2- Avoid eating raw vegetables grown by sewerage irrigation and night soil.
3- Always wash hands with soap after going to the toilet before eating food.
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