This document provides information about protozoology and the parasitic protozoan Entamoeba histolytica. It begins with an introduction to protozoology and classifications of protozoa. It then discusses the general characteristics, life cycles, and importance of protozoa. The document focuses on E. histolytica, outlining its habitat, transmission, morphology, life cycle within the human host, virulence factors, epidemiology, pathogenesis, symptoms of infection, laboratory diagnosis, treatment and prevention. E. histolytica causes amebiasis and can lead to intestinal or extraintestinal disease such as liver abscesses if the parasite invades tissues.

1. Protozoology &
Entamoeba spp.
By: Mustafa Masood

2. Outlines
Introduction
General characteristics
Classification
Stages and transmissions
Life cycle
Ecological and industrial importance of protozoans

4. Protozoology:
Is a branch of zoology that is concerned with the study of protozoa.
Branches:
• Veterinary Protozoology
• Medical Protozoology
• Soil Protozoology
Medical Protozoology/Parasitic Protozoa:
Is a branch that is largely concerned with the study of parasitic protozoa that infect and cause
diseases in humans.
Introduction

5. Introduction
• Single-celled eukaryotic microorganisms belonging to kingdom Protista
are classified as Protozoa.
• Biologists group more than 40,000 species of protozoa in the phylum
Protozoa.
• Parasitic protozoa are adapted to different host species(plant. Animal).
• Out of 10,000 species of parasitic protozoa, Human harbours only about
70 species.
All Protozoa are parasite ?

6. Protozoa of medical importance to human

7. Classification of living things

8. Classification of Protista
Animal-like protists are
sometimes called
Protozoa.

9. Classification of Protozoa
Based on the mode of locomotion, protozoa can be divided into 4 main
groups.
Amoeboid Flagellates Sporozoa Ciliates

10. General characteristics
• The single protozoa cell performs all functions.
• The body wall is covered by cell membrane.
• Its cytoplasm is made up of ectoplasm and endoplasm.
• The nucleus is usually single but may be double or multiple.
• Reproduction can be asexual or sexual.
• Most ciliates have two types of nuclei:
micronuclei and macronuclei.
• Amoeba has one nuclei.

11. General characteristics
• Most parasitic protozoa in humans are less than 50 μm in size.
• All protozoa are heterotrophic (no photosynthetic).
• Deriving nutrients from other organisms, either by ingesting them whole or
by consuming their organic tissue or waste products.
• Some protozoans take in food by phagocytosis, engulfing organic particles
with pseudopodia (amoeba).
• Or taking in food through a mouth-like aperture called a cytostome (cell
mouth).
• Other protozoans absorb dissolved nutrients through their cell
membranes, a process called osmotrophy.

12. is a very thin
layer of protein
that protects cell
membranes
is used to
capture and
digest
bacteria
Allows the flow of water
from the cytoplasm and then
discharges this externally by
the opening of a permanent
narrow neck
Restricted opening
through which the
buccal cavity opens
to the cell surface.
paramecium
absorb wastewater
and materials from
the surrounding
cytoplasm which
eventually will get
transported out of
the cell

13. They catch food, using
pseudopodia, a process
termed phagocytosis.

14. Protozoa vs Bacteria
• Protozoa are one-celled organisms, like bacteria. But they are
bigger than bacteria and contain a nucleus and other cell
structures, making them more like plant and animal cells.

15. Stages and Transmissions
Trophozoites: is a general term for the active, feeding, motile,
multiplying stage of most protozoa.
Cyst: Non-motile, survives the environment because has thick wall, cyst
do not multiply.

18. LIFE CYCLE
• Single host: Protozoa like intestinal flagellates and
ciliates require only one host, within which they multiply
asexually in trophic stage and transfer from one host to
another by the cystic form.
• Second host: In some protozoa like Plasmodium, asexual
method of reproduction occurs in on e host (man )
and sexual method of reproduction in another host
(mosquito).

19. Ecological and industrial importance of protozoans
• Protozoa play important roles in the fertility of soils.
• They regulate bacterial populations.
• Protozoa play important roles in wastewater treatment processes.
• Scientific Study: Many protozoa are used in biological and medical
researches.
• Several protozoa control harmful insects
by persisting their bodies.

20. Sources
1. Protozoology -Definition, Examples, Classification and Characteristics (microscopemaster.com)
2. Paniker's Textbook of MEDICAL PARASITOLOGY
3. Jawetz, Melnick, & Adelberg’s Medical MicrobiologyTwenty-Eighth Edition.
4. Medical ParasitologyA Textbook, Rohela Mahmud Yvonne Ai Lian Lim

21. Entamoeba histolytica

22. Outlines
Scientific name
Normal habit
morphology
Life cycle ( hosts )
Epidemiology
Pathogenesis and symptoms
Complications
Laboratory diagnosis
Prognosis
Treatment
Prevention and control

23. Entamoeba histolytica
• Entamoeba histolytica is a protozoa that causes Amebiasis.
E. histolytica has three sub species:
1. E. dispar
2. E. moshkovskii
3. E. Bangladeshi
are generally not associated with disease although investigations into
pathogenic potential are ongoing.

24. Habitat
Entamoeba histolytica is found in the human colon.
Distribution
Entamoeba histolytica has a worldwide prevalence, especially where
sanitation is poor and is more common in developing countries of the
tropics. Majority of cases are asymptomatic.

25. Mode of transmission
• Fecal-oral route (most common): By ingestion of contaminated
food or water with mature cysts.
• Sexual contact: Rare, either by anogenital or urogenital contact.
(especially among homosexual males).
• Vector: Very rarely, flies and cockroaches may mechanically transmit
the cysts from feces, and contaminate food and water.

26. Morphology
• Entamoeba histolytica occurs in 3 forms.
• 1. Trophozoite : the form that feeds, multiplies, and possesses
pseudopods, and cysts, the nonfeeding stage characterized
• 2. Pre-cyst : that develops into a cyst.
• 3. Cyst : nonfeeding stage characterized
by a thick protective cell wall.

27. cyst

28. Excystation and Encystation
• Excystation the morphologic conversion from the cyst form into the
trophozoite form, occurs in the ileocecal area of the intestine.
Replication only occurs in the trophozoite stage. ( by binary fission ).
• The conversion of trophozoites to cysts, a process known as
Encystation, occurs in the intestine when the environment
becomes unacceptable for continued trophozoite multiplication.

29. Life cycle
1. The cysts (usually found in formed stools) and trophozoites (in loose
stools) are passed out in faeces of infected human.
2. cysts are ingested via contaminated food or water.
3. In the intestine, the cysts undergo excystation and form trophozoites.
4. As the trophozoite passes down the intestine, it undergoes
encystation and is excreted in the faeces.
E. histolytica completes its life cycle in human host. In the majority of
cases, E. histolytica remains as a commensal in the large intestine. They
are carriers or asymptomatic cyst passers and are responsible for
maintenance and transmission of infection in the community.

31. Life cycle of
Entamoeba
histolytica

32. Virulence factors of Entamoeba histolytica
• Cysteine proteases
They degrade extracellular matrix, responsible for invasion, secreted
only by trophozoites.
• Hydrolytic enzymes
Such as RNAse, neutral protease and phosphatases—help in the
destruction of the target tissue.
• Neuraminidase and metallocollagenase
Help in invasion.

33. Epidemiology
• Amebiasis is a major cause of morbidity and mortality worldwide
after malaria.
• More than any other causes, parasitic diseases are contributing
significantly to the burden of illnesses, leading sometimes to death,
and affecting people in developing and in developed world, even in
regions that include high-income countries
• About 80-90% of infections are asymptomatic.

34. Clinical Syndrome
1. Asymptomatic carriage:
• The parasite is a low-virulence strain.
• The inoculation into the host is low.
• The patient’s immune system is intact.
1. Intestinal Amebiasis
2. Extraintestinal Amebiasis

35. Pathogenesis and symptoms
• Incubation period 1-4 weeks.
• The majority of infections restricted to the lumen of the intestine (luminal
amebiasis).are asymptomatic.
• Amebic colitis, or invasive intestinal amebiasis, occurs when the mucosa is
invaded.
• Symptoms include severe dysentery and associated complications.
• Severe chronic infections may lead to further complications such as peritonitis,
perforations, and the formation of amebic granulomas (ameboma).
• Amebic liver abscesses are the most common manifestation of extraintestinal
amebiasis. Pleuropulmonary abscess, brain abscess, and necrotic lesions on the
perianal skin and genitalia have also been observed.

36. Extraintestinal Amebiasis and Complications
• Amebic liver abscesses are the most common manifestation of
extraintestinal amebiasis.
• Pleuropulmonary abscess
• brain abscess
• necrotic lesions on the perianal skin and genitalia have also been
observed
• Pneumonitis
• spleen

37. •Symptoms of Amebiasis
•diarrhea (which may be bloody)
•stomach pains.
•cramping.
•nausea.
•loss of appetite.
•fever.

39. Laboratory diagnosis
Microscopy method
Fresh stool: wet mounts
Molecular method: detection parasite DNA or RNA in feces
Immunologically methods:
Enzyme-linked immunosorbent assay (ELISA)
Indirect hemagglutination(IHA)
Gel Diffusion Precipitin (GDP)
Indirect Immunofluorescence (IIF)

40. Treatment
• Metronidazole (Flagyl) or tinidazole (Fasigyn) are used to treat Amebiasis.
If this does not work.
• Chloroquine. and dehydroemetine can be used.
• Eliminating cysts in carriers who do not have symptoms is accomplished
with diloxanide.
• Nitazoxanide is a newer drug that shows promise against not only E.
histolytica but many other parasites as well.

41. Prevention and control
• Uncontaminated water is essential.
• This may be accomplished by boiling or treating with iodine crystals
(the cyst is resistant to routine chlorination).
• Properly washing food products.
• Avoiding the use of human feces as fertilizer.
• Good personal hygiene and sanitation practices.
• Protection of food from flies and cockroaches.
• The avoidance of unprotected sexual practices.

42. Sources
1. CDC - DPDx – Amebiasis
Books:
1. Clinical parasitology a practical a pproach.
2. Essentials of Medical parasitology.

43. Thank you