Protozoa: Entamoeba, Giardia

Protozoa: Entamoeba, Giardia
Dr. Amal Abdul-Rasheed El-Moamly


Objectives:
• Describe the life cycle of Entamoeba histo& Giardia. 
• Describe the infective stage, the diagnostic stage , the mode of infection, and the habitat of both protozoal parasites.
• Describe the pathological changes, clinical manifestations, and complications of both parasites.
• Determine the main diagnostic methods of both parasites.
• List the drugs used in the treatment of both parasites.
• Explore the strategy for prevention and control. 

Introduction
• Protozoa: Unicellular organisms (one-cell).
• Each protozoa is made of cytoplasm and nucleus.
• Nucleus function: reproduction.
• Cytoplasm functions: nutrition, respiration, excretion, protection, locomotion.
• Locomotion:
    - Pseudopodia: Amoeba    - Flagella: Giardia& Trichomonas, leishmania   - Cilia: Blantidium coli

Introduction
• In this year we will study the following protozoal parasites:
1. Entamoeba histolytica
2. Giardia
3. Malaria
4. Leishmania
5. Cryptosporidium

Introduction
     
Amebiasis:Entamoeba histolytica

Amebiasis: Entamoeba histolytica
• Parasitic Amoeba can be:
1. Pathogenic Amoeba: Entamoeba histolytica.
2. Non-pathogenic: e.g. Entamoeba coli

Entamoeba histolytica
Life 
Cycle

Life Cycle
• Infection occurs by ingestion of mature cysts in fecally contaminated food, water, or hands. 
• Cysts excyst in the intestine and trophozoites   are released.
• The trophozoites multiply by binary fission in large intestine and produce cysts.
• Some trophozoites  pass through the blood stream to extra-intestinal organs.   

Life Cycle
• Both stages (cysts and trophozoites) are passed in the feces. Cysts (in formed stool), trophozoites (in diarrheal stool).
• Trophozoites passed in the stool are destroyed outside the body.
• Ingestion of mature cysts infect  human. 


Life Cycle
• Infective stage: Mature cyst (contains 4 nuclei)
• Diagnostic stage: Cyst and trophozoite in the stool.
• Habitat: Large intestine.
• Mode of Infection: ingestion of mature cysts   in fecally contaminated food, water, or hands.
• No Intermediate host. 

Pathology
• In many cases, the trophozoites remain confined to the intestinal lumen (noninvasive infection) : asymptomatic carriers, passing cysts in their stool.
•   In some patients the trophozoites invade the intestinal mucosa (intestinal disease), or, through the bloodstream, extraintestinal sites such as the liver, brain, and lungs
    (extra-intestinal disease)    

Clinical features:
• Asymptomatic infection (luminal amebiasis).
• Invasive intestinal amebiasis (amebic dysentery, colitis, appendicitis, toxic megacolon, amebomas).
• Invasive extraintestinal amebiasis (liver abscess, peritonitis, pleuropulmonary abscess, cutaneous and genital amebic lesions).

Lab diagnosis
• Microscopic detection of cysts and trophozoites in the stool.
• E. histolytica cyst and trophozoites should be differentiated from other non-pathogenic Amoeba such as E. coli.

• Antibody and antigen-detection tests.

Lab diagnosis
E. histolytica trophozoites, 1 nucleus, cytoplasm with pseudopodia, moving organism
 
Lab diagnosis
E.coli cyst ( non-pathogenic): >4 nuclei up to 8 nuclei
E. histolytica cyst: 1-4 nuclei, Cigar-shaped chromatoid bodies
   
Treatment
• Metronidazole (Flagyl): kill lumin and tissue parasites
• Furamide: kill only luminal parasite.

Prevention and Control
• Avoid contaminated food and drink.
• Avoid uncleaned street food.
• Control of flies and other insects as cockroaches.
• Safe water supply and sewage disposal.
• Don’t use human feces as fertilizers.
• Examination and treatment of food handlers. 

Giardiasis 

Life Cycle

Life Cycle
• Infection occurs by the ingestion of cysts in contaminated water, food, or by the fecal-oral route.
• In the small intestine, excystation releases trophozoites (each cyst produces two trophozoites)  .  
• Trophozoites multiply by longitudinal binary fission, remaining in the lumen of the proximal small intestine.
• Some trophozoites form cysts.
• Both trophozoites and cysts appear in the stool.

Pathology & clinical features
• The disease varies from asymptomatic carriage to severe diarrhea and malabsorption.  
•   Symptoms include diarrhea, abdominal pain, bloating, nausea, and vomiting.  
• In chronic giardiasis the symptoms are recurrent and malabsorption, weight loss and debilitation may occur. 
• Parasites may reach the biliary passage causing cholecystitis.

Life Cycle
• Infective stage: cyst (contains 4 nuclei)
• Diagnostic stage: Cyst and trophozoite in the stool.
• Habitat: small intestine.
• Mode of Infection: ingestion of cysts   in fecally contaminated food, water, or hands.
• No Intermediate host. 

Lab Diagnosis
• identification of cysts or trophozoites in the feces.
• Duodenal aspirate may reveal the parasite.
• Antigen detection in the stool. 

Lab Diagnosis
Trophozoites of Giardia: pear-shaped and measure 10-20 micrometers in length.  2 large nuclei are usually visible.  The sucking disks (used for attaching to the host’s mucosal epithelium), median bodies, and flagella (8) may also be seen. 
 
Lab Diagnosis
Giardia cysts: oval to ellipsoid and measure 10-14 µm.  Mature cysts have 4 nuclei, while immature cysts have two.  Nuclei and fibrils are visible. 
 
Treatment
• Metronodazole (Flagyl)

Prevention and Control
• Same as for Entamoeba histolytica

Thank You