M

1. Parasites Infecting Gastro-Intestinal Tract

2. Parasites of Small Intestine
Cystoda of Small Intestine:
• Diphylobothrium latum
• Taenia saginata
• Taenia solium
• Hymenolepis nana
• Hymenolepis diminuta
• Dipylidium caninum
Trematoda of Small Intestine:
• Heterophyes heterophyes
Nematoda of Small Intestine:
• Ascaris lumbricoides
• Ancylostoma duodenale
• Strongyloides stercolaris
• Capillaria philippinensis
• Trichostrongylus colubriformis
• Trichinella spiralis
Protozoa of Small Intestine:
• Giardia lamblia
• Cryptosporidium
• Isospora belli
• Cyclospora cayetanensis
• Intestinal Microsporidia

3. Classification of Protozoa according to their effect on
the body of the patient
• Pathogenic protozoa:
Protozoa that exist in human body and cause harm to infected human.
• Commensal protozoa:
Protozoa that exist human body but does not cause harm to infected human.
• Opportunistic protozoa:
weak protozoa that cause minimal effect to infected healthy man but has severe effect
on infected immunocompromized man.
• Potentially pathogenic free-living protozoa:
free-living in nature away from man but some of them may cause disease if they enter
the human body by certain route.

4. Intestinal Protozoa
Entamoeba histolytica
Balantidium coli
Giardia lamblia
Cryptosporidium parvum
Isospora belli
Cyclospora cayetanensis
Intestinal Microsporidia
Pathogenic
Opportunistic
Large intestine
Small intestine

5. Giardia lamblia

6. By the end of this lecture, you will be able to recognize Giardia lamblia
regarding its:
 Geographical distribution
 Life cycle
 Mode of infection
 Pathogenesis
 Clinical picture
 Diagnosis
 Treatment
 Epidemiology
 Prevention and control
Objectives

7. Giardia lamblia
Geographical Distribution: cosmopolitan, warm climate
Reservoir host: rodents, rats & beavers
Cyst
Trophozoite
• A flagellate pathogenic intestinal protozoan parasite.
• Causes Giardiasis
• More common in children.

8. Giardia lamblia Life Cycle
Ingestion of Giardia lamblia cyst:
1- In contaminated food or water
2- Through flies & food handlers
3- Faeco-oral route (hand to
mouth)
External Autoinfection
Mode of infection
Infected Man
Giardia cyst
Definitive host
Infective stages
Giardia Cyst & Trophozoite
Diagnostic stages
Duodenum, upper part
of small intestine, bile
ducts and gall bladder
Habitat
Longitudinal Binary fission

9. Pathogenesis & Clinical Picture
Trophozooites feed on mucus secretions
• Epigastric pain, anorexia, nausea and vomiting
• Digestive disturbances: diarrhea, flatulence
• Stool is voluminous, foul smelling, light in color and greasy, no blood
• Traveler's diarrhea
I) Uncomplicated symptomatic giardiasis:
• Attachment of trophozoites to the epithelial cells of duodenal and jejunal
villi by their ventral suckers hyperaemia and inflammation
I) Asymptomatic
Duodenitis & jejunitis and atrophy of villi
• Interference with fat metabolism
malabsorption
steatorrhea

10. Pathogenesis and Clinical Picture
III) Complicated chronic giardiasis:
In immunocompromised patients as hypogammaglubinaemia,
decreased IgA in small intestine, decreased gastric acidity or
achlorohydia
Severe manifestations
Persistent diarrhea, steatorrhea, Fatty dyspepsia
hypoproteinaemia, deficiency of fat soluble vitamins (vit. A, D, E, K), folic acid
Chronic malabsorption syndrome
Stunted growth
Cholangitis, cholecystitis
jaundice
Biliary colic

11. Pathogenesis and Clinical Picture
Attachment of trophozoites by their ventral suckers

12. Diagnosis
Clinically
Laboratory
Direct stool examination:
• Trophozoites are detected in diarrhoeic stool
• Cysts are detected in formed stool
Repeated stool examination is recommended
Serological tests:
• Copro-antegin detection
• Antibodies detection is of limited value

13. Diagnosis (cont.)
3- string test (enterotest)
For detection of giardia trophozoites in duodenal fluid
using microscope

14. Treatment
Metronidazole

15. Prevention and Control