1. Unicellular organisms
Protozoa
Unicellular organisms
Pathogenic protozoa:
Protozoa that exist in human body and cause harm to infected human (E.histolytica, G.lamblia, B.coli)
Commensal protozoa:
Protozoa that exist human body but does not cause harm to infected human ( e.g. E.coli, E.dispar, E.hartmanni)
Opportunistic protozoa:
weak protozoa that cause minimal effect to infected healthy man but has severe effect on infected immunocompromized man ( e.g. Cryptosporidium parvum)
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.
DR. RAAFAT MOHAMED

2. Cryptosporidium parvum
Cyclospora cayetanensis
Isospora belli
Causes cryptosporidiosis
Causes cyclosporiasis
Causes isosporiasis
Geog. Distribution: worldwide
Parasite takes the shape of oocyst containing sporozoites
Man is infected by ingestion of the sporulated oocyst
4-6µ
8-10µ
30X12µ
DR. RAAFAT MOHAMED

3. Infected human complains of watery diarrhoea
Habitat of Sporozoa
Small intestine
Affect epithelial cells
villi
Cryptosporidium
Sporozoite
Infected human complains of watery diarrhoea
Cyclospora
Isospora
DR. RAAFAT MOHAMED

4. Development of Cryptosporidium in human body
Thick-walled oocysts
Sporozoite attack brush border of epithelial cells
External autoinfection
Thin-walled oocysts
Internal autoinfection
Zygote ♂
Meront with merozoites ♀
gametocyte
Gametogony (sexual reproduction)
Merogony (asexual reproduction)
DR. RAAFAT MOHAMED

5. Mode of Infection with Cryptosporidium parvum
Ingestion of thick-walled oocysts:
In contaminated food or drink (called heteroinfection).
By faeco-oral route (hand to mouth) in already infected patient ( called external autoinfection).
Thin-walled oocysts in intestinal lumen of already infected patient causes internal autoinfection.
Thick-walled
Thin-walled
DR. RAAFAT MOHAMED

6. DR. RAAFAT MOHAMED

7. Life cycle of Cryptosporidium in human body
The sporozoites are released from the oocyst
Merogony and gametogony occur within the brush border of the infected cells
Meronts released merozoites which invade adjacent cells and repeat the cycle
Gametogony: micro and macrogametes are formed by some merozoite
Zygote is formed by fusion of gametes
Thin wall oocyst is formed(endogenous autoinfection)
Thick walled oocysts are excreted in stool
DR. RAAFAT MOHAMED

8. Cryptosporidium
80%
20%
DR. RAAFAT MOHAMED

9. Development of Cyclospora in human body
Sporozoite attack brush border of epithelial cells
Sporulated oocyst Infective stage
Unsporulated oocyst
Pass in stool of the patient
Zygote ♂ ♀
merozoites
gametocyte
Autoinfection DOES NOT occur
DR. RAAFAT MOHAMED

10. DR. RAAFAT MOHAMED

11. Development of Isospora in human body
Sporulated oocyst Infective stage
Sporozoite enters epithelial cells
Unsporulated oocyst
Pass in stool of the patient
Zygote ♂ ♀
merozoites
gametocyte
Autoinfection MAY OCCUR
DR. RAAFAT MOHAMED

12. Cyclospora cayetanensis Isospora belli
Mode of Infection of
Cyclospora cayetanensis
Isospora belli
Ingestion of sporulated oocysts in contaminated food or drink.
Autoinfection DOES NOT occur
Autoinfection MAY occur
Pass out in patient’s stool
Sporulation occurs on the ground
Patient passes both unsporulated and sporulated oocysts in stool
Unsporulated oocyst
DR. RAAFAT MOHAMED

13. Pathogenesis of Intestinal Sporozoa
Intestinal villi show:
Inflammatory changes
Atrophy
Crypt hyperplasia
In immunosuppressed patients
Dissemination of the parasite to:
Oesophagus, gall bladder, respiratory tract, urinary bladder
DR. RAAFAT MOHAMED

14. enterocyte Cryptosporidium Closely associated to the apical
plasma membrane in
PARASITOPHOROUS VACUOLE
DR. RAAFAT MOHAMED

15. Clinical Picture of Intestinal Sporozoa
In immunocompetent subject
Mild self-limited diarrhoea for 2 weeks
In children
Abdominal discomfort, diarrhoea, anorexia, fever, nausea, weight loss
In immunocompromized patient
Severe life-threatening diarrhoea, dehydration, malabsorption
DR. RAAFAT MOHAMED

16. Diagnosis of Cryptosporidium
Clinical picture: diarrhoea
Stool analysis is done by:
1- Direct smear method.
2- Concentration method using Shaether’s sugar floatation technique.
Oocysts are seen by:
- Staining stool smear with modified Ziehl Neelsen stain.
- Immunofluorescence assay.
Intestinal biopsy: to detect meronts and gamonts
Gamonts
Meronts
DR. RAAFAT MOHAMED

17. Diagnosis of Cyclospora & Isospora
Stool examination to detect unstained and stained oocysts
Unstained oocyst
Unsporulated Isospora
Sporulated Isospora
Cyclospora
Stained oocyst by MZN stain
Unsporulated Isospora
Sporulated Isospora
Cyclospora
DR. RAAFAT MOHAMED

18. DR. RAAFAT MOHAMED

19. Cyclospora cayetanensis
Oocysts in faeces
3-5 m
Cryptosporidium
8-10m
DR. RAAFAT MOHAMED

20. Isospora belli
in intestine
Oocysts in faeces
DR. RAAFAT MOHAMED

21. Epidemiology and Control
Treatment
Immunocompetent: self-limited
Immunocompromized:
Paromomycin (Cryptosporidium)
Trimethoprim + Sulphamethoxazole (Cyclo /Isospora)
Fluid and electrolyte replacement
Cryptosporidiosis is a zoonotic disease
Oocysts are highly resistant to chemicals
Faeco-oral infection occurs (external autoinfection)
Proper washing of green vegetables
Pure water supply
Epidemiology and Control
DR. RAAFAT MOHAMED

22. State True Or False
Cryptosporidium parvum produces severe watery diarrhoea in the immunocompetent patient.
Cryptosporidium parvum can be detected in stool only after staining stool smear by MZN stain.
Autoinfection may occur in isosporiasis.
Both unsporulated and sporulated Cyclospora oocysts are infective to man.
Cryptosporidiosis is a pure human disease.
Cryptosporidium sporozoites invade the brush border of epithelial cells lining the rectum.
False
True
True
False
False
False
DR. RAAFAT MOHAMED

23. Case
An AIDS patient developed severe watery diarrhoea with no mucus or blood. Stool examination showed no eggs of helminths. Diagnosis was confirmed by microscopic examination of stained stool smear by special stain.
a- What is (are) the revealed causative parasite (s)?
C.parvum, C.cyaetenensis, I.belli, Microsporidia.
b- Name the type of stain used to reveal the causative parasite (s)?
Modified Ziehl-Neelsen stain.
c- If the parasite could be transmitted by autoinfection, what would be your diagnosis?
C.parvum infection and may be I.belli infection.
DR. RAAFAT MOHAMED

24. Microsporidia
Polar Filament
Injects Sporoplasm
DR. RAAFAT MOHAMED