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

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

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

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

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

DR. RAAFAT MOHAMED

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

Cryptosporidium 80% 20% DR. RAAFAT MOHAMED

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

DR. RAAFAT MOHAMED

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

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

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

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

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

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

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

DR. RAAFAT MOHAMED

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

Isospora belli in intestine Oocysts in faeces DR. RAAFAT MOHAMED

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

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

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

Microsporidia Polar Filament Injects Sporoplasm DR. RAAFAT MOHAMED