Schistosomiasis Dr. Gamal Allam

Learning outcomes By the end of the lecture, you should be able to: 1- Mention Causal Agent of schistosomiasis. 2- Mention systematic position of Schistosoma spp. 3- Mention geographic distribution of schistosomiasis. 4- Enumerate Intermediate, Definitive and Reservoir hosts of Schistosoma spp. 6- Explain life cycle of Schistosoma spp. 7- Mention habitat of Schistosoma spp. 8- Mention mode of infection by Schistosoma spp. 9- Mention pathology and clinical features of schistosomiasis. 10- Diagnose schistosomiasis. 11- Mention prevention and control means of schistosomiasis Dr. Gamal Allam

Causal Agents Schistosomiasis is caused by digenetic blood trematodes. Three main species infecting humans: Schistosoma haematobium Schistosoma mansoni Schistosoma japonicum Dr. Gamal Allam

Systematic position Phylum: Platyhelminthes Class: Termatoda Genus: Schistosoma (S.) 5 species of can infect human: S. haematobium S. mansoni S. japonicum S. mekongi S. intercalatum Dr. Gamal Allam

Geographic Distribution Schistosoma mansoni is found in parts of South America and the Caribbean, Africa, and the Middle East. Schistosoma haematobium in Africa and the Middle East. Schistosoma japonicum in the Far East.  Dr. Gamal Allam

Geographic Distribution…… cont. Schistosoma mansoni S. haematobium Dr. Gamal Allam

Morphology of Schistosoma Stages Adult, Egg, Miracidium, Sporocyst, Cercaria, Schistosomule Dr. Gamal Allam

Adult Worm Separate sex( male and female worms) The male has a gynecophoric canal in which it carries the female during the life cycle. 10-20 mm long. Dr. Gamal Allam

Egg S. haematobium S. mansoni S. japonicum Oval (S. haematobium & S. mansoni) or Round (S. japonicum) Translucent Contains mature miracidium With terminal spine (S. haematobium), lateral spine (S. mansoni), or rudimentary lateral spine (S. japonicum) S. haematobium S. mansoni S. japonicum (110-170 x 40-70µm) (115-175 x 45-70µm) (70-100 x 50-70µm) Dr. Gamal Allam

Miracidium Pyriform Ciliated ~200µm long Dr. Gamal Allam

Sporocyst Sac- like Contain germinal cells masses Dr. Gamal Allam

Cercaria Has a body and tail Has furcocercous ( forked) tail 400-600µm long Dr. Gamal Allam

Life Cycle In human(Definitive host), male & female mature and pair up in the liver. The couple migrate against the blood stream direction to favoured site where female deposit eggs: mainly mesenteric venules of large bowel & rectum (S. mansoni), mesenteric venules of small intestine (S. japonicum), or pelvic and vesical venous plexus (S. haematobium). About 50% of deposited eggs passed out of body and 50% trapped in tissues. Eggs are released with feces (S. mansoni & S. japonicum) or urine (S. haematobium) . Dr. Gamal Allam

Life Cycle…. cont In fresh water and under optimal conditions the eggs hatch and release miracidia, which swim and penetrate specific snail intermediate hosts: Biomphalaria sp. (S. mansoni), Bulinus sp. (S. haematobium), or Oncomelania sp. (S. japonicum) In the snail (intermediate host) asexual replication occur including 2 generations of sporocysts and the production of cercariae. Upon release from the snail, cercariae (the infective stage) swim, penetrate the skin of the human host , and shed their forked tail, becoming schistosomulae (Skin schistosomulae). Dr. Gamal Allam

Life Cycle…. cont The schistosomulae migrate through blood vessel to the lungs (lung schistosomulae ) and then to the liver which mature to adult worm. Adult worms in humans reside in the mesenteric venules in various locations, which at times seem to be specific for each species as mentioned previously . The females deposit eggs in the small venules of the portal and perivesical systems. The eggs are moved progressively toward the lumen of the intestine (S. mansoni and S. japonicum) and of the bladder and ureters (S. haematobium), and are eliminated with feces or urine, respectively . Dr. Gamal Allam

Life Cycle Dr. Gamal Allam

Intermediate and Reservoir hosts Intermediate host Reservoir hosts S. mansoni Biomphalaria rodents and monkeys S. haematobium Bulinus ------------------ S. japonicum Oncomelania dogs, cats, rodents, pigs, and goats. Dr. Gamal Allam

Clinical Features Acute schistosomiasis (Katayama's fever) occur weeks after the initial infection, especially by S. mansoni and S. japonicum. Manifestations include: fever, cough, abdominal pain and diarrhea, hepatospenomegaly, eosinophilia. Dr. Gamal Allam

Clinical Features…..cont. Chronic infection cause granulomatous reactions and fibrosis in the affected organs, which may result in manifestations that include: colonic polyposis with bloody diarrhea (S. mansoni). portal hypertension with hematemesis and splenomegaly (S. mansoni, S. japonicum); cystitis and ureteritis with hematuria, which can progress to bladder cancer (S. haematobium). pulmonary hypertension (S. mansoni, S. japonicum) glomerulonephritis (S. haematobium). may central nervous system lesions. Dr. Gamal Allam

Hepatic granuloma Dr. Gamal Allam

Clinical Features…..cont. Dr. Gamal Allam

Laboratory Diagnosis Microscopic identification of eggs in stool or urine is the most practical method for diagnosis. Stool examination should be performed when infection with S. mansoni or S. japonicum is suspected. Urine examination should be performed if S. haematobium is suspected. Dr. Gamal Allam

Eggs of Schistosoma spp. S. haematobium Schistosoma mansoni Dr. Gamal Allam

Schistosoma japonicum eggs Dr. Gamal Allam

Prevention and Control Avoidance of wading, bathing, swimming in or drinking polluted water. Wearing protective clothes (gloves, boots........). Quick and through drying of exposed skins. Abstinence from defecation and micturation in water canals. Mass treatment of all infected cases. Control of Snail ( intermediate host) through: Physical methods : changing the suitable environmental conditions like canal coverage Biological methods :introduction of natural enemies as competitive snails or fish Chemical methods using molluscicides eg: copper sulphate Dr. Gamal Allam

1-Infective stage of Schistosoma is Furcocercus cercaria 2- Bulinus trancatus snail is the intermediate host of Schistosoma mansoni 3- One of the following parasite live in blood Dr. Gamal Allam

Thank You Dr. Gamal Allam