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Questions and Answers
What is the primary method to prevent schistosomiasis infection?
What is the primary method to prevent schistosomiasis infection?
Which of the following is a chemical method used to control the snail host of schistosomiasis?
Which of the following is a chemical method used to control the snail host of schistosomiasis?
Which of the following describes a mode of infection by Schistosoma spp.?
Which of the following describes a mode of infection by Schistosoma spp.?
What role do intermediate hosts play in the life cycle of Schistosoma spp.?
What role do intermediate hosts play in the life cycle of Schistosoma spp.?
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What is the main pathogenic effect of schistosomiasis on the human body?
What is the main pathogenic effect of schistosomiasis on the human body?
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Which stage of Schistosoma is infective to the human host?
Which stage of Schistosoma is infective to the human host?
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What is the primary intermediate host in the life cycle of Schistosoma?
What is the primary intermediate host in the life cycle of Schistosoma?
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What type of reaction occurs due to chronic schistosomiasis?
What type of reaction occurs due to chronic schistosomiasis?
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Which symptom is associated with acute schistosomiasis?
Which symptom is associated with acute schistosomiasis?
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Which species of Schistosoma is associated with bladder cancer?
Which species of Schistosoma is associated with bladder cancer?
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What is the initial site of infection for cercariae in humans?
What is the initial site of infection for cercariae in humans?
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Which diagnostic method is used for identifying Schistosoma eggs?
Which diagnostic method is used for identifying Schistosoma eggs?
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What is one of the potential complications of chronic S. mansoni infection?
What is one of the potential complications of chronic S. mansoni infection?
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What is the primary causal agent of schistosomiasis?
What is the primary causal agent of schistosomiasis?
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Which Schistosoma species is primarily found in the Middle East?
Which Schistosoma species is primarily found in the Middle East?
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What is notable about the male Schistosoma during its life cycle?
What is notable about the male Schistosoma during its life cycle?
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Which of the following eggs is characterized by having a terminal spine?
Which of the following eggs is characterized by having a terminal spine?
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What is the length of the cercaria in the life cycle of Schistosoma?
What is the length of the cercaria in the life cycle of Schistosoma?
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Which of the following is the primary habitat where female Schistosoma deposit their eggs?
Which of the following is the primary habitat where female Schistosoma deposit their eggs?
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Which snails serve as intermediate hosts for Schistosoma japonicum?
Which snails serve as intermediate hosts for Schistosoma japonicum?
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Inside the host, where do female Schistosoma primarily deposit their eggs?
Inside the host, where do female Schistosoma primarily deposit their eggs?
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Study Notes
Schistosomiasis
- Caused by digenetic blood trematodes: Schistosoma spp.
- Five species infect humans:
- S. haematobium
- S. mansoni
- S. japonicum
- S. mekongi
- S. intercalatum
- Phylum: Platyhelminthes
- Class: Trematoda
- Genus: Schistosoma
Morphology of Schistosoma Adult Worm
- Separate sexes (male and female)
- Male has a gynecophoric canal to carry female
Morphology of Schistosoma Eggs
- 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)
Morphology of Miracidium
- Pyriform
- Ciliated
Intermediate Hosts of Schistosomes
- S. mansoni: Biomphalaria sp.
- S. haematobium: Bulinus sp.
- S. japonicum: Oncomelania sp.
Intermediate and Reservoir Hosts
| Schistosoma Species | Intermediate Host | Reservoir Hosts |
|---|---|---|
| S. mansoni | Biomphalaria | Rodents and monkeys |
| S. haematobium | Bulinus | |
| S. japonicum | Oncomelania | Dogs, cats, rodents, pigs, and goats |
Sporocyst
- Sac-like
- Contain germinal cell masses
Cercaria
- Has a body (head) and tail
- Has furcocercous (forked) tail
Life Cycle
- Cercariae migrate through circulatory system, pair in liver capillaries
- Migrate to favored site (mesenteric venules of large bowel, mesenteric venules of small intestine, or pelvic/vesical venous plexus).
- 50% of eggs are passed out of body, 50% are trapped in tissues.
- Eggs released with feces (S. mansoni & S. japonicum) or urine (S. haematobium)
- Eggs hatch in water, release miracidia (penetrate snails)
- Asexual reproduction in snail (sporocysts → cercariae)
- Cercariae penetrate human skin → schistosomula → lungs → liver → adult worms
Infection
- Infective stage: Cercaria
- Infection route: Cutaneous
- Intermediate host(s): Snail
- Mode of Infection: Cercarial penetration of the skin
- Infection sites:
- Mesenteric venules of large bowel & rectum (S. mansoni)
- Mesenteric venules of small intestine (S. japonicum)
- Pelvic & vesical venous plexus (S. haematobium)
Clinical Features
- Acute schistosomiasis (Katayama's fever): Occurs weeks after infection (especially S. mansoni & S. japonicum) due to sudden egg release, symptoms include fever, cough, abdominal pain, diarrhea, hepatosplenomegaly, eosinophilia.
-
Chronic schistosomiasis: Granulomatous reactions and fibrosis in affected organs, resulting in:
- Colonic polyposis (small clumps of cells on colon lining), with bloody diarrhea (S. mansoni)
- Portal hypertension, with hematemesis (vomiting of blood) and splenomegaly (S. mansoni & S. japonicum)
- Cystitis (bladder inflammation), ureteritis, hematuria, and possibly bladder cancer (S. haematobium)
- Pulmonary hypertension (S. mansoni & S. japonicum)
- Glomerulonephritis (kidney inflammation) (S. haematobium)
- Central nervous system lesions
Laboratory Diagnosis
- Microscopic identification of eggs in stool (S. mansoni or S. japonicum) or urine (S. haematobium)
Prevention and Control
- Avoiding contaminated water (wading, bathing, swimming, drinking)
- Protective clothing (gloves, boots)
- Quick drying of exposed skin
- Avoiding defecation/urination in canals
- Treatment/control of all infected cases in affected areas
- Controlling snails (physical, biological, and chemical methods)
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Description
Test your knowledge on Schistosomiasis, a disease caused by the Schistosoma species. This quiz covers the species infecting humans, their geographic distribution, and the morphology of adult worms and eggs. Challenge yourself with questions about this important parasitic infection.
