Schistosomiasis Overview Quiz

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Questions and Answers

What is the primary method to prevent schistosomiasis infection?

  • Frequent bathing in contaminated areas
  • Avoiding exposure to polluted water (correct)
  • Using infected water for irrigation
  • Drinking untreated water

Which of the following is a chemical method used to control the snail host of schistosomiasis?

  • Covering water canals
  • Altering pH levels of the water
  • Using copper sulphate (correct)
  • Biological introduction of fish

Which of the following describes a mode of infection by Schistosoma spp.?

  • Contaminated soil exposure
  • Ingestion of infected food
  • Airborne transmission
  • Direct contact with infected water (correct)

What role do intermediate hosts play in the life cycle of Schistosoma spp.?

<p>They provide an environment for larval development. (A)</p> Signup and view all the answers

What is the main pathogenic effect of schistosomiasis on the human body?

<p>Increased organ size due to inflammation (C)</p> Signup and view all the answers

Which stage of Schistosoma is infective to the human host?

<p>Cercaria (D)</p> Signup and view all the answers

What is the primary intermediate host in the life cycle of Schistosoma?

<p>Snail (C)</p> Signup and view all the answers

What type of reaction occurs due to chronic schistosomiasis?

<p>Granulomatous reactions (B)</p> Signup and view all the answers

Which symptom is associated with acute schistosomiasis?

<p>Cough (D)</p> Signup and view all the answers

Which species of Schistosoma is associated with bladder cancer?

<p>S. haematobium (B)</p> Signup and view all the answers

What is the initial site of infection for cercariae in humans?

<p>Skin (A)</p> Signup and view all the answers

Which diagnostic method is used for identifying Schistosoma eggs?

<p>Microscopic examination of stool (D)</p> Signup and view all the answers

What is one of the potential complications of chronic S. mansoni infection?

<p>Colonic polyposis (D)</p> Signup and view all the answers

What is the primary causal agent of schistosomiasis?

<p>Schistosoma spp. (C)</p> Signup and view all the answers

Which Schistosoma species is primarily found in the Middle East?

<p>Schistosoma haematobium (A)</p> Signup and view all the answers

What is notable about the male Schistosoma during its life cycle?

<p>It carries the female in a gynecophoric canal. (D)</p> Signup and view all the answers

Which of the following eggs is characterized by having a terminal spine?

<p>S. haematobium (B)</p> Signup and view all the answers

What is the length of the cercaria in the life cycle of Schistosoma?

<p>400-600µm (A)</p> Signup and view all the answers

Which of the following is the primary habitat where female Schistosoma deposit their eggs?

<p>In mesenteric venules of large bowel and rectum (D)</p> Signup and view all the answers

Which snails serve as intermediate hosts for Schistosoma japonicum?

<p>Oncomelania sp. (A)</p> Signup and view all the answers

Inside the host, where do female Schistosoma primarily deposit their eggs?

<p>The pelvic and vesical venous plexus (C)</p> Signup and view all the answers

Flashcards

Schistosomiasis causal agent

Blood fluke (trematode) species of the Schistosoma genus.

Schistosoma Species

5 species infect humans: S. haematobium, S. mansoni, S. japonicum, S. mekongi, and S. intercalatum.

Intermediate Host (Snails)

Specific snail species are needed for the parasite's life cycle. Examples are Biomphalaria, Bulinus, and Oncomelania.

Miracidium

Free-swimming larval stage of the parasite that infects the snail.

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Cercaria

Infective larval stage that penetrates human skin.

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Definitive host

The human host in the life cycle where the adult parasites live.

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Egg Deposition Site

Different Schistosoma species deposit eggs in different locations in the human body (e.g. intestines etc.).

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Adult Worm

Adult flukes have separate sexes and live in human blood vessels.

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Schistosoma Life Cycle

The Schistosoma parasite has a complex life cycle involving two hosts: a snail (intermediate host) and a human (definitive host). It starts with eggs released in human feces or urine, which hatch into miracidia that infect snails. Inside the snail, the parasite develops into cercariae that leave the snail and penetrate human skin.

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Schistosomiasis Transmission

People get infected with schistosomiasis by coming into contact with water contaminated with cercariae. These are the larval stage of the parasite that can penetrate human skin.

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Schistosomiasis Symptoms

Symptoms of schistosomiasis vary depending on the organism and severity of infection. Some individuals experience mild symptoms, while others develop more serious complications like liver damage or bladder cancer.

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Schistosomiasis Diagnosis

Diagnosis of schistosomiasis is done through microscopic examination of stool or urine samples to find Schistosoma eggs. Serological tests are also used to detect the presence of antibodies to the parasite.

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Schistosomiasis Prevention

Prevention of schistosomiasis involves preventing contact with contaminated water. This can be done by wearing protective clothing, avoiding swimming or wading in contaminated water and using safe water sources.

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Schistosomiasis Infection Route

Cercariae penetrate human skin, entering the bloodstream.

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Schistosomiasis Life Cycle Stages

The parasite goes through multiple stages, including miracidia, cercariae, and adult worms.

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Schistosomiasis: What are the eggs doing?

Eggs are released into the environment through feces or urine.

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Acute Schistosomiasis: What causes it?

Acute symptoms occur when a large number of eggs are released in the body, causing an inflammatory response.

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What is 'Katayama's Fever'?

This is a name for the acute symptoms of schistosomiasis, especially seen in S. mansoni and S. japonicum infections.

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Schistosomiasis: Chronic Complications

Long-term infections can lead to organ damage and fibrosis due to egg accumulation.

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Schistosomiasis: How are eggs diagnosed?

Eggs are identified in stool (S. mansoni, S. japonicum) or urine (S. haematobium) through microscopic examination.

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Schistosomiasis: What are some complications?

Long-term infections can cause symptoms like bloody diarrhea, liver damage, bladder inflammation, and even cancer.

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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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Lecture 9: Schistosomiasis PDF

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