Schistosomes Flashcards

1
Q

Explain the life cycle of Schistosomes

A

Free swimming cercariae

  • gets into blood supply to liver portal vein and then to mesenteric veins on to the small intestine, colon or bladder
  • coat themselves with plasma protein to appear “self”
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2
Q

What animal is the intermediate host for Schistosoma mansoni?

A

Non-segmented, specific snails

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3
Q

What are the clinical manifestations of “swimmer’s itch”? Or dermatitis?

A

Penetrating cercariae

- papular pruritic rash (minor)

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4
Q

What are the clinical manifestations of Acute Schistosomiasis (Katayama fever)

A

Large # of worms
Worms mature and deposit eggs
- fever, cough, hepatosplenomegaly, lymphadenopathy (serum sickness) with immune complex formation against egg Ag’s
- Eosinophils in blood due to tissue invasion
- generally resolves

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5
Q

What are the clinical manifestations of chronic schistosomiasis?

A

Mature worms, heavy egg deposition
- fatigue, abdominal pain, diarrhea, hepatomegaly (enlarged liver), hematuria (blood in urine) hematemesis (cough up blood)

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6
Q

How do you diagnose schistosomiasis?

A

Index of suspicion in those who have a travel history and fresh water swimming, rash, etc. Would be common in those areas

  • eggs in stool or urine – quantify, repeat, concentrate if necessary
  • Ab detection– check with CDC
  • Eosinophilia (blood count) – not diagnostic, but suggestive if other things line up
  • tissue bx may demonstrate eggs if stool/urine are negative
    • bladder (S. haematobium)
    • rectal for other species
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7
Q

How do you treat Schistosomes? (flat or fluke)

A

PRAXIQUANTEL for all species – only actually treats active infection, not late sequelae
- consult ID

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8
Q

How do you prevent Schistosomes?

A
  • Avoid fresh water swimming in endemic areas.
  • Rapid/vigorous toweling ???
  • Reduce snail population (probably not)
  • better sanitation
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9
Q

What regions are endemic to schistosomes?

A

Africa, South America, the Caribbean, Middle East, and Asia

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10
Q

How many people are infected with schistosomiasis? (According to MedScape)

A

207 million people, 85% of whom live in Africa are infected

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11
Q

What is the infectious larvae form known as?

A

Cercariae - free swimming

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12
Q

How can a chronic reaction occur?

A

Liver/intestines/bladder chronic inflammation with granuloma due to secondary reaction of tissues to eggs.
- can cause fibrosis/cirrhosis leading to portal hypertension or polyps/diarrhea if in the colon
- ascites (accumulation of fluid in the peritoneal cavity)
- eggs can lodge in lungs, spinal cord, etc.
Sc

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