Schistosomes Flashcards
Explain the life cycle of Schistosomes
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”
What animal is the intermediate host for Schistosoma mansoni?
Non-segmented, specific snails
What are the clinical manifestations of “swimmer’s itch”? Or dermatitis?
Penetrating cercariae
- papular pruritic rash (minor)
What are the clinical manifestations of Acute Schistosomiasis (Katayama fever)
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
What are the clinical manifestations of chronic schistosomiasis?
Mature worms, heavy egg deposition
- fatigue, abdominal pain, diarrhea, hepatomegaly (enlarged liver), hematuria (blood in urine) hematemesis (cough up blood)
How do you diagnose schistosomiasis?
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
How do you treat Schistosomes? (flat or fluke)
PRAXIQUANTEL for all species – only actually treats active infection, not late sequelae
- consult ID
How do you prevent Schistosomes?
- Avoid fresh water swimming in endemic areas.
- Rapid/vigorous toweling ???
- Reduce snail population (probably not)
- better sanitation
What regions are endemic to schistosomes?
Africa, South America, the Caribbean, Middle East, and Asia
How many people are infected with schistosomiasis? (According to MedScape)
207 million people, 85% of whom live in Africa are infected
What is the infectious larvae form known as?
Cercariae - free swimming
How can a chronic reaction occur?
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.
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