Schistosoma: Difference between revisions
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Schistosoma
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==Background== |
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* Infection with a species of the genus ''Schistosoma'' |
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*Trematode (blood fluke) |
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== Species == |
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===Microbiology=== |
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* ''S. mansoni'': liver and gut |
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* ''S. haematobium'': GU/pelvis |
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* ''S. japonicum'': liver and gut |
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* ''S. mekongi'': Mekong basin |
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*Three main species affecting humans: |
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== Risk Factors == |
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**[[Schistosoma mansoni]]: liver and gut |
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**[[Schistosoma haematobium]]: GU/pelvis |
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**[[Schistosoma japonicum]]: liver and gut |
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*Also: [[Schistosoma mekongi]], [[Schistosoma intercalatum]], [[Schistosoma guineensis]], and case reports of hybrid schistosomes of cattle origin that can infect humans |
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*Non-human-host schistosomes (of birds and mammals) can cause [[cercarial dermatitis]] |
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===Risk Factors=== |
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* Fresh water exposure in endemic countries |
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*Fresh water exposure in endemic countries |
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== Clinical Presentation == |
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== |
=== Epidemiology === |
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{| class="wikitable" |
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!Region |
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!Species |
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!Seroprevalence in Migrants[[CiteRef::asundi2019pr]] |
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|- |
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|Latin America and the Caribbean |
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|[[Schistosoma mansoni]] (Brazil, Venezuela, Suriname, Caribbean) |
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|20% |
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|- |
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|Middle East and northern Africa |
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|[[Schistosoma haematobium]], [[Schistosoma mansoni]] (sporadic reports in Arabian Peninsula) |
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|6% |
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|- |
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|Sub-Saharan Africa |
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|[[Schistosoma mansoni]], [[Schistosoma haematobium]], [[Schistosoma intercalatum]] (DRC), [[Schistosoma guineensis]] (West Africa) |
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|24% |
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|- |
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|South Asia |
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|None |
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|0% |
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|- |
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|East Asia and the Pacific |
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|[[Schistosoma japonicum]] (China, Philippines, Sulawesi), [[Schistosoma mekongi]] (Cambodia, Laos) |
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|5% |
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|} |
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==Clinical Manifestations== |
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* Labs |
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** CBC, showing eosinophilia |
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** Schisto serology (only positive 6 weeks after infection) |
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** Egg detection in stool, urine, semen, or tissue biopsy |
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* Imaging |
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** Eggs can cause granulomatous disease in various organs |
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** Bladder polyps and obstruction may be seen on ultrasound |
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===Swimmer's Itch=== |
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== Management == |
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*Cercariae penetrate exposed skin and cause prickling sensation and occasionally urticaria, followed hours later by a macular rash |
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* Acute |
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*Caused by schistosomes that do not cause systemic illness |
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** Praziquantel 40mg/kg/d |
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*Common in Great Lakes region of North America, New England in the US, and other parts of North America and Europe |
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*** Can cause nausea, dizziness, and fever |
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* Chronic |
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** Prevention |
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== |
===Katayama Fever=== |
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*Syndrome of acute schistosomiasis that follows 4 to 8 weeks (range 2 to 12 weeks), after the flukes have migrated, developed into adults, and have started producing eggs |
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* Increased risk of squamous cell carcinoma, which increase with young age at infection, duration of infection, high burden of infection, and bladder wall fibrosis |
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*The syndrome represents a hypersensitivity reaction to the eggs produced by adult worms |
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*More common with [[Schistosoma japonicum]] and [[Schistosoma mansoni]], and less common with [[Schistosoma haematobium]] |
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*Symptoms include abrypt onset of fever, chills, fatigue, headache, myalgias, abdominal pain, diarrhea, and occasionally bloody stool |
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*Most also develop cough, dyspnea, chest pain, and diffuse infiltrates on chest x-ray |
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**Lung nodules contain granulomas around eggs |
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*Hepatomegaly, splenomegaly, and lymphadenopathy are common |
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*Eggs may not be seen in stool until later in the course of the disease |
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*Symptoms usually resolve within 2 to 10 weeks |
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*Can involve symptoms anywhere the worms migrate and deposit eggs: CNS, genital tract, and skin |
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**However, an induced small-vessel vasculitis can also cause neurological symptoms |
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===Chronic Schistosomiasis=== |
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{{DISPLAYTITLE:''Schistosoma'' species}} |
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[[Category:Parasites]] |
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*Can be asymptomatic or paucisymptomatic |
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*Chronic granulomatous inflammation causes weight loss, anemia, stunted growth |
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*[[Eosinophilia]] is common |
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=== Pulmonary Hypertension === |
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* Primarily [[Schistosoma mansoni]][[CiteRef::knafl2020sc]] |
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==Investigations== |
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*Labs |
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**CBC, showing eosinophilia |
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**Schistosoma serology (only positive 6 weeks after infection) |
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**Egg detection in stool, urine, semen, or tissue biopsy |
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*Imaging |
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**Eggs can cause granulomatous disease in various organs |
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**Bladder polyps and obstruction may be seen on ultrasound |
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== Diagnosis == |
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* Usually based on serology |
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** Can cross-react with other helminth co-infections, including [[trichinosis]] and [[filariasis]] |
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** Can remain positive and even fluctuate for years after cure[[CiteRef::yong2010lo]] |
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==Management== |
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*Acute |
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**[[Is treated by::Praziquantel]] 40mg/kg given over one day split into 3 doses |
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*Chronic |
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**[[Is treated by::Praziquantel]] 20-40 mg/kg or 40-60 mg/kg (if at risk for ''S. japonica'') |
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**Given over one day split into 3 doses |
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**May be repeated 6 weeks later, though this practice is not universal |
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**No role for test-of-cure serology |
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==Prognosis== |
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*Increased risk of squamous cell carcinoma, which increase with young age at infection, duration of infection, high burden of infection, and bladder wall fibrosis |
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{{DISPLAYTITLE:''Schistosoma''}} |
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[[Category:Protozoa]] |
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Latest revision as of 13:50, 18 November 2025
Background
- Trematode (blood fluke)
Microbiology
- Three main species affecting humans:
- Schistosoma mansoni: liver and gut
- Schistosoma haematobium: GU/pelvis
- Schistosoma japonicum: liver and gut
- Also: Schistosoma mekongi, Schistosoma intercalatum, Schistosoma guineensis, and case reports of hybrid schistosomes of cattle origin that can infect humans
- Non-human-host schistosomes (of birds and mammals) can cause cercarial dermatitis
Risk Factors
- Fresh water exposure in endemic countries
Epidemiology
| Region | Species | Seroprevalence in Migrants1 |
|---|---|---|
| Latin America and the Caribbean | Schistosoma mansoni (Brazil, Venezuela, Suriname, Caribbean) | 20% |
| Middle East and northern Africa | Schistosoma haematobium, Schistosoma mansoni (sporadic reports in Arabian Peninsula) | 6% |
| Sub-Saharan Africa | Schistosoma mansoni, Schistosoma haematobium, Schistosoma intercalatum (DRC), Schistosoma guineensis (West Africa) | 24% |
| South Asia | None | 0% |
| East Asia and the Pacific | Schistosoma japonicum (China, Philippines, Sulawesi), Schistosoma mekongi (Cambodia, Laos) | 5% |
Clinical Manifestations
Swimmer's Itch
- Cercariae penetrate exposed skin and cause prickling sensation and occasionally urticaria, followed hours later by a macular rash
- Caused by schistosomes that do not cause systemic illness
- Common in Great Lakes region of North America, New England in the US, and other parts of North America and Europe
Katayama Fever
- Syndrome of acute schistosomiasis that follows 4 to 8 weeks (range 2 to 12 weeks), after the flukes have migrated, developed into adults, and have started producing eggs
- The syndrome represents a hypersensitivity reaction to the eggs produced by adult worms
- More common with Schistosoma japonicum and Schistosoma mansoni, and less common with Schistosoma haematobium
- Symptoms include abrypt onset of fever, chills, fatigue, headache, myalgias, abdominal pain, diarrhea, and occasionally bloody stool
- Most also develop cough, dyspnea, chest pain, and diffuse infiltrates on chest x-ray
- Lung nodules contain granulomas around eggs
- Hepatomegaly, splenomegaly, and lymphadenopathy are common
- Eggs may not be seen in stool until later in the course of the disease
- Symptoms usually resolve within 2 to 10 weeks
- Can involve symptoms anywhere the worms migrate and deposit eggs: CNS, genital tract, and skin
- However, an induced small-vessel vasculitis can also cause neurological symptoms
Chronic Schistosomiasis
- Can be asymptomatic or paucisymptomatic
- Chronic granulomatous inflammation causes weight loss, anemia, stunted growth
- Eosinophilia is common
Pulmonary Hypertension
- Primarily Schistosoma mansoni2
Investigations
- Labs
- CBC, showing eosinophilia
- Schistosoma serology (only positive 6 weeks after infection)
- Egg detection in stool, urine, semen, or tissue biopsy
- Imaging
- Eggs can cause granulomatous disease in various organs
- Bladder polyps and obstruction may be seen on ultrasound
Diagnosis
- Usually based on serology
- Can cross-react with other helminth co-infections, including trichinosis and filariasis
- Can remain positive and even fluctuate for years after cure3
Management
- Acute
- Praziquantel 40mg/kg given over one day split into 3 doses
- Chronic
- Praziquantel 20-40 mg/kg or 40-60 mg/kg (if at risk for S. japonica)
- Given over one day split into 3 doses
- May be repeated 6 weeks later, though this practice is not universal
- No role for test-of-cure serology
Prognosis
- Increased risk of squamous cell carcinoma, which increase with young age at infection, duration of infection, high burden of infection, and bladder wall fibrosis
References
- ^ Archana Asundi, Alina Beliavsky, Xing Jian Liu, Arash Akaberi, Guido Schwarzer, Zeno Bisoffi, Ana Requena-Méndez, Ian Shrier, Christina Greenaway. Prevalence of strongyloidiasis and schistosomiasis among migrants: a systematic review and meta-analysis. The Lancet Global Health. 2019;7(2):e236-e248. doi:10.1016/s2214-109x(18)30490-x.
- ^ Daniela Knafl, Christian Gerges, Charles H. King, Marc Humbert, Amaya L. Bustinduy. Schistosomiasis-associated pulmonary arterial hypertension: a systematic review. European Respiratory Review. 2020;29(155):190089. doi:10.1183/16000617.0089-2019.
- ^ Michelle K. Yong, Carolyn L. Beckett, Karin Leder, Beverley A. Biggs, Joseph Torresi, Daniel P. O’Brien. Long‐Term Follow‐Up ofSchistosomiasisSerology Post‐Treatment in Australian Travelers and Immigrants. Journal of Travel Medicine. 2010;17(2):89-93. doi:10.1111/j.1708-8305.2009.00379.x.
