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Schistosoma Species - Schistosomiasis. ARUP Consult®. Retrieved November 04, 2024, https://arupconsult.com/content/schistosoma-species

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Schistosoma Species - Schistosomiasis

Last Literature Review: September 2024 Last Update:

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Jackson

Brian R. Jackson, MD, MS
Brian R. Jackson, MD, MS
Adjunct Professor of Pathology and Biomedical Informatics, University of Utah
Medical Director, Business Development, ARUP Laboratories

Schistosomiasis (also known as bilharziasis) is a parasitic tropical disease, found especially in sub-Saharan Africa, that causes substantial morbidity and mortality. In developed countries, the disease is typically seen in travelers returning from endemic areas or in previous residents of those areas.  Chronic infection is possible without treatment and may lead to increased risk of liver fibrosis or bladder cancer. Schistosomiasis is often asymptomatic, particularly in chronic disease. Laboratory testing strategies should be informed by careful review of travel and residence history, in addition to clinical evaluation. Schistosomiasis is generally diagnosed by detection of ova in stool and/or urine samples. Serology may also be useful in some situations, including for retrospective diagnosis. 

Quick Answers for Clinicians

Who should be tested for schistosomiasis?

Laboratory testing for schistosomiasis can be considered in patients with a history of travel to or residence in an endemic or high-risk area,  such as southern and sub-Saharan Africa. Individuals who have had contact with freshwater sources in these areas should be considered at risk for schistosomiasis.  Schistosomiasis may present with rash, fever, headache, myalgia, respiratory symptoms, and eosinophilia. When present, symptoms generally occur within 2-12 weeks of infection. However, it is not uncommon for patients to be asymptomatic in both acute and chronic disease. ,  Patients with possible exposure should be considered for testing, even in the absence of symptoms. 

Indications for Testing

Laboratory testing for schistosomiasis is appropriate in travelers returning from or previous residents of endemic areas, especially those exposed to contaminated fresh water. 

Laboratory Testing

Ova and Parasite Examination

Ova and parasite examination of stool or urine is the recommended laboratory test to diagnose schistosomiasis in most cases. Specimen type should be informed by the type of suspected schistosome, based on travel history.  Stool specimens are preferred when Schistosoma mansoni or S. japonicum is suspected, whereas urine specimens are preferred when testing for S. haematobium.  Because light or intermittent shedding of eggs is possible, multiple separate specimen collections and examinations are suggested. When repeat testing is negative but infection is still suspected, rectal tissue biopsy can be considered to identify the presence of Schistosoma eggs. 

Serology

Serology is useful for infections with a low parasite count, given that ova and parasite examination has particularly low sensitivity in such cases. Serology can also be used to provide a retrospective diagnosis of past schistosomiasis or to identify asymptomatic people who may have been exposed during travel and could benefit from treatment.  Serology cannot distinguish between past and current infection  and may be subject to cross-reactivity among members of the Schistosoma spp.  Additionally, serologic tests are generally not effective until 6-12 weeks after initial exposure. 

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References