DPDx is an education resource designed for health professionals and laboratory scientists. For an overview including prevention and control visit www.cdc.gov/parasites/schistosomiasis.
[Schistosoma haematobium] [Schistosoma intercalatum] [Schistosoma japonicum] [Schistosoma mansoni] [Schistosoma mekongi]
Microscopic identification of eggs in stool or urine is the most practical method for diagnosis. Stool examination should be performed when infection with S. mansoni or S. japonicum is suspected, and urine examination should be performed if S. haematobium is suspected. Eggs can be present in the stool in infections with all Schistosoma species. The examination can be performed on a simple smear (1 to 2 mg of fecal material). Since eggs may be passed intermittently or in small amounts, their detection will be enhanced by repeated examinations and/or concentration procedures (such as the formalin-ethyl acetate technique). In addition, for field surveys and investigational purposes, the egg output can be quantified by using the Kato-Katz technique (20 to 50 mg of fecal material) or the Ritchie technique. Eggs can be found in the urine in infections with S. haematobium (recommended time for collection: between noon and 3 PM) and with S. japonicum. Detection will be enhanced by centrifugation and examination of the sediment. Quantification is possible by using filtration through a Nucleopore® membrane of a standard volume of urine followed by egg counts on the membrane. Tissue biopsy (rectal biopsy for all species and biopsy of the bladder for S. haematobium) may demonstrate eggs when stool or urine examinations are negative.
Antibody detection can be useful to indicate schistosome infection in patients who have traveled in schistosomiasis endemic areas and in whom eggs cannot be demonstrated in fecal or urine specimens. Test sensitivity and specificity vary widely among the many tests reported for the serologic diagnosis of schistosomiasis and are dependent on both the type of antigen preparations used (crude, purified, adult worm, egg, cercarial) and the test procedure.
At CDC, a combination of tests with purified adult worm antigens are used for antibody detection. All serum specimens are tested by FAST-ELISA using Schistosoma mansoni adult microsomal antigen (MAMA). A positive reaction (greater than 9 units/µl serum) indicates infection with Schistosoma species. Sensitivity for S. mansoni infection is 99%, 95% for Schistosoma haematobium infection, and <50% for Schistosoma japonicuminfection. Specificity of this assay for detecting schistosome infection is 99%. Because test sensitivity with the FAST-ELISA is reduced for species other than S. mansoni, immunoblots of the species appropriate to the patient's travel history are also tested to ensure detection of S. haematobium and S. japonicum infections. Immunoblots with adult worm microsomal antigens are species-specific and so a positive reaction indicates the infecting species. The presence of antibody is indicative only of schistosome infection at some time and cannot be correlated with clinical status, worm burden, egg production, or prognosis. When submitting specimens, please include the patient's travel history so the appropriate Schistosoma species will be tested by immunoblot.
Tsang VC, Wilkins PP. Immunodiagnosis of schistosomiasis. Immunol Invest 1997;26:175-188.