Schistosoma Japonicum - Diagnosis

Diagnosis

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.

Since the eggs of S. japonicum are small, concentration techniques may be required. Biopsies are mostly performed to test for chronic schistomiasis with no eggs. An ELISA test can be performed to test for antibodies specific to schistosomes. A positive result indicates a present or recent infection (within the past two years). Ultrasonographic examination can be performed to assess the extent of hepatic and spleen-related morbidity. The problems with immunodiagnostic methods are that 1) It is only positive a certain time after infection 2) They can cross interact with other helminthes infections.