Schistosomiasis

Q: A 19-year-old male arrives with his family as a refugee from Sudan, and as part of an initial health assessment he is found to have a positive titre (1:640) for schistosomiasis antibody.

What further tests are required in the follow-up of this case and what are the possible clinical sequelae?

A: Despite successful eradication campaigns in some regions (notably Japan), the global burden of schistosomiasis has remained unchanged for the last few decades.

The two major human pathogens in Africa are Schistosoma mansoni and Schistosoma haematobium – with the latter predominating. Schistosomiasis is a notifiable disease in Australia.

This man’s test result is indicative of schistosoma infection but is not predictive of either disease or intensity of infection. He requires a thorough clinical evaluation to determine gastrointestinal or hepatic disease (S. mansoni) or genitourinary disease (S. haematobium).

Serology does not differentiate the infecting species. Most available assays use S. mansoni adult worm antigens (therefore some infections with S. haematobium and S. japonicum can be missed by serology).

Further parasitological investigations are therefore essential. This includes:

1. Three faecal specimens. Microscopy of concentrated specimens may demonstrate the typical S. mansoni eggs.

2. Three urine specimens are necessary for microscopy to identify S. haematobium eggs. Terminal urine is preferred, and is best collected between 1200 and 1400h. It is essential to inform the laboratory that a diagnosis of schistosomiasis is being considered, as “routine” urine microscopy may be falsely negative.

3. Biopsy of intestinal or bladder mucosa may be diagnostic in patients with clear disease syndromes that have negative parasitological investigations.

4. Serum creatinine and aminotransferase concentrations provide additional supporting evidence.

5. Ultrasound examinations of the liver and upper urinary tract are crucial to determine the presence of fibrosis in the liver, ureters or bladder and exclude ureteric obstruction.

Praziquantel is the only treatment available for schistosomiasis and is curative. Determination of the infecting species facilitates prescription of the correct dose. Reinfection will not occur unless the patient travels to an endemic area.

A proactive clinician would attempt to identify schistosomiasis in the family members of the index case.

Dr Paul Benedict Bartley is a Fellow of the Royal College of Pathologists of Australasia.