High-dose or multi-day praziquantel for imported schistosomiasis? A systematic review

Schistosomiasis affects more than 260 million people worldwide, mostly in sub-Saharan Africa, where more than 280 000 deaths per year are estimated. In the past few years, the increasing flow of migrants from endemic areas and the upward number of international travels have caused the emergence of the disease also in non-endemic areas. A single course of praziquantel (PZQ) 40 mg/kg is the first-line treatment recommended by the World Health Organization, mainly based on clinical trials conducted in endemic countries. No trials have been performed in non-endemic areas.

We carried out a systematic review of case reports and case series published between 1956 and August 2017 on cases of chronic schistosomiasis (infection acquired >3 months before) diagnosed in non-endemic areas and treated with PZQ. Primary outcome was to assess the number of different therapeutic regimens deployed and their frequency of use, calculated as the number of reports for each regimen over the total number of included cases.

The final database included 99 case reports and 51 case series, for a total of 1433 patients. In 57 of the 150 records (38%) the administered treatment was different from the one recommended by the World Health Organization. The proportion of 'alternative' regimens included increased doses of PZQ (up to 80 mg/kg) and/or prolonged duration of treatment and/or doses repeated some days/weeks apart. About 50% of the records regarding Western short-term travellers reported a non-standard treatment.

This is the first complete catalogue of the published experience with PZQ outside of endemic areas in the situation where reinfection is not an issue. We found a wide heterogeneity of the therapeutic regimens reported. Multicenter clinical trials conducted in non-endemic areas and guidelines specifically addressing the treatment of imported cases of chronic schistosomiasis are needed.