Persistence of Schistosoma haematobium infection despite multiple courses of therapy with praziquantel.

A 7-year-old boy, who had returned to the United States in June 1991 after a 3-year stay in Malawi, was evaluated in October 1991 because of hematuria. He was excreting Schistosoma haematobium eggs and was treated with praziquantel (PZQ; approximately 40 mg/kg). He may have spit up < or = 30% of this dose, and a concomitant Giardia lamblia infection might have caused malabsorption of PZQ. Because of persistent excretion of viable eggs, he was retreated with PZQ in January and May 1992. Egg excretion was first quantified 2 months following his second course of PZQ; at that time it was 35 eggs per 10 mL of urine. He excreted viable eggs at least as late as October 1992, 5 months after his third PZQ course. Experimental administration of chemotherapy to hamsters infected with the S. haematobium strain demonstrated that it was susceptible to PZQ. Repeated courses of therapy with PZQ may be necessary to cure S. haematobium infection, and both parasite and host factors should be considered if infection persists.