Praziquantel has only limited effect against schistosomules,26 see more and if the infection is treated in the invasive phase, low cure rates can be expected. Grandiére-Pérez et al. studied the efficacy of praziquantel in patients recently exposed to schistosomiasis and found that early treatment could prevent development of symptoms of acute schistosomaisis but failed to prevent chronic

schistosomiasis in 17 of 18 patients.18 Doherty reports treating 16 patients with Katayama syndrome, 7 patients required further courses of praziquantel because of continuing symptoms, persisting eosinophilia and/or a subsequent rise in the antibody titer.27 In a study conducted by Rabello et al. patients were treated day 26 to 57 postexposure and at follow-up, viable ova were found in fecal samples from 4 of 18 patients,21 in spite of the fact that the sensitivity of microscopy of feces is relatively low, when the parasite burden is low. Roca et al. reports treating 14 traveler of whom 4 had Katayama syndrome and click here received a 3d course of praziquantel 40 mg/kg. Treatment

was repeated after 3 to 4 weeks. All patients were considered cured as ova could not be detected in feces 3 months after treatment.20 Drug resistance could be a cause of the observed high rate of treatment failure, but even though some studies have shown that schistosomes in certain areas have reduced sensitivity to praziquantel, clinically significant drug resistance has not been documented.28 In the studies summarized in Table 2, treatment failure occurred among traveler, who had acquired the infection in many different areas where occurrence of drug resistance has not been suspected. Studies conducted in endemic areas have generally shown higher cure rates than those found among traveler.29 This could be because of the use of less sensitive methods (ie, Kato-Katz

technique for fecal samples) when assessing results of treatment in endemic areas. Another explanation might be that host-immunity is an important factor for the efficacy of praziquantel in the treatment of schistosomiasis.7,30 The finding, that in endemic areas cure rates are higher in adults than in children,31 further supports this hypothesis. Repeated doses of praziquantel SDHB might improve treatment outcome in nonimmune traveler. Whitty et al. found that treatment failure was less common in patients treated for 3 days versus those treated 1 day, but the difference was not statistically significant, possibly owing to the overall low rate of treatment failure documented.8 To our knowledge there are no prospective, clinical studies comparing the efficacy of different regiments of praziquantel in treatment of the chronic phase of imported schistosomiasis. Given the high rate of treatment failure among traveler, such studies are needed.