Efficacy of artemisinin-naphthoquine phosphate against Schistosoma haematobium adult flukes: dose-effect relationship and tegumental alterations.

Schistosoma haematobium and Schistosoma mansoni infections have broadly overlapping geographical distributions. Praziquantel is the only treatment for human schistosomiasis, so drug tolerance and/or resistance are major concerns. Artemisinin-naphthoquine phosphate (CO-ArNp), an artemisinin-based combination therapy endorsed by the World Health Organization as a gold standard therapy for malaria, has also been identified as a promising treatment for S. mansoni. In this in vitro study, we tested the effect of 1-40 μg/ml CO-ArNp on S. haematobium worms, and inspected tegumental changes by using scanning electron microscopy (SEM), aiming to determine if this combination therapy has a broad-spectrum antischistosomal activity. Incubation of S. haematobium adults with 20 or 30 μg/ml CO-ArNp caused 100% mortality of worms within 72 or 48 h, respectively. SEM examination showed extensive tegumental alterations such as oedema, constriction, shortening and loss of spines, fissuring, sloughing and perforation, resulting in exposure of the underlying basal lamina, mainly in treated male schistosomes. Besides the well-established potent efficacy, bioavailability, tolerability and safety of the antimalarial artemisinin-naphthoquine phosphate combined therapy, these results may also suggest its possible utilization as a new broad-spectrum antischistosomal agent.