Artemisia Species and Their Active Constituents for Treating Schistosomiasis

Schistosomiasis, a neglected tropical disease, affects millions of lives and accounts for thousands of deaths each year. The Schistosoma parasites depend on two hosts during their lifecycle: snails as intermediate hosts and human beings as definitive hosts. Therefore, to control and ultimately eliminate schistosomiasis relies on the reduction of snail populations as well as the prevention and treatment of schistosomiasis infections. Praziquantel is the primary drug for prevention and treatment, and although it is considered safe and efficacious, concerns exist regarding emerging drug resistance due to mass drug administration. For this reason, novel antischistosomal drugs are in need and the genus Artemisia might be a promising source. Notably, Artemisia species not only have been evaluated for their antischistosomal effects against Schistosoma parasites, but also for their molluscicidal effects against the snail vectors. Extracts of Artemisia afra seem to be the most active, with IC50 values comparable with the positive control, praziquantel. The antimalarial drug artemisinin, obtained from A. annua, and its semisynthetic derivatives artemether, artesunate, and artemisone have also been evaluated against both schistosomes and snail vectors. Artemether and artesunate have been found to be notably active against the adult and juvenile stages of schistosomes, whereas artemisone was shown to be effective in treating hosts harboring juvenile schistosomes. Artemisinin on the other hand in combination with praziquantel presents as a good lead combination in curing schistosomiasis.