I suggest medicinal plants are more effective

Yes there are proven treatment medication for schistosomiasis. Infections with all major Schistosoma species can be treated with praziquantel. The timing of treatment is important since praziquantel is most effective against the adult worm and requires the presence of a mature antibody response to the parasite. For travelers, treatment should be at least 6-8 weeks after last exposure to potentially contaminated freshwater. (cdc.gov)

As stated by Global Health Division of Parasitic Diseases, one study has suggested an effect of praziquantel on schistosome eggs lodged in tissues. Limited evidence of parasite resistance to praziquantel has been reported based on low cure rates in recently exposed or heavily infected populations; however, widespread clinical resistance has not occurred. Thus, praziquantel remains the drug of choice for treatment of schistosomiasis. Although a single course of treatment is usually curative, the immune response in lightly infected patients may be less robust, and repeat treatment may be needed after 2 to 4 weeks to increase effectiveness. If the pre-treatment stool or urine examination was positive for schistosome eggs, follow up examination at 1 to 2 months post-treatment is suggested to help confirm successful cure.

Praziquantel is the drug of chice

Praziquantel is effective if properly administered.

Initial management of acute schistosomiasis syndrome consists of reduction of inflammation with corticosteroids. The optimum dose and duration of corticosteroids are uncertain; treatment with prednisolone 20 to 40 mg daily for five days is generally sufficient to suppress symptoms.

Subsequently, praziquantel should be administered; the optimal timing is uncertain since treatment with praziquantel may aggravate symptoms of acute schistosomiasis. In general, administration of praziquantel is most effective at least four to six weeks following exposure when infection is well established and the worms have fully matured. Data on optimal timing of treatment are limited; most favour administration of praziquantel after acute symptoms have subsided followed by repeat treatment four to six weeks thereafter.

Praziquantel should be initiated only after acute symptoms have resolved and should be administered concomitantly with corticosteroids. Corticosteroids reduce plasma levels of praziquantel, although data are limited regarding whether the dosing of praziquantel warrants adjustment in the setting of corticosteroids. Patients with schistosomiasis should be treated with praziquantel.

Since praziquantel is not effective against the larval stages of schistosomes, treatment is most effective from four to six weeks after exposure onwards, when infection is well established and worms have fully matured.

Only praziquantel is practically available for treatment of schistosomiasis. It is questionable whether resistance will occur in a few individual cases. Alternative medications are metrifonate for treatment of S. haematobium infection and Oxamniquine for the therapy of S. mansoni infection - both drugs are usually not available. Mefoquine, artesunate and artemisinin combination therapies have been tested in clinical studies, but have not yet been sufficiently evaluated.