Anti-schistosomal drugs: observations on the mechanism of drug resistance to hycanthone, and on the involvement of host antibodies in the mode of action of praziquantel

This paper reports recent observations from our laboratory dealing with the anti-schistosome drugs hycanthone (HC) and praziquantel (PZQ). In particular, we discuss a laboratory model of drug resistance to HC in Schistosoma mansoni and show that drug sensitive and resistant lines of the parasite can be differentiated on the basis of restriction fragment length polymorphisms using homologous ribosomal gene probes. In addition, we summarize data demonstrating that effective chemotherapy of S. mansoni infection with PZQ in mice requires the presence of host anti-parasite antibodies. These antibodies bind to PZQ treated worms and may be involved in an antibody-dependent cellular cytotoxicity reactions which result in the clearance of worms from the vasculature.

Patterns of antischistosomal drug usage in Qalyubia Governorate of the Nile Delta.

To further investigate factors responsible for the recently documented changes in schistosomiasis patterns in the Nile Delta, questionnaire-derived information on antischistosomal drug usage was obtained from a 25% systematic sample of 609 residents of a stable village in the south-central Delta. Ten percent of the population had received antischistosomal drugs during the previous 4 years. Most of the drugs administered were injectable compounds, and 92% of individuals receiving them failed to complete the treatment regimen. Additional sources of information from a village physician, a pharmacist and a major pharmaceutical corporation confirmed and expanded the survey findings, indicating that antischistosomal drug usage cannot explain the recently observed changing patterns of human schistosome infections in the Nile Delta region.