Resistance to praziquantel: Direct evidence from Schistosoma mansoni isolated from Egyptian villagers

Recent evidence suggest that resistance to praziquantel (PZQ) may be develo ping. This would not be surprising in countries like Egypt where the drug h as been used aggressively for more that 10 years. The classic phenotype of drug resistance is a significant increase in the 50% effective dose value o f isolates retrieved from patients not responding to the drug. In a previou s publication, we reported that such phenotypes have been isolated from hum ans infected with Schistosoma mansoni. Since the action of PZQ may be depen dent upon the drug and host factors, most notably the immune system, we ana lyzed the quantitative effects of PZQ on single worms that differed in thei r response to PZQ when maintained in mice. Our hypothesis was that the in v itro action of the drug would correlate with it in vivo action. We confirme d this hypothesis and conclude that the in vitro action of the drug is rela ted to its in vivo action. Knowing this relationship will assist in our abi lity to detect or survey for the PZQ resistant phenotype in human populatio ns.