A NOVEL PROTOCOL FOR INDUCTION OF PRAZIQUANTEL RESISTANCE IN Schistosoma mansoni IN MICE

The control of Schistosomamansoni infection by mass chemotherapy that is being attempted in the
absence of effective drug regulation will ultimately create a major socio-economic and public health
problem. The aim of the present study was to see how rapidly resistance to PZQ could be induced in S.
mansoni, by giving sub-curative doses of the drug to mice infected with this parasite. Eighty mice, in
eight groups of 10 mice each, were each infected with 150 S. mansoni cercariae, maintained until their
parasites were adult worms, and then either left untreated (one group of negative controls) or given PZQ
in various doses and regimens. Some treatments led to infections that were at least partially resistant to a normally effective treatment (i.e. a single dose of praziquantel at 40mg/kg). Three treatments at 8mg/kg produced infections that were more resistant to the drug than those produced using five doses at the same level (p<0.05). Given the current dependence on PZQ for the treatment of human schistosomiasis in endemic areas, including regions where drug control and regulation are poor, it is likely that S. mansoni isolates in the field will be subject to curative doses similar to those used in the present study. Therefore, careful surveillance to detect resistance to PZQ in the field is advocated.