title: Evaluation of a method for induction of praziquantel resistance in Schistosoma mansoni.
abstract: BACKGROUND
  Praziquantel (PZQ) is a highly efficacious anthelmintic against many flatworms including schistosomes. PZQ has been in use for more than 25 years, and concern is increasing that resistance has emerged in human schistosomes in Egypt and other endemic countries.
  
  
  OBJECTIVE
  The current study was designed to evaluate a recently described method for induction of PZQ resistance in Schistosoma mansoni.
  
  
  METHODS
  Successive subcurative drug treatments of Biomphalaria alexandrina snails infected with an Egyptian strain of S. mansoni were undertaken. Cercariae shed from snails exposed and unexposed to PZQ were used to infect mice. Forty-five days after infection, mice were treated with a single oral dose of PZQ in 2% aqueous solution of Cremophor-EL®. The concentration of PZQ was 0, 200, 400, or 800 mg/kg. Thirty-three days after treatment, all groups of mice were dissected to collect the S. mansoni worms by the perfusion technique. In addition, the oogram pattern was examined to study the production, maturity, and death of S. mansoni eggs in the different groups of mice.
  
  
  RESULTS
  The present study has shown that the sublethal dose for induction of PZQ resistance in the intra-molluscan S. mansoni stages was 500 mg/kg. The worm count and the percentage of immature eggs in different groups of mice were significantly affected by the intra-molluscan exposure to PZQ and the drug concentration used to treat infected mice.
  
  
  CONCLUSIONS
  The results obtained herein confirm the possibility of using successive drug treatments of infected B. alexandrina to induce PZO resistance in S. mansoni.
authors.affiliation: Department of Parasitology, Medical Research Institute, Alexandria University , Alexandria , Egypt and.
authors.forename: Wael M
authors.initials: WM
authors.lastname: Lotfy
authors.forename: Mohamed G
authors.initials: MG
authors.lastname: Hishmat
authors.forename: Ahmed S
authors.initials: AS
authors.lastname: El Nashar
authors.forename: Hanaa M
authors.initials: HM
authors.lastname: Abu El Einin
mesh_terms: D000818:Animals; D000871:Anthelmintics / Q000494:pharmacology* / Q000627:therapeutic use; D004353:Drug Evaluation, Preclinical / Q000379:methods; D004351:Drug Resistance / Q000187:drug effects; D051379:Mice; D011223:Praziquantel / Q000494:pharmacology* / Q000627:therapeutic use; D012550:Schistosoma mansoni / Q000187:drug effects*; D012555:Schistosomiasis mansoni / Q000188:drug therapy / Q000401:mortality; D012908:Snails / Q000187:drug effects* / Q000469:parasitology
chemical_list: D000871:Anthelmintics; D011223:Praziquantel
keywords: Antischistosomal; Biomphalaria alexandrina; drug; intra-molluscan; sub-curative