Effect of praziquantel on the immature stages of Schistosoma haematobium.
Schistosoma mansoni is known to be refractory to praziquantel treatment in the pre-patent period of infection. Since Schistosoma haematobium has a much longer pre-patent period (10-12 weeks vs. 5-6 for the former species), we asked the question whether a correspondingly longer period of insusceptibility exists in urinary schistosomiasis. In hamsters treated at different times after infection, S. haematobium was partially refractory to praziquantel when treatment was given at week 5, but showed practically full sensitivity at 7-8 weeks and later times. Schistosoma haematobium worms obtained at different times after infection and exposed in vitro to praziquantel were refractory to low drug concentrations between 4 and 6 weeks, but were clearly affected at higher concentrations and at later time points. We conclude that S. haematobium does not have a praziquantel-insensitive window longer than in S. manson, in spite of its much longer maturation period. In addition, refractoriness of immature stages can be overcome at higher drug concentrations.
Department of Pharmacology, Theodor Bilharz Research Institute, Giza 12411, Egypt.
Sanaa
S
Botros
Livia
L
Pica-Mattoccia
Samia
S
William
Naglaa
N
El-Lakkani
Donato
D
Cioli
D000818:Animals; D000871:Anthelmintics / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D008647:Mesocricetus; D011223:Praziquantel / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D012548:Schistosoma haematobium / Q000187:drug effects* / Q000254:growth & development; D012553:Schistosomiasis haematobia / Q000188:drug therapy* / Q000469:parasitology
D000871:Anthelmintics; D011223:Praziquantel