Determination of minimum effective concentration of praziquantel in in vitro cultures of protoscoleces of Echinococcus granulosus.

The minimum effective concentration of praziquantel against protoscoleces of Echinococcus granulosus (ovine strain) was determined in vitro; 20 micrograms/litre gave statistically significant results. No difference was seen between the sensitivity of ovine and equine protoscoleces at 50 micrograms/litre. Morphological observations on treated protocsoleces and passage into gerbils both suggested that the eosin-exclusion technique overestimates viability. Electron microscopy of treated protoscoleces showed severe, disruptive tegumentary damage. Praziquantel is thus an extremely active protoscolicidal agent that may have an important peri-operative role in preventing recurrence.