RESUMO
To study the biological differences of PZQ susceptible and insusceptible S. mansoni isolates; three S. mansoni isolates were studied in this work. The first one is the susceptible [Mo] isolate obtained from Egyptian villagers cured after a single oral dose PZQ [40 mg/kg]. The other two insusceptible isolates [Mt22, Mt24] were originally obtained from Egyptian villagers not cured alit three curative doses of PZQ,two doses of 40 mg / kg b.w followed by 60 mg/kg b.w This study revealed the lower PZQ efficacy on both insuceptible isolates [Mt22, Mt24] than on susceptible [Mo] isolate. Under the same circumstances the number of worm burden as well as their biological fitness [egg count/gm liver] were higher in both insusceptible isolates than susceptible one. Also, egg hatchability was low in both insusceptible isolates when compared with its absence in the susceptible one