larvaIn untreated (control) cercaria larva AChE activity ranged from1.09 to 1.13 mole ‘SH’ hydrolyzed/min/mg protein (Table 3).Four hour treatment with 60% of 4 h, LC50of citral, ferulic acid,umbelliferone, azadirachtin and allicin caused significant (p < 0.05)inhibition in AChE activity of the whole cercaria larva (Table 3).Maximum reduction in AChE activity up to 1.71% of control wasnoted in the cercaria exposed to 60% of 4 h LC50of allicin in month ofJune. Significant (p < 0.05) variation in AChE activity in cercaria larvawas observed in different months of the year 2011–2012. There wasa significant (p < 0.05) rank correlation in between the treated con-centration of active components and corresponding change in theAChE activity of cercaria larva