Experiments were conducted to evaluate the molluscicidal and anticholinesterase activity of aqueous leaf and stem-bark extract of
Pedialanthus tithymaloide
(Family- Euphorbiaceae)
Lymnaea (
Radix)
acuminata
(Lamarack) and
Indoplanorbis exustus
(Deshyas) - intermediate hosts of endemic schistosomiasis and fascioliasis diseases in cattle and livestock. The toxic effect of both extracts was time-as well as dose-dependent. There was a significant negative correlation between LC values and exposure periods observed, thus the LC
10 values of
P. tithymaloide leaf decreased from 24.7 mg/L (24 h) to 15.4 mg/L (96 h); LC
50 decreased from 69.4 mg/L (24 h) to 27.4 mg/L (96 h); LC
90 decreased from 194.6 mg/L (24 h) to 48.9 mg/L (96 h) against
L. acuminata and LC
10 values of
P. tithymaloide leafdecreased from 5.5 mg/L (24 h) to 0.6 mg/L (96 h); LC
50 decreased from 35.8 mg/L (24 h) to 4.3 mg/L (96 h); LC
90 decreased from 233.1 mg/L (24 h) to 32.1 mg/L (96 h) against
Indoplanorbis exustus
. Similar trend was also observed for the aqueous stem-bark extract of
P.tithymaloide. Sub-lethal exposure at 24h and 96h of the aqueous leaf and stem-bark extract of
P. tithymaloide causedsignificant (P < 0.05) time- and dose-dependent inhibition of the activity of enzyme acetylcholinesterase (AChE) in the nervous tissues of
L. acuminata after 24 h or 96 h exposure periods.Withdrawal study also shows that there was a significant recovery in the acetylcholinesterase activity in both the tissues of snail after the 7
th day of the withdrawal of treatment.Thus, the aqueous extract of
P. tithymaloide leaf and stem-bark are environmentally safe candidate molluscicides for controlling vector snails of schistosomiasis and fascioliasis.
