Molluscicidal activity of crude water leaf extracts of Alternanthera sesselis on Bulinus (phy) globosus

Abstract

Evaporated and unevaporated extracts were prepared from both dried and fresh leaves sample and subjected to a 24 h static bioassay. A reference molluscicide niclosamide (Baylusicide) was used as
standard and rainwater as untreated control. Reaction of the snails on coming in contact with the test medium is either shock or distress. The distress reaction started with retraction of tentacles and ended
in some cases with death. Shock reaction results when snails are immersed in a more concentrated crude water extract which usually resulted in the death of the snails. Statistical analysis of average
mortality figures by the use of probit gave LC50 of 40.42 (35.15 – 46.47) for the unevaporated crude water while the evaporated crude water extract had LC50 of 48.07 (42.81 – 54.28) for the dried leaf extract. For the fresh leaves the unevaporated crude water extract had LC50 of 32.57 (27.15 – 39.08) and evaporated crude water gave 45.00 (39.09 – 51.79). This results show that the molluscicidal properties of the leaf extract was dose dependent as mortality increases with the relative increase in concentration of the
extract. Furthermore, the bioavailability of the active component is more in the fresh leaves sample when compared to the lethal concentration values of the dried leaves extract and the potential of the
crude water extract in integrated schitosomiasis control is discussed.