This study evaluated, using replicated laboratory bioassays, the toxicities of the crude aqueous and
ethanolic extracts of
Dalbergia Sissoo
Roxb. 1832 (family Leguminosae) fruits, leaves, roots and stem bark
against egg masses of
Biomphalaria Pfeifferi
(Krauss, 1848), the snail intermediate host of
Schistosoma mansoni
(Sambon, 1907) in Nigeria. Viable 0-24 hr-old embryonated egg masses were separately exposed to five
different concentrations (7.81-2000 mg/l) of extracts for 24 hrs, washed in dechlorinated tap water and incubated
at room temperature for a maximum of 4 weeks. The LC
50 and LC
90 values of test extracts for egg masses were
calculated by probit analysis. The activities of the tested extracts were concentration-dependent. However, only
the ethanolic extract of the fruits demonstrated significant activity (24 hr-LC
90 value < 100 mg/l: 89.29 mg/l).
Mortalities of eggs were manifested at the gastrula/exogastrula and or the prehatch snail stage of development.
The percentage of dead embryos at the prehatch snail stage decreased while the deaths of embryos at the
gastrula/exogastrula stage increased, with increasing concentration of extract. Lethality of the ethanolic extract
of
D. sissoo fruits to embryonated egg masses of
B. pfeifferi is an added advantage to its potential development
for use as a plant molluscicide, as the overall efficacy of a molluscicide is greatly enhanced if it also shows
significant toxicity towards snail eggs.
