WEI Fonghua, XU Xingjian, DAI
Yuhai and LIU Jianbin
Hubei Institute of Schistosomiasis
Control, Wuhan, China
Oncomelania hupensis is a unique intermediate host
of Schistosomiasis japonicum, therefore snail control is
a one of most important approaches of morbidity and mortality
control to S. japonicum. The snail control it is still
adopted the chemical molluscicide with niclosamide at the high
risk area of the snail habitats in China. Where are more than
700 million square meters of the snail habitats in Hubei province,
in which about 60 % is distributed around the residence area.
People and cattle contact infected water frequently by daily work.
It is easy infected or reinfected the S. japonicum.
Especially this area is formed network of canal and ditches, where
are very hard to change the situation by environmental modification
to do the snail control in this area. Hence, except health education
and chemotherapy currently, the molluscicide is still a effective
measures to control the disease.
The study of plant molluscicide
with Solanum xanthocarpum extraction was performed by means
of biological determination to target snail and non-target living
things as well as safety evaluation in accordance with WHO recommended
the method and Guidelines of Organization of Economic Cooperation
and Development (OECD). It is expected to find out the source
of cheap, effective and environmental acceptable non-chemical
molluscicide that potency to both of amphibious snail and fresh
water snail in the endemic area of schistosomiasis in the world.
For exploring a novel plant molluscicide that has a high potency
to target snail and low toxicity to non-target living things.
Our institute collaborated with Central China Normal University
to screen a lot of plant molluscicidal since 1980's. Recent years,
the research is focused on one and two high potency plant molluscicde
to perform the isolation, purification and extraction as well
as biological effect determination to the target snail. The initial
test result showed that the immersion method was used to the amphibious
snail of intermediate host of S. japonicum, adult Oncomelania
hupensis; fresh water snail of intermediate host of S.
mansoni, adult Biomphalara glabrata and the intermediate
host of Fascioliasis, adult Lymnaea stagnalis by
the extraction of Solanum xanthocarpum under the room temperature
25 C for 48 hours. The LC50 of O. hupensis was 0.332 ppm
and 95% confidence limits was 0.264-0.418ppm; of B. glabrata
was 0.858ppm and 95% confidence limits was 0.661-1.114 ppm; of
L. Stagnalis was 0.747 ppm and 95% confidence limits was
0.575-0.971 ppm. None of three kinds of snail can be seen the
water-leaving behaviour in the concentration of 2.16 ppm that
was the death rate of above 90% to the snail for 48 hours. The
death rate of 100% that for O. hupensis was 4.32 ppm and
for B. glabrata and L. Stagnalis was 8.64 ppm for
48 hours. As the time of immersing snail prolongation, the concentration
of 100% death rate for the snail is also decreased gradually.
It is evidenced that the extraction of S. xanthocarpum
has a high potency not only to amphibious snail in China and also
to the fresh water snail at abroad.
It was reported by Kusano, G et. al. that S. xanthocarpum has a nature of soap and some steroidal and alkaloid materials could be extracted from the plant which could enhance the contraction and tension of the atrium of cat and the heart of frog in vitro. However, it is unknown what bioactive molluscicidal properties of S. xanthocarpum that could kill the three kinds of snail. The research result would be provided the basic data for further mechanism research and the synthetic for the molluscicidal properties as well as the field application. It is expected a novel weapon for the snail control will be found out.
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created 21/12/00
