Impact of - IDL-BNC @ IDRC - International Development Research ...

MoDuscicide- and pesticide-development
strategy
Molluscicides are crucial for the control and prevention of schistosomiasis. Of
the commercial molluscicides available, only bayluscid (niclosamide) is recommended
by the World Health Organization (WHO). However, bayluscid is
costly: in 1974, 1 t cost 26 000 USD. Most countries where the disease is
endemic cannot afford to spend such sums to attack transmission sites.
The possibility of using a naturally and locally produced plant molluscicide
to remove the intermediary vector of schistosomiasis has been recognized
since the early 1930s. The most promising plant, Phytolacca dodecandra (endod),
was identified in 1964 (Lemma 1965) and tested in field trials at Adwa,
Ethiopia, between 1969 and 1973 (Lemma etal. 1978). Several researchers have
suggested that a plant molluscicide grown by farmers and integrated with
chemotherapy could provide a cheap and efficient means to control schistosomiasis
in village and farm communities in infected areas (Webbe and
Lambert 1983; Lambert et al. 1985).
One reason why endod had not received support in the past was because the
toxicologic tests required to determine its suitability as a molluscicide were
too expensive for the Ethiopian authorities and university laboratories. Few
developing countries have the resources (technical or financial) to conduct a
full-scale analysis of the potential risks of pesticides before allowing their use
in local environments. At the same time, there is little incentive for industry
to complete the tests without obtaining patent rights.
No industrialized country will advocate the use of a botanical pesticide that
has not first been exposed to well-established testing procedures. Although
endod has been used for many years as a detergent for washing clothes, it has
not been subjected to safety evaluation tests. If it is to be used as a molluscicide,
such tests are mandatory.
In 1985, the International Development Research Centre (IDRC) and the
United Nations Financing System for Science and Technology for Development
(UNFSSTD) agreed to examine the basic requirements for evaluation of
the toxicology of endod and make recommendations for research and development.
Before 1985, numerous toxicity tests had been carried out using
extracts of endod (Lemma et al. 1984). However, none of these tests used a
standard endod preparation.
At a 1986 meeting sponsored by IDRC, it was concluded that, before endod
could be considered for general field use, an endod standard had to be
developed and tested. The standard would meet established composition
parameters and exhibit consistency of efficacy and safety. Second, tier I tests
for registration patterned after premarketing guidelines of the Organisation
for Economic Co-operation and Development (OECD) would meet the minimal
data requirements. The following tests were to be carried out:
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