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Role of Ambrosia maritima in controlling
schistosomiasis transmission
J. Duncan
Weston, Hitchin, Hartfordshire, UK
Ambrosia maritima L. (Compositae) is indigenous to Egypt. It is an
annual, growing up to I m high by May in moist habitats, typically on
the banks of irrigation watercourses. The schistosorniasis-transmission
season in the Nile Delta is from May to December peaking from June to
August. When whole, dried A. maritima was applied to irrigation
watercourses in May at 35 mg/L, snail numbers fell to low levels and did
not recover until the following year. This suggests that a correctly timed,
single, annual treatment might control transmission. Village communities
have been encouraged to participate in cultivating and applying
A. maritima to provide a cost-effective delivery system. Monthly surveys
have shown that snail control appears to be adequate at the village level.
However, the mobility of the villagers indicates the need for the control
program to be pursued over a larger area.
Ambrosia maritima L. (Compositae) is an annual with a tendency to perennate.
Known in Egypt as damsissa, it prefers moist soils and grows to I m high. Its
molluscicidal properties were first noted 40 years ago when malariaeradication
teams working in the Nile Delta reported the absence of snails
where Ambrosia grew on the banks of irrigation watercourses. Preliminary
field experiments in the 1970s indicated that applications at about 70 mg/L
would reduce snail populations to low levels (El Sawy et al. 1981).
Over the last 16 years, research at the High Institute of Public Health, Alexandria,
has been aimed at establishing a practical delivery system for reducing
schistosomiasis transmission and at conducting toxicologic studies (El Sawy
et al. 1983, 1984, 1987, 1989).
Work to date has included:
Field trials to determine the application level of the plant required to
provide a marked reduction in snail numbers;
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