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Results from toxicity tests on nontarget organisms are encouraging, but the
data relate only to acute contact toxicity. More detailed laboratory work and
field trials are required to extend knowledge in this area.
Tests for mutagenicity using light petroleum and chloroform extracts have
indicated no obvious mutagenic potential of the plant material. In contrast,
the methanol fraction caused a slight increase in the number of revertants. A
water extract of Ambrosia was shown to contain large amounts of histidine.
Jongen and Koeman (1983) have shown that methanol extracts of other plants
containing high levels of histidine increase the number of spontaneous revertants
obtained in the mutagenicity test.
The information available on the toxicology of Ambrosia and related plants has
been reviewed with particular reference to allergenic reactions in humans and
animals (Duncan 1987). The chrysanthemum, another member of the Cornpositae,
is one of the most common causes of allergenic contact dermatitis in
florists and horticulturists. Dermatitis as a result of ragweed (a common name
for the genus Ambrosia) is a well-known problem in the United States. Some
very severe, generalized reactions occurred after the accidental introduction
of Parthenium in grain imported to India in the late 1950s. The number of
people handling Ambrosia during the project in Egypt has been relatively
small, but no allergic reactions have been reported so far. This aspect, however,
must investigated thoroughly before large-scale field trials are undertaken.
Ambrosia is commonly taken in Egypt as a strong decoction for renal colic and
to aid in the expulsion of kidney stones (Sherif and El Sawy 1962). The basis
for the apparent success of this remedy is not known. The sesquiterpene
lactones, such as ambrosin and damsin, thought to be responsible for the
plant's molluscicidal action are not likely to survive the lengthy boiling
involved in preparation of this remedy. They were, in any case, shown to have
very little pharmacological action in a number of laboratory tests (Abu-Shady
and Some 1953).
One of the main advantages of a plant molluscicide should be its availability
at schistosomiasis-transmission sites, thus avoiding the cost of acquiring and
importing commercial products. Any cost saving depends on participation of
local communities in the production and application of the plant molluscicide.
The feasibility of field delivery systems must be established on a small scale
and backed up by detailed toxicologic studies. Currently, data are emerging
to support the use of Ambrosia by village communities and the early toxicity
studies are promising.
The Egyptian study has recently been extended into a nearby area of land
reclaimed from the desert, where transmission appears to be more focused. As
in the original experimental area, the main aim will be to develop a simple
delivery system for the plant based on community participation. Enlisting
participation may prove difficult, but the potential savings using this
approach are evident. Egypt may, in fact, have a remedy for a long-standing
disease problem literally growing in its own backyard.
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