RED FLAG FOR GREEN SPRAY
May 29, 1999
According to this story, French researchers have found that inhaling the
spores of Bacillus thuringiensis, or Bt, sprayed on organic crops as a
pesticide can cause lung inflammation, internal bleeding and death in
The story notes that dried Bt spores have been used as a pesticide for
more than 30 years and are one of the very few insecticides sanctioned for
organic crops in Europe. Bt is also widely used to combat pest such as the
spruce budworm, a caterpillar that attacks trees.
Last year, French scientists isolated a strain of Bt that destroyed tissue
in the wounds of a French soldier in Bosnia. The strain, known as H34,
also infected wounds in immunosuppressed mice (This Week, 30 May 1998, p
7). Now the same team has found that H34 can kill mice with intact immune
systems if they inhale the spores.
oise Ramisse of le Bouchet army research laboratories near Paris and
her colleagues were cited as finding that healthy mice inhaling 108 spores
of Bt H34 died within eight hours from internal bleeding and tissue
damage. Spores from mutants of the same strain which did not produce the
insecticide were equally lethal to mice, suggesting that it was not to
blame. Ramisse and
her colleagues presented their results at a conference in Paris last
The researchers think that the symptoms are caused by other toxins. The
bacterium's close cousin, Bacillus cereus, produces a toxin that ruptures
cell membranes. And in 1991, Japanese researchers showed that B.
thuringiensis produces the same toxin. In fact, when the French
researchers ran samples from the soldier from Bosnia through an automated
medical analyser, it seemed to show that the bacterium was B. cereus.
Ramisse suggest that companies producing Bt spores might make them safer
by deleting the promoter sequence that activates the gene for the
Although H34 is not used as a pesticide, commercial strains of Bt tested
by the researchers also killed some mice or caused lung inflammation when
inhaled. The team obtained these strains from Abbott Laboratories, a major
supplier of Bt based in Chicago. Ramisse points out that the strains are
sprayed on forest pests at concentrations of 1011 spores per square
metreQand so might pose a danger to people in the immediate vicinity. But
Abbott maintains that Bt is safe. Linda Gretton, a company spokeswoman,
was quoted as saying, "We stand by our products." The French researchers
have not yet tested strains made by other companies.
The story notes that recorded infections by Bacillus pathogens are
comparatively rare. Known pathogenic species can have very distinctive
symptoms. Anthrax, for instance, is caused by B. anthracis. But where such
tell-tale signs are absent, Ramisse suspects that doctors often fail to
recognise that the bacteria are responsible, dismissing any Bacillus in
patients' cultures as contamination. Consequently, the cultures are often
When Bt was sprayed in towns in Oregon in 1991 to combat gypsy moths, the
bacterium was found in clinical samples from 55 patients who had been
admitted to hospital for a variety of other reasons.
Robert Haward of the Soil Association, which represents Britain's organic
farmers, was cited as saying that they may have to use masks and take more
care when spraying the spores on crops.
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healing. Proverbs 12:18
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