Malaria is attaining near epidemic proportions in the country but researchers in Madras hold out a ray of hope. They have produced an environmentally safe pesticide that kills mosquito larvae.
AN ENVIRONMENTALLY safe,
biotechnological toxin that kills
mosquito larvae has been produced
by the Centre for Biotechnology
(CBT) at Anna University in Tamil
Nadu. Named Biocide-S because it is
produced from the Bacillus sphaericus bacterium, the pesticide has been
successfully field-tested in a yearlong project at Kochi in Kerala. The
Madras municipal corporation is also
carrying out a six-month pilot project
in the city.
Biocide-S is expected to hit the
market soon. The Tuticorin Alkali
Chemicals and Fertilisers Ltd, a sister
concern of Southern Petrochemical
Industries Corp, has bought the
scaled-up technology from CBT, but
will first test it semi-commercially by
producing about 100 tonnes per
annum before'full-scale launch of its
Rs 5-crore project.
Biocide-S kills mosquito
larvae. Explained
G Suresh of CBT, "When
the biocide formulation
is sprayed on stagnant
water bodies
like drains,
wells and tanks, it is
absorbed by the
quito larvae which are
filter-feeders (they filter
in soluble
matter from
the water). The Bacillus
sphaericus, which is
Jan Mar May
July Oct 1991 Jan Mar May July Oct
retained in the larva's
larvicidal protein (the
protein that kills the larvae) released causes
pores in the gut of the
larva, leading to gut
paralysis and death."
In the 1991 Kochi
project, biocide was
9prayed in a trial area of
8 sq km once a fortnight.
At another test site halfa-kilometre away, a chemical pesticide called
Beytex was sprayed, The
Centre for Research in
Medical Entomology (CRME) in
Madurai, which evaluated the project, reported that though the fall in
breeding in both areas was almost
identical in March, by October the
trial area drop in breeding was more
than in the chemically tested site. An
opinion poll conducted as part of the
evaluation also showed that 85.4 per
cent of the people living in the area
reported a significant fall in
mosquito numbers in the trial area.
The gene in Bacillus sphaericus
that produces the larvicidal toxin
was first discovered in 1984 by
Kunthala Jayaraman and an associate. Four years later, Jayaraman, who
had by then joined CBT, discovered a
second gene that produces another
toxic protein. Said Jayaraman, "The
discovery of two genes gave us confidence that there was less chance of
mosquitoes developing resistance-to
our product."
However, identification of the
genes was not enough. Large-scale
production required upgrading of
technology. A large part of the funds
came from the Swiss Deyelopment
Corp. CBT opted for a sopbe'anbased medium thdt could produce
large quantities at comparatively low
costs. While the first 10 litres were
pr-oduced in the CBT laboratory,
mass production of upto 3,000 litres
was successfully carried out at
Zurich in Switzerland. Tests at
the Hindustan Antibiotics Ltd
plant in Pune followed, with technology upscaled to produce 23,000
litres.
CBT is now working on transferring the toxin-producing genes in
Bacillus sphaericus to another
bacterium, Escherichia coli.
This technique has been successful
in the laboratory and is expected
to reduce costs even further when
commercial production becomes
possible.
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