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TITLE:  GM strains of bacteria developed to kill larvae in bid to fight
        malaria
        Ban on open field trials worrisome
SOURCE: The Bangkok Post, Thailand, by Ranjana Wangvipula
        http://www.bangkokpost.com/News/06May2003_news09.html
DATE:   May 6, 2003

------------------ archive: http://www.gene.ch/genet.html ------------------


GM strains of bacteria developed to kill larvae in bid to fight malaria
Ban on open field trials worrisome

Thai scientists have developed three new strains of genetically modified
bacteria that are believed to destroy mosquito larvae more effectively
than natural bacteria.

According to molecular biologist Boonhiang Promdonkoy of the National
Centre for Genetic Engineering and Biotechnology (Biotec), two killer
bacteria, known as Bacillus thuringiensis (Bti) and Bacillus sphaericus
(Bs), appear to have lost their power to kill the larvae with their toxin.

"Mosquitoes have already developed resistance to the Bs toxin," he said.

Bs is a natural killer of two types of mosquito larvae that carry malaria
and elephantiasis diseases, while Bti can eliminate the young of a dengue
carrier which is most worrying to public health officials.

While there have been no reports of mosquitoes developing resistance to
Bti, Mr Boonhiang said the bacterium could not float on the water surface
for as long as the Bs does, thus becoming less effective in killing the
larvae, which usually lives near the water surface as oxygen is a must
for its survival.

"Since none of the bacteria individually packs all the killer blows,
we've combined them to build new strains," he said, adding his research
team used the genetic modification technique (GM) to remove preferred
genes from Bti and Bs, made some adaptations, and added them to another
bacterium, making it a super killer of the mosquito larvae. And they
produced three such strains.

But improvements and help are still greatly needed, said Mr Boonhiang.

The GM bacteria stay on the water surface for a longer period, which
gives them enough time to release poisonous protein to kill the larvae,
although the amount of toxin is smaller than that released by Bti and Bs.

Researchers are also worried about the current ban on open field trials
of GM creations aimed at protecting the environment against contamination
from GM plants. Mr Boonhiang complained that the ban made it difficult to
know whether the new strains of bacteria could survive.

So far the Ministry of Public Health has advised the public to drain
water from containers to get rid of mosquito larvae or add a chemical
like Temephos, vinegar or salt in water to kill them, said Somsak
Prajakwong, director of the Bureau of Vector Borne Diseases.

He said the ongoing research of the new bacteria would help officials
cope with mosquito-borne diseases.

Last year, around 100,000 people had dengue fever, a disease that has not
seen a decrease while the number of malaria and elephantiasis cases had
decreased in recent years, he said.