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Transgenic Mosquitoes Enlisted in Fight Against Malaria |
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By Mario Osava*
Results
could emerge in a decade from research to eradicate this disease
that poses a public health threat in 90 countries, home to 40 percent
of the global population
RIO DE JANEIRO - Brazil's René Rachou Research
Center has genetically modified a mosquito to remove its ability
to transmit the parasite that causes malaria.
If this mosquito can reproduce in nature, and replace the original
disease-carrying mosquito, it would help control a disease that
affects 300 to 500 million people each year -- 90 percent in Africa
-- and claiming one million lives annually.
But it is still a long way off, "a minimum of 10 years," scientist
Luciano Andrade Moreira told Tierramérica. He coordinates the research
that began in 2003 at the Rachou Center, of the Oswaldo Cruz Foundation,
in Belo Horizonte, capital of the eastern Brazilian state of Minas
Gerais.
The genetic modification of the mosquito involves introducing into
its genes a protein that produces an enzyme to block the malaria
parasite. Five years ago, U.S. researchers discovered the enzyme
in bee venom. Its function is to prevent the parasite from leaving
the insect's intestine.
So far, only the Aedes fluviatilis mosquito -- the vector for malaria
in chickens -- has been genetically modified, not the Anopheles
mosquito, whose stings lead to the disease in humans.
That initial choice was due to the ease of multiplying that mosquito
species in the laboratory and to similarities between the parasites,
as well as to the issue of safety -- if the transgenic mosquitoes
escaped the laboratory, it would not pose a threat to human health,
explained the scientist.
The next step is to work with the Anopheles aquasalis, which lives
where there is saltwater. But for the strategy to be effective it
will be necessary to genetically modify the mosquito most responsible
for spreading malaria in Brazil, which is the Anopheles darlingi,
which scientists have not yet been able to multiply in the laboratory
setting.
After creating the appropriate transgenic insects in the lab, they
will be tested for their ability to survive and reproduce normally
in nature. The genetically modified mosquito will have to proliferate
at least at the level of the conventional mosquito if it is going
to replace it and reduce the spread of malaria, said Moreira.
This strategy in the fight against malaria has been studied for
some 20 years, searching for mosquito species that transmit the
plasmodium parasites. Scientists in the United States and some European
countries developed the technique, concentrating on the African
vectors -- the most deadly.
Moreira learned the technique when he studied for his doctorate
degree in the United States, and applied it to Brazilian mosquito
species -- the first project of its kind in a developing country.
But this will not be the definitive solution to the malaria problem,
which requires a combination of different strategies, including
the conventional ones, like improved medical assistance and sanitation,
and a reduction in the number of mosquitoes, he admitted.
It is unlikely that a vaccine would be completely effective, because
the parasite "is versatile, it changes, and is different in Africa,
Asia and Brazil," he said.
Malaria threatens public health in 90 countries, home to 40 percent
of the global population.
In 2005 there were 591,000 new cases recorded in Brazil, claiming
88 lives. The most common malaria parasite here is less lethal than
the African variety. Almost all of the Brazilians infected live
in the Amazon region.
Similar studies are under way at the University of Sao Paulo, but
focus on dengue -- another mosquito-borne disease.
The research contributes to knowledge of the mosquito physiology,
its antibodies, development cycles and their interaction with parasites.
This could bring other benefits, such as a vaccine to block transmission
of the disease, if some protein with that property can be identified,
Moreira gave as an example.
Such a vaccine, applied to a person, would not prevent infection,
but the mosquito that stings the person would lose the ability to
spread the disease.
One obstacle will be the resistance of anti-transgenic activists.
Any sort of genetic modification is cause for concern because it
involves risks -- and potentially more so with an insect that can
move about, as opposed to crop plants, said Gabriel Fernandes, coordinator
of the Campaign for a Transgenic-Free Brazil.
"There are other, safer methods for controlling malaria," he told
Tierramérica. And genetic modification "is not a panacea." Applied
to agriculture, this science has produced just two types of effective
products -- resistant to pesticides and to insects -- after 30 years
of research and 10 years in commercial use, Fernandes said.
When the time comes for field tests of the transgenic mosquitoes,
all measures of safety and control will be in place, says Moreira.
The insects would be released in a restricted area surrounded by
a belt of insecticides to prevent live mosquitoes from leaving the
area.
But for now it is not a question of biological safety, "because
the 'product' does not yet exist", its viability has yet to be proved,
and the experiment is limited to contained laboratory spaces, said
Silvio Valle, coordinator of the biosafety division at the Oswaldo
Cruz Foundation of Rio de Janeiro.
There should be a prior assessment of whether the conventional methods
for fighting malaria have been exhausted -- encompassing the economic,
environmental, social and ethical issues -- and whether there are
less costly and more beneficial alternatives, Valle said in a Tierramérica
interview.
* Mario Osava is an IPS correspondent.
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