A new front has been opened up in the battle against malaria with the
release of the first ever genetically modified mosquitoes in Africa.
Scientists are hoping to eliminate malaria(疟疾)by developing a
genetically modified mosquito that cannot transmit the disease. Malaria
has long troubled the populations of South America, Africa, and Asia,
where mosquito bites infect up to 500 million people a year with this
serious and sometimes fatal parasitic blood disease. For generations,
scientists have been trying to eliminate malaria by developing new drugs
and using pesticides(杀虫剂)to wipe out local mosquito populations. But
these measure aren’t working — and some scientists, like Greg Lanzaro,
say that because of drug resistance and population changes, malaria is
actually more prevalent now than it was 20 years ago. Lanzaro says he
has a better way to stop the spread of malaria: genetically modifying
mosquitoes so they are unable to carry the disease.
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Lanzaro and his colleagues are planning a multi-year project to
produce malaria-resistant mosquitoes — and he thinks they can do it
within five years. “We can get foreign genes into mosquitoes and they go
where they’re supposed to go,” Lanzaro says, pointing out that
scientists have already succeeded in genetically engineering mosquitoes
that cannot transmit malaria to birds and mice. And, he says, scientists
are quickly making progress on genes that block transmission of the
disease to humans as well.
Some 10,000 sterile male mosquitoes will be released in Burkina Faso, a
country at the front line of the war against the disease. Last year
there were 9.8m cases of malaria here, resulting in almost 4,000 deaths.
The most difficult part scientifically, Lanzaro says, is figuring
out how to get the lab-engineered mosquitoes to spread their genes into
natural populations. After all, he points out, it’s useless to engineer
mosquitoes in the lab that can’t transmit malaria when there are
millions out in the wild that can. To solve this problem, Lanzaro wants
to load up a mobile piece of DNA with the malaria-resistant gene, and
then insert it into a group of mosquito embryos. The malaria-resistant
gene would be integrated directly into the mosquitoes’ DNA, making it
impossible for those mosquitoes to transmit the parasite that causes
malaria.In this way a small group of lab-raised mosquitoes could be
released into the wild, and by interbreeding with wild mosquitoes,
eventually transmit the beneficial gene to the entire population.
Mosquitoes have an extraordinary ability to target humans far away and
fly straight to their unprotected skin.Regrettably, mosquitoes can do
more than cause an itchy wound.Some mosquitoes spread several serious
diseases, including Dengue, yellow fever and malaria.
46.One reason for malaria to be widespread now is that .
皇家88平台，Malaria is the biggest killer of children under five in Africa and the
most up-to-date figures show that there were 216 million malaria cases
worldwide, and an estimated 445,000 malaria deaths.
A.more people have moved to malaria-infected areas
Over one million people worldwide die from these mosquito-borne diseases
each year.New research now shows how mosquitos choose who to bite。
B.mosquitoes have become resistant to pesticides
This is the first step in a program to dramatically reduce the mosquito
population in the country, and hopefully beyond. The initial release of
the mosquitoes will enable researchers to gather more data about the
longevity and dispersal of the insects, as well as how they interact
with the natural insect population.
C.genetically modified mosquitoes still transmit the disease
Mosquitoes need blood to survive.They are attracted to human skin and
breath.They smell the carbon dioxide gas — which all mammals breathe
out.This gas is how mosquitoes know that a warm-blooded creature is
D.mosquitoes bite as many as 500 million people a year
Researchers also hope to gain operational experience and improve
understanding of their work among regulators and locals.
47.Lanzaro is hopeful that in a few years man can .
But mosquitoes also use their eyes and sense of touch.Michael Dickinson
is a professor at the California Institute of Technology.His research
shows how these small insects, with even smaller brains, use three
senses to find a blood meal。
A.start to eliminate malaria