SCIENCE IN THE NEWS - Using Mosquitoes to Help Fight Malaria

SCIENCE IN THE NEWS -June 11, 2002: Using Mosquitoes to Help Fight Malaria¹ / Can Aspirin² Reduce
Colon³-Cancer Risk? / Tsetse Flies a Threat to Agriculture

Broadcast: VOICE ONE:
This is Sarah Long.
VOICE TWO:
And this is Bob Doughty⁴ with Science in the News, a VOA Special English program about recent developments

in science. Today, we tell about mosquitoes that were genetically⁷ changed to reduce the spread of malaria. We
tell about a possible use of aspirin to reduce the risk of colon cancer. And we tell about the threat of the tsetse
(TSET-see) fly to agriculture.

((THEME)
)
VOICE ONE:
Scientists have reported progress in efforts to disarm⁸ mosquitoes that carry the disease malaria. The scientists say

they changed the genes⁹ of some mosquitoes so that the insects are less effective in spreading malaria.

 

The study is said to be the first to suggest that genetic⁶ engineering could be used to fight
the deadly disease. Genetic engineering is the technology of changing the genes of
living things.

VOICE TWO:

A common anopheles
mosquito

Malaria is caused by an organism carried by some kinds of mosquitoes. Mosquitoes take
in the organism when they feed on the blood of an infected person or animal. The malaria parasite¹⁰ then moves
from the insect’s stomach into the salivary¹¹ glands¹³ near its mouth. When the mosquito bites its next victim, the
parasite enters the victim’s blood.

As many as five-hundred-million people around the world are infected with malaria each year. The disease kills
as many as three-million people each year. Most of the victims are children in Africa, south of the Sahara Desert.

Experts say traditional methods are failing to control the mosquitoes that carry malaria. Chemical sprays can be
harmful to both human health and the environment. Also, the malaria parasite is becoming increasingly resistant¹⁴
to many drugs.

VOICE ONE:

In the new study, an international team of scientists changed the genes of a version of mosquitoes that infects
mice with malaria. Marcelo Jacobs-Lorena (mahr-SELL-oh JAY-cubs-luh-REHN -ah) of Case Western Reserve
University in Cleveland, Ohio, directed the study.

Last year, his team identified a molecule¹⁵ called S-M-One. S -M-One stops the malaria parasite from passing from
a mosquito’s stomach to its salivary gland¹². The team put the gene⁵ for the molecule into the mosquitoes. The
gene was added to a molecular¹⁶ system that produces the enzymes¹⁸ the insects need to feed on blood.

VOICE TWO:

The scientists carried out two kinds of experiments with the genetically-engineered mosquitoes. In the first, they
studied what happened to the mosquitoes when they bit malaria -infected mice. The scientists found that only half
of the insects became infected with malaria parasites¹⁹.

The results of the second experiment were even more successful. The scientists wanted to see if the genetically


engineered mosquitoes could pass malaria to uninfected mice. In two of three tests, none of the mice bitten by the
mosquitoes became infected with the disease. In the other test, the number of mice that became infected was
greatly reduced.

Scientists say genetically engineered mosquitoes could possibly be mated with wild mosquitoes to produce
insects that could not spread the malaria parasite.

VOICE ONE:

Nature magazine published the findings. The magazine also published comments by other scientists. Fotis
Kafatos (FOH-tis kah-FAH-toes) of the European Molecular Biology Laboratory in Germany praised the study.

He said this is the first time that humans have reduced the ability of mosquitoes to spread malaria. However, he
said it is not known if the research would work with malaria in humans. A different form of the parasite causes
the disease in humans.

((MUSIC BRIDGE))

VOICE TWO:

Aspirin is one of the world’s oldest, least costly²⁰ and most widely used drugs. Aspirin is a common treatment for
headaches, colds and flu. It reduces other kinds of pain, such as pain caused by arthritis²¹ in the areas where bones
are joined.

Aspirin also may help prevent some forms of cancer. One recent study showed that it can
slow the development of unusual growths, or adenomas, in the colon. Adenomas are early
signs of changes that can lead to colon cancer.

VOICE ONE:

Colon cancer is the second leading cause of death from cancer in the United States, after
lung cancer. The National Cancer Institute estimates fifty-six -thousand Americans will die from the disease this
year. The group says that about one-third of those deaths could be avoided by testing to find and remove
adenomas.

John Baron²² of Dartmouth Medical School in Lebanon, New Hampshire, directed the new study. He reported his
team’s findings at a meeting of the American Association for Cancer Research.

VOICE TWO:

The study involved more than one-thousand patients in nine American cities. All the patients had had at least one
adenoma removed within the past three months. The patients had no known heart disease or other conditions
sometimes treated with aspirin. They also had no history of cancer in their families.

The patients were divided into three groups. Some patients took one common three-hundred-twenty-five
milligram aspirin each day. Another group of patients took one low -strength aspirin that was only eighty
milligrams. The other patients took an inactive substance.

VOICE ONE:

Doctors examined the patients for new adenomas a year or more after the study started. The study found that the
people who took one low-strength aspirin each day reduced their risk of developing new adenomas by nineteen
percent.

Among patients who had a more aggressive kind of adenoma, the low -strength aspirin reduced the risk by forty
percent. Doctor Baron believes aspirin may block the action of an enzyme¹⁷ needed for the growth of cancer
tumors. However, the normal strength aspirin did not have this same preventive effect.

VOICE TWO:


Millions of Americans take a low-strength aspirin every day to prevent heart attacks. The results of the study
suggest that aspirin may be helping²³ these people in other ways. The results confirm increasing amounts of
evidence that aspirin can reduce the risk of some cancers.

However, doctors do not believe aspirin is safe for everyone. The drug often causes problems in the stomach or
intestines²⁴, especially if taken in large amounts. These problems can include life-threatening bleeding.

((MUSIC BRIDGE))

VOICE ONE:

The tsetse fly is a serious problem in many parts of Africa. Tsetse flies cause
problems in an area of almost ten-million square kilometers. The United Nations
Food and Agriculture Organization says some of this area is fertile land that could
be used for agriculture. F-A-O officials say stopping the insect would help African
farmers reclaim²⁵ land and increase food production.

Tsetse flies feed on the blood of humans and animals. The fly carries a parasite that attacks the blood and nervous
system of its victims. This organism causes Trypanosomiasis (trih-PAN-oh-so-MY-ah-sis), a disease known as
nagana (nah-GAH-nah) in farm animals. In humans, the disease is called sleeping sickness.

VOICE TWO:

Trypanosomiasis kills eighty percent of infected victims. The disease affects an estimated five-hundred-thousand
people. It kills three-million farm animals each year. Thirty-seven countries in Africa are affected²⁶ by tsetse flies.
Jorge Hendrichs is an insect control expert with the F-A-O. He says the tsetse fly keeps people poor by

preventing them from producing the food they need to survive. The tsetse fly and trypanosimiasis have slowed

the development of agriculture in Africa.
One-hundred-fifty-five -million cattle are being raised in tsetse-free areas south of the Sahara Desert. The area of
land that is tsetse-free is small. It is being overused by both cattle and people.

VOICE ONE:
One method that has proved successful in fighting the tsetse is the sterile²⁷ insect treatment. Male flies treated with

radiation become sterile, or unable to reproduce. The insects then are released into areas with other flies. After
mating, the eggs of the wild females do not develop.
The F-A-O says the sterile insect treatment has been used with traps and other methods to end the tsetse fly

problem on the Tanzanian island of Zanzibar. Mister Hendrichs says these efforts have no long-lasting side
effects on the environment.
((THEME)
)
VOICE TWO:
This SCIENCE IN THE NEWS program was written and produced by George Grow. This is Bob Doughty.

VOICE ONE:
And this is Sarah Long. Join us again next week for more news about science in Special English on the Voice of
America.

 

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1 malaria   

n.疟疾

参考例句：

• He had frequent attacks of malaria.他常患疟疾。
• Malaria is a kind of serious malady.疟疾是一种严重的疾病。

2 aspirin   

n.阿司匹林

参考例句：

• The aspirin seems to quiet the headache.阿司匹林似乎使头痛减轻了。
• She went into a chemist's and bought some aspirin.她进了一家药店，买了些阿司匹林。

3 colon   

n.冒号，结肠，直肠

参考例句：

• Here,too,the colon must be followed by a dash.这里也是一样，应当在冒号后加破折号。
• The colon is the locus of a large concentration of bacteria.结肠是大浓度的细菌所在地。

4 doughty   

adj.勇猛的，坚强的

参考例句：

• Most of successful men have the characteristics of contumacy and doughty.绝大多数成功人士都有共同的特质：脾气倔强，性格刚强。
• The doughty old man battled his illness with fierce determination.坚强的老人用巨大毅力与疾病作斗争。

5 gene   

n.遗传因子，基因

参考例句：

• A single gene may have many effects.单一基因可能具有很多种效应。
• The targeting of gene therapy has been paid close attention.其中基因治疗的靶向性是值得密切关注的问题之一。

6 genetic   

adj.遗传的，遗传学的

参考例句：

• It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
• Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。

7 genetically   

adv.遗传上

参考例句：

• All the bees in the colony are genetically related. 同一群体的蜜蜂都有亲缘关系。
• Genetically modified foods have already arrived on American dinner tables. 经基因改造加工过的食物已端上了美国人的餐桌。 来自英汉非文学 - 生命科学 - 基因与食物

8 disarm   

v.解除武装，回复平常的编制，缓和

参考例句：

• The world has waited 12 years for Iraq to disarm. 全世界等待伊拉克解除武装已有12年之久。
• He has rejected every peaceful opportunity offered to him to disarm.他已经拒绝了所有能和平缴械的机会。

9 genes   

n.基因( gene的名词复数 )

参考例句：

• You have good genes from your parents, so you should live a long time. 你从父母那儿获得优良的基因，所以能够活得很长。 来自《简明英汉词典》
• Differences will help to reveal the functions of the genes. 它们间的差异将会帮助我们揭开基因多种功能。 来自英汉非文学 - 生命科学 - 生物技术的世纪

10 parasite   

n.寄生虫；寄生菌；食客

参考例句：

• The lazy man was a parasite on his family.那懒汉是家里的寄生虫。
• I don't want to be a parasite.I must earn my own way in life.我不想做寄生虫，我要自己养活自己。

11 salivary   

adj. 唾液的

参考例句：

• Small doses depress salivary and bronchial secretion and sweating. 小剂量可抑制唾液分泌、支气管分泌及出汗。
• The five pairs of salivary glands open into the mouth. 有五对唾液腺通向口腔。

12 gland   

n.腺体，(机)密封压盖，填料盖

参考例句：

• This is a snake's poison gland.这就是蛇的毒腺。
• Her mother has an underactive adrenal gland.她的母亲肾上腺机能不全。

13 glands   

n.腺( gland的名词复数 )

参考例句：

• a snake's poison glands 蛇的毒腺
• the sebaceous glands in the skin 皮脂腺

14 resistant   

adj.(to)抵抗的，有抵抗力的

参考例句：

• Many pests are resistant to the insecticide.许多害虫对这种杀虫剂有抵抗力。
• They imposed their government by force on the resistant population.他们以武力把自己的统治强加在持反抗态度的人民头上。

15 molecule   

n.分子，克分子

参考例句：

• A molecule of water is made up of two atoms of hygrogen and one atom of oxygen.一个水分子是由P妈̬f婘̬ 妈̬成的。
• This gives us the structural formula of the molecule.这种方式给出了分子的结构式。

16 molecular   

adj.分子的；克分子的

参考例句：

• The research will provide direct insight into molecular mechanisms.这项研究将使人能够直接地了解分子的机理。
• For the pressure to become zero, molecular bombardment must cease.当压强趋近于零时，分子的碰撞就停止了。

17 enzyme   

n.酵素，酶

参考例句：

• Above a certain temperature,the enzyme molecule will become unfolded.超过一定温度，酶分子将会展开。
• An enzyme that dissolves the fibrin of blood clots.能溶解血凝块中的纤维的酶。

18 enzymes   

n. 酶，酵素

参考例句：

• It was said that washing powders containing enzymes remove stains more efficiently. 据说加酶洗衣粉除污更有效。
• Among the enzymes which are particularly effective are pepsin, papain. 在酶当中特别有效的是胃朊酶、木瓜酶。

19 parasites   

寄生物( parasite的名词复数 )； 靠他人为生的人； 诸虫

参考例句：

• These symptoms may be referable to virus infection rather than parasites. 这些症状也许是由病毒感染引起的，而与寄生虫无关。
• Kangaroos harbor a vast range of parasites. 袋鼠身上有各种各样的寄生虫。

20 costly   

adj.昂贵的，价值高的，豪华的

参考例句：

• It must be very costly to keep up a house like this.维修这么一幢房子一定很昂贵。
• This dictionary is very useful,only it is a bit costly.这本词典很有用，左不过贵了些。

21 arthritis   

n.关节炎

参考例句：

• Rheumatoid arthritis has also been linked with the virus.风湿性关节炎也与这种病毒有关。
• He spent three months in the hospital with acute rheumatic arthritis.他患急性风湿性关节炎，在医院住了三个月。

22 baron   

n.男爵；(商业界等)巨头，大王

参考例句：

• Henry Ford was an automobile baron.亨利·福特是一位汽车业巨头。
• The baron lived in a strong castle.男爵住在一座坚固的城堡中。

23 helping   

n.食物的一份&adj.帮助人的，辅助的

参考例句：

• The poor children regularly pony up for a second helping of my hamburger. 那些可怜的孩子们总是要求我把我的汉堡包再给他们一份。
• By doing this, they may at times be helping to restore competition. 这样一来, 他在某些时候,有助于竞争的加强。

24 intestines   

n.肠( intestine的名词复数 )

参考例句：

• Perhaps the most serious problems occur in the stomach and intestines. 最严重的问题或许出现在胃和肠里。 来自辞典例句
• The traps of carnivorous plants function a little like the stomachs and small intestines of animals. 食肉植物的捕蝇器起着动物的胃和小肠的作用。 来自辞典例句

25 reclaim   

v.要求归还，收回；开垦

参考例句：

• I have tried to reclaim my money without success.我没能把钱取回来。
• You must present this ticket when you reclaim your luggage.当你要取回行李时，必须出示这张票子。

26 affected   

adj.不自然的，假装的

参考例句：

• She showed an affected interest in our subject.她假装对我们的课题感到兴趣。
• His manners are affected.他的态度不自然。

27 sterile   

adj.不毛的，不孕的，无菌的，枯燥的，贫瘠的

参考例句：

• This top fits over the bottle and keeps the teat sterile.这个盖子严实地盖在奶瓶上，保持奶嘴无菌。
• The farmers turned the sterile land into high fields.农民们把不毛之地变成了高产田。