SCIENCE IN THE NEWS - Scientists Meet in Cameroon to Discuss（在线收听）

SCIENCE IN THE NEWS - Scientists Meet in Cameroon to Discuss Malaria
By Oliver Chanler and Caty Weaver

Broadcast: Tuesday, November 22, 2005

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VOICE ONE:

This is SCIENCE IN THE NEWS in V.O.A. Special English. I'm Bob Doughty.

VOICE TWO:

And I'm Pat Bodnar. Hundreds of scientists, health care experts and policy makers met in Cameroon last week to talk about the deadly disease malaria. Today, we tell about that conference. We also explain the causes of and treatments for malaria.

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VOICE ONE:

A group called the Multilateral Initiative on Malaria organized the conference in Yaounde, Cameroon. Sixty-five countries were represented at the six days of meetings.

 
Malaria conference
The representatives met in the continent most troubled by malaria. Each year, the disease kills more than one million people. Most of those killed are children in Africa. Health experts say malaria kills one African child every thirty seconds.

VOICE TWO:

A common insect, the mosquito, is responsible for the spread of malaria. The Anopheles mosquito carries the parasite that causes the disease. Very small parasites develop in the stomach of the mosquito. Parasites are organisms that live on or in another animal and get their food from that animal.

The general name for the malaria parasite is Plasmodium. Mosquitoes pass the parasites to people when they drink blood through the skin. However, only the female Anopheles mosquitoes drink blood. The males feed only on plant juices.

VOICE ONE:

 
 
The female Anopheles mosquito drinks blood from people and animals by breaking through the skin with its long, tube-like feeding device. The parasites enter the blood of the victim. The blood carries the parasites to the victim's liver. From there they invade cells and reproduce.

After nine to sixteen days, the parasites return to the blood and enter the red blood cells. Then they reproduce again. As they do this, they destroy the blood cells. In a short time, the victim develops a high body temperature. The victim becomes weak and is unable to carry out normal activities.

Other signs of malaria include pain in the muscles or head and shaking. Patients with severe malaria may develop liver and kidney failure, seizures and become unable to communicate.

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VOICE TWO:

These signs of malaria have been observed since the beginning of history. Scientists examining bodies of ancient Egyptians have found evidence of the disease in people who lived at least three thousand years ago. And scientists have found mosquitoes in fossil remains millions of years old.

At one time, it was believed that malaria was caused by bad air. People believed this bad air came from areas of water that were not deep and did not move. It seemed that malaria was most common near these swamps.

Ancient people suspected that mosquitoes were linked to malaria. The Greek historian Herodotus lived about two thousand four hundred years ago. He noted that in swampy areas of Egypt, some people slept in tall structures where mosquitoes could not go. Or they slept under special material called nets that mosquitoes could not go through.

VOICE ONE:

In eighteen seventy-six, British scientist Patrick Manson discovered that mosquitoes were responsible for passing the disease to human beings. More exactly, he found that insects carry the parasites and pass them to humans.

In eighteen eighty, a French doctor, Alphonse Laveran, discovered that the Plasmodium parasite causes the disease. In eighteen ninety-seven, a British scientist, Ronald Ross, found the malaria parasite in the Anopheles mosquito.

For his discovery of the cause of malaria and other work, Doctor Laveran received the Nobel Prize for Medicine in nineteen-oh-seven. Mister Ross received the Nobel Prize for Medicine in nineteen-oh-two for his work on malaria. The discoveries of the three scientists soon led to efforts to control malaria. Then, the discovery of the insect poison D-D-T led to efforts to end the disease completely.

VOICE TWO:

Between nineteen fifty-five and nineteen sixty-nine, the World Health Organization organized a series of campaigns against the disease. The goal was to use chemicals to kill mosquitoes inside homes around the world.

The effort was successful in large areas of North America, southern Europe, the former Soviet Union and some parts of Asia and South America. The spread of the disease in these areas was halted.

However, the disease remained in Central America, parts of South America, and some Asian countries. The W-H-O program never was attempted in Africa. This is because it was too difficult and costly for most African countries.

VOICE ONE:

In nineteen sixty-eight, malaria suddenly spread among people in Sri Lanka, where it was believed the disease no longer existed. The disease also spread in Central America, in Southeast Asian nations, and in parts of Africa.

Efforts to end malaria throughout the world were suspended in nineteen sixty-nine. Today, the W-H-O says that malaria control programs must be developed for local areas. It says such programs must involve everyone in each community -- citizens, health experts and people involved in development.

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VOICE TWO:

There are four different kinds of malaria. They are caused by four different kinds of parasites. Three of them cause victims to suffer high body temperatures, or fevers, every few days. But they do not cause death. However, the most common malaria parasite also is the most dangerous. This parasite causes infections that can lead to death.

The best way to prevent malaria is to avoid the mosquitoes that carry the malaria parasites. The female Anopheles mosquito takes blood from its victims mainly at night.

So, people can place special nets treated with insect poison over their beds at night while they sleep. People can also put anti-insect chemicals on their skin, on clothing and in sleeping areas. They also can wear clothes that cover most of the body.

VOICE ONE:

If the mosquitoes get past barriers used to block them, drugs are necessary for treatment. Drugs can destroy the malaria parasite as soon as it enters the human body. This prevents the parasites from entering the red blood cells and dividing.

Some drugs can prevent the parasite from establishing itself in the liver. However, malaria must be treated early for the treatment to be effective.

Before the fifteenth century, people in what is now Peru knew that the covering or bark from the cinchona tree was effective in treating the signs of malaria. In eighteen-twenty, two French scientists identified the substance in the bark as quinine. Until the twentieth century, quinine was the chief drug used to prevent and cure some forms of malaria.

Today, manufactured drugs are mostly effective in treating the disease. These drugs are designed to prevent the parasites from developing in the body and causing malaria.

VOICE TWO:

The most commonly used malaria prevention drug is chloroquine. It is suggested for use in Mexico, Central America, Haiti, the Dominican Republic, and the Middle East. Another drug, called mefloquine, is used in all other areas where malaria is a threat. Both drugs must be taken once a week on the same day each week. Another commonly used anti-malaria drug is doxycycline. It must be taken every day.

Scientists are currently testing a medicine to protect humans from malaria. In Cameroon, scientists said the medicine has protected children from the disease for as long eighteen months. One thousand four hundred children in Mozambique were involved in the study. The boys and girls were given the protective medicine, or vaccine, in two thousand three. They were then observed for a year and a half.

Doctors say the vaccine reduced the total number of malaria cases by thirty-five percent. They also said life threatening cases of malaria were cut by almost fifty percent. The drug company GlaxoSmithKline is developing the vaccine.

VOICE ONE:

Conference delegates discussed other ideas for malaria prevention and treatment. But they said much more work is needed. Aid groups have offered to help in those efforts.

The largest amount of new money for the fight against malaria was announced before the conference. The Bill and Melinda Gates Foundation said it would provide more than one hundred million dollars for continued research on the Glaxo-Smith-Kline vaccine. The rest will go to other malaria research and prevention methods.

 
Bill & Melinda Gates
Bill Gates is the richest man in the world. He told reporters that malaria can be defeated. And, he said it would be fought harder if the children dying from were in rich countries.

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VOICE TWO:

This program was written by Oliver Chanler and Caty Weaver. She also was the producer. I'm Pat Bodnar.

VOICE ONE:

And I'm Bob Doughty. Join us again next week for more news about science in Special English on the Voice of America.