SCIENCE IN THE NEWS -June 4, 2002: Malaria
By Oliver Chanler
VOICE ONE:
This is Bob Doughty.
VOICE TWO:
And this is Sarah Long with Science in the News, a VOA Special English program about recent developments in
Science. Today, we tell about malaria, a disease that affects millions of people around the world.
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)
VOICE ONE:
Malaria is a common and serious disease that has affected people for thousands of years. Today, it continues to
be a major public health problem throughout the world. It is most common in developing countries, especially in
Africa, Asia, and Central and South America.
The World Health Organization estimates that as many as five-hundred-million cases of malaria develop each
year. More than one-million people die from the disease each year. Most of them are children in African
countries.
VOICE TWO:
Malaria is spread by a common insect, the mosquito. 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 male Anopheles mosquitoes feed
only on plant juices.
VOICE ONE:
The female Anopheles mosquito drinks blood from humans and animals by breaking through the skin with its
long, tube-like feeding device. The parasites enter the victim’s blood. 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, headache, chills and shaking. Patients with severe malaria may develop liver and kidney failure,
seizures and coma.
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VOICE TWO:
These signs of malaria have been observed since the beginning of history. Researchers studying 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. However, the real cause of the disease
was unknown to ancient peoples.
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 the spread of malaria. 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 humans. More exactly, he discovered that insects carry the parasites and pass them to
humans.
In Eighteen-Eighty, 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 scientific 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 try to end the disease completely.
VOICE TWO:
Between Nineteen-Fifty-Five and Nineteen-Sixty-Nine, the World Health Organization’s Global Malaria
Eradication Program carried out 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 continued in Central America, some parts of South America,
and most 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 rapidly among people in Sri
Lanka, where it was believed the disease no longer existed. The disease also spread
in Central America and Southeast Asian countries, as well as 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 kinds of
parasites 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.
(Picture -Nico Colombant/VOA)
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.
Well 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 researchers 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 of the world 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.
Although these drugs are effective in preventing malaria, great numbers of people still die every year from the
disease. In almost all cases, this is because of delayed treatment or no treatment at all. International health
organizations are increasing efforts to reduce the deaths from malaria in the next ten years.
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VOICE ONE:
This SCIENCE IN THE NEWS program was written by Oliver Chanler. It was produced by George Grow. This
is Bob Doughty.
VOICE TWO:
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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