The Buzz About Diseases Spread by Mosquitoes
The insects cause millions of deaths throughout the world. Transcript of radio broadcast:
25 May 2009
VOICE ONE:
This is SCIENCE IN THE NEWS in VOA Special English. I’m Shirley Griffith.
VOICE TWO:
And I’m Steve Ember. Today, we tell about diseases spread by mosquitoes — the most widely hated insects in the world.
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VOICE ONE:
There are more than two thousand different kinds of mosquitoes. Female mosquitoes bite people to drink their blood. Male mosquitoes do not drink blood. They drink fluids from plants. The female mosquito uses its thin sucking tube to break the skin, find blood and inject the victim with a substance that keeps blood flowing.
The female mosquito drinks the blood and uses it to produce as many as two hundred fifty eggs. The insect leaves the eggs in any standing water.
VOICE TWO:
The eggs produce worm-like creatures called larvae in two days to a few months. However, some eggs can stay in water for years until conditions are right for development. The larvae feed on organisms in the water. After four to ten days, they change again, into creatures called pupas. The pupas rise to the surface of the water. Adult mosquitoes pull themselves out of the pupas and fly away.
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VOICE ONE:
The World Health Organization says mosquitoes carry organisms that cause disease and death for millions of people throughout the world. The most important disease spread by mosquitoes is malaria. The W.H.O. says two hundred forty-seven million people became infected with malaria in two thousand six. Malaria caused almost one million deaths, mostly among children in Africa. The disease is found in more than one hundred countries in Africa, Asia, the western Pacific Ocean, the Middle East and Central and South America.
VOICE TWO:
Malaria parasites enter a person’s blood through a mosquito bite. These organisms travel to the liver. They grow and divide there. After a week or two, the parasites invade red blood cells and reproduce thousands of times. They cause the person’s body temperature to rise. They also may destroy major organs. People with malaria may suffer kidney failure or loss of red blood cells.
Some medicines are generally effective in preventing and treating malaria. They are designed to prevent the parasites from developing in the body. People die from malaria because they are not treated for the disease or the treatment is delayed.
VOICE ONE:
The World Health Organization says mosquito control efforts are improving in many areas. But it warns that mosquitoes are becoming increasingly resistant to pesticides, the products used to kill insects.
This month, the W.H.O. joined with other groups to announce a new effort against malaria. The goal is to reduce use of the pesticide known as DDT. The United States banned most uses of DDT in nineteen seventy-two.
The W.H.O. announced ten projects to test non-chemical methods for fighting mosquitoes. These include trees that repel mosquitoes and fish that eat the larvae. However, officials say any reduction in the use of pesticides must make sure that disease control efforts are not weakened.
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VOICE TWO:
Mosquitoes also carry dengue fever. The insects can survive in new and different environments. They can spread diseases to new areas. For example, experts say only nine countries had dengue fever before nineteen seventy. Since then, the disease has spread to more than one hundred countries.
The World Health Organization says about fifty million people suffer from dengue fever each year. There is no cure. Children may develop a kind of the disease that is not serious. They may have a high body temperature and some areas of skin may turn red.
VOICE ONE:
Older adults suffer from dengue fever much more. They may develop reddish skin and lose their sense of taste. They also may have pain in the head or behind their eyes. And they may experience pain in joints such as the elbow or knee. This kind of joint pain is the reason why dengue fever is sometimes known as breakbone fever.
The most severe kind of the disease is called dengue hemorrhagic fever. People who have this disease bleed from the nose or other openings in the body. Dengue hemorrhagic fever kills about five percent of all people it infects. The only treatment involves controlling the bleeding and replacing lost body fluids.
VOICE TWO:
Yellow fever is another disease carried by mosquitoes. There are no effective drugs against yellow fever. Doctors can only hope that a person’s defense system is strong enough to fight the disease. Yellow fever is found mainly in Africa, the northern part of South America and the islands of the Caribbean Sea. The World Health Organization says there are an estimated two hundred thousand cases of the disease and thirty thousand deaths each year.
A virus causes yellow fever. A few days after a mosquito bite, the victim experiences high body temperature and pain in the head or muscles. Victims also may expel food they ate. Most patients improve after three to four days.
VOICE ONE:
However, fifteen percent of patients develop a more serious condition. High body temperatures return and the body turns yellow in color. The victim bleeds from the nose, mouth, eyes or stomach. Half the people with this condition die within ten to fourteen days.
A vaccine can prevent yellow fever. Experts say the vaccine is safe and very effective. The protection continues for at least ten years and possibly for life.
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VOICE TWO:
Mosquitoes also carry lymphatic filariasis, also known as elephantiasis. The disease has affected more than one hundred twenty million people. One-third of those infected live in India. Another third are in Africa. The others live in South Asia or islands in the Pacific Ocean.
Mosquito bites spread the worms that cause elephantiasis. People usually begin to develop the disease as children. Many children never experience signs of the disease. But it may cause hidden damage to the body’s lymphatic system and kidneys.
The worst signs of elephantiasis appear in adults. The signs are more common in men than in women. These include damage to the arms, legs and reproductive organs. Two drugs are effective in treating the disease.
VOICE ONE:
Another disease carried by mosquitoes is encephalitis. It causes an infection or swelling of the brain. Many different viruses cause different kinds of the disease. One virus lives naturally in birds and horses. Mosquitoes spread it to people. Mosquitoes in several Asian countries spread a kind of encephalitis known as Japanese encephalitis. A vaccine can prevent this sickness.
Other kinds of encephalitis include West Nile, Saint Louis and Eastern Equine. Most healthy people infected with the virus show no signs. Or they become sick for only a day or two. But those with weak natural defenses may develop a severe infection. They may suffer from high body temperature, head pain, shaking and even death.
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VOICE TWO:
Experts have learned many things about mosquitoes. For example, the insects can smell carbon dioxide in the breath of a person or animal from as far away as sixty meters. Mosquitoes often like the blood of animals better than the blood of people.
The insects also like dark colors. They do not bite women who are bleeding during their fertility period. But they do bite pregnant women. Many kinds of mosquitoes are most active in the early morning and early evening. They eat mostly at night.
VOICE ONE:
Experts say the best way to prevent the diseases carried by mosquitoes is not to be bitten by one. There are several ways to prevent mosquito bites. Do not keep standing water anywhere near your home.
Remove all containers that could provide a place for mosquitoes to live. Stay in an enclosed area when mosquitoes are most active. Wear clothes that cover most of the body.
Other ways to prevent mosquito bites are to put anti-insect products on the skin, clothing and sleeping areas. Also, place nets treated with insect poison on windows and over the bed at night.
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VOICE TWO:
This SCIENCE IN THE NEWS was written by Nancy Steinbach. Brianna Blake was our producer. I’m Steve Ember.
VOICE ONE:
And I’m Shirley Griffith. Join us again next week for more news about science in Special English on the Voice of America.
Looking for New Uses for Spices — in the Medical Lab
Researchers learn that spices may be good for more than cooking. Transcript of radio broadcast:
18 May 2009
VOICE ONE:
This is SCIENCE IN THE NEWS, a program in VOA Special English. I’m Bob Doughty.
VOICE TWO:
And I’m Faith Lapidus. Herbs and spices help to sharpen the taste of many foods. Today, we tell about these food additives.
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VOICE ONE:
People have used herbs and spices in food for thousands of years. Some of these substances are valued for their sharp taste. Others are chosen for their smell.
Generally, herbs come from the green leaves of plants or vegetables. Spices come from other parts of plants and trees. For example, cinnamon comes from the hard outer cover of cinnamon plants. The spice ginger comes from the part of the ginger plant that grows underground.
VOICE TWO:
Herb and spice plants grow in many countries. For example, the Molucca Islands in Indonesia are famous for producing spices like cloves, nutmeg or mace. Vanilla comes from plants growing in South America.
Many people grow herb and spice plants near their homes. Then they dry the plants for later use. Some spices can even be grown in a house if they are placed in sunny areas next to windows.
VOICE ONE:
Spices have influenced world history. For example, the Goth people of Europe defeated Roman forces in battle more than sixteen centuries ago. After the fighting ended, the leader of the Goths is said to have demanded five thousand pounds of gold and three thousand pounds of pepper.
More recently, Marco Polo and Christopher Columbus discovered new lands while seeking to expand trade with spice-growing areas in Asia. The Italian cities of Genoa and Venice became powerful because they were at the center of the spice trade. The trade was so important to national economies that rulers launched wars in their struggle to control spices.
VOICE TWO:
Herbs and spices are commonly used because they can make food taste better. Several years ago, two American researchers reported another reason for spice use in cooking.
Researchers Paul Sherman and Jennifer Billing worked at Cornell University when their study was published in nineteen ninety-eight. They said spices contain substances that kill or slow the growth of dangerous bacteria in food. Some spices destroy bacteria. Spices have long been used to keep food safe to eat. In the past, spices also helped to prevent the wasting away of dead bodies.
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VOICE ONE:
A more recent study found that adding spices to meat before cooking at high temperatures may reduce harmful chemicals. Researchers from Kansas State University reported last year on their experiments with steaks.
The researchers found a major decrease in unwanted chemicals by preparing the meat with spice and herb marinades. The study showed that this may decrease formation of heterocyclic amines, also known as HCAs. The researchers say these chemicals may cause cancer in some people.
VOICE TWO:
America’s National Cancer Institute says cooking meat at very high temperatures produces the most HCAs. The chemicals form when amino acids react with creatine, a chemical found in muscles. But meats from organs and non-meat protein sources have little or no HCA.
Research on HCAs has made some people afraid to prepare meat on a grill – the place where meat is cooked on hot coals or an open fire. Cooking meat this way is a traditional favorite of many Americans during warm weather.
VOICE ONE:
The Kansas State University study, however, may show a way that reduces risk for people who grill on high heat. The K.S.U. researchers placed some steaks in already prepared spice mixes, or marinades. The meat then was grilled for five minutes on each side at a temperature of more than two hundred degrees Celsius. The researchers also cooked steaks marinated without spices, and steaks that were not marinated. They were prepared at the same temperature as meat with the marinade mixes.
The researchers compared levels of the HCAs in all the steaks. They found the HCAs in the meat marinated in spices had decreased up to eighty-eight percent. The study appeared in the publication Journal of Food Science.
VOICE TWO:
The Mayo Clinic operates three medical centers in the United States. Its Health Letter publication of November two thousand seven provided more evidence that herbs and spices can aid health.
For example, Mayo Clinic experts said people could reduce salt use by using herbs and spices instead. Too much salt is a problem for people with health problems like high blood pressure.
The experts said some plant chemicals are high in antioxidants — substances that remove harmful chemicals from the body. These plants include allspice, cloves, cinnamon, ginger, oregano, sage, thyme and turmeric.
VOICE ONE:
The experts also said antioxidants like garlic, rosemary, saffron and turmeric have qualities that could fight cancer. And, it said limited evidence shows that cinnamon, fenugreek and turmeric may affect blood sugar levels in people with diabetes.
Not all studies agree that spices could help diabetes patients. But some studies have suggested they could because of a suspected link between inflammation and diabetes. Inflammation is the body’s way of reacting to infection or other attack. Cinnamon may help reduce the inflammation in people with diabetes.
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VOICE TWO:
Last year, researchers from the University of Georgia reported that cinnamon could help reduce blood sugar. The researchers tested twenty-four common herbs and spices. The tests showed that many of the substances contained high levels of antioxidant chemicals known as polyphenols.
The researchers found that ground clove had the most polyphenols. Cloves were the most effective at calming inflammation of any spice or herb they tested. Cinnamon was second. But K.S.U. scientist James Hargrove noted that cinnamon gets more use in cooking than ground cloves. He said that means it could affect the health of more people. But the Mayo Clinic warns that cinnamon cannot replace proven medicines for diabetes.
VOICE ONE:
Other studies also note possible health effects from curry, a seasoning or sauce. Many people like to use curry to sharpen the taste of foods like meat, fish, rice and potatoes.
Several years ago, scientists in Singapore investigated curcumin, from the curry spice turmeric. The scientists based their study on earlier evidence that turmeric has strong antioxidant and anti-inflammatory qualities. They said turmeric also has been shown to reduce evidence of damage in the brains of patients with Alzheimer’s disease. But they said evidence was lacking about cases of Alzheimer’s in curry users, compared with people who did not use curry.
VOICE TWO:
For that reason, the researchers designed a study that examined results from a mental-performance test of older Asian adults. The people in the study were sixty to ninety three years old. None had severe memory losses. Those who sometimes ate curry, or ate it often or very often, did better than individuals who rarely or never ate curry. The American Journal of Epidemiology published a report about the study. The writers suggested that more studies were needed.
VOICE ONE:
Black cohosh is an herb that comes from the root or underground stems of a tall plant in the buttercup family. Black cohosh is sometimes called bugbane. American Indians used it for a number of women’s health conditions, including monthly menstrual pain.
Some women today have continued the tradition. They use the herb to help fight unpleasant conditions at the end of their reproductive years. These include difficulty sleeping at night and hot flashes, or sudden hot sweats.
Millions of people have used black cohosh without problems. However, the Office of Dietary Supplements of the National Institutes of Health notes that pregnant women may want to avoid it. The same is true of women with breast cancer and patients with liver problems. Should signs of liver disease develop, people should stop taking black cohosh and contact a doctor.
VOICE TWO:
This SCIENCE IN THE NEWS program was written by Jerilyn Watson. Our producer was Brianna Blake. I’m Faith Lapidus.
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.
Oldest Examples of Two Coral Species Are Found
Also: A study shows American bird populations are under stress. Transcript of radio broadcast:
11 May 2009
VOICE ONE:
This is SCIENCE IN THE NEWS in VOA Special English. I’m Bob Doughty.
VOICE TWO:
And I’m Faith Lapidus. This week, we will tell about newly-found organisms that are said to be among the oldest living organisms on Earth. And, we will tell about the first complete report of bird populations in the United States.
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VOICE ONE:
Hawaiian coral that is more than 4,200 years old
Hawaiian coral that is more than 4,200 years old
A research team says it has found corals that are more than four thousand years old. The corals were discovered at the bottom of the Pacific Ocean, near the Hawaiian Islands. The team made the discovery with a vehicle designed to operate deep underwater. At depths of nearly four hundred meters, the researchers found the oldest examples of two species of coral. One is a kind of deep-water black coral called Leiopathes. The other was a gold coral, called Gerardia.
A report on the team’s discovery was published recently in the Proceedings of the National Academy of Sciences.
VOICE TWO:
The team collected pieces of the coral and then used radio-carbon dating methods to find their age. The tests showed the organisms were, in fact, much older than reported in earlier estimates.
One of the researchers was Brendan Roark of Texas A-and-M University. He says the Leiopathes corals were shown to be about four thousand two hundred sixty-five years old. The Gerardia is believed to be about two thousand seven hundred forty-two years old.
The age of the corals would make them among the oldest living creatures in existence. Scientists know that some of the Bristlecone pines in northern California are also more than four thousand years old.
VOICE ONE:
Deep sea corals face numerous threats. They include illegal harvesting and activities linked to deep-sea fishing. Other threats include human pollution, acidification from carbon dioxide and rising temperatures in Earth’s atmosphere.
Professor Roark says corals are important because they support many other forms of sea life. He says they also can show part of the ocean’s ancient history. Corals have hard, stony skeletons that grow like tree trunks. The skeletons have growth rings that represent ocean water conditions at the time.
Professor Roark says knowing the age of the corals might help scientists understand earlier water conditions and ocean surface productivity. And, he says the discovery will add to what scientists know about Earth’s changing climate.
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VOICE TWO:
We share our environment with many organisms. But few give us more pleasure than birds. Their beauty and songs have become part of our understanding of what a healthy environment should support.
Yet a report released in March shows that many kinds of American birds are in trouble. The report is called “The State of the Birds United States Two Thousand Nine.” It says that nearly one third of about eight hundred bird species in the United States are threatened in some way.
VOICE ONE:
The report is said to provide the first complete study of American bird populations. It was based on three separate studies by a partnership of government agencies and environmental groups. The groups include the Cornell Lab of Ornithology, the National Audubon Society and the American Bird Conservancy.
Much of the information came from observations made by thousands of volunteers in more than four thousand places over forty years. The United States Fish and Wildlife Service led the effort to combine the information into one report.
VOICE TWO:
Interior Secretary Ken Salazar praised the report as an important scientific document on the health of American birds. But it is not only a warning about falling bird populations. The health of bird species tells researchers a lot about the condition of the environment.
The study grouped birds by the environments in which they live. It said grassland bird populations fell by about forty percent in forty years. That was the biggest drop reported. One reason for this is the disappearance of grasslands in the central United States. The report says only two percent of the grasslands that existed two centuries ago remain today.
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Birds depend on their environment to provide food and shelter. The report said loss of habitat is the biggest threat to American birds. Sixty-seven species are federally listed as endangered or threatened. But the report lists one hundred eight-four species that are considered in danger because of limited habitat, serious threats or falling populations.
The report also notes successes in bird conservation efforts. For example, the numbers of many wetland birds have recovered since measures were taken to protect more than twelve million hectares of wetlands.
One hundred thirty-nine wetland species have increased in number since the late nineteen-seventies. Pelicans, herons and geese are just a few of many recovering wetland species.
VOICE TWO:
Numbers of America’s national bird, the bald eagle, have recovered largely because of measures to fight pollution. In nineteen seventy-two, the federal government banned most uses of the insecticide D.D.T. The chemical used to kill mosquitoes also caused bird egg shells to thin and break. Species like the bald eagle, peregrine falcon and osprey nearly disappeared. Now, their populations seem secure.
But threats to other species continue to grow. Land development and agriculture are just two uses of natural resources that change and destroy environments that birds need. The cutting of forests is threatening woodland species like the Northern Spotted Owl.
VOICE ONE:
In addition to loss of habitat, birds face many other man-made threats. The report says up to one billion birds die each year from flying into objects like power lines, windows and tall buildings.
Environmentalists are studying ways to reduce this number, but these efforts are only beginning.
Climate change is one of the least understood threats to birds. The report says temperatures are estimated to increase by several degrees Celsius in the next one hundred years. And sea levels could rise by one half meter.
Already, rising temperatures have had an effect on migratory birds. Studies show that some American Robins are appearing in their nesting areas two weeks earlier than thirty years ago. Other birds, like the red-winged blackbirds and eastern bluebirds, are laying eggs earlier because of warmer temperatures. The fear is that, as birds move to nesting areas earlier, they will arrive before food is available.
VOICE TWO:
Birds native to one state are of special concern to wildlife experts. More than one third of all threatened or endangered bird species in America live on the Hawaiian Islands. Each island is home to a rich collection of animal and plant life. One hundred thirteen bird species are found nowhere else.
Seventy-one bird species have disappeared forever since people first arrived on the Hawaiian Islands one thousand seven hundred years ago. Today, thirty-one Hawaiian species are federally listed as endangered or threatened.
Non-native plants, animals and diseases are the main threats. Non-native animals like rats, cats and mongooses kill flightless birds and raid nests. Also, the loss of habitat to development and agriculture continue to endanger many rare species.
VOICE ONE:
Alicia King works for the Fish and Wildlife Service. She says the main message of the report is that conservation measures work when they are put in place. The successful recovery of some well-known species is evidence of this. But more needs to be done. She says there currently are not enough programs to study bird numbers and behavior.
Partnerships between public, private and tribal groups can help to provide the resources needed to protect America’s birds. But Miz King says the American people are an important part of the solution, too.
Americans spend one hundred twenty-two billion dollars on watching wildlife each year. And, millions of Americans enjoy watching birds. But the economic value of wild birds is only part of their importance. They also represent a part of a healthy environment that cannot be replaced.
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VOICE TWO:
This SCIENCE IN THE NEWS was written by Mario Ritter and Brianna Blake, who was also our producer. I’m Faith Lapidus.
VOICE ONE:
And I’m Bob Doughty. Read and listen to our programs at voaspecialenglish.com. Join us again next week for more news about science in Special English on the Voice of America.
