[ti:SCIENCE IN THE NEWS] [ar:Voice of America] [al:VOA Special English] [by:WWW.51VOA.COM] [00:00.00]51VOA.COM [00:14.69]This is SCIENCE IN THE NEWS [00:16.71]in VOA Special English. [00:19.37]I'm Shirley Griffith. [00:20.81]And I'm Steve Ember. [00:22.36]Today,we tell about diseases [00:25.14]spread by mosquitoes [00:27.17]the most widely hated insects in the world. [00:31.31](MUSIC) [00:39.91]There are more than two thousand [00:42.13]different kinds of mosquitoes. [00:44.45]Female mosquitoes bite people [00:47.74]to drink their blood. [00:49.43]Male mosquitoes do not drink blood. [00:52.74]They drink fluids from plants. [00:55.99]The female mosquito uses its thin sucking tube [01:01.26]to break the skin, [01:03.07]find blood and inject the victim [01:06.46]with a substance that keeps blood flowing. [01:09.54]The female mosquito drinks the blood [01:13.03]and uses it to produce [01:15.22]as many as two hundred fifty eggs. [01:18.36]The insect leaves the eggs [01:20.74]in any standing water. [01:22.87]The eggs produce worm-like creatures [01:27.25]called larvae in two days to a few months. [01:31.25]However,some eggs can stay in water for years [01:36.14]until conditions are right for development. [01:39.61]The larvae feed on organisms in the water. [01:43.66]After four to ten days, [01:46.50]they change again, [01:48.11]into creatures called pupas. [01:50.83]The pupas rise to the surface of the water. [01:54.57]Adult mosquitoes pull themselves [01:58.05]out of the pupas and fly away. [02:01.29]The World Health Organization says [02:05.28]mosquitoes carry organisms [02:07.68]that cause disease and death [02:10.62]for millions of people throughout the world. [02:13.82]The most important disease [02:16.74]spread by mosquitoes is malaria. [02:19.76]The W.H.O.says [02:22.62]two hundred forty-seven million people [02:25.96]became infected with malaria [02:29.03]in two thousand six. [02:31.01]Malaria caused almost one million deaths, [02:35.68]mostly among children in Africa. [02:39.20]The disease is found in more than [02:42.50]one hundred countries in Africa,Asia, [02:46.73]the western Pacific Ocean, [02:48.96]the Middle East and Central and South America. [02:52.91]Malaria parasites enter a person's blood [02:58.10]through a mosquito bite. [02:59.98]These organisms travel to the liver. [03:03.27]They grow and divide there. [03:06.73]After a week or two, [03:09.03]the parasites invade red blood cells [03:12.71]and reproduce thousands of times. [03:16.42]They cause the person's body temperature to rise. [03:20.77]They also may destroy major organs. [03:24.75]People with malaria may suffer kidney failure [03:29.24]or loss of red blood cells. [03:32.22]Some medicines are generally effective [03:36.51]in preventing and treating malaria. [03:39.45]They are designed to prevent the parasites [03:42.81]from developing in the body. [03:45.04]People die from malaria [03:47.91]because they are not treated for the disease [03:51.32]or the treatment is delayed. [03:54.36]The World Health Organization says [03:57.64]mosquito control efforts are improving [04:01.07]in many areas. [04:02.65]But it warns that mosquitoes [04:06.11]are becoming increasingly resistant to pesticides, [04:09.95]the products used to kill insects. [04:13.13]This month,the W.H.O.joined with other groups [04:18.08]to announce a new effort against malaria. [04:21.78]The goal is to reduce use of the pesticide [04:26.34]known as DDT. [04:28.60]The United States banned most uses of DDT [04:33.40]in nineteen seventy-two. [04:36.02]The W.H.O.announced ten projects [04:40.85]to test non-chemical methods [04:43.82]for fighting mosquitoes. [04:45.69]These include trees that repel mosquitoes [04:49.70]and fish that eat the larvae. [04:52.45]However, [04:53.88]officials say any reduction [04:56.28]in the use of pesticides must make sure [04:59.84]that disease control efforts are not weakened. [05:03.82](MUSIC) [05:32.52]Mosquitoes also carry dengue fever. [05:35.12]The insects can survive in new [05:38.30]and different environments. [05:40.56]They can spread diseases to new areas. [05:43.93]For example, [05:45.54]experts say only nine countries [05:49.39]had dengue fever before nineteen seventy. [05:53.31]Since then, [05:54.93]the disease has spread [05:56.67]to more than one hundred countries. [05:59.25]The World Health Organization says [06:02.76]about fifty million people suffer [06:05.53]from dengue fever each year. [06:07.88]There is no cure. [06:09.98]Children may develop a kind of the disease [06:13.79]that is not serious. [06:15.39]They may have a high body temperature [06:18.95]and some areas of skin may turn red. [06:23.07]Older adults suffer from dengue fever much more. [06:27.79]They may develop reddish skin [06:30.80]and lose their sense of taste. [06:33.59]They also may have pain in the head [06:37.09]or behind their eyes. [06:39.10]And they may experience pain in joints [06:43.01]such as the elbow or knee. [06:45.74]This kind of joint pain is the reason [06:49.55]why dengue fever is sometimes [06:52.57]known as breakbone fever. [06:55.15]The most severe kind of the disease [06:58.69]is called dengue hemorrhagic fever. [07:01.35]People who have this disease bleed [07:05.20]from the nose or other openings in the body. [07:08.71]Dengue hemorrhagic fever kills about [07:12.85]five percent of all people it infects. [07:16.65]The only treatment involves [07:19.47]controlling the bleeding [07:20.84]and replacing lost body fluids. [07:24.24]Yellow fever is another disease [07:27.84]carried by mosquitoes. [07:29.34]There are no effective drugs [07:32.11]against yellow fever. [07:33.82]Doctors can only hope [07:36.27]that a person's defense system is strong enough [07:40.04]to fight the disease. [07:41.69]Yellow fever is found mainly in Africa, [07:45.98]the northern part of South America [07:49.18]and the islands of the Caribbean Sea. [07:52.33]The World Health Organization says [07:55.79]there are an estimated [07:57.60]two hundred thousand cases of the disease [08:00.95]and thirty thousand deaths each year. [08:04.90]A virus causes yellow fever. [08:08.47]A few days after a mosquito bite, [08:11.66]the victim experiences high body temperature [08:15.30]and pain in the head or muscles. [08:18.63]Victims also may expel food they ate. [08:23.26]Most patients improve after three to four days. [08:27.69]However,fifteen percent of patients [08:32.60]develop a more serious condition. [08:35.35]High body temperatures return [08:38.54]and the body turns yellow in color. [08:42.03]The victim bleeds from the nose,mouth, [08:46.29]eyes or stomach. [08:48.46]Half the people with this condition die [08:52.08]within ten to fourteen days. [08:54.56]A vaccine can prevent yellow fever. [08:58.50]Experts say the vaccine is safe [09:02.28]and very effective. [09:04.20]The protection continues for [09:07.30]at least ten years and possibly for life. [09:11.22](MUSIC) [09:26.52]Mosquitoes also carry lymphatic filariasis, [09:30.11]also known as elephantiasis. [09:32.75]The disease has affected more than [09:35.33]one hundred twenty million people. [09:38.00]One-third of those infected live in India. [09:42.62]Another third are in Africa. [09:45.73]The others live in South Asia or islands [09:49.88]in the Pacific Ocean. [09:51.77]Mosquito bites spread the worms [09:54.97]that cause elephantiasis. [09:57.20]People usually begin to develop the disease [10:01.37]as children. [10:02.33]Many children never experience signs [10:06.64]of the disease. [10:08.06]But it may cause hidden damage [10:11.27]to the body's lymphatic system and kidneys. [10:15.16]The worst signs of elephantiasis [10:18.51]appear in adults. [10:20.51]The signs are more common in men than in women. [10:24.86]These include damage to the arms, [10:28.47]legs and reproductive organs. [10:32.13]Two drugs are effective in treating the disease. [10:36.62]Another disease carried [10:39.62]by mosquitoes is encephalitis. [10:42.36]It causes an infection or swelling of the brain. [10:46.81]Many different viruses [10:49.38]cause different kinds of the disease. [10:52.18]One virus lives naturally in birds and horses. [10:57.35]Mosquitoes spread it to people. [11:00.47]Mosquitoes in several Asian countries [11:04.32]spread a kind of encephalitis [11:06.76]known as Japanese encephalitis. [11:09.99]A vaccine can prevent this sickness. [11:13.39]Other kinds of encephalitis include West Nile, [11:18.78]Saint Louis and Eastern Equine. [11:22.19]Most healthy people infected with the virus [11:26.35]show no signs. [11:28.59]Or they become sick for only a day or two. [11:32.63]But those with weak natural defenses [11:36.62]may develop a severe infection. [11:39.60]They may suffer from high body temperature, [11:43.16]head pain,shaking and even death. [11:47.44](MUSIC) [12:07.47]Experts have learned many things [12:09.31]about mosquitoes. [12:10.67]For example, [12:12.02]the insects can smell carbon dioxide [12:15.36]in the breath of a person or animal [12:18.20]from as far away as sixty meters. [12:22.06]Mosquitoes often like the blood of animals [12:26.29]better than the blood of people. [12:28.75]The insects also like dark colors. [12:32.94]They do not bite women who are bleeding [12:36.34]during their fertility period. [12:38.67]But they do bite pregnant women. [12:42.09]Many kinds of mosquitoes are most active [12:46.44]in the early morning and early evening. [12:50.11]They eat mostly at night. [12:53.38]Experts say the best way [12:56.76]to prevent the diseases [12:58.48]carried by mosquitoes [13:00.13]is not to be bitten by one. [13:02.61]There are several ways [13:05.01]to prevent mosquito bites. [13:06.82]Do not keep standing water anywhere [13:10.42]near your home. [13:11.64]Remove all containers [13:14.82]that could provide a place [13:16.25]for mosquitoes to live. [13:18.03]Stay in an enclosed area [13:21.05]when mosquitoes are most active. [13:24.01]Wear clothes that cover most of the body. [13:28.27]Other ways to prevent mosquito bites [13:31.95]are to put anti-insect products on the skin, [13:35.83]clothing and sleeping areas. [13:38.67]Also,place nets treated with insect poison [13:43.47]on windows and over the bed at night. [13:46.87](MUSIC) [14:01.75]This SCIENCE IN THE NEWS program [14:04.15]was written by Nancy Steinbach. [14:06.35]Brianna Blake was our producer. [14:08.97]I'm Steve Ember. [14:10.61]And I'm Shirley Griffith. [14:12.41]Join us again next week [14:14.76]for more news about science [14:17.37]in Special English on the Voice of America.