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VOA慢速英语 2007 1218a

时间:2008-03-20 03:10来源:互联网 提供网友:蓝静子   字体: [ ]
    (单词翻译:双击或拖选)

This is the VOA Special English Agriculture Report.

 
 
Exotic Newcastle disease is a bird virus found in many parts of the world. Many kinds of birds carry it. But it especially affects chickens and a few others.

It spreads very fast and there is no treatment. Many birds die without appearing sick. The infection does not present a serious health threat to humans. But economic losses can be huge as birds are destroyed and trade is restricted to contain outbreaks.

Exotic Newcastle disease, also known as END, is the most severe form of Newcastle disease.

Experts say the easiest way to prevent the virus is to import birds from flocks that are disease-free. Vaccines1 are also used, although experts say the virus may sometimes cause deaths even in vaccinated2 flocks.

In the United States, the Agriculture Department says poultry3 birds are rarely vaccinated against the virus unless an outbreak happens. The most recent outbreak began in two thousand two in California. State officials said it cost more than one hundred sixty million dollars to fight. California was declared disease-free the next year, after the killing4 of more than three million birds.

The Global Invasive Species Database says signs of the disease may appear from two to fifteen days after a bird is infected. An infected hen lays fewer or no eggs, or eggs with thin shells. A sick bird may develop breathing and intestinal5 problems and twist its head and neck. It may run around in circles or not move at all.

Exotic Newcastle disease spreads fastest among birds kept close together. The virus is spread through bird droppings and fluid from the nose, mouth and eyes.

To control outbreaks, experts advise quick destruction of infected flocks. They also advise limiting entry to farms and disinfecting vehicles as they come and go.

People can also transport the virus on their shoes and clothes. The virus can survive several weeks in a warm, moist environment. And there seems to be no limit if it is frozen. But ultraviolet rays in sunlight can kill it.

To reduce infection risks, the Organization for World Animal Health warns against keeping any pet birds on a farm. It even advises against hiring pet bird owners as farm workers. The Agriculture Department says Amazon parrots, for example, can spread the virus for more than a year but not get sick.

And that's the VOA Special English Agriculture Report, written by Jerilyn Watson. I'm Steve Ember.

 


点击收听单词发音收听单词发音  

1 vaccines c9bb57973a82c1e95c7cd0f4988a1ded     
疫苗,痘苗( vaccine的名词复数 )
参考例句:
  • His team are at the forefront of scientific research into vaccines. 他的小组处于疫苗科研的最前沿。
  • The vaccines were kept cool in refrigerators. 疫苗放在冰箱中冷藏。
2 vaccinated 8f16717462e6e6db3389d0f736409983     
[医]已接种的,种痘的,接种过疫菌的
参考例句:
  • I was vaccinated against tetanus. 我接种了破伤风疫苗。
  • Were you vaccinated against smallpox as a child? 你小时候打过天花疫苗吗?
3 poultry GPQxh     
n.家禽,禽肉
参考例句:
  • There is not much poultry in the shops. 商店里禽肉不太多。
  • What do you feed the poultry on? 你们用什么饲料喂养家禽?
4 killing kpBziQ     
n.巨额利润;突然赚大钱,发大财
参考例句:
  • Investors are set to make a killing from the sell-off.投资者准备清仓以便大赚一笔。
  • Last week my brother made a killing on Wall Street.上个周我兄弟在华尔街赚了一大笔。
5 intestinal DbHzX     
adj.肠的;肠壁;肠道细菌
参考例句:
  • A few other conditions are in high intestinal obstruction. 其它少数情况是高位肠梗阻。 来自辞典例句
  • This complication has occasionally occurred following the use of intestinal antiseptics. 这种并发症偶而发生在使用肠道抗菌剂上。 来自辞典例句
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