VOA标准英语2015--Study: Rats Pose Plague Risk in Croplands

Study: Rats Pose Plague Risk in Croplands

Efforts to boost food production in East Africa may increase the risk of plague. A new study says the conversion¹ of natural lands into croplands in Tanzania has been accompanied by a large increase in the rodent² population. The rodents³ are often infested⁴ with plague-carrying fleas⁵.

Dr. Kristofer Helgen, curator in charge of mammology at the Museum of Natural History in Washington – part of the Smithsonian Institution,  says plague is an ancient disease caused by a bacterium⁶ called Yersinia pestis.

“It captures the imagination when people hear about plague or the bubonic plague. I think we are instantly are transported to sometime in our imagination, distant in the past, where we think about the Black Death in European history," he said. "It maybe surprises people to learn that plague remains⁷ a public health concern in various parts of the world, especially in Africa south of the Sahara.”

Helgen said in recent decades croplands have expanded by 70 percent in northern Tanzania. In areas where maize⁸ was planted, the rodent population doubled compared to neighboring land that had not been cultivated.

“Plague circulates in small mammals and rodents. And when the conditions are right it’s a disease that can spread to people and it can still be a deadly disease," Helgen said. "Now, plague is a disease that is treatable with antibiotics⁹. And in that regard, it’s considerably¹⁰ maybe less scary, less alarming than other emerging diseases like Ebola. But we should remember that this is a disease that is still on the ground in Africa and remains a public health concern.”

Helgen said that animal populations vary according to land use.

“As natural conserved¹¹ lands in parts of East Africa are converted to human-use habitats, specifically agriculture -- we’re especially studying crop fields of corn – not surprisingly the animals that live of those landscapes are changing, too. And one of the most profound changes is the rodents that live in those landscapes,” he said.

Natural land has certain kinds of rodents, while farmland attracts others.

“When we study a conserved landscape in the area we see a particular community of rodents -- quite a few different species doing different things for a living, Helgen said. "When we study crop fields right next to that space what we see if that we have a very different community of rodents. And, in fact, in comes to be dominated by perhaps one species in particular that is very good at living in these human modified landscapes. That animal is called the African rat, or sometimes we call it the multimamate [it can feed 12 baby rats at one time] rate.”

“As agriculture expands it’s a perfect habitat for this animal. Population numbers can breed-up very rapidly along the front of moving and expanding croplands," he continued. "And this is an animal that we often will call a commensal rodent species. And literally¹² that word commensal means ‘eating from the same table.’ In other words, the notion that this is a rat that does go into people’s houses and villages and interacts with people in their living spaces.”

There are thousands of species and they are very successful, including the African rat.

“This species that we’re talking about today and others have huge, huge impacts on people’s lives as crop pests – consuming people’s food and their livelihood¹³ – and as animals that spread disease. Plague is just one of many different diseases that are rodent-borne in Africa and some are even, you know, more scary and more deadly,” he said.

One of them is Lassa fever, which can be mistaken for Ebola.

Also, the rats living in agricultural areas carry a larger number of plague-carrying fleas than rats in the forest. They’re also infested with types of fleas not found on forest rats.

The World Health Organization and the U.N. Food and Agriculture Organization are concerned about such rat populations and their possible effect on future food security.

1 conversion   

n.转化，转换，转变

参考例句：

• He underwent quite a conversion.他彻底变了。
• Waste conversion is a part of the production process.废物处理是生产过程的一个组成部分。

2 rodent   

n.啮齿动物；adj.啮齿目的

参考例句：

• When there is a full moon,this nocturnal rodent is careful to stay in its burrow.月圆之夜，这种夜间活动的啮齿类动物会小心地呆在地洞里不出来。
• This small rodent can scoop out a long,narrow tunnel in a very short time.这种小啮齿动物能在很短的时间里挖出一条又长又窄的地道来。

3 rodents   

n.啮齿目动物( rodent的名词复数 )

参考例句：

• Rodents carry diseases and are generally regarded as pests. 啮齿目动物传播疾病，常被当作害虫对待。 来自《简明英汉词典》
• Some wild rodents in Africa also harbor the virus. 在非洲，有些野生啮齿动物也是储毒者。 来自辞典例句

4 infested   

adj.为患的，大批滋生的（常与with搭配）v.害虫、野兽大批出没于( infest的过去式和过去分词 )；遍布于

参考例句：

• The kitchen was infested with ants. 厨房里到处是蚂蚁。
• The apartments were infested with rats and roaches. 公寓里面到处都是老鼠和蟑螂。

5 fleas   

n.跳蚤( flea的名词复数 )；爱财如命；没好气地（拒绝某人的要求）

参考例句：

• The dog has fleas. 这条狗有跳蚤。
• Nothing must be done hastily but killing of fleas. 除非要捉跳蚤，做事不可匆忙。 来自《简明英汉词典》

6 bacterium   

n.(pl.)bacteria 细菌

参考例句：

• The bacterium possibly goes in the human body by the mouth.细菌可能通过口进入人体。
• A bacterium is identified as the cause for his duodenal ulcer.一种细菌被断定为造成他十二指肠溃疡的根源。

7 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

8 maize   

n.玉米

参考例句：

• There's a field planted with maize behind the house.房子后面有一块玉米地。
• We can grow sorghum or maize on this plot.这块地可以种高粱或玉米。

9 antibiotics   

n.（用作复数）抗生素；（用作单数）抗生物质的研究；抗生素，抗菌素( antibiotic的名词复数 )

参考例句：

• the discovery of antibiotics in the 20th century 20世纪抗生素的发现
• The doctor gave me a prescription for antibiotics. 医生给我开了抗生素。

10 considerably   

adv.极大地；相当大地；在很大程度上

参考例句：

• The economic situation has changed considerably.经济形势已发生了相当大的变化。
• The gap has narrowed considerably.分歧大大缩小了。

11 conserved   

v.保护，保藏，保存( conserve的过去式和过去分词 )

参考例句：

• He conserved his energy for the game. 他为比赛而养精蓄锐。 来自《简明英汉词典》
• Under these conditions, the total mechanical energy remains constant, or is conserved. 在这种条件下，总机械能保持不变或机械能保存。 来自辞典例句

12 literally   

adv.照字面意义，逐字地；确实

参考例句：

• He translated the passage literally.他逐字逐句地翻译这段文字。
• Sometimes she would not sit down till she was literally faint.有时候，她不走到真正要昏厥了，决不肯坐下来。

13 livelihood   

n.生计，谋生之道

参考例句：

• Appropriate arrangements will be made for their work and livelihood.他们的工作和生活会得到妥善安排。
• My father gained a bare livelihood of family by his own hands.父亲靠自己的双手勉强维持家计。