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新东方网为大家带来2020托福听力练习：鸡味可驱蚊防疟疾（下载），希望对大家有所帮助!更多内容请随时关注新东方网!
In Africa's battle against malaria, two low-tech tactics—insecticides and bed nets—have done a decent job killing off mosquitoes. "But it's mainly one species that's been affected. That's a species called Anopheles gambiae, often referred to the African malaria mosquito." Rickard Ignell, a chemical ecologist at the Swedish University of Agricultural Sciences.
He says, despite that success, the problem is far from solved. For one, mosquitoes are developing resistance to insecticides. And two, there are many other species that can spread the disease. Including one that's common in the horn of Africa: Anopheles arabiensis.
Unlike the pickier gambiae, its palate is wide-ranging. Arabiensis sucks the blood of cattle, sheep, goats. But… not chickens. "Chickens like mosquitoes. So they'll actively feed on mosquitoes and other insects. So avoiding chickens could be a way of surviving, and evolving a way of smelling the chickens could be an early warning system for them."
And it turns out, that aversion to chickens can be used against the insects. Ignell and his colleagues isolated chemical compounds from chicken feathers, and dispensed them next to a human sleeping under a bed net—a human lure. And they found that fewer mosquitoes came round for a snack, due to the repellent chemicals. The findings appear in the Malaria Journal.
Ignell says this chicken cologne won't be immediately available. "Ideally the world would be like that, that we could bottle it up and send it off and they don't have to pay anything. But that's not the case usually." Luckily, there's an equally effective substitute. "We can actually reduce the number of mosquitoes indoors by just using a chicken. So that's probably the cheapest option."
翻译见下页
非洲在对抗疟疾时用了两种低科技手段：杀虫剂和蚊帐，这两种方法有效地杀死了蚊子。“但是，这两种方法只能对一个物种产生影响。这个物种是冈比亚按蚊，常被称为非洲疟蚊。”瑞典农业科学大学的化学生态学家理查德·伊格内尔说道。
他表示，虽然这两种方法取得了成功，但问题远远没有解决。一方面，蚊子已经对杀虫剂产生了抗药性。另一方面，还有很多其它物种可以传播疾病。其中一个物种就是在非洲之角这一地区常见的阿拉伯按蚊。
与更为挑剔的冈比亚按蚊不同，阿拉伯按蚊的口味更为广泛。阿拉伯按蚊会吸牛、绵羊、山羊的血，但是……却不会吸鸡的血。“首先，鸡喜欢蚊子。所以它们会以蚊子和其他昆虫为食。因此，对蚊子来说，不吸鸡的血可能是一种生存方式，而使闻鸡类味道的能力得到进化可以成为早期预警系统。”
事实证明，可以利用这种对鸡类的厌恶感来对抗昆虫。伊格内尔和同事从鸡的羽毛中分离出化合物，然后将这种化合物放置在睡在蚊帐里的人类的旁边，这是一种人为诱惑。他们发现，由于讨厌这种化学物质，很少有蚊子会进入蚊帐吸血。这项研究结果发表在《疟疾杂志》上。
伊格内尔表示，现在还不能马上提供这种鸡味古龙香水。“最理想的情况是，我们可以把它装进瓶子里，然后让味道散发出去，它们不需要付出什么。但是显然情况并非如此。”幸运的是，有一个同样有效的替代品，“我们可以用一只鸡来减少室内蚊子的数量。可能这是最便宜的选择。”
重点讲解：
kill off 被全部杀死;被灭绝;
例句：Their natural predators have been killed off.
它们的天敌被全部杀死。
2. be far from 根本不;远远不;
例句：His explanation was far from satisfactory.
他的解释一点也不令人满意。
3. turn out 结果发现;结果是;
例句：It turned out to be a wild-goose chase.
结果证明这只不过是一场徒劳。
4. due to 由于;因为;
例句：Accidents due to driving at high speed were very common that weekend.
在那个周末因高速驾驶造成的交通事故很多。
以上是新东方网为大家带来的2020托福听力练习：鸡味可驱蚊防疟疾（下载），希望认真积极的备考，早日取得优异的成绩。更多内容请随时关注新东方网!
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