牧羊人的烦恼

丁黎明

肠道寄生虫总是困扰着澳大利亚和新西兰的牧羊人，如今，或许有新的方法可以帮助解决这一问题。

1 Sheep farmers in Australia and New Zealand have a problem. Their animals are affected by worms （寄生虫） which cause them to become extremely thin and can， in severe cases， kill them.

2 Dr Paz of the University of Western Australia knew from past work that sheep with severe worm problems tended to have abnormal bacterial populations in their waste. This led him to wonder whether the worms in the intestines （肠） of resistant sheep were somehow hampering the worms activities. He and his team therefore looked at a flock of 200 sheep at a farm in Western Australia and selected ten that had particularly high loads of worm eggs in their waste （1，940 per gram， on average） and ten that had low loads （410 per gram， on average）.

3 As they had imagined， the researchers did indeed find systematic differences between the two groups. These differences were particularly notable in the small intestine， where the worms live， with resistant sheep having richer and more diverse bacterial populations in this part of the intestines than vulnerable animals did. In particular， the team noticed that populations of bacteria were especially abundant in the resistant animals.

4 It is， of course， possible that the worms are affecting the sheeps micro?organisms in the intestines， rather than the other way around. But Dr Paz thinks this is unlikely， because all of the sheep seem to have some worms. Rather， he suspects， genetically resistant sheep are providing an intestinal environment beneficial to bacteria which either produce chemical elements that drive away the worms or consume resources which the worms depend on. If that is correct， it opens up a third approach to worm control， which is to employ probiotics（益生菌） to shape the intestine micro?organism of flocks directly， rather than relying on selective breeding to do it.

1. What effect might worms have on sheep farmers？

A. They may suffer a economic loss.

B. They may become too thin.

C. They may be killed by worms.

D. They have to raise more sheep.

2. What does the underlined word “hampering” in paragraph 2 mean？

A. Contributing to. B. Helping.

C. Preventing. D. Managing.

3. What are the new findings of Dr Paz？

A. Bacteria particularly like to live in sheeps small intestine.

B. Healthier sheep have more diverse bacteria populations in their intestines.

C. Sheep in Western Australia have more worms than those in New Zealand.

D. Sheep with serious worm problems tend to have abnormal bacterial populations.

Difficult sentence in the text

These differences were particularly notable in the small intestine， where the worms live， with resistant sheep having richer and more diverse bacterial populations in this part of the intestines than vulnerable animals did. 這些差异在寄生虫生活的小肠中尤其显著，与易受感染的羊相比，对寄生虫有抵抗力的羊在肠道的这部分拥有更丰富和更多样化的细菌种群。

【点石成金】本句是一个主从复合句，where引导的是非限制性定语从句，另有with的复合结构作状语。

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