FOR decades, the overuse of antibiotics has encouraged the evolution of drug-resistant bacteria which, though they have never broken out and caused an epidemic in the way that was once feared, have nevertheless been responsible for many deaths that might otherwise have been avoided. Now something similar seems to be happening in agriculture. The overuse of drugs against parasitic worms which infest stock animals means that these, too, are becoming drug-resistant. That is bad for the animals health and welfare, and equally bad for farmers profits.几十年来，普遍用于抗生素增进了耐药病菌的演化。尽管它们根本没失控，愈演愈烈人们一度为止不安的大规模瘟疫，但还是造成了大量本来可以防止的丧生。

现在畜牧业中或许也有类似于现象。人们对家畜身上的寄生虫过分用于药物，这让它们也有了抗药性。这对动物的身体健康与安乐毕竟好事，某种程度也不会增加圈养它们的农民的利润。This, at least, is the conclusion drawn by Ray Kaplan, a parasitologist at the University of Georgia who has just published a review of research on the problem. His results, which appear in Veterinary Parasitology, make grim reading.这最少是乔治亚大学（University of Georgia）寄生虫病学家雷?卡普兰（Ray Kaplan）在他最近公开发表的有关这一问题的研究综述中得出结论的结论。

他公开发表在《兽医寄生虫学》（Veterinary Parasitology）上的文章读来让人心情沉重。Sheep and goats are the worst affected. Studies in Australia, Brazil and the United States suggest that animals in half or more of farms in many parts of those countries are infested with drug-resistant worms. In some cases the parasites are resistant to every drug that can be thrown at them. The proportion of infested farms is lower in New Zealand, a country that has a huge population of sheep, but even there it is rising at a worrying rate.绵羊与山羊不受的影响仅次于。在澳大利亚、巴西和美国所做到的研究指出，在这些国家的许多地区，一半或更加多的农场中的家畜身上有耐药寄生虫。

有些农场的寄生虫对所有能用药物有抗药性。新西兰的农场圈养着大量绵羊，它们受到影响的比例较为较低；但即使在该国，不受影响农场比例的增长速度还是令人担心。

Cattle, too, are afflicted. Dr Kaplan cites work done in Argentina, Brazil and New Zealand. And horses suffer as well, with resistant worms turning up in both America and Europe.家牛也身受其害。卡普兰博士提到了在阿根廷、巴西和新西兰所做到的研究工作。马也是受害者，美国与欧洲的马身上都找到了抗药寄生虫。

The root of the problem is what Dr Kaplan refers to as global worming-giving drugs prophylactically to all livestock rather than reserving them for use as a treatment when an animal actually becomes infested. It is common sense, of course, to try to prevent infestation rather than merely treating it once it has arisen.问题的根源是卡普兰博士称作全球防虫的现象——预防性地对所有家畜用药，而不是在动物身上确实经常出现了寄生虫时投药化疗。当然，防病败于医治是常识。

Unfortunately, such promiscuous use of drugs is the best way to put selection pressure on the worms and encourage the evolution of resistant strains.意外的是，这样的预防性用药是在寄生虫身上产生自由选择压力的最佳方法，需要增进抗药品种的演化。What is needed, says Dr Kaplan, is more selective drug use, and better management. Worms are not evenly distributed. Instead, a minority of animals play host to most of them. Aiming treatment at those animals would reduce the likelihood of resistance emerging without harming a farmers ability to control infestations. Better husbandry might help, too. Not grazing so many animals on a given patch of land would discourage transmission.卡普兰博士指出，现在必须做到的是强化管理与更加有选择性地用药。

寄生虫并非均匀分布宿主在各种动物身上。有少数动物是大多数寄生虫的宿主。集中于化疗这些动物则不会减少耐药性再次发生的可能性，同时也会伤害农民掌控虫害的能力。改良圈养方法也许也有益处。

不出一块草地上过量耕种动物不会减低虫害传播。That, though, would bring problems of its own, as it would reduce the number of animals which could be raised on a given farm. Which leads to the nub of the issue: it is hard to work out exactly how much damage resistant worms are doing, and thus how much effort should be put into trying to stop the spread of resistance-not least because, as Dr Kaplan found out when he conducted his survey, the data are pretty sporadic. But they are worrying enough to be worth following up, for if resistance did get out of hand the consequences could be very expensive indeed.但这本身也不会带给问题，因为这不会增加一座农场能圈养的家畜数目。这就引向了问题的症结：人们很难确认抗药寄生虫不会导致多大的危害，因此也不告诉该花上多少代价来制止抗药性蔓延到，因为很最重要的是，卡普兰博士在纵观研究结果时找到有关数据非常零散。

但这些数据还是很令人担忧，有一点更进一步追踪，因为一旦人们无法控制抗药性，就显然可能会代价惨烈的代价。No one farmer is to blame. This is a tragedy of the commons, in which sensible individual decisions have led to a collective difficulty. But it might behove farmers to think more about how they use anti-worm drugs. If they do not, they may find that those drugs have become useless.无法早已责备某个农民。这是一个公地悲剧 [录]，许多明智的个人要求造成了群体的艰难。但也许农民们有责任多看看他们应当如何用于外用寄生虫药物。

如果退出这一责任，他们也许有一天不会找到这些药物显得毕竟多余。

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