科技。

　　Parasitology

　　寄生虫学

　　The risks of global worming

　　全球防虫的危险

　　Widespread use of anti-parasite drugs is reducing their value

　　广泛使用抗寄生虫药物正在降低其疗效

　　Safely grazing?

　　正在安全地吃草？

　　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，广泛使用抗生素促进了耐药病菌的进化。尽管它们从来没有失控，爆发人们一度为止恐惧的大规模瘟疫，但还是造成了大量本来可以避免的死亡。现在畜牧业中似乎也有类似现象。人们对家畜身上的寄生虫过分使用药物，这让它们也有了抗药性。这对动物的健康与安乐绝非好事，同样也会减少饲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.

　　这至少是乔治亚大学（University of Georgia）寄生虫病学家雷?卡普兰（Ray Kaplan）在他最近发表的有关这一问题的研究综述中得出的结论。他发表在《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.

　　绵羊与山羊受的影响最大。在澳大利亚、巴西和美国所做的研究表明，在这些国家的许多地区，一半或更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可用药物有抗药性。新西兰的农场饲养着大量绵羊，它们受到影响的比例比较低；但即使在该国，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。卡普兰博士引用了在阿根廷、巴西和新西兰所做的研究工作。马也是受害者，美国与欧洲的马身上都发现了抗药寄生虫。

　　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为"全球防虫"的现象——预防性地对所有家畜用药，而不是在动物身上真正出现了寄生虫时投药治疗。当然，防病胜于治病是常识。

　　Unfortunately, such promiscuous use of drugs is the best way to put selection pressure on the worms and encourage the evolution of resistant strains.

　　不幸的是，这样的预防性用药是在寄生虫身上施加选择压力的最佳方法，能够促进抗药品种的进化。

　　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 farmer's ability to control infestations. Better husbandry might help, too. Not grazing so many animals on a given patch of land would discourage transmission.

　　卡普兰博士认为，现在需要做的是加强管理与更有选择性地用药。寄生虫并非均匀寄生在各种动物身上。有少数动物是大多数寄生虫的寄主。集中治疗这些动物则会降低耐药性发生的可能性，同时也不会损害农民控制虫害的能力。改进饲养方法或许也有益处。不在一块草地上过量放牧动物会减轻虫害传播。

　　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.

　　但这本身也会带来问题，因为这会减少一座农场能饲养的家畜数目。这就引出了问题的症结：人们很难确定抗药寄生虫会造成多大的危害，因此也不知道该花多少代价来阻止抗药性蔓延，因为很重要的是，卡普兰博士在纵观研究结果时发现有关数据相当零散。但这些数据还是很令人忧虑，值得进一步跟踪，因为一旦人们无法控制抗药性，就确实可能会付出惨重的代价。

　　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.

　　无法就此责备某个农民。这是一个公地悲剧 [注]，许多明智的个人决定导致了群体的困难。但或许农民们有责任多想想他们应该如何使用抗寄生虫药物。如果放弃这一责任，他们或许有一天会发现这些药物变得全然无用。