狗能嗅出柑橘业最具毁灭性的病原体威胁

狗能嗅出柑橘业最具毁灭性的病原体威胁

One of the most severe crop pandemics in modern times is that to citrus trees, caused by a bacterium that jumped from the animal to plant kingdom within the last 200 years. Once a tree is infected with the exotic pathogen, called huanglongbing (HLB), it will die. There is no cure, and the disease can spread fast. The only method to halt an entire crop collapse? Eliminate the tree.

现代最严重的农作物流行病之一是柑橘树，它是由一种细菌引起的，这种细菌在过去200年里从动物王国跳到植物王国。一旦树木被外来病原体黄龙病(HLB)感染，它就会死亡。目前还没有治愈的方法，而且这种疾病可以迅速传播。唯一能阻止作物全面崩溃的方法是什么?毁掉所有的树。

"Proportionally, this epidemic has affected a larger proportion of the worldwide host population than most emerging zoonotic and botanical epidemics,” write the team in Proceedings of the National Academy of Sciences. "Originating in Asia in the previous century, HLB has spread to the majority of citrus-producing areas of the world, emerging throughout the Western Hemisphere with devastating results."

研究小组在《美国国家科学院院刊》上写道:“从比例上看，这种流行病对全球宿主人口的影响比大多数新出现的人畜共患病和植物流行病更大。”“HLB起源于上个世纪的亚洲，现已传播到世界上大部分的柑橘产区，并在整个西半球出现，带来了灾难性的后果。”

Florida lost around 80 percent of its citriculture production and around 70 percent of its juice plants. The team warn that if not curtailed, the pathogen could destroy Florida’s citrus industry, previously the second largest in the world. This is nothing to scoff at: Citrus fruits are among the highest-value fruit crop for international trade, with oranges topping the list, followed by grapefruits, lemons, and limes.

佛罗里达损失了大约80%的柑橘生产和大约70%的果汁工厂。研究小组警告说，如果不加以限制，这种病菌可能会摧毁佛罗里达的柑橘产业。这并不是什么值得嘲笑的事情:柑橘类水果是国际贸易中价值最高的水果作物之一，其中橙子位居榜首，其次是葡萄柚、柠檬和酸橙。

"As a consequence, over the last 13 years, citrus industries in the United States alone have dedicated over $100 million to research of this new pathosystem with no imminent solution for HLB control," the team write.

“结果，在过去的13年里，仅美国的柑橘产业就投入了1亿多美元来研究这种新的病理系统，而HLB控制还没有迫在眉睫的解决方案，”该团队写道。

The researchers instead turned to our favorite sniffers out there: detector dogs. They used Belgian malinois, German shepherds, hybrids between the two, and springer spaniels as "an ancient technology", as the team call them, to rapidly survey large plantings without the time-consuming and laborious work of collecting and analyzing samples by hand. The canine species were chosen for their instinct to hunt by odor, ability to traverse long distances, and their endurance.

研究人员转而求助于我们最喜欢的嗅探犬:侦缉犬。他们使用比利时马里诺瓦犬、德国牧羊犬、两者的杂交犬和施普林格西班牙猎犬作为“一项古老的技术”，正如研究小组所称，他们可以快速地调查大面积的植物，而不需要手工收集和分析样本，既耗时又费力。之所以选择犬科动物，是因为它们有通过气味进行捕猎的本能、长途跋涉的能力和耐力。

Detector canine 'Szaboles'. Image courtesy of Tim R. Gottwald

The "ancient technology" is a throwback to when canines were used by early humans as chemical detectors to hunt some 12,000 years ago. Now, the modern-day dog detectors have switched from animal prey to citrus pathogens, identifying infections with 99 percent accuracy up to weeks to years before a visual survey and molecular methods would have done so. The pet pooches were remarkably specific, discriminating HLB from other pathogens that could have distracted them. When two dogs were used, the detection accuracy was near 100 percent.

这项“古老的技术”可以追溯到大约12000年前，早期人类用犬科动物作为化学探测器来狩猎。现在，现代的狗狗探测器已经从动物猎物变成了柑橘类的病原体，在进行视觉调查和分子方法之前的数周甚至数年，它们识别感染的准确率高达99%。宠物狗非常专一，能区别HLB和其他可能分散它们注意力的病原体。当使用两只狗时，检测准确率接近100%。

Each canine went through 8 to 20 weeks of obedience and sensitization training, consisting of verbal praise and a toy reward for correct identifications. When a tree was infected with HLB, the dog would sit nearby and not move from the target until a reward was received. The number of false-positive errors was low, with 4 to 15 errors (0.0004 to 0.0015) per 950 to 1,000 trees per canine. The study suggests dogs are more effective and economical than current methods used for disease detection.

每只狗都经过了8到20周的服从和敏感训练，包括口头表扬和对正确识别的玩具奖励。当一棵树感染了HLB，狗会坐在附近，直到收到奖励才会离开目标。假阳性的错误率很低，每950到1000棵树每犬有4到15个错误率(0.0004到0.0015)。这项研究表明，与目前用于疾病检测的方法相比，狗更有效、更经济。

"Because canine detection is direct and immediate, this method has potential for use in real-time detection of bacterial, viral, and fungal exotic and endemic pathogens in field situations," the team write. "Deployment of canine teams for detection of CLas in commercial and research orchards began in Southern California in 2018 to 2019."

“因为犬类的检测是直接和及时的，这种方法有潜力在野外实时检测细菌、病毒和真菌的外来和地方性病原体，”研究小组写道。“2018年至2019年，南加州开始部署警犬团队，在商业和科研果园检测CLas。”