It's hard to believe just how much Georg Christoph Otto needs to hunt down a tiny pest. Eradicating（根除） bedbugs is the Champions League of Pest Control. They're among the nastiest and most dangerous animals out there. And you have to think like a bedbug. Where would you hide? Where do they move?

  Where are the eggs? It's one of the toughest jobs in pest control. Christoph Otto's job often requires some fairly large pieces of equipment. When a call from a customer comes in, he tries to prepare himself for anything he may encounter. His pest control vehicle is a regular car with no indication of his line of work. His clients appreciate the discretion（判断力） so that it doesn't alarm the neighbours.

  Bedbugs are making a real comeback. They were thought to have been eradicated, but they've made a massive return here in recent years. And their resurgence is happening not just in urban environments, but increasingly in idyllic（ 田园诗的） rural regions like here in southern Germany. Bedbugs are just mean. They come out at night in the dark. You can't find where they're hiding.

  It all adds to why people are so afraid of them. They drink our blood, like vampires. It's just awful. Today the pest controller is off to a youth hostel in Upper Bavaria. Pest controllers are often asked to enter discreetly through a back entrance, but hostel manager Mark Hochluss has decided to tackle the issue openly. And so begins the search for the needle in the haystack.

  Contrary（相反的） to popular belief, bedbugs have nothing to do with poor hygiene. We've not touched anything. Great, everything can stay as is. We had two people with bites that seemed to be from bedbugs. I immediately came up and said, we don't know what's up with the room, but we have to vacate（腾出） it now. The faster the response to an infestation, the better.

  Tracking down these "masters of stealth" tends to be exceedingly difficult. In this case, some telltale（泄密的） signs did turn up. Here's one that was crushed（压碎） by some poor host. You can tell（ 告诉） it's a bedbug from the shape of its body. So the suspicions（ 怀疑） of the hostel manager are confirmed. The pest controller tries to determine the scale of the infestation.

  That's the tricky thing about bedbugs. They've got thousands of options. It could be a tiny, cranny one you can't even fit your fingernail into, but they can squeeze（压） in. They return hungry to their hideouts and await（等候） the next victim. How long can they survive without a host? There are studies that say they can live up to a year without feeding.

  I thought starving them would be an option. That we just wouldn't use the room for two months. Starving them won't work（使工作）, unfortunately. Although the infestation is still small, Mark Hochluss wants the room given（做） a thorough treatment in order to prevent the problem from spreading. Back in the 20th century, these bugs the size of apple seeds were almost wiped（擦） out in many parts of the world through the use of DDT and other now-banned insecticides. The pests developed a resistance（阻力） to subsequent products.

  So now the blood-sucking（吸） insects are back. It's not just France and Germany. Britain is also facing a new bedbug plague. And here, too, the problem is not just found in big cities. Entomologist Richard Naylor lives in Chepstow on the Welsh-English border. He spent the last 20 years studying bedbugs.

  His research lab includes an incubator（培养的器具） with up to 50,000 specimens（范例） from a variety of strains（张力）. Naylor has a very special relationship to his bedbugs. This almost daily ritual（典礼） certainly wouldn't be to everyone's taste. The researcher volunteers himself as host. Um, so bedbugs respond to carbon dioxide from our breath. And so if I...

  In order to tell them it's feeding time, I breathe heavily into the pot. And they all wake up and realise that there's food about and become very active and start running around. So it's just telling the bedbugs it's time to feed. And the permeable（有浸透性的） lids allow the bugs to do just that. I use my own blood because it works the best. I've tried rabbit blood, chicken blood, sheep blood, pig blood.

  And whenever you use an artificial membrane system, you have to treat the blood with some kind of anticoagulant to stop it clotting. And that just doesn't seem to be very good for bedbugs. And so fresh blood is just the best. It's the best in terms of the numbers of eggs they produce and their overall health, yeah. But while he painstakingly（ 细心地） ensures the wellbeing of his bedbugs, what about his own health? I can feel a slight tingling sensation（感觉）.

  I can't feel individual bites, but I can kind of feel... Maybe slightly itchy. But yeah, I've been doing it long enough to... I don't scratch anymore. Bedbugs do not at least transmit diseases. Naylor allows them to feed on his arm and sometimes leg for his own experiments, as well as for research institutes and the pest control industry.

  I noticed when I really feed lots, when we get big orders for thousands and thousands, I noticed that I was becoming anemic, I had to test for that. And so when it's like that, I take iron supplements（补遗） to stop myself becoming anemic. The recent surge（巨涌） in bedbug numbers means that business is booming for his lab. In the adjacent（邻近的） building, Alexia Naylor is busy getting an order ready as her husband arrives with the freshly（新近） fed insects. And how's his arm doing? Not too bad.

  You can see my skin's a bit red. Yeah, it's a little bit red, it's not too swollen and it'll go away in an hour or so. But it doesn't feel anything at all, it's not itchy or anything like that. It's a little bit warm perhaps, yeah. I react a bit more than Richard does, but not too bad. So I fed a couple of pots today so you can just see that my arm's similar to Richard's.

  I only feed bedbugs as a last resort time, the kind of backup（后补）. The couple are careful to check that potential buyers are trustworthy. After all, some could have dubious（可疑的） intentions. Sometimes we asked for maybe 200 bedbugs to flatten（击败） New York or something and there's no email or explanation for why they would need that and so these ones we refund（退还） them and we try and avoid those people, yeah. Bugs in various stages of life are transferred to these small vials, which are then sealed（封） tight prior to packaging and sending. This order will be used to train canine bedbug hunters.

  Protection dog teams will hide these around the bedroom, maybe in a hotel or in a hostel or something like that and use that to train the dog to search for bedbugs and then they'll offer that service to hotels, hostels, shelters, housing, all the places that release trouble with bedbugs, yeah. Hostels or five-star hotels, bedbugs aren't fussy about their lodgings（寄宿）. But these pests are particularly hard to control up in the mountains, which is why sniffer dogs are often brought in. Stefan Weihausen is a sniffer dog handler. He's trained Derek and Roma to track down bedbugs. Today he's come to meet Robert Koibitsch and Mika-Ilfra Karo from the German Alpine（高山的） Club.

  They're headed up the Nibelhorn to inspect（检查） a mountain lodge where there was an incident of bedbugs last year.