Bart Weetjens

How I taught rats to sniff out land mines

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I'm here today to share with you an extraordinary journey - extraordinarily rewarding journey, actually - which brought me into training rats to save human lives by detecting landmines and tuberculosis. As a child, I had two passions. One was a passion for rodents. I had all kinds of rats, mice, hamsters, gerbils, squirrels. You name it, I bred it, and I sold them to pet shops. (Laughter) I also had a passion for Africa. Growing up in a multicultural environment, we had African students in the house, and I learned about their stories, so different backgrounds, dependency on imported know-how, goods, services, exuberant cultural diversity. Africa was truly fascinating for me.


I became an industrial engineer, engineer in product development, and I focused on appropriate detection technologies, actually the first appropriate technologies for developing countries. I started working in the industry, but I wasn't really happy to contribute to a material consumer society in a linear, extracting and manufacturing mode. I quit my job to focus on the real world problem: landmines. We're talking '95 now. Princess Diana is announcing on TV that landmines form a structural barrier to any development, which is really true. As long as these devices are there, or there is suspicion of landmines, you can't really enter into the land. Actually, there was an appeal worldwide for new detectors sustainable in the environments where they're needed to produce, which is mainly in the developing world. We chose rats.


Why would you choose rats? Because, aren't they vermin? Well, actually rats are, in contrary to what most people think about them, rats are highly sociable creatures. And actually, our product — what you see here. There's a target somewhere here. You see an operator, a trained African with his rats in front who actually are left and right. There, the animal finds a mine. It scratches on the soil. And the animal comes back for a food reward. Very, very simple. Very sustainable in this environment. Here, the animal gets its food reward. And that's how it works. Very, very simple.


Now why would you use rats? Rats have been used since the '50s last century, in all kinds of experiments. Rats have more genetic material allocated to olfaction than any other mammal species. They're extremely sensitive to smell. Moreover, they have the mechanisms to map all these smells and to communicate about it. Now how do we communicate with rats? Well don't talk rat, but we have a clicker, a standard method for animal training, which you see there. A clicker, which makes a particular sound with which you can reinforce particular behaviors. First of all, we associate the click sound with a food reward, which is smashed banana and peanuts together in a syringe. Once the animal knows click, food, click, food, click, food — so click is food — we bring it in a cage with a hole, and actually the animal learns to stick the nose in the hole under which a target scent is placed, and to do that for five seconds — five seconds, which is long for a rat. Once the animal knows this, we make the task a bit more difficult. It learns how to find the target smell in a cage with several holes, up to 10 holes.


Then the animal learns to walk on a leash in the open and find targets. In the next step, animals learn to find real mines in real minefields. They are tested and accredited according to International Mine Action Standards, just like dogs have to pass a test. This consists of 400 square meters. There's a number of mines placed blindly, and the team of trainer and their rat have to find all the targets. If the animal does that, it gets a license as an accredited animal to be operational in the field — just like dogs, by the way. Maybe one slight difference: we can train rats at a fifth of the price of training the mining dog.


This is our team in Mozambique: one Tanzanian trainer, who transfers the skills to these three Mozambican fellows. And you should see the pride in the eyes of these people. They have a skill, which makes them much less dependent on foreign aid. Moreover, this small team together with, of course, you need the heavy vehicles and the manual de-miners to follow-up. But with this small investment in a rat capacity, we have demonstrated in Mozambique that we can reduce the cost-price per square meter up to 60 percent of what is currently normal — two dollars per square meter, we do it at $1.18, and we can still bring that price down. Question of scale. If you can bring in more rats, we can actually make the output even bigger. We have a demonstration site in Mozambique. Eleven African governments have seen that they can become less dependent by using this technology. They have signed the pact for peace and treaty in the Great Lakes region, and they endorse hero rats to clear their common borders of landmines.


But let me bring you to a very different problem. And there's about 6,000 people last year that walked on a landmine, but worldwide last year, almost 1.9 million died from tuberculosis as a first cause of infection. Especially in Africa where T.B. and HIV are strongly linked, there is a huge common problem. Microscopy, the standard WHO procedure, reaches from 40 to 60 percent reliability. In Tanzania — the numbers don't lie — 45 percent of people — T.B. patients — get diagnosed with T.B. before they die. It means that, if you have T.B., you have more chance that you won't be detected, but will just die from T.B. secondary infections and so on. And if, however, you are detected very early, diagnosed early, treatment can start, and even in HIV-positives, it makes sense. You can actually cure T.B., even in HIV-positives.


So in our common language, Dutch, the name for T.B. is "tering," which, etymologically, refers to the smell of tar. Already the old Chinese and the Greek, Hippocrates, have actually published, documented, that T.B. can be diagnosed based on the volatiles exuding from patients. So what we did is we collected some samples — just as a way of testing — from hospitals, trained rats on them and see if this works, and wonder, well, we can reach 89 percent sensitivity, 86 percent specificity using multiple rats in a row. This is how it works, and really, this is a generic technology. We're talking now explosives, tuberculosis, but can you imagine, you can actually put anything under there.


So how does it work? You have a cassette with 10 samples. You put these 10 samples at once in the cage. An animal only needs two hundredths of a second to discriminate the scent, so it goes extremely fast. Here it's already at the third sample. This is a positive sample. It gets a click sound and comes for the food reward. And by doing so, very fast, we can have like a second-line opinion to see which patients are positive, which are negative. Just as an indication, whereas a microscopist can process 40 samples in a day, a rat can process the same amount of samples in seven minutes only. A cage like this — (Applause) A cage like this — provided that you have rats, and we have now currently 25 tuberculosis rats — a cage like this, operating throughout the day, can process 1,680 samples. Can you imagine the potential offspring applications — environmental detection of pollutants in soils, customs applications, detection of illicit goods in containers and so on.


But let's stick first to tuberculosis. I just want to briefly highlight, the blue rods are the scores of microscopy only at the five clinics in Dar es Salaam on a population of 500,000 people, where 15,000 reported to get a test done. Microscopy for 1,800 patients. And by just presenting the samples once more to the rats and looping those results back, we were able to increase case detection rates by over 30 percent. Throughout last year, we've been — depending on which intervals you take — we've been consistently increasing case detection rates in five hospitals in Dar es Salaam between 30 and 40 percent. So this is really considerable. Knowing that a missed patient by microscopy infects up to 15 people, healthy people, per year, you can be sure that we have saved lots of lives. At least our hero rats have saved lots of lives.


The way forward for us is now to standardize this technology. And there are simple things like, for instance, we have a small laser in the sniffer hole where the animal has to stick for five seconds. So, to standardize this. Also, to standardize the pellets, the food rewards, and to semi-automate this in order to replicate this on a much larger scale and affect the lives of many more people. To conclude, there are also other applications at the horizon. Here is a first prototype of our camera rat, which is a rat with a rat backpack with a camera that can go under rubble to detect for victims after earthquake and so on. This is in a prototype stage. We don't have a working system here yet.


To conclude, I would actually like to say, you may think this is about rats, these projects, but in the end it is about people. It is about empowering vulnerable communities to tackle difficult, expensive and dangerous humanitarian detection tasks, and doing that with a local resource, plenty available. So something completely different is to keep on challenging your perception about the resources surrounding you, whether they are environmental, technological, animal, or human. And to respectfully harmonize with them in order to foster a sustainable world.


Thank you very much.



No one knows exactly how many landmines still litter the world, but it's safe to say: millions, waiting to kill and maim unsuspecting civilians. Clearing them is slow, expensive and dangerous. The founder of Apopo, Bart Weetjens, talks about his extraordinary project: training rats to sniff out land mines. He shows clips of his "hero rats" in action, and previews his work's next phase: teaching them to turn up tuberculosis in the lab.

About the speaker
Bart Weetjens · Product developer

The founder of Apopo, Bart Weet­jens, is train­ing rats to detect landmine explosives in minute amounts.

The founder of Apopo, Bart Weet­jens, is train­ing rats to detect landmine explosives in minute amounts.