Even today, landmines planted as far back as World War II are still being discovered, posing a serious threat to civilians in 69 countries worldwide. Approximately 70 people are killed every day as a result of a landmine explosion in accidents that should be avoidable; a lack of efficiency in clearing out areas which have been covered with landmines and the difficulty of detecting hidden and buried landmines make them a persistent threat to innocent men, woman, and children.

Over the past few years, however, landmine detection methods have slowly become more sophisticated, and researchers are starting to tackle the issue with more creativity. One effective approach has been the use of rats as landmine detectors, as they are the smaller and lighter counterparts of landmine detecting dogs. The concept of using rats to sniff out landmines began with HeroRats, giant African pouched rats who, after nine months of training, can detect TNT even when the source is underground. When a HeroRat catches the telltale scent of TNT, it scratches at the ground and makes a clicking noise to let its handler know that it has come across a buried landmine. Two HeroRats and a handler can cover 300 square feet in under two hours, as compared to the two days that it would take two people with metal detectors to cover the same area.

Researchers at Hunter College in New York also began recruiting mice (dubbed MouSensors) to sniff out landmines; however, to eliminate the training step, they genetically modified their mice so that they were extremely sensitive to the smell of DNT, a close relative of TNT. 

Our olfactory system is what enables us to detect and identify odors in our environment. When we smell something, we are really picking up on airborne compounds which have attached themselves to receptors on specialized olfactory nerve cells in our nose. Researchers genetically manipulated their landmine-detecting mice to express the receptor for DNT at levels 500 times higher than normal, so that over 50% of their olfactory nerves have DNT receptors on their surface. TNT acts on the same receptors as DNT, making them exquisitely sensitive to the scent of TNT as well. 

Before the MouSensors can be of use as bewhiskered landmine detectors, researchers still need to develop a ‘readout’ for their sensitivity, or some signal which would indicate the presence of TNT comparable to the HeroRats' clicking and scratching. Charlotte D’Hulst, the lead researcher on the MouSensor project, has proposed measuring olfactory nerve activity to alert the mouse handlers to the presence of a landmine. When a compound binds to its receptor on an olfactory nerve, a signal is sent to the brain indicating that a particular smell is present. When a MouSensor sniffs out TNT at high concentrations, however, so many signals are sent to the brain all at once that there is a burst of electrical activity in the brain resembling that of a seizure. D’Hulst and her team have postulated that a chip implanted under the skin of the genetically modified mice can be used to report back to a computer at a remote location and could be used to monitor the MouSensor’s behavior and any changes that occur when it is in the proximity of high levels of TNT. Although the MouSensors have yet to be tested in the field, D’Hulst hopes that the MouSensors will be ready to use in the field within five years. 

Throughout all of this, of course, the safety of our beady-eyed, furry friends would be ensured, as they are too small and light to trigger a landmines. Ben Lark, the head of the International Committee, has warned that the mice would only be one possible approach to detecting hidden landmines: multiple methods should always be used, whether it is human landmine detectors, machines, or landmine sniffing dogs. 

At the very least, however, the mice could be used to do an initial survey of the area, eliminating the risk for the next detector. Landmines still remain a deadly threat to civilians, primarily in third world countries, and so there is still much more work to be done. Improved, low-risk landmine detection methods means fewer innocent deaths, and so the effort to clear out long-lost landmines continues. 

Abstract: http://www.sfn.org/am2012/pdf/press/InvisibleWounds.pdf
Front page image credit: Photograph - Feinstein Lab, Hunter College; Link- Guardian