The Dogs that Sniff Out Sickness

We are all accustomed to the idea of police tracker dogs searching for hidden drugs or explosives, sniffing out evidence at a murder scene or following the trail of a missing person. But what if a dog could use its remarkable sense of smell for another purpose, such as detecting disease within the human body? The idea sounds like something out of a science-fiction novel, but for some time dogs have been used to detect and warn against all kinds of medical conditions. So finely tuned are these dogs’ ultra-sensitive noses that they are capable of picking up trace odours that are the equivalent of dropping a teaspoon of sugar into two Olympic-sized swimming pools. The charity Medical Detection Dogs (MDD), based in Milton Keynes, is at the forefront of research into medical sniffer dogs, and MDD’s researchers already have animals capable of spotting the scent of malaria, cancer and Parkinson’s disease. Since the Covid-19 pandemic began, however, attention has turned to whether the dogs would be able to detect traces of coronavirus on skin and clothing.

Covid detectives

“When we have a particular disease or condition our odour changes, and a dog is able to detect this odour and, when trained, to tell us about it,” explained the charity’s Chief Executive Dr Claire Guest, speaking recently to ITV News. It turns out that the coronavirus that caused the Covid-19 pandemic has its own distinctive chemical signature that can be detected by carefully trained sniffer dogs. MDD currently has several dogs in Covid training and Dr Guest comments that “The study is moving forwards very well and the signs are all really positive.” One dog in particular has shown a remarkable ability to detect the coronavirus odour, unfailingly pointing it out on each test. After eight weeks in the laboratory during the first phase of training, the dogs will move on to use their newly learned skill in real-life situations. The charity, which has been working with the London School of Tropical Medicine and Durham University, ultimately hopes that the scheme can be expanded. The plan is to station dogs in places such as testing centres and airports, where they will be able to screen up to 250 people per hour.

The secrets of the canine nose

Dogs owe their extraordinary sense of smell to the complex structure inside their noses. Whereas a human has around five million scent receptors, dogs have over 300 million. Specialised bones in the dog’s nasal cavity create more space for these scent receptor cells, and the part of the brain that processes scents is particularly large in a dog. This gives them an incredible ability not just to pick out single odours, but to detect subtle differences within a complex group of scents. This ability, when combined with dogs’ intelligence and willingness to learn, makes them the best biosensors known to man. Clearly there is huge potential to develop this area of medicine and the results speak for themselves: dogs are able to pick out blood samples from people with cancer with almost 97 percent accuracy. Let’s hope that this fascinating field of research continues to receive the funding and support it so richly deserves.