A dog’s sense of smell is undoubtedly his most powerful sense. Just look at the applications of dogs in everyday use – from sniffing out drugs and bombs to survivors of natural disasters, all rely heavily on the powerful ability of dogs to detection of scents. With that in mind, it may come as no surprise that this canine ability is becoming increasingly useful in the detection of disease.
Whilst the research into how a dog can detect disease by these means is only in its infancy, researchers are now suggesting that work should begin on creating an ‘Electric nose’ that could rival our furry friends.
Cancer Detection by Dogs
Several studies have now been published that show dogs are able to detect amongst others, breast, lung, bladder, ovary, prostate and skin cancers. That’s right, there is scientific evidence that shows dogs are able to detect cancers of all the above types. The dogs are trained to recognise the diseased state of cancer patients.
During this training the dogs are exposed to the patients for a period of time and it is believed they are able to become familiar with the cancerous scent. They are able to pick up on this scent despite other confusing smells that can be picked up around a hospital. After a few weeks of training, the dogs were able to identify from a group of seemingly healthy patients (i.e. no visible signs of disease), which individuals had cancer – with a relatively high degree of accuracy. The fact that there were no visible clues to the disease is substantial evidence that the detection is based on smell.
The History of Scent Diagnosis
Diagnosis by scent is not a new thing; in fact it is only in relatively recent history that doctors have stopped using smell to diagnose patients. Reports from both Chinese and Medieval history suggest the use of smell for diagnosis. In fact medieval doctors relied heavily on the colour, taste and smell of urine for diagnosis! For example, diabetes was often diagnosed by testing how sweet the urine tasted.
Human vs. Canine Sense of Smell
Dogs have around 200 million olfactory (smell) receptors made up from around 800 variations of receptors. This large amount of receptors is encoded for by 6% of the total genome. This might not sound a lot, but considering the genome is the information that encodes for every single cell, receptor and enzyme in the body, 6% is quite a lot.
Humans in comparison aren’t as far behind dogs in terms of sense of smell as you might have thought, with 2% of the genome being used to encode for around 5 million olfactory receptors.
|Olfactory (Smell) Receptors||
|Encoded by % of Genome||
The Future of Scent Diagnosis?
Considering disease diagnosis by scent is now beginning to be understood by scientists and the sheer amount of diseases dogs are able to detect by smell alone, the next step is surely the movement to electrical scent diagnosis?
Dogs are able to detect everything from cancer to an oncoming heart attack with just the power of their nose – they require no visible signs and provide a rapid diagnosis. If scientists could replicate this, wouldn’t that be an amazing step forward? Imagine a ‘heart attack detector’ next to your smoke alarm that detects minute levels of the chemicals released before a heart attack, this could be wired to instantly dial the emergency services and possibly prevent a lot of deaths.
Of course, it isn’t as simply as that but attempts are underway to replicate a human sense of smell (with a canine sense of smell being the next goal). In these attempts, scientists have an array of around 32 chemical sensors that are able to generate a ‘smell fingerprint’ as each sensor is engineered to respond in a different way to different chemicals.
The first steps towards making this a serious piece of medical diagnostic equipment have been made, in fact such scent sensor arrays have been adapted for medical use to detect lung cancer, schizophrenia and wound infections.
Whilst this may all sound like science fiction, it is truly an exciting development. Whilst the ‘Electric Canine Nose’ may be a way off, efforts are being made to understand, train and implement a dog’s sense of smell for diagnosis of disease. You never know, dog’s could soon be making their way in to paramedic teams!
What are your thoughts? Do you believe that one day we could actually be using a dog or some form of ‘electric nose’ to detect disease?
Post adapted from R. P. Arasaradnam, et al. (2011). `Electronic nose versus canine nose: clash of the titans’. Gut 60(12):1768.