In case you needed another reason to admire our four-legged friends, dogs trained to sniff out human disease are helping scientists develop medical diagnostic technology.
In the early stages of cancer, or just before having a seizure or dangerous drop in blood sugar levels, a patient’s breath, urine and skin smell slightly different.
It’s these minuscule odour differences between a healthy and diseased person that a dog’s nose can pick up.
Scientists hope harnessing the sensory power of a dog’s nose could be used in non-invasive early disease detection.
Dogs against malaria
A critical battle in the global war against malaria is stopping its spread into areas that are completely or nearly malaria-free, public health entomologist Steven Lindsay from Durham University said.
And how do you detect a malaria-infected person in 1,000 healthy people?
“We know that people that have malaria produce a distinct odour in their breath, and if mosquitoes can detect parasites in people through their odours, then why not dogs which have an extraordinary sense of smell?”
Research presented by Professor Lindsay at the American Society of Tropical Medicine and Hygiene annual meeting today found dogs trained to detect the smell of malaria parasites in children’s socks correctly identified infected samples 70 per cent of the time, and uninfected samples 90 per cent of the time.
“Instead of taking blood samples, we collected odour samples from children in Gambia by giving them nylon socks to wear overnight,” he said.
“The samples were sent back to the UK where the dogs identified them.”
At the moment, the research is only at the proof-of-concept stage but offers a non-invasive alternative to finger-pricking thousands of uninfected people.
“The trainers think the dogs might be able to pick out a malaria-infected person in a large crowd,” Professor Lindsay said.
“We want to work alongside the national malaria control programs in these countries to produce dogs that are useful for them.
“But really the idea would be to develop a chemical detector that you could take into the field.”
Early cancer detection
When Tim Edwards first encountered scent-detecting animals in science during his PhD, they weren’t dogs.
But it made him wonder how other animals could be used to help humans detect and fight diseases.
Given their history as lab animals, working with rats is pretty straightforward, according to Dr Edwards, a behavioural psychologist at Waikato University, but dogs are better at detecting some scents.
“It’s all odour specific. Even humans are very good at olfaction when it comes to specific odours,” he said.
Dr Edwards chose to focus on training dogs to detect lung cancer after realising lung cancer is often caught too late to be treated.
“The dogs will be able to pick up the lung cancer early, and do it with a very non-invasive and simple sample-collection method.” Dr Edwards said.
“It’s not going to be a single compound [that they detect]. It’s going to be more like a profile.
“There are things that may be present in the breath of healthy people, but in people with lung cancer, the proportions are wrong.”
And dogs may be a valuable stopgap while researchers develop technology that emulates their disease-sniffing prowess.
“We think dogs can expedite the development of machine-based technology for this purpose because the main concern with using animals is their reliability.”
In other words, researchers can calibrate an electronic sensor to certain levels, but dogs and other animals are always in calibration mode — always learning.
Despite dogs already being trained to detect different human diseases, little is known about how they do it.
And that knowledge is leading scientists like Macquarie University materials engineer Noushin Nasiri to tap into their sniffing skills.
“We know dogs have 60 times more receptors in their olfactory system, and the area in the brain that processes scents is around 40 times larger,” Dr Nasiri said.
“But the reality is that we don’t know exactly how they can detect biomarkers at very low concentrations.”
Scientists have long known diseases can be detected in odours, but the challenge was making a sensor sensitive enough to pick up those tiny changes.
“The sensor is only 2 per cent material, and the rest is air — reflecting the structure of a dog’s nose, which is super spongy and porous,” she said.
“The air can penetrate the whole sensor, not just the surface, so it’s easier to detect compounds in the air.”
Dr Nasiri started investigating biosensors for human disease after a friend died from lung cancer.
“She died only four months after being diagnosed for lung cancer because it was detected very late,” she said.
“And I was thinking that if there was a small, portable device everyone can have at home, we can actually check our health more frequently.
“If a sensor response is positive, we go to the doctor.”
Listen to Ockham’s Razor this Sunday, November 4 to hear more about Dr Nasiri’s research.
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