“It’s not unlike people who have incredible intelligence, but often struggle in other ways,” says Guest of Asher’s transformation.The news that dogs such as Asher could be deployed to detect Covid-19 might have an “and finally…” ring to it. But there is serious science behind the idea. There has long been anecdotal evidence that many, perhaps all, diseases have a telltale odour. Yellow fever, for example, is said to smell like raw meat; tuberculosis starts out as wafts of stale beer, but later becomes more like soggy cardboard with notes of brine. These are just the ones that humans can notice – and compared to most animals, we have an abysmal sense of smell. Our olfactory epithelium, the area of the nasal cavity responsible for detecting odours, is 30% smaller than a canine’s. This leads to a staggering disparity: the ability of a dog to place an odour is estimated to be somewhere between 10,000 and 100,000 times better than that of the average human.
“If a dog comes up to something they like the odour of, they sniff really hard and rapidly, don’t they?” explains Guest. “You can hear that sniff-rate go up and they’re actually able to push air in and out of their nostrils at slightly different rates. This produces a little vortex that pulls up the volatiles that much more quickly. They’ve also got an ability to push old air out of the slits of their nose, the sides, and pull new air in at the same time. This information goes to two different parts of the brain and these two bits talk. Then they recognise the odour.”‘So far there’s never been a disease we can’t find’: Dr Claire Guest with Asher. Photograph: Pål Hansen/The Observer“We could detect a spoonful of sugar in a cup of tea, but a dog could detect a spoonful of sugar in two Olympic-sized swimming pools,” adds Professor James Logan, head of the department of disease control at the London School of Hygiene and Tropical Medicine. “It’s that level.”Logan, who may be familiar from his TV work, including Channel 4’s Embarrassing Bodies, has spent two decades investigating body odours, and specifically how they can be used as a form of communication between insects, plants and animals. He began working with Medical Detection Dogs two years ago. His research on malaria found that when someone contracts the disease their body odour changes. No human would be able to detect any difference, but mosquitoes certainly can, and find these people more attractive, which speeds up the transmission of the disease. Logan figured that dogs would too, and his hunch has proved to be right. The implications of this finding could be significant. Malaria remains a risk for half the world’s population and one of the problems with containing the disease is that some people are infectious, but don’t show any symptoms, because they have some degree of immunity to it. If dogs could point out these individuals, who could then be isolated and receive treatment, then the spread of malaria could be radically restricted.Logan and Guest were planning to roll out the malaria project when Covid-19 hit. Both of them, pretty well simultaneously, had the same thought: could the same principles be applied to the new virus? “We know that infections cause changes in body odour, that’s scientifically proven now,” says Logan on a video call. “And we know that dogs can detect odours and learn the smell of odours very effectively. That is also scientifically proven and well-known. So to me, it was a no-brainer.”
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The pair put together a pitch for a UK government grant to investigate further. Bio-detection dogs are already a familiar sight at international ports of entry and border crossings where they are used to find drugs, explosives and other contraband. Each dog can screen up to 250 people per hour. “Essentially what you’re doing is you’re diverting their attention from drugs and explosives to a disease,” explains Logan.In May, Logan’s team at the London School of Hygiene and Tropical Medicine, in collaboration with Medical Detection Dogs and Durham University, was awarded £500,000 of government funding. The hope is that dogs will be able to assist with early identification of Covid-19 and reduce the need for quarantine for travellers arriving to the UK. Guest is clearly confident: “So far there’s never been a disease we can’t find.”
‘A dog’s sense of smell is between 10,000 and 100,000 times better than the average human’s’: Digby. Photograph: Pål Hansen/The Observer
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It is not hardto imagine that there might be some scepticism about the project. “I know some people think it’s a wacky idea,” says Guest. “When it was discovered that dogs could smell some of these diseases, you immediately got people saying, ‘OK, that’s fine but how are you going to roll a dog out to every doctor’s surgery?’ But that was really never where this was ultimately going to go.”
A behavioural psychologist by training, Guest spent many years working with hearing dogs for the deaf. Over time, she kept coming across reports of dogs who had alerted their owners to serious illnesses. “I had a colleague whose dog warned her about a melanoma on her calf when she was in her early 20s,” she recalls. “From her description, I knew this dog had smelt it, but I had no idea how I’d manage to ever prove this.”The research became personal for Guest, too. She started Medical Detection Dogs in 2008, and a year later, she noticed that her own dog, a fox-red labrador called Daisy, was acting strangely around her. Normally placid, she kept jumping up at Guest, pawing at her chest. Guest checked and felt a lump. “It was very, very deep-seated under that lump, but I had breast cancer; I was 45,” she recalls. “My consultants both said that had Daisy not warned me, my prognosis would have been very different. I wouldn’t have had a mammogram for another five years probably.” Medical Detection Dogs currently has around 100 dogs assisting people one-to-one with a range of illnesses, including type 1 diabetes and postural orthostatic tachycardia syndrome (PoTS). They are trained to alert their owners to tiny odour changes, which might be a precursor to an emergency. The charity also has a smaller division of bio-detection dogs, who are trained to find neurological diseases, such as Parkinson’s, as well as cancer and malaria.The Covid-19 project is currently in the phase of sample collection. Sterilised socks and stockings made from nylon, which clings to body odours especially well, and face masks have been sent out to around 3,200 NHS staff, who will wear them for a standardised amount of time before returning them to Logan’s lab for analysis. Crucially, all the NHS workers taking part in the trial will be asymptomatic. “We’ll end up with a very high number of samples from people who are uninfected, and a smaller group of samples from people who are infected,” says Logan. “And that’s fine. Because, actually, we need a lot of controls. We need a lot of background noise for the dogs to ignore.”
Getting to nose you: Daisy studying scents.An initial selection of six dogs, meanwhile, is undergoing training under Guest’s supervision in Milton Keynes. They are an assortment of cocker spaniels and labradors, and one labradoodle, Digby. Asher is the eldest (one to two is peak age for a bio-detection dog). Guest typically starts them on a smell they like to find: sometimes a synthetic “unique training odour”, but often just a tennis ball. “But don’t get me wrong, these dogs are going down to very, very low levels,” says Guest. “So in training, they wouldn’t be finding a whole tennis ball. They’d be finding the residual odour on something that has been touched by the tennis ball. And only touched it for about 30 seconds.”
The rescue dog is thought to have been tortured and beaten by his previous owners (Picture: Joanne Lowen) But Menios is now settling in to a loving and warm home (Picture: Joanne Lowen)Most of the time it cannot spread outside but once it breaks out onto the breast tissue it can occasionally spread to other parts of the body.
Once Logan’s samples have been processed, they will be cut up into small pieces: some will be sent for further analysis, the rest will go to the dogs and their handlers, initially labelled but ultimately double-blind. If Covid-19 does have a distinctive smell and the dogs can detect it, the trial will then move to practical outreach. Logan imagines they will work with an airport, probably Heathrow, and travel hubs, such as train stations, that have a heavy footfall of commuters.“If you’ve got a plane with 500 people coming off, 10% may be asymptomatic or pre-symptomatic,” says Guest. “The dog can quickly say, ‘Bang, bang, bang. You, you, you.’ It’s a 0.5 second sniff. The dog won’t make the final decision. The person will have a test. But at the moment there’s no other way of rapidly screening people like that – especially asymptomatics.”
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For Logan, who hopes to have initial results from the project in August or September, the dogs could be “a quick win” while the search for a Covid-19 vaccine continues elsewhere. “Any strategy that puts all your eggs into one basket is not a good strategy,” he says.
Logan is especially encouraged that he has already had messages from people convinced the virus does have a distinct odour. He says, “We’ve had a lot of people contact us, particularly medical workers, people that are in care homes, and people in hospitals who are saying, ‘We can smell it. I can walk into a room and I can tell there are patients in here with Covid-19.’ We’ve got to take that with a pinch of salt, because that’s not scientific proof, but it gives us further hope that it does exist.”In the future, it is likely that a device, perhaps even our smartphone, will tell us we are ill before we have any idea ourselves. Medical Detection Dogs is currently partnering with Dr Andreas Mershin, a quantum physicist at the MIT Center for Bits and Atoms, in Massachusetts, on using dogs to teach artificial-intelligence technology how to recognise the smell of prostate cancer. Logan is also convinced that we will make increasing use of sensors, maybe one that’s worn on your skin or a device you blow into, similar to a breathalyser.
For now, though, our best hope might be dozing on Guest’s floor, after a hard morning sniffing for tennis balls. In fact, Asher won’t be deployed in Covid-19 searches, because of his previous experience with malaria, it couldn’t be guaranteed which disease he was stopping for. His main contribution will be in confirming that Covid-19 does have its own smell. “Because Asher has more experience, he’ll be able to tell me, ‘There’s definitely a difference here. Let’s crack on,’” says Guest. “He won’t go to the final phase, he’ll peel off and a young girl will come in.”
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Guest looks over at Asher fondly and whispers, “But we haven’t told him that yet…”