How can dogs follow a smell

Dogs can sniff out COVID-19

For the pilot study at the University of Helsinki, the dogs trained as medical diagnostic assistants were trained on the hitherto unknown odor signature of the novel COVID-19 pathogen. With amazing success: after just a few weeks, the first dogs were able to accurately distinguish urine samples from COVID-19 patients from urine samples from healthy people.

"We have a lot of experience training dogs to identify diseases," said Anna Hielm-Björkman, senior lecturer in clinical research on pets at the University of Helsinki Faculty of Veterinary Medicine. "But it was fantastic to see how quickly they learned to recognize the new smell." After a short time, the animals identified the urine of SARS-CoV-2 infected people almost as reliably as a common PCR test.

Important insights for other teams

The very quick and promising findings from Finland are also important for the other research teams, for example in Great Britain and France, who are currently training sniffer dogs to recognize COVID-19.

The colleagues from the German Assistance Dog Center also benefit from the Finnish results: "Nobody could tell us with certainty whether training with the aggressive pathogen was dangerous or harmless for humans and dogs. We wanted to collect more information before we start training, because the German virologists advised us against it - after all, so little is known about the virus so far, "explains Luca Barrett from the German Assistance Dog Center.

In France, too, dogs are trained for the novel COVD-19 pathogen

The Finnish scientists are now preparing a randomized, double-blind study in which the dogs will sniff a larger number of patient samples. Only then should the scent tests be used in clinical practice.

Where does the characteristic smell come from?

So far it is unclear which substances in the urine produce the apparently characteristic COVID-19 odor. Since the new SARS CoV-2 not only attacks the lungs, but also causes damage to blood vessels, kidneys and other organs, the urine smell of the patients presumably also changes, which the dogs with their highly sensitive olfactory organs notice immediately.

Certain diseases appear to have a specific smell signature that dogs trained on can sniff out with amazing accuracy, Barrett said. "According to a study, dogs have a 93 percent chance of diagnosing breast cancer, for example. Lung cancer, for example, has a 97 percent chance."

But dogs could also identify skin cancer, colon cancer, ovarian cancer or prostate cancer very reliably. "In the last few years in particular, the hit rate has increased enormously, which was not so good in the early days of training," says Barrett.

Hit rate is crucial

In addition to cancer, the dogs can also recognize Parkinson's. A Parkinson's patient smells different, even years before they have the disease. "This is how it came about training dogs as a kind of Parkinson's early warning system," explains Luca Barrett.

Luca Barrett co-founded the German Assistance Dog Center

Dogs are also trained for malaria, but the hit rate is not yet satisfactory. So far, the dogs recognize 7 out of 10 infected people, that is not enough.

A high hit rate is of course also absolutely necessary for training with the aggressive SARS-CoV-2 pathogen, said Barret: "We hope that the hit rate with Corona is significantly higher for the fully trained dogs, after all, it would be very dangerous if COVID-19 would not be detected. "

Trained sniffers

Dogs have about a million times better smell than humans. Humans have around five million olfactory cells, the dachshund 125 million and the German shepherd 220 million.

Dogs inhale up to 300 times per minute in short breaths, so their olfactory cells are constantly supplied with new odor particles. In addition, the dog's nose perceives differently to the right and left, so dogs can even smell spatially and follow a track accordingly.

During the training, the dogs - preferably Labrador retrievers, retrievers in general, but also cocker spaniels or sheepdog breeds - are each trained on a smell. These can be drugs and explosives, or the odor signature of a special disease. So a dog cannot detect multiple types of cancer.

The animals are trained with containers that contain, for example, breath or sweat samples. As soon as they have identified the smell they are looking for, the dogs hear a click and receive a treat. According to this reward principle, they are reliably trained on the one smell.

Great potential, great skepticism

Not only drug and explosives detection dogs are already in use, the trained medical odor detection dogs are already being used in hospitals. For example, they scan the bodies of patients suspected of having skin cancer for the disease. Of course only with their consent. The dogs help with a good nose in diagnosing and early detection.

However, so far there are very few medical scent-detection dogs. The committed dog owners almost always work on a voluntary basis, the trained sniffers live in a completely normal household. There is great skepticism, especially among traditional doctors and health insurance companies. Although further medical tests have to follow the first indication from the dog anyway and a lot of time and follow-up costs can be saved through early cancer detection.

Possible uses in the fight against Corona

If the experiences now made in Finland are confirmed, the sniffer dogs with their extremely sensitive sense of smell could prove to be of great help in the fight against the novel corona virus.

Corona detection dogs could also be used at airport ports

Luca Barrett from the German Assistance Dog Center can well imagine that corona detection dogs are used at hotspots with a high risk of infection, for example during admission controls for football games and other major events.

Or also when entering airports. "When the dogs walk off the line, they can tell whether someone is 'healthy' and can enter. If a person smells like COVID-19, the dog handler can then send that person to a corona test center instead," said Barrett. Because of course you still need a second test for confirmation after the first sniff.

Barrett said dogs could also be used to search for the virus on surfaces. Before passengers get on a plane, for example, the four-legged friend could first check whether the machine is COVID-free. Something similar is planned for medical practices, old people's or nursing homes that had to be evacuated due to corona cases. Before these are used again, a sniffer dog could check whether the environment is "clean".

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