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Dogs’ incredible sense of smell makes them more effective at detecting covid than gold standard tests. Why then, has this less expensive and more user-friendly technique remained confidential?
Hundreds of millions of olfactory receptors
Dogs’ noses are highly evolved, with both physical and neural optimizations for smell. Dogs have hundreds of millions of olfactory receptors, compared to about five to six million for humans, and a third of their brain is devoted to interpreting smells, compared to only 5% in the human brain. “They can detect the equivalent of a drop of an odorous substance in 10.5 Olympic swimming pools“said Prof. Tommy Dickey of UC Santa Barbara.
With Heather Junqueira of BioScent, Inc., they brought together the various studies on the subject. A total of 29 peer-reviewed studies – which include over 400 scientists from over 30 countries and 31,000 samples – were reviewed. The verdict is clear: trained scent hounds are “as effective and often more effective“than antigen tests and even PCR tests deployed in clinics and hospitals. Not only can dogs detect the SARS-CoV-2 virus faster, but they can do so non-intrusively, without the environmental impact related to single-use plastics.
A more efficient, faster and more user-friendly method
In some cases, dogs were able to detect COVID in presymptomatic and asymptomatic patients whose viral load was too low for conventional tests to work. And not only that, Prof. Dickey added, dogs can distinguish between COVID and its variants in the presence of other potentially confounding respiratory viruses, such as those of the common cold or flu. “And they are so fast“, he added. “They can tell you yes or no in seconds, if they smell you directly“.
In some scenarios, the dog would quickly sniff the person, sitting down to indicate the presence of COVID. In other cases, the dog was given a sweat sample to smell, a process that could take a few minutes. Speed is especially important in situations like the earlier phase of the pandemic, when a gap of days between test and result could mean an exponential increase in infections if the person tested positive, or scenarios that involve a high volume of people.
A technique to be deployed in the event of a pandemic
Dogs with recognized scents such as beagles, basset hounds and coonhounds have been enrolled but studies have shown that a variety of other dogs are up to the job regardless of age, breed and gender.
Despite these rave reviews, challenges remain in bringing man’s best friend into the mainstream of medical diagnostics, although animals have been successful in detecting other conditions, such as diabetes and cancer.
“There’s quite a bit of research, but it’s still seen by many as something of a curiosity“, said Prof. Dickey. The places that were open to using dogs in field experiments tended to be smaller countries like Finland and Colombia, where there was a desire to explore rapid and cost-effective methods of detecting COVID without having to wait for expensive tests to be developed or for reagents to become available.
In conclusion, the authors judge that “After conducting this comprehensive review, we believe scent dogs deserve their place as a serious diagnostic methodology that could be especially useful in future pandemics, potentially as part of rapid routine health screenings in public spaces.“.