Trained dogs have been used to find lost individuals, wildlife droppings, invasive species, illicit goods and even cancers. A new study has shown that dogs may even be better at detecting Covid-19 than PCR tests.
The dogs’ powerful snoots identified positive Covid-19 cases among 335 people with 97% accuracy after taking a puff of human sweat samples, reports Aria Bendix for BNC News. And in testing, the team found that the canines found all 31 cases of Covid-19 in the 192 patients with no symptoms. The study, led by Dominique Grandjean at the Alfort School of Veterinary Medicine in the Paris suburbs, was published in PLOS A. This suggests that with the right sense of smell, dogs could help get test results quickly in mass screening efforts and reduce the need for invasive nasal swab testing.
Anecdotal evidence also suggests that dogs can detect asymptomatic cases 48 hours before individuals test positive on PCR tests, reports Tina Hesman Saey for Scientific News. However, dogs have sometimes confused another respiratory virus with SARS-CoV-2. The authors did not seem concerned with these cases – of the 17 false positives (cases where dogs mistakenly thought a sample was positive for SARS-CoV-2), only two were positive for another respiratory virus, although both cases are another type of coronavirus.
For the study, the researchers used dogs from the French fire service and the United Arab Emirates’ Ministry of Interior. Each pup was rewarded with toys like tennis balls if they managed to detect the virus in sweat samples. The training lasted between three and six weeks, depending on the dog’s experiences with scent detection, for Scientific News. According to Conversation Hassan Vally.
Each pup sniffed cones containing sweat samples from the human participant’s armpits, although swabbing sweat from the subjects’ necks and the masks used also work well as samples, says Grandjean. Scientific News. If a dog sniffed a sample it thought was positive for Covid-19, it would sit in front of it. It took the dogs about 15 seconds to sift through 10 sweat samples from 10 different individuals that neither the dogs nor handlers had interacted with before. In addition to detecting the virus, the dogs were also asked to find negative samples and identified Covid-free samples with 91% accuracy, NBC News reports.
Grandjean and his colleagues found that dogs could detect infections earlier than PCR tests, so they hypothesize that a person who may test negative on a PCR test but positive on a dog may likely test positive on a PCR test two days later.
“Even with what we call a rapid test, you’re still going to have to wait tens of minutes or even hours where the dog within seconds or even fractions of seconds can respond,” said Kenneth Furton, a chemist . at Florida International University not involved in the study says Scientific News.
Although they can detect cases of Covid, researchers still don’t know what dogs smell specifically. Instead of a single chemical, it may be a mixture of decreasing or increasing aromas – receptors in the nose often do not detect a single molecule but detect complex mixtures. And just because dogs can smell Covid in sweat samples doesn’t mean animals can smell it on a full human body, which offers a greater combination of aromas.
“That’s one of the big challenges – getting the dog to learn to translate from a sample to a whole human being, which is a much more complex scent,” Cynthia Otto, director of the Penn Vet Working Dog Center at the University of Pennsylvania, not involved in the study told NBC News.