Dogs are as reliable as lab tests at detecting COVID-19 cases, and may even be better than PCR tests at identifying infected people without symptoms. One bonus: Canine teeth are cuter and less invasive than swabs on the nose.
On June 1, the researchers PLoS One. The dogs identified all 31 cases of COVID-19 in 192 people who were asymptomatic.
Dominique Grandjean, a veterinarian at the National Veterinary College of Alfredo, said the findings prove that dogs can be effective in mass screening efforts at venues such as airports or concerts, and may provide a friendly alternative to testing for people reluctant to take nasal swabs. Maisons-Alfort, France.
“Dogs don’t lie,” but there are many ways a PCR test can go wrong, Grandjean said. Canine noses also found more cases of COVID-19 than antigen testing (SN: 12/17/21), Grandjean and colleagues found, which is similar to many home tests but sometimes mistaken another respiratory virus for a coronavirus. What’s more, anecdotal evidence suggests that these dogs can detect asymptomatic cases up to 48 hours before people test positive by PCR, he said.
In the study, dogs from the French fire service and the United Arab Emirates’ Ministry of the Interior were trained to test for Covid-19, and they were rewarded with toys, usually tennis balls. “It’s their game time,” Grandjean said. Based on dog smell detection experience, it takes about three to six weeks to train dogs to pick out COVID-19 cases from sweat samples.
The dogs then sniffed the cones of sweat samples collected from the armpits of human volunteers. Wiping the sweat off the backs of people’s necks or letting the woofers smell a used mask can be just as effective, Grandjean said.
These results suggest that odors from multiple body parts can be used for canine screening, said Kenneth Furton, a forensic chemist at Florida International University in Miami, who was not involved in the study.
These results are similar to previous small studies that also found dogs to perform as well or better than PCR tests at detecting SARS-CoV-2, the virus that causes COVID-19, Furton said. He and colleagues have used dogs in schools, music festivals and small trials to screen airline employees for coronavirus infections.
One of the dogs’ biggest advantages over other tests is their speed, Furton said. “Even with what we call a rapid test, you still have to wait tens of minutes or even hours, while the dog can respond in seconds or even fractions of a second.”
It’s unclear what exactly dogs smell when they detect COVID-19 or other illnesses, said Cynthia Otto, director of the Center for Working Dogs at the University of Pennsylvania School of Veterinary Medicine, who was not involved in the study. It may not be a single chemical, but a pattern of increasing and decreasing levels of certain aromas. “It’s not like you can create a scented perfume bottle with the smell of COVID,” she said.
Even with repeated studies proving dogs’ ability to detect COVID, some doctors, scientists and government officials remain skeptical of the claims, Grandjean said. He finds the reluctance puzzling because dogs have been used to sniff out drugs and explosives and are being tested for other diseases, such as cancer, he said. “Every time you fly, it’s because the dog keeps sniffing your luggage [and found] No explosives. So you trust them when you fly, but you don’t want to trust them on COVID? “
One challenge dogs face, Furton said, is that they’re not considered high-tech like electronic sensors. “But dogs are one of the most high-tech devices we have. They’re just biological sensors, not electronic sensors,” he said.
Another disadvantage of dogs, Otto said, is that they take time to train, and there aren’t even enough dogs currently trained to detect explosives, let alone disease. “A dog that performs well in a laboratory setting may not perform well in an interpersonal setting,” she said. Handlers can also influence the dog’s responses and must be able to read the dog well, she said. “We need more good dogs.”