Dogs can be trained to detect COVID-19 by sniffing out human sweat, according to a proof-of-concept study published yesterday.
Detection dogs are already common in airports and other public places; they are usually sniffing out drugs, weapons, or explosives.
But specially trained dogs have also been taught to detect infections and diseases, such as colon cancer, malaria, and Parkinson’s disease.
Now, many countries around the world are exploring the possibility of using dogs as a fast, reliable, and relatively inexpensive way to pre-screen people for COVID-19 or conduct rapid checks in certain circumstances, such as at airports.
In the UK, a team from the London School of Hygiene and Tropical Medicine is training six dogs in the hope that they can detect people who are positive for COVID, even if they show no symptoms.
In Finland, a group of sniffer dogs trained to detect COVID-19 began work at Helsinki airport in September in an effort to identify those who contracted the virus and in Chile police dogs are being trained to sniff out COVID-19 in humans.
COVID-19 odor detection
In this new study, researchers based in France and Lebanon took sweat samples from the armpits of a total of 177 patients from four hospitals in Paris and one in Beirut: 95 had tested positive for COVID-19, while 82 had tested negative. .
It was important that both negative and positive samples came from the same hospitals so that the dogs did not detect a particular “hospital odor,” the researchers said.
Using some of the sweat samples, they trained 14 dogs that had been working as explosives detection dogs, search and rescue dogs or colon cancer detection dogs to participate in the study.
The scientists did not use trained dogs to detect illicit drugs because they could not rule out whether the study patients who had provided sweat samples had used prohibited substances.
Six dogs, Guess, Maika, Gun, Oslo, Bella, and Jacky, had their sniffing skills formally tested in the studio. Five of them were Belgian Malinois, a common breed for French working dogs, and Jacky was a Jack Russell terrier.
The researchers asked the animals to detect a positive COVID-19 sweat sample in an olfactory cone from a line of three to four cones that contained negative or mock samples.
Scientists believe that dogs detect a specific odor produced by volatile organic compounds generated by catabolites, substances produced by the replication of the virus that escape from the body through sweat.
During the testing period, the dogs performed dozens of tests, with a success rate of between 76% and 100%.
Jacky and Bella, the two dogs who specialized in detecting colon cancer, had a 100% success rate in the 68 tests they completed.
Additionally, during testing, two of the dogs repeatedly marked two samples collected from individuals who tested negative.
The relevant hospitals were informed and in subsequent tests these individuals were positive.
The study was published yesterday in the journal PLOS One.
By filming the trials, the researchers were able to understand why the dogs were sometimes unsuccessful.
In one case, a horse walked near a test site that was located in a veterinary school.
However, the reasons for the failure to detect were not always obvious, but the researchers said this was not necessarily negative.
“Even if trained dogs can correctly discriminate symptomatic COVID-19 positive from asymptomatic negative individuals, they should not be considered a perfect diagnostic test, but rather a complementary tool,” the study said.
The study, the researchers said, was a “promising first step” in providing some evidence that dogs can detect COVID-19 samples collected from sweat.
However, the scientists said their study had some limitations, including that the sweat samples had to be reused and the researchers couldn’t rule out that the dog was memorizing the scent, although they didn’t think memory played a role. More research is needed, they said.
For safety, the researchers did not use any samples to train or test the dogs within 24 hours of collection.