By Jed Weisberger
Last week, an NBC News report cited a study proving scent-detection dogs, with their extraordinary sense of smell, can detect people infected with Covid, not to mention several other diseases, just by different odors.
In addition to that report, two IWDBA members, Dr. Esther Schalke and Nele Ten Hagen, both affiliated with groups at the University of Veterinary Medicine in Hannover, Germany, have been involved with a pair of published studies proving just how well these dogs diagnose both Covid and other maladies.
Schalke, an IWDBA Board member who has worked with the German Armed Forces School for Service Dogs since 2019, and Ten Hagen, who is pursuing her Ph.D. at The University of Veterinary Medicine, spoke at IWDC 2021 about the confirmed abilities of the canines.
“It all has to do with the different odors for different diseases that the dogs detect,” said Ten Hagen in her IWDC talk. “We already know dogs can detect diabetes, cancer, Parkinson’s Disease and other issues.”
Schalke’s group conducted a study proving dogs can detect Covid-19 in October 2021, while Ten Hagen’s group proved dogs can differentiate between Covid-19 and other viruses in a study presented a few weeks later.
In Schalke’s group, a pilot study with 10 dogs were trained to detect SARS-CoV-2 infections in beta-propiolactone inactivated saliva samples. They were able to discriminate between samples from infected patients and negative controls. The cognitive transfer performance for the recognition of non-inactivated sample material and detection accuracy were tested on three different non-inactivated body fluids (saliva, urine, sweat) in a random double-blind controlled study.
Dogs were tested on a total of 5,242 random samples. They detected non-inactivated saliva samples with an average sensitivity of 84% (95% CI: 62·5–94·44%) and specificity of 95% (95% CI: 93·4–96·0%). In a subsequent experiment to compare the scent recognition between the three non-inactivated body fluids, diagnostic sensitivity and specificity were 95% (95% CI: 66·67–100%) and 98% (95% CI: 94·87–100%) for urine, 91% (95% CI: 71·43–100%) and 94% (95% CI: 90·91–97·78%) for sweat, 82% (95% CI: 64·29–95·24%), and 96% (95% CI: 94·95–98·9% ) for saliva respectively.
In conclusion, detection dogs were able to transfer the conditioned scent detection of inactivated saliva samples to non-inactivated saliva, urine and sweat samples, with a sensitivity more than 80% and specificity of more than 94%. All three fluids were equally suited for SARS-CoV-2 detection by dogs and could be used for disease-specific recognition. This shows detection dogs may provide a reliable screening method for SARS-CoV-2 infections.
“The dogs can sniff it out,” said Schalke.
Ten Hagen’s group premised, because of their outstanding sense of smell, dogs could be an essential asset in mass screening testing strategies.
Previous research demonstrated dogs’ ability to detect SARS-CoV-2- infections but had not investigated whether dogs can distinguish between SARS-CoV-2 and other viral infections.
To address that question, a study was performed with swab from individuals and samples from cell culture, each infected with one of 15 viruses causing acute respiratory symptoms. In all, 12 dogs were trained to detect SARS-CoV-2 positive samples. In the first test (Scenario I), swabs from individuals with a variety of viral respiratory tract infections were presented and the dogs achieved a mean diagnostic sensitivity of 73.8% (95% CI: 66.0–81.7%) and a specificity of 95.5% (95% CI: 92.6–97.7%).
When using cell culture supernatant from different coronavirus infections (Scenario II and III) the dogs detected SARS-CoV-2 samples with a mean diagnostic sensitivity of 61.2% (95% CI: 50.7–71.6%) and 75.8% (95% CI: 53.0–98.5%), respectively.
The specificities were 90.9% (95% CI: 87.3–94.6%) and 90.2% (95% CI: 81.1–99.4%), respectively. The results demonstrate dogs’ ability to differentiate viral respiratory tract infections by their odor.
Nevertheless, compared to earlier studies the diagnostic sensitivities in this study were found subpar. To deploy COVID-19 detection dogs as a reliable screening method, a variety of samples from different viral respiratory tract infections should be included in dog training to ensure a successful discrimination process, it was concluded.
An automatic system of training was used for both studies, in which a dog approached a machine with several scent locations and was rewarded upon successfully finding the scent that was the goal, hearing a buzzer sound and earning a reward.
Again, it must be mentioned, “A dog’s nose knows.”