Dogs have a much more powerful sense of smell than humans: while we have roughly five to six million scent receptors in the nose, dogs have about 300 million. Due to this amazing capacity, dogs have been used to detect various diseases, ranging from Parkinson’s, cancer, and diabetes to Covid-19.
Now, a research team from the University of Veterinary Medicine in Hannover, Germany has found that dogs trained to detect Covid-19 infections are also able to reliably identify long Covid cases, which are characterized by a constellation of lingering or new post-infection symptoms that can last for several months, including fatigue, shortness of breath, heart palpitations, musculoskeletal pain, or brain fog.
Since April 2020, scientists have trained a group of dogs to detect by smell Covid-19 infections. “Dog odor detection is far better than the general public can imagine,” said study co-author Dr. Esther Schalke, a veterinary behaviorist at the Bundeswehr Medical Service in Koblenz, Germany. “We were amazed at how quickly our dogs could be trained to recognize samples from SARS-CoV-2 infected individuals.”
In the new study, the scientists had nine dogs dip their noses into scent holes containing samples of long Covid patients’ saliva, as well as Covid-19 positive and negative samples of saliva, sweat, and urine. Overall, the dogs managed to correctly identify 85 percent of long Covid samples.
When long Covid cases were presented next to negative Covid-19 samples, the dogs could more accurately detect them (94 percent) than when these cases were presented next to positive virus samples (86 percent). According to the researchers, this indicates that the “disease-specific odor” of Covid-19 was still detectable by the dogs in the long Covid samples, although not to the same extent as in samples of patients with acute Covid-19.
“These results suggest that the disease-specific odor of acute Covid-19 is still present in the majority of long Covid samples,” the authors explained. “The study should be regarded as a pilot study due to inclusion of a limited number of patients. Further research with more patients and samples acquired from the same patient at different time points is needed, to evaluate to what extent the sensitivity of medical detection dogs may vary throughout the course of the infection,” they concluded.
The research is published in the journal Frontiers in Medicine.