Dogs’ acute sense of smell can even surpass effectiveness of some clinical laboratory testing in detecting certain diseases in humans

When it comes to COVID-19 testing, a recent Italian study demonstrates that trained dogs can detect SARS-CoV-2 with accuracy comparable to rapid molecular tests used in clinical laboratories. The researchers wanted to determine if dogs could be more effective at screening people for COVID-19 at airports, schools, and other high-traffic environments as a way to detect the coronavirus and reduce the spread of this infectious disease.

Scientists at the State University of Milan in Italy conducted a study that shows dogs can be trained to accurately identify the presence of the COVID-19 infection from both biological samples and by simply smelling an individual.

For their validation study, the Italian team trained three dogs named Nala, Otto, and Helix, “to detect the presence of SARS-CoV-2 in sweat samples from infected people. At the end of the training, the dogs achieved an average sensitivity of 93% and a specificity of 99%, showing a level of accuracy highly consistent with that of the RT-PCR [reverse transcription polymerase chain reaction] used in molecular tests and a moderate to strong reproducibility over time,” Nature reported.

RT-PCR tests are the current gold-standard for SARS-CoV-2 detection. This is yet another example of scientists training dogs to smell a disease with “acceptable” accuracy. This time for COVID-19.

The researchers published the results of their study in the journal Scientific Reports titled, “Sniffer Dogs Performance is Stable Over Time in Detecting COVID-19 Positive Samples and Agrees with the Rapid Antigen Test in the Field.” Their findings support the idea that biosensing canines could be used to help reduce the spread of the SARS-CoV-2 coronavirus in high-risk environments.

“We only recruited dogs that showed themselves predisposed and positively motivated to carry out this type of activity. One of the fundamental aspects was not to cause stress or anxiety in the subjects used,” Federica Pirrone, PhD (above), Associate Professor, Department of Veterinary Medicine and Animal Sciences, University of Milan, and one of the authors of the study told Lifegate. “Training always takes place using positive reinforcement of a food nature: whether it’s a particularly appetizing morsel, a biscuit, or something that associates the dog’s search with a rewarding prize.” In some instances, dogs have been shown to be as good or more effective at detecting certain diseases than clinical laboratory testing. (Photo copyright: Facebook.)

Dogs More Accurate than Rapid Antigen Testing

Nala and four other dogs (Nim, Hope, Iris and Chaos) were later trained by canine technicians from Medical Detection Dogs Italy (MDDI) to identify the existence of the SARS-CoV-2 virus by directly smelling people waiting in line in pharmacies to get a nasal swab to test for the coronavirus.

Working with their handlers, the five dogs accurately signaled the presence or absence of the virus with 89% sensitivity and 95% specificity. That rate is “well above the minimum required by the WHO [World Health Organization] for rapid swabs for SARS-CoV-2,” according to Nature.

“The results of studies published so far on the accuracy of canine smell in detecting the presence of SARS-CoV-2 in biological samples (e.g., saliva, sweat, urine, trachea-bronchial secretions) from infected people suggest that sniffer dogs might reach percentages of sensitivity and specificity comparable to, or perhaps even higher, than those of RT-PCR,” the scientists wrote in Scientific Reports.

“However, although most of these studies are of good quality, none of them provided scientific validation of canine scent detection, despite this being an important requirement in the chemical analysis practice. Therefore, further applied research in this field is absolutely justified to provide definitive validation of this biodetection method,” the researchers concluded.

Other Studies into Using Dogs for Detecting Disease

In a similar study published in the journal Frontiers in Medicine titled, “Dogs Detecting COVID-19 from Sweat and Saliva of Positive People: A Field Experience in Mexico,” researchers found that dogs could be trained to detect the presence or absence of the SARS-CoV-2 coronavirus from human sweat and saliva samples.

Scientists from the Division of Biological and Health Sciences, Department of Agriculture and Livestock at the University of Sonora; and the Canine Training Center Obi-K19, both in Hermosillo, Mexico, conducted the study “as part of a Frontiers of Science Project of the National Council of Science and Technology (CONACYT), in which in addition to analyzing sweat compounds, trained dogs are put to sniff the samples and make detections in people who show symptoms or could be positive for coronavirus,” Mexico Daily Post reported.

The researchers trained four dogs with sweat samples and three dogs with saliva samples of COVID-19 positive patients. The samples were obtained from a health center located in Hermosillo, Sonora, in Mexico. The dogs were restricted to spend five minutes per patient and the researchers calculated the performance of the dogs by measuring sensitivity, specificity, and their 95% confidence intervals (CI).

The researchers concluded that all four of the dogs could detect COVID-19 from either sweat or saliva samples “with sensitivity and specificity rates significantly different from random [sampling] in the field.” According to the Frontiers in Medicine study, the researchers found their results promising because, they said, it is reasonable to expect the detection rate would improve with longer exposure to the samples.  

The objective of the Mexican researchers is for the dogs to ultimately reach the sensitivity range requested by WHO for the performance of an antigen test, which is at least 80% sensitivity and 97% specificity. If that goal is achieved, dogs could become important partners in the control of the COVID-19 pandemic, the scientists wrote. 

In “German Scientists Train Dogs to Detect the Presence of COVID-19 in Saliva Samples; Can a Canine’s Nose Be as Accurate as Clinical Laboratory Testing?” Dark Daily reported on a pilot study conducted by researchers at the University of Veterinary Medicine Hannover (TiHo), the Hannover Medical School, and the University Medical Center Hamburg-Eppendorf involving eight specialized sniffer dogs from the Bundeswehr (German armed forces) to determine if the dogs could find people infected with the SARS-CoV-2 coronavirus. After only one week of training, the dogs were able to accurately detect the presence of the COVID-19 infection 94% of the time.

And in “New Study Shows Dogs Can be Trained to Sniff Out Presence of Prostate Cancer in Urine Samples,” we covered how scientists from Johns Hopkins University School of Medicine, University of Texas, Harvard Medical School, Massachusetts Institute of Technology (MIT), and others, had conducted a pilot study that demonstrated dogs could identify prostate samples containing cancer and discern between cancer positive and cancer negative samples.

Data obtained so far from these studies indicate that biosensing dogs may represent an effective method of screening for COVID-19 as well as other diseases. More studies and clinical trials are needed before the widespread use of dogs might become feasible. Nevertheless, scientists all over the world are finding that Man’s best friend can be a powerful ally in the fight against the spread of deadly diseases.

In the meantime, the gold standard in COVID-19 testing will continue to be the FDA-cleared assays used by clinical laboratories throughout the United States.

—JP Schlingman

Related Information:

Sniffer Dogs Performance is Stable Over Time in Detecting COVID-19 Positive Samples and Agrees with the Rapid Antigen Test in the Field

COVID: Goodbye Swabs, the Dogs Will Sniff It

There Are Dogs That Are Able to “Sniff Out” Diseases

Antigen-detection in the Diagnosis of SARS-CoV-2 Infection

Dogs Detecting COVID-19 from Sweat and Saliva of Positive People: A Field Experience in Mexico

German Scientists Train Dogs to Detect the Presence of COVID-19 in Saliva Samples; Can a Canine’s Nose Be as Accurate as Clinical Laboratory Testing?

New Study Shows Dogs Can Be Trained to Sniff Out Presence of Prostate Cancer in Urine Samples