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.
“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
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.
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.
Though only in the pilot study phase, results correlate with earlier studies where both dogs and humans were able to “smell” specific diseases in people
Man’s best friend has risked life and limb to save humans for centuries. Now, researchers in Germany have discovered that pooches may be useful in the fight against COVID-19 as well, along with the added benefit that such testing would be non-invasive. In fact, some people believe disease-sniffing dogs may give clinical laboratory testing a run for its money.
Further, even if this approach were not warranted as a clinical diagnostic procedure, trained dogs could be deployed at airports, train stations, sporting events, concerts, and other public places to identify individuals who may be positive for SARS-CoV-2, the coronavirus that causes the COVID-19 illness. Such an approach would make it feasible to “screen” large numbers of people as they are on the move. Those individuals could then undergo a more precise medical laboratory test as confirmation of infections.
After only one week of training, the dogs were able to accurately detect the presence of the infection 94% of the time.
According to a live interview, which featured Holger Volk, PhD, Department Chair and Clinical Director of the Small Animal Clinic at the University of Veterinary Medicine Hannover and Maren von Köckritz-Blickwede, PhD, Professor of Biochemistry of Infections and Head of Scientific Administration and Biosafety at the Research Center for Emerging Infections and Zoonoses at TiHo, “The samples were automatically distributed at random and neither the dog handlers involved nor the researchers on site knew which samples were positive and which were used for control purposes. The dogs were able to distinguish between samples from infected (positive) and non-infected (negative) individuals with an average sensitivity of 83% and a specificity of 96%. Sensitivity refers to the detection of positive samples. The specificity designates the detection of negative control samples.
In their published study, the authors wrote, “Within randomized and automated 1,012 sample presentations, dogs achieved an overall average detection rate of 94% with 157 correct indications of positive, 792 correct rejections of negative, 33 false positive and 30 false negative indications.” They concluded, “These preliminary findings indicate that trained detection dogs can identify respiratory secretion samples from hospitalized and clinically diseased SARS-CoV-2 infected individuals by discriminating between samples from SARS-CoV-2 infected patients and negative controls. This data may form the basis for the reliable screening method of SARS-CoV-2 infected people.”
In the live interview, Dr. Köckritz-Blickwede said, “We think that this works because the metabolic processes in the body of a diseased patient are completely changed,” adding, “We think that the dogs are able to detect a specific smell of the metabolic changes that occur in those patients.”
Using Dogs as Part of Clinical Laboratory Testing
The American Kennel Club (AKC) estimates that a dog’s sense of smell is 10,000 to 100,000 times greater than that of humans. This gives dog’s the ability to detect diseases in early stages of development.
“The next steps will be that we try to differentiate between sputum samples from COVID patients versus other diseases, like, for example from influenza patients,” said Köckritz-Blickwede. “That will be quite important to be able to differentiate that in the future.”
“This method could be employed in public areas such as airports, sport events, borders or other mass gatherings as an addition to laboratory testing, helping to prevent further spreading of the virus or outbreaks,” the live interview description states.
During a pandemic, employers might be able to use dogs to screen employees as they arrive for work. Dogs also could be used as an alternative or in addition to clinical laboratory testing to help prevent the spread of COVID-19. But more work must be done.
“What has to be crystal clear is that this is just a pilot study,” said Volk. “So, there is a lot of potential to take this further to really make it possible to use these dogs in the field.”
By contrast, humans have only six million sensory receptor sites in their nasal cavity. The area of a dog’s brain that is dedicated to the analysis of odors is about 40 times larger than the comparable part of a human brain and dogs are capable of detecting odors thousands of times better than humans.
The article also further explains how dog’s olfactory glands are very unique when compared to other animals and humans. “Unlike humans, dogs have an additional olfactory tool that increases their ability to smell. Jacobson’s organ is a special part of the dog’s olfactory apparatus located inside the nasal cavity and opening into the roof of the mouth behind the upper incisors. This amazing organ serves as a secondary olfactory system designed specifically for chemical communication.
“The nerves from Jacobsen’s organ lead directly to the brain and are different from the other nerves in the nose in that they do not respond to ordinary smells. In fact, these nerve cells respond to a range of substances that often have no odor at all. In other words, they work to detect “undetectable” odors.”
VCA Hospitals is a chain of veterinary hospitals with more than 1,000 facilities located in 46 states and five Canadian provinces.
Dogs are amazing, that’s for sure. But for canines to become widely used to detect infections there would have to be a way to validate each dog’s ability to detect diseases, so that the diagnostics would be consistent across all the dogs being used.
So, while there appears to be potential for utilizing a dog’s uncanny sense of smell to detect disease—including COVID-19—more research is needed before development of clinical testing can take place. And, perhaps, a set of canine billing codes.
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