This is yet another example that dogs can be highly accurate screeners for disease. But are they ready to be included in clinical laboratory diagnostic tests?
Thailand researchers have trained dogs to screen for COVID-19 infections in humans, despite the country’s “spicy and flavorful cuisine,” the AP reported. This is just the latest example of a country using dogs to identify individuals who are infected with the SARS-CoV-2 coronavirus. Clinical laboratory managers and pathologists have seen other examples of dogs being trained to identify different diseases or health conditions.
In fact, dogs have been shown to be highly accurate at spotting disease in humans and the practice is becoming common worldwide. But could dogs achieve the required clinical accuracy and reproducibility in detecting disease for the procedure to be translated into clinical practice?
Smelling Disease as a Clinical Laboratory Diagnostic
Clinical laboratory professionals are quite familiar with the concept of the human body producing volatile chemicals that can serve as biomarkers for disease or illness. Dark Daily has previously reported on multiple breath/aroma-based diagnostic clinical laboratory tests going as far back as 2013.
“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,” we wrote. “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.”
According to the researchers, individuals with a COVID-19 infection emit a unique odor that is present in sweat samples. The six Labrador retrievers used in the research were able to detect the presence of COVID-19 with an impressive 95% accuracy rate in more than 1,000 samples presented to them, the AP reported.
To perform the study, the scientists placed sweat samples in metal containers and allowed the dogs to sniff each sample. If no trace of the infection was present, the dogs simply walked past the container. If the disease was detected in a particular sample, the dogs would sit down in front of the container.
Would Spicy Food Interfere with Dogs’ Ability to Detect COVID-19?
The head of the research team, Professor Kaywalee Chatdarong, PhD, noted that other countries also have been using canines to detect the presence of COVID-19. She did have some concerns that the utilization of dogs for this purpose may not work in Thailand due to their often-spicy cuisine. However, since the samples used were from students and faculty at the university, as well as people from the surrounding area, the cuisine did not seem to affect the study results, the AP reported.
Thailand is facing a surge in COVID-19 cases with recent clusters reported at construction sites, crowded neighborhoods, and large markets. The research team plans to use the canines in mobile units in communities suspected of being hotspots for the disease.
A major plus of using dogs to sniff out the disease from sweat samples is the ability to test people who may not be able to get out of their homes to be tested.
“People can simply put cotton balls underneath their armpits to collect sweat samples and send them to the lab,” Suwanna Thanaboonsombat, a volunteer who collects samples and brings them to the clinical laboratory for testing, told the AP. “And the result is quite accurate.”
According to the US Centers for Disease Control and Prevention (CDC), dogs can become infected with the SARS-CoV-2 coronavirus. However, their chances of transmitting the disease to humans is extremely low. Nevertheless, to ensure the dogs do not become infected with COVID-19 themselves, the researchers designed the sample containers to avoid contact between the samples and the dogs’ noses.
Living Animals Come with Limitations
While dogs can provide a quick and inexpensive method of testing for COVID-19, they do have limitations.
“5 p.m. is their dinner time. When it’s around 4:50, they will start to be distracted. So, you can’t really have them work anymore,” Chatdarong told the AP. “And we can’t have them working after dinner either because they need a nap. They are living animals and we do have to take their needs and emotions into consideration. But for me, they are heroes and heroines.”
Using Dogs to Detect COVID-19 in Other Countries
Last fall, the Helsinki Airport in Finland announced it would use a team of trained dogs to detect the presence of COVID-19 among visitors to the airport to ensure the health and safety of its customers and their families, and to help prevent the spread of SARS-CoV-2 in Finland.
“We are among the pioneers. As far as we know no other airport has attempted to use canine scent detection on such a large scale against COVID-19,” said Airport Director Ulla Lettijeff in a Finavia press release. “This might be an additional step forward on the way to beating COVID-19.”
In addition to being “man’s best friend,” dogs serve valuable purposes in the medical community. Their strong sense of smell may render them useful in the detection of and fight against illnesses, including COVID-19.
Whether the performance and accuracy of individual dogs can be validated with acceptable quality control (QC) procedures remains to be seen. Medical laboratory managers and pathologists understand the challenges presented with demonstrating accuracy and reproducibility with this method of diagnostic testing. That obstacle has prevented research outcomes from being translated into clinical practice.
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.