Medical Detection Dogs and Their Impressive Ability to Help Us
Dogs can detect several types of cancer, an epileptic seizure that is about to occur, infections by Clostridium difficile, and much more.
Canine Friends and Helpers
Dogs can be wonderful companions and family members—but they don’t perceive the world in exactly the same way as us. For example, they can’t see as many colors as us, but their senses of smell and hearing are much better than ours. And since dogs are clever animals that are often eager to cooperate with us, their enhanced senses can be very useful to humans.
One exciting discovery about dog behavior is that the animals can detect certain diseases and medical problems in humans. Sometimes they need to be trained to accomplish these tasks, but in other instances, dogs can identify a problem on their own without any training.
Dogs can detect several types of cancer, an epileptic seizure that is about to occur, and infections by Clostridium difficile. Evidence suggests that they can also detect the SARS-CoV-2 virus that causes the COVID-19 disease after suitable training. They might be able to detect low blood sugar (or hypoglycemia) as well, though this is a somewhat controversial idea.
Dogs are believed to detect diseases with their amazing sense of smell. This sense is at least 10,000 times stronger than ours and may even be up to 100,000 times stronger. A dog's nose and brain have special adaptations for sensing and analyzing odors, which we lack.
Golden retrievers such as Sam have a great sense of smell, which is very useful in a medical detection dog.
Linda Crampton
Researchers have been performing scientific studies with medical detection dogs for at least fifteen years. In this article, I describe research projects from various points in this time period. They aren’t the only ones that exist, but they should give the reader an idea of the fascinating and useful abilities of the dogs.
How Do Dogs Detect Cancer?
Cells produce and release volatile organic compounds, or VOCs. Cancer cells produce a different set of VOCs from healthy cells. Some of the VOCs are different from those made by normal cells, while others are the same but are present in a different proportion.
Volatile organic compounds escape from cells and leave the body in exhaled air, saliva, sweat, blood, urine, or feces. Dogs can smell and recognize the distinct VOC or combination of VOCs made by cancer cells and can distinguish them from the ones made by normal cells.
Dogs detect the presence of the abnormal VOCs in sample containers very quickly. They are trained to show that they've found the chemicals by performing specific behaviors, such as tapping the sample container with their paw or nose or sitting in front of it.
Cancer Types Detected by Dogs
Dogs can be trained to detect several different kinds of cancer.
Lung Cancer
Detecting early-stage lung cancer is difficult. There are generally no obvious symptoms, and the normal detection methods aren't very reliable. It's very important to identify any cancer in its earliest stages to give the best chance for recovery.
Researchers in a 2011 experiment tested the ability of trained dogs to detect cancer VOCs in exhaled air. The dogs detected 71 cancer samples out of a total of 100. The dogs also detected that 372 samples out of a possible 400 did not contain cancer VOCs.
Interestingly, the dogs were not confused by the presence of cigarette smoke particles in the samples or by chemicals released by people suffering from COPD (chronic obstructive pulmonary disease). There does seem to be a specific chemical (or chemicals) released by lung cancer cells.
A 2019 experiment with three trained beagles showed that the dogs were 97% accurate in detecting lung cancer by smelling blood serum. They were tested after eight weeks of training. The research team is also training the dogs to detect breast and colorectal cancer.
Lung and Breast Cancer
The Pine Street Foundation is a non-profit organization designed to support cancer patients and research the disease. In 2006, scientists representing the foundation trained five dogs to detect chemicals in the exhaled breath of lung and breast cancer patients.
In an experiment, the researchers found that the dogs detected 99% of the lung cancer samples and gave a false positive result to only 1% of the normal samples. The dogs correctly identified 88% of the breast cancer samples and had no false positives.
In one experiment, a Labrador retriever was able to detect compounds released by colon cancer cells. This is Owen as a puppy.
Linda Crampton
Colon Cancer
In 2011, another researcher studied the ability of one specially trained Labrador retriever to detect colon cancer in breath or stool samples. The dog correctly identified the presence or absence of cancer chemicals in 33 out of 36 breath samples and in 37 out of 38 stool samples. The stool experiment results were as accurate as colonoscopy results. This is a standard test for the presence of colon cancer and involves the use of a camera to photograph the inside of the colon.
Prostate Cancer
Dogs may also be able to detect prostate cancer by smelling urine. In 2015, the results of an experiment with two bomb-sniffing German shepherds were published. The dogs were given urine from 332 men with prostate cancer and 540 people without the disease. One of the dogs was 100% accurate in detecting the presence or absence of cancer. The other was 98.6% accurate.
In one trial, two German shepherds were very successful at detecting prostate cancer.
Double-Blind Experiments
It's very important that experiments with cancer-detecting dogs are "double-blind" experiments. At the start of a double-blind experiment, the dogs and the observers are both unaware of which test containers contain cancer compounds and which are cancer-free. This is very important since observers may give unconscious signals with their body if they see that a dog is approaching the correct container. Dogs can pick up these signals and may indicate that a container contains cancer compounds simply because they notice that the observer is reacting in some way, even if the reaction is very slight.
How Do We Interpret Results?
When assessing any experimental results, it's important to consider factors that may have affected the outcome, such as sample size and the use or lack of a double-blind procedure. It's also important to note whether another organization is able to replicate the experiment and its results.
Experimental Results
The results of the experiments with cancer detection dogs range from good to excellent. Possible reasons for this variability could be factors such as the differing abilities of the individual dogs or dog breeds used in the experiments, differences in their prior training or willingness to participate in the experiment, or differences in the experimental design. The type and stage of cancer may also play a role. Dogs may be able to detect some types of cancer better than others, or they may be able to detect cancer at one stage of development better than at another stage. More experiments need to be done, and they need to involve a larger number of dogs.
Research with dogs is very important, not only because dogs can indicate the presence of cancer very quickly but also because their behavior demonstrates that cancer cells release specific chemicals. The ultimate goal is not to have groups of dogs working in medical labs. Instead, researchers hope to identify the molecules that the dogs are detecting and then create instruments that can correctly identify the presence of these molecules.
Seizure Alert Dogs
Some dogs can predict that a person with epilepsy is going to have a seizure soon, even when the person doesn't realize this. The warning time ranges from under a minute to forty-five minutes—or even longer—before the seizure starts. The advantage of the prediction is that the person can move to a safe area so that they aren't injured during the seizure.
Dogs are being taught to take care of people during and after a seizure. The ability to predict a seizure is a special behavior shown by certain dogs and can't be trained, although it may be encouraged.
Some scientists think that seizure alert dogs are actually detecting the very early stages of a seizure that has already started rather than predicting the seizure. The changes in the person's brain may be creating chemicals which the dogs can smell. The dogs may also be detecting subtle changes in the person's behavior. Whatever the true explanation, dogs can be very helpful for epileptics.
The dogs indicate their discovery to their owner in a number of different ways. Some paw their owners or bark. Others circle their owners, lick them, nudge them, push them into a sitting position, or stare at them.
In 2019, a report published in journal "Nature" showed that distinct chemicals are released during a seizure and that the odors of these chemicals could be detected by the dogs involved in the research. The dogs sniffed breath and skin secretions from people experiencing a seizure and from other people and were able to distinguish the seizure chemicals.
A Beagle That Can Detect the Clostridium Difficile Superbug
Clostridium difficile, or C. diff, is a very troublesome bacterium that produces infections in hospitals, care homes, and communities. It causes inflammation in the intestine and diarrhea, which are sometimes severe.
In late 2012, an article published in the British Medical Journal described the efforts of a two-year-old beagle named Cliff. Cliff was trained to detect C. diff in stool and in the air around hospital patients. After Cliff had received two months of training, he was given 50 stool samples contaminated with C. diff and 50 samples without C. diff. Cliff correctly identified all 50 samples with the bacteria and 47 of the ones without bacteria.
Cliff was then taken to two hospital wards to smell the air around patients. He identified 25 out of 30 cases of infection and 265 out of 270 cases without the infection—and he took only ten minutes to inspect one ward. This is a much faster way to detect Clostridium difficile than using a conventional medical test. The faster the diagnosis, the sooner the treatment can begin.
Cliff is not the only dog capable of detecting C. diff. A health agency near my home uses two English Springer Spaniels to detect the bacteria and says that the team has 97% accuracy.
Warning
Dogs can be infected by Clostridium difficile. I have read that the infection is more common in dogs that are immunocompromised. Anyone who hopes to use a dog to detect the bacterium should seek a veterinarian’s opinion with respect to safety for their animal, even if the dog is healthy.
Beagles have an excellent sense of smell, which can be very helpful for humans.
Canines seem to detect coronavirus infections with remarkable accuracy, but researchers say large-scale studies are needed before the approach is scaled up.
— Holly Else, via nature.com
Canine Detection of the SARS-CoV-2 Virus
In various experiments, researchers have discovered that the ability of dogs to detect the SARS-CoV-2 coronavirus that causes COVID-19 ranges from good to excellent. The dogs are given fluid from a human to smell, such as sweat or saliva. Researchers don’t know exactly what chemicals the dogs are smelling. Some researchers suspect that the dogs are detecting VOCs released by the body when it’s infected by the coronavirus instead of the virus itself.
Based on the results that I’ve seen, the number of dogs in each project has been quite small. Research with a larger number and variety of dogs is needed. Given the seriousness of the coronavirus situation, however, it could be understandable why dogs are already being used to detect the virus at some airports.
Rapid identification of a patient infected by the virus that causes COVID-19 could be very important in places such as airports. Infected patients could be isolated and then tested again by a conventional mechanism that requires more time. This routine of quick isolation could greatly reduce the spread of the disease. The identification of infected people by dogs would be especially useful in the case of patients who don’t have symptoms and don’t realize that they are carrying the virus in their body and shedding it.