Amazing Dog Behavior: Detecting Cancer and Disease in Humans
Canine Friends and Helpers
Dogs can be wonderful companions and family members. They don’t perceive the world in exactly the same way as us, however. For example, they can’t see as many colors as us, but their senses of smell and hearing are much better than ours. 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, low blood sugar in diabetics, the fact that an epileptic seizure is about to occur, and—according to the results of research with one dog—an infection by Clostridium difficile.
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 be up to 100,000 times stronger. A dog's nose and brain have special adaptations for sensing and analyzing odors, which we lack.
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 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.
According to the American Kennel Club, the ten dogs with the best sense of smell (in alphabetical order) are the basset hound, beagle, Belgian malinois, black and tan coonhound, bloodhound, bluetick coonhound, dachshund, German shepherd, golden retriever, and Labrador retriever.
Cancer Types Detected By Dogs
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.
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 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.
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.
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.
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.
Training Medical Detection Dogs
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 the 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.
Diabetes and Hypoglycemia
What is Type 1 Diabetes?
Blood glucose (or blood sugar) is an important substance because it's used by cells as an energy source. Insulin, a hormone made by the pancreas, triggers glucose to leave the blood and enter cells. In a person with type 1 diabetes the pancreas doesn't make insulin, so the person must obtain the hormone through injections or an insulin pump in order for their cells to absorb the necessary glucose.
What is Hypoglycemia?
Blood sugar can fall to a dangerously low level if a diabetic person receives too much insulin relative to the amount of glucose in their blood. This condition is called hypoglycemia, or low blood sugar.
Hypoglycemia can also develop if the person exercises too much, which uses up blood glucose, or if the person doesn't eat enough food, since the digested food supplies glucose to the blood.
Nighttime is especially risky for a person with Type 1 diabetes, since the blood sugar level may fall during sleep. Diabetics need to monitor their blood glucose level frequently and make adjustments to their insulin and glucose intake if necessary.
A Diabetic Alert Dog in the Family
Common Symptoms of Hypoglycemia
Common symptoms of hypoglycemia include sweating, shaking, weakness, anxiety, dizziness, headache, a rapid heart beat, and confusion. Severe hypoglycemia can lead to seizures, coma, and death. An affected person may not realize that their blood sugar is low, however, because the warning signs may be too weak or because of the confusion that develops. This is why a diabetic alert dog as a companion may be a life-saver as well as a friend.
Anyone who experiences symptoms that might indicate the presence of hypoglycemia should visit a doctor for a diagnosis and treatment plan.
Diabetic Alert Dogs
Diabetic Alert Dogs are thought to sense a change in body or breath odor when a person with Type 1 diabetes is entering a hypoglycemic state, although it isn't known what chemical or chemicals the dogs are perceiving. Some dogs can detect high blood sugar as well as low blood sugar.
The dogs are trained to warn their owner in some way when they detect the signs of low blood sugar. They may jump up on their owner, lick them extensively, nudge them, or sit and stare at them, for example. They may also be trained to bring insulin kits or food to the person or to contact other people. Some parents say that the diabetic alert dog in the family will wake them up during the night if their child is experiencing a dangerous drop in blood sugar.
There hasn't been much scientific research into the ability of dogs to detect low or high blood sugar, but scientists say that this ability is definitely plausible. Many diabetics who own diabetic alert dogs say that their dog's alerts are accurate and agree with the data recorded by their blood glucose monitor. They also say that their dog has given them a wonderful feeling of freedom and peace of mind and is a very close friend.
In 2016, scientists from the University of Cambridge reported that the level of exhaled ispoprene is greatly increased in people with type 1 diabeties who are experiencing hypoglycemia. It's known that dogs can detect isoprene. Despite the headlines, however, the researchers didn't prove that dogs identify hypoglemia via detecting the isoprene level in exhaled air.
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 the Nature journal showed that distinct chemicals are released during a seizure and that the odours 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, or communities. It causes inflammation in the intestine and diarrhea, which are sometimes severe.
In late 2012, an article was published in the British Medical Journal which 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 Clostridiumdifficile than using a conventional medical test. The faster the diagnosis, the sooner the treatment can begin.
Cliff's ability to detect Clostrium difficile is very impressive, but he is only one animal. We need to discover whether other dogs share Cliff's abilities.
Using Medical Detection and Alert Dogs
It's unlikely that dogs will be regularly used to detect samples for the presence of cancer or bacteria. Some people have pointed out that like other intelligent animals, dogs can get bored with doing the same thing over and over again. In addition, they like to be rewarded for success, which is often motivating for them. If they experience long periods of inspecting samples with no positive results and no chance for a reward, they may lose interest in the project. This is why it's important to understand how dogs are detecting disease. This may enable us to create artificial devices that detect the same chemicals as the dogs.
Dogs that can detect medical conditions that may periodically cause emergencies, such as hypoglycemia and epilepsy, can be very useful. In addition, their companionship may be comforting for the affected person. Medical alert dogs for certain conditions can be purchased. They undergo extensive training and are sometimes expensive to buy, costing many thousands of dollars. It's important that anyone who wants to buy one of these dogs goes to a reputable organization that trains and treats their animals well.
Potential Benefits of More Research
Hopefully more researchers will explore the ability of dogs to detect health problems. If the research shows that the animals can detect disease, more funding may be provided to the training organizations. This might eventually lead to better detection of some medical problems. In addition, the price of medical alert dogs may decrease, enabling more people to buy them.
Dogs can be wonderful and very loving pets. It's great that some of them can help us with medical problems as well. As more research is done, we may well discover more about the amazing abilities of dogs.
- Dogs and human cancer detection from Psychology Today
- Sniffer dogs can be used to detect lung cancer from the ScienceDaily news service
- Lung and creast cancer detection from Sage Journals
- Dogs can accurately sniff out early stage bowel cancer from ScienceDaily
- Prostate cancer from the NHS (National Health Service)
- The detection of low blood sugar by dogs from the University of Cambridge
- Dogs can detect the scent of seizures from Scientific American
- Detecting a superbug from EurekAlert
This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.
© 2012 Linda Crampton