The next time your dog decides to dive belly first into a pile of rotting fish or writhe in ecstasy in another dog’s feces, keep in mind that this seemingly horrifying urge could one day help save your life.
Dogs have long been used to sniff out explosives and drugs, track criminals and find missing children. Now, researchers are attempting to harness the olfactory powers of canines for use in the field of medicine.
Scientists are training dogs in the hopes that they may one day be able to reliably diagnose certain forms of cancer by smell, and help doctors catch these diseases earlier than conventional diagnostic tools currently allow.
Already dogs are used to warn of epileptic seizures, low blood sugar and heart attacks, although whether they are detecting changes in smell or physical behavior is still unknown. And, while they may not be able to perform CPR or operate a cardiac defibrillator (at least not yet), some canines do know how to call 911.
'This isn't anything magic'
Much of the research in this area is based on the theory that disease causes subtle chemical changes in the body or alterations in metabolism, which in turn releases a different smell, or chemical marker.
“This isn’t anything magic,” says Dr. Larry Myers, associate professor at the Auburn University College of Veterinary Medicine in Auburn, Ala., who has personally tested the olfactory capabilities of more than 4,000 dogs over the last two decades. “Physicians have always used their own senses to determine the presence or absence of disease.”
For instance, diabetes was once diagnosed by the smell or taste of a patient’s urine. Certain infections in burn victims can be detected by the smell of a patient’s skin, and bad breath is often a sign of gum disease.
Recent small-scale studies of dogs’ ability to detect the chemical markers of cancer, specifically melanoma, have shown promising results. The phenomenon was first briefly reported in 1989 in the British journal The Lancet and, since then, preliminary evidence has slowly been accumulating that suggests dogs may indeed be able to differentiate between healthy skin cells and cancerous ones.
A sophisticated sense of smell
Work is also under way to determine whether dogs can accurately diagnose prostate cancer. If the thought of a dog sniffing your private parts sounds just a little too, well, weird, have no fear: The dogs don’t actually smell men’s genitalia directly, they sniff urine samples instead.
Part of what makes a dog's sense of smell so sophisticated is its ability to smell multiple layers of chemicals, says Myers. Dogs don't detect a single chemical but a combination of them. "If (they were identifying) just a single chemical, medicine might have picked up on it. The dog may be doing something a little better," says Myers.
Surprisingly enough, no breed has a monopoly in the olfactory department; most studies have involved a number of different kinds of dogs. “There’s this mythology behind the bloodhound, but I’ve tested a miniature poodle that had a sense of smell that was as good as the bloodhound’s,” says Myers. “There’s enormous variability within the breed and on an individual level.”
The biggest challenge for scientists lies in designing experiments that can accurately determine dogs’ success rate in detecting disease and whether or not they perform better than existing diagnostic methods. Implementing rigorous controls has been a major obstacle, as has been finding adequate numbers of willing patients and doctors.
Correctly training the dogs themselves has also posed a difficulty for researchers. “You’re asking the dog to discriminate something by smell without knowing what the smell is,” says Dr. Jim Walker, director of the Sensory Research Institute at Florida State University, whose research on training dogs to detect melanoma will be published in Applied Animal Behaviour Science.
While it’s unlikely a canine will be joining the cast of ER anytime soon, researchers say if dogs do turn out to possess an ability to accurately detect disease, they could make a significant contribution to public health.
“It’s going to be very useful for large-scale screening of populations,” says Myers. “And it’s certainly going to be effective in third-world countries that don’t have the resources to do sophisticated (laboratory) tests.”
'He's given me my life'
Dogs that diagnose cancer may be a ways away, but some medical pooches are already on the job, warning their owners of epileptic seizures, high blood pressure, heart attacks, migraines and low blood sugar.
Leigh Meyer, of Huntersville, N.C., has suffered from severe epilepsy since she was 17. Now 35, Meyer credits her ability to live independently and take care of her four daughters to her seizure alert dog Cyrano.
“He’s given me my life,” says Meyer. “He’s offered me a chance to have a little bit of normalcy.”
A giant schnauzer who spends most of his time as a docile couch potato, Cyrano’s mood changes abruptly about 30 minutes before the onset of Meyer's seizures. Suddenly he becomes nervous and antsy, and begins pawing at Meyer and leaning on her. This signal gives her time to stop whatever she’s doing, move away from her children and prepare.
Once the seizure starts, Cyrano stands next to her until the episode is over, usually from two to four minutes. Because Meyer’s seizures are often very violent — she has broken several fingers, both collar bones and her feet during convulsions — she relies on Cyrano to keep her children out of the way. And, if a seizure occurs in a public location, she has taught him to herd the children to prevent them from wandering off.
Little research has been done to unravel the mystery behind dogs' ability to warn of a seizure or other medical crisis, but most observers believe it is based on canines' keen observational skills, sense of smell, or a combination of both.
"There would have to be some type of chemical change or physiological change in the body," says Sharon Hermansen, executive director of Canine Seizure Assist Society of North Carolina, and Cyrano's trainer. "People can't tell when (a seizure) is coming on, so there's something the dogs are doing that we can't figure out."
Each pooch chooses its own signals
Whether a dog has been trained to predict seizures, heart attacks or low blood sugar in diabetics, each animal develops its own set of signals to warn its owner. Some will walk in front of a person and refuse to move, others will knock their owner into a chair, while some will simply freeze and stare.
And yes, dogs have even been trained to call 911 on their own in the event of a medical emergency. Given that most telephones aren't made for use by large furry paws, trainers have had to use more dog-friendly devices, such as step lights and pull cords, says Joan Bussard, founder of Amazing Tails Inc., a service and alert dog training program based in Oxford, Pa.
The most difficult part of training alert dogs is not teaching them to warn of a medical crisis — they can either do this on their own or they can't — but training owners to recognize their pet's signals, says Bussard.
"Sometimes it's very clear and other times it's very subtle. You have to play a guessing game," says Bussard. "When they learn to talk, we'll be in good shape."