DOG CARE

APPLICATION OF SNIFFING DOGS AS A DIAGNOSTIC TOOL IN INFECTITOUS DISEASES

September 19, 2022

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APPLICATION OF SNIFFING DOGS AS A DIAGNOSTIC TOOL IN INFECTITOUS DISEASES

Dogs are famous for their sense of smell. This sense is so advanced in dogs that they can smell disease or medical conditions. With over 220 million scent receptors—compared to five to 10 million in humans—dogs can smell things that seem unfathomable to us. Dogs’ ability to detect odors is 10,000 to 100,000 times that of humans. They can detect some odors in parts per trillion, and they can detect countless subtleties in scnts.

Dogs are used to sniff out bombs and contraband drugs in the medical field as well as certain types of cancer, diabetes and even Parkinson’s Disease. The process, termed as ‘biodetection’, is now being used to detect Covid.

According to the US government’s

National Center for Biotechnology Information (NCBI), dogs are known for their extremely sensitive olfactory system that can even detect substances at concentrations as low as 1.5 parts-per-trillion. When someone is ill, the human body releases specific volatile organic compounds or VOCs, this is emitted as gas and has a specific smell per infection. So, people who have been infected with Covid-19 with their unique VOC give out a distinct odour that can be pinpointed by ‘biodetection dogs’.

But it takes time to train such dogs, and their availability and time is limited. Scientists have been hunting for ways of automating the amazing olfactory capabilities of the canine nose and brain, in a compact device. Now, a team of researchers at MIT and other institutions has come up with a system that can detect the chemical and microbial content of an air sample with even greater sensitivity than a dog’s nose. They coupled this to a machine-learning process that can identify the distinctive characteristics of the disease-bearing samples.

Numerous studies have shown that trained dogs can detect many kinds of disease — including lung, breast, ovarian, bladder, and prostate cancers, and possibly Covid-19 — simply through smell. In some cases, involving prostate cancer for example, the dogs had a 99 percent success rate in detecting the disease by sniffing patients’ urine samples.

Dogs have been trained to detect a dozen human diseases and most recently, COVID-19.

Dogs are famously known for their sense of smell. Their genetics and physiology make them perfectly suited for sniffing. Dogs have so many more genes that code for olfactory ability, and many more olfactory nerve cells than humans. And for centuries now, humans have taken advantages of this exquisite sense of smell to hunt, search and detect drugs and explosives and now diseases.

With about 220 million scent receptors – humans only have 5 million – dogs can smell things that seem unfathomable to us. Dogs have smell receptors 10,000 times more accurate than humans’, which means their nose is powerful enough to detect substances at concentrations of one part per trillion – a single drop of liquid in 20 Olympic-size swimming pools!

Smelling in stereo

Not only that, but dogs also inhale up to 300 times per minute in short breaths, meaning that their olfactory cells are constantly supplied with new odour particles. AND their noses differentiate between right and left.

Dogs’ sense of smell is so subtle that they can notice the slightest change in human scent caused by disease. The tiniest shifts in hormones or volatile organic compounds released by diseased cells can be picked out by dogs. Consequently, dogs have been trained to sniff out the markers of disease that might even go unnoticed with medical tests.

Dogs can help disease diagnosis

Dogs are most famously known for detecting cancer. They can be trained to sniff out a variety of types including skin cancer, breast cancer and bladder cancer using samples from known cancer patients and people without cancer.

In a 2006 study, five dogs were trained to detect cancer based on breath samples. Once trained, the dogs were able to detect breast cancer with 88 percent accuracy, and lung cancer with 99 percent accuracy. They could do this across all four stages of the diseases. More recently, a study has even shown that dogs can use their highly evolved sense of smell to pick out blood samples from people with cancer with almost 97 percent accuracy.

And these are only a few of many studies on the matter. The results could lead to new cancer-screening approaches that are inexpensive and accurate without being invasive. As early detection offers the best hope of survival, dogs might save thousands of lives.

Dogs can detect different types of cancer from varied samples, but also many other diseases. Malaria is one of them. Canines proved to be able to correctly pick out the scent of children infected with malaria parasites 70 percent of the time, from socks they had worn all night,

Besides cancer and malaria, dogs can also detect Parkinson’s disease. Parkinson’s sufferers smell different even years before they have the disease. Dogs could therefore be used in detecting early onset of the disease and treating patients pre-emptively, before the symptoms get irremediably too severe.

Detecting warning signs of disease

But even before humans get sick, animals can help to detect the warning signs of disease.

Dogs can for example detect if a patient is about to go into epileptic seizure or have a narcoleptic moment. Both events can be dangerous if in the wrong place at the wrong time.

A study published in 2013, found that two trained dogs detected 11 out of 12 narcolepsy patients using sweat samples, demonstrating that dogs can detect a distinct scent for the disorder. The dogs pick up on biochemical changes in the body that lead to an attack and help with different tasks to avoid injury. But most importantly, they can provide a warning up to 5 minutes before an attack comes on, giving their handler a chance to get to a safe place or a safe position.

The capacity of dogs to pre-empt seizure is a bit more controversial about the level of accuracy. A small 2019 study found that dogs were able to clearly discriminate a general epileptic “seizure odour.” But researchers had previously reported that four out of seven seizure alert dogs turned out to be warning their masters of psychological, rather than epileptic seizures.

Increasingly, dogs are also helping diabetics know when their blood sugar level is dropping or spiking. The dogs detect isoprene, a common natural chemical found in human breath that rises significantly during episode of low blood sugar. People can’t detect the chemical, but the researchers believe that the dogs are particularly sensitive to it and can be trained to tell when their owner’s breath has high levels of it.

Dog scan also help predict migraines. And for those who suffer migraines, having a warning before one comes on can mean the difference between managing the problem or succumbing to hours of pain. And it turns out the 54% of migraine sufferers with dogs noticed changes in the behaviour of their pets during or preceding migraines. Nearly 60 percent of these subjects indicated that their dog had alerted them to the onset of a headache — usually an hour or two in advance.

Similar to diabetic alert dogs that can smell when their handler has low blood sugar, migraine alert dogs can hone in on the scent of serotonin, a chemical that skyrockets when the body is about to have a migraine. By alerting to the danger long before their handlers might feel any symptoms, these dogs can warn them to take preventative medication.

Dogs against COVID-19

The latest example of dogs detecting disease is with coronavirus SARS-CoV-2, that has caused the worldwide COVID-19 pandemic.

In a pilot study at the University of Helsinki, dogs were taught to recognise the previously unknown odour signature of the COVID-19 disease caused by the novel coronavirus. And in only a few weeks, the first dogs were able to accurately distinguish urine samples from COVID-19 patients from urine samples of healthy individuals, almost as reliably as a standard PCR test.

The Finnish scientists are now preparing a randomised, double-blind study in which the dogs will sniff a larger number of patient samples. Only then will the scent tests be used in clinical practice.

In the meantime, institutes in France, USA, Germany and Great Britain are looking into the matter too.

It is still unclear which substances in urine produce the apparently characteristic COVID-19 odour. Since SARS-CoV-2 not only attacks the lungs, but also causes damage to blood vessels, kidneys and other organs, it is assumed that the patients’ urine odour also changes. Researchers have high hopes it is the case since respiratory diseases like COVID-19 change our body odour, so there is a very high chance that dogs will be able to detect it.

Dogs as a new diagnostic tool could revolutionise our response to COVID-19 in the short term, but particularly in the months to come, and could impact in disease management particularly in high risk events.

Dogs would be able to screen anyone, including those who are asymptomatic in a fast, effective and non-invasive way. Along with testing and vaccine research, dogs’ highly sensitive noses may be on the front lines to tackle the worldwide pandemic.

There are dogs who have sniffed out medical issues that even doctors weren’t aware of. Dogs can pick up on tiny changes in the human body, from a small shift in our hormones to the release of volatile organic compounds, or VOCs, released by cancer cells. Researchers and dog trainers are just beginning to understand how dogs do this and how we might put them to work in being our helpers in health care.

Cancer

Perhaps the condition dogs are most famous for detecting is cancer. Dogs have been able to sniff out a variety of types including breast cancer, prostate cancer, bladder cancer, and lung cancer.

There are quite a few stories of a pet dog obsessing about an owner’s mole or some part of their body, only to discover in a doctor’s appointment that the dog was actually sensing cancer. In one study, a patient’s dog kept licking a mole behind his ear. When the mole was examined, it was confirmed to be a malignant melanoma.

A 2019 study found that dogs can correctly pick out blood samples from people who have cancer with 97% accuracy. Using clicker training with four beagles, lead researcher Heather Junqueira found that the dogs focused their efforts on blood samples from patients with lung cancer, and with one exception, they were highly successful. The work is part of a larger study of canine scent detection in non-small-cell lung carcinoma and breast cancer samples.

Five dogs were trained to detect cancer based on breath samples for a 2006 study.⁶ Once trained, the dogs were able to detect breast cancer with 88 percent accuracy, and lung cancer with 99 percent accuracy. They were able to do this across all four stages of the diseases.

A trained dog presented with urine samples from patients with cervical cancer, cervical abnormalities, benign uterine disease, and healthy volunteers was able to successfully distinguish the sample of patients with cervical cancer each time.

Study after study has shown that dogs can detect cancer in people, but it may be awhile before your doctor employs a hound for your annual checkup. Researchers still don’t know exactly which chemical compounds for different types of cancers the dogs are sensing in these samples to alert to the presence of the disease. This remains a hurdle both for better training of cancer-sniffing dogs and for creating machines that can more accurately detect cancer in the early stages.

How Does the Dog Behave?

The dog’s behavior shifts from what might be considered normal. It could paw or sniff repeatedly, and you could have trouble pushing it away. It may nip or lick at lesions, in an attempt to get rid of them for you.

Narcolepsy

Narcolepsy is a disorder that affects the ability to control sleep-wake cycles. A person with narcolepsy can suddenly fall asleep, even in the middle of a task. It’s a dangerous condition as someone who has an attack could be injured falling to the ground or in a car accident if it happens while driving.

Mary McNeight, director of training and behavior for Service Dog Academy, has been training narcolepsy service dogs since 2010. She believes that the dogs are able to pick up on a scent when a narcolepsy attack is coming on.

In a study published in 2013, Luis Dominguez-Ortega, M.D., Ph.D., found that two trained dogs detected 11 of 12 narcolepsy patients using sweat samples, demonstrating that dogs can detect a distinct scent for the disorder.

How Does the Dog Behave?

A dog trained to detect narcolepsy will warn the owner by barking, nudging, or licking. This indicates the importance of sitting or lying down. The dog may stand over the person’s lap when an attack comes on, which prevents them from sliding out of a chair onto the floor; they can also stand over the person to protect them if they are out in public; or they can go get help. Most importantly, they can provide a warning up to five minutes before the onset of an attack, giving their handler a chance to get to a safe place or a safe position.

While large dogs can be helpful in giving a narcoleptic sufferer extra support in balance and mobility after an attack, these dogs don’t have to be big to be supportive. It might help to end the episode by licking the owner’s face or waking the owner if they sleep through an alarm clock.

Migraines

For those who suffer migraines, having a warning before one comes on can mean the difference between managing the problem or succumbing to hours or days of intense pain. Fortunately, some dogs have a talent for sniffing out the signs that a migraine is on the way.

A survey of migraine sufferers who owned dogs asked if they noticed a change in their dogs’ behavior before or during a migraine. Of the 1,029 participants, 54 percent noted changes in their dog’s behavior either right before or at the onset of the migraine. Behavior differences reported included an increase in attentiveness with the dog sitting on or near the owner and deliberate pawing at the owner. The breeds that owners reported were most likely to alert them to a migraine were mixed breeds, toy breeds, terrier breeds, and sporting breeds.

It’s important to note that the study was conducted with self-reports rather than observation by researchers. Even so, the study shows evidence that many dogs seem to detect and point out a change in their human companion’s health.

How Does the Dog Behave?

A dog sensing a migraine about to start could alert you by licking, circling, nudging, staying right by your side, staring at you, pacing, or barking. This could serve as a reminder to take medication that would stave off the worst of the headache.

Low Blood Sugar

Increasingly, dogs are being trained to help people with diabetes by alerting them when their blood sugar level is dropping or spiking. Dogs4Diabetics is one organization that trains and places service dogs with insulin-dependent persons with diabetes. These dogs undergo extensive training to be able to detect and alert their handlers to changes in blood sugar levels.

A 2016 study published in the American Diabetes Association journal Diabetes Care found that dogs detect isoprene, a common natural chemical found in human breath that rises significantly during an episode of low blood sugar.People can’t detect the chemical, but the researchers believe that the dogs are particularly sensitive to it and can tell when their owner’s breath has high levels of it.

A 2013 study published in PLOS ONE showed that for people with diabetes having an alert dog seems to provide significant improvements in both the safety and quality of life of insulin-dependent persons with diabetes.Positive effects reported by clients with dogs included a decrease in episodes of unconsciousness, fewer paramedic calls, and an increase in independence.

Several theories exist as to how dogs are able to sense hypoglycemia including chemical changes that the dogs are able to smell as well as changes in behavior.There’s still uncertainty about whether or not dogs can accurately alert handlers to a blood sugar change at a level beyond chance. A 2016 study of eight dogs that evaluated the reliability of dogs trained to detect and alert for hypoglycemia showed that the animals provided timely alerts 36 percent of the time. A slightly larger study of 27 dogs in 2019 showed an 81 percent rate of alerts when blood sugar levels were out of range. The high degree of variation in the success rate shown in these studies indicates that more research is needed.

How Does the Dog Behave?

A trained dog can wake up or alert an owner whenever blood sugar drops to the level of hypoglycemia, “a condition that can cause shakiness, loss of consciousness, and, if untreated, death.” They could do this by jumping up, pawing, or nudging at owner. An untrained dog may show signs of discomfort or anxiety. Retrievers and labradors are often used for detection purposes, since they’re quick learners and a good size.

Seizures

The scientific study of canine response to epileptic seizures is insufficient.¹⁶ While there is anecdotal evidence that some dogs can and do detect the onset of a seizure, most of this has come from small samples and subjective surveys of owners. The level of accuracy and, most importantly, our ability to train dogs to alert a handler to an oncoming seizure remains uncertain.

Scientists don’t yet know if there are specific seizure onset cues (such as scent) that dogs can be trained to understand. We can, however, train dogs how to respond to and assist a handler when a seizure occurs. Some service dogs that are placed with seizure patients do develop the ability to detect when a seizure is coming and can provide an alert if the handler pays close attention to the signals the dog provides.

A small 2019 study of five canines found that the dogs were able to differentiate the odor of a patient during an epileptic seizure from the odor of the same patient when they were not experiencing a seizure.Because the study only involved a small handful of dogs and used odor samples that were previously collected, researchers acknowledge that much more extensive testing would need to be done to see if dogs could actually predict seizures before they happened and if other dogs would respond similarly.

In a survey of epilepsy patients in 2003, nine of the 29 patients who had dogs reported that their dogs responded to a seizure. The researchers recognize that while these findings may indicate an innate ability in some dogs to alert or respond to seizures, additional research is needed to learn how to train dogs to be as effective as possible.

How Does the Dog Behave?

A dog detecting a seizure may bark or paw at their owner, behaving in ways that differ from the norm. Since these could be very subtle cues, the owner would likely need a close bond with the dog to be able to detect the difference. Some dogs are trained to assist the owner during a seizure, but cannot necessarily detect one coming on. These will stay with the owner, standing or lying with them, and sometimes licking their face.

Fear and Stress

The age-old notion that dogs can smell fear is an accurate one. Dogs can smell when we are feeling fear or are experiencing an increased level of stress, even if we aren’t showing outward signs. What dogs are smelling is the surge of hormones our bodies release to respond to stressful situations, including adrenaline and cortisol. When dogs smell fear, they show signs of stress.

Thankfully, this can be used to humans’ benefit, as dogs can signal a handler that they (or someone else) needs to take a few deep breaths. Dogs that alert handlers of the change in their emotional state—a change that often people aren’t even aware they’re experiencing—can help prevent panic attacks and other possible episodes associated with post-traumatic stress disorder or other issues.

According to an extensive study of 3.4 million people in Sweden, dog ownership lowers the risk of stress and cardiovascular disease.

We still have a long way to go to discover exactly what dogs are smelling about us, let alone how we can train them to be as accurate as possible about a change in our bodies. Even though many details are not yet known, it’s clear that dogs have an uncanny ability to sniff out certain medical issues, and that’s a skill that could be a real lifesaver.

EDITED BY-DR. SN MADHAWAN,PUNE

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