Following extensive training and appropriate assessments, assistance dogs are helping people with physical disabilities or diseases in everyday life. The responsibilities can differ vastly; dogs use their olfactory sense as a diagnostic tool for cancer and COVID-19 and even to open doors for disabled people. Assistance dogs also perform other duties, including the following:
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Guide dogs lead people with impaired vision, direct them through traffic, and help them with tasks such as crossing the street.
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Service dogs help patients with multiple sclerosis, spina bifida, Parkinson’s disease, cerebral palsy, or other diseases through targeted assistance. They turn on light switches, open doors, or pick up small objects that have fallen down.
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Signal dogs, also called hearing dogs, react to noises such as the telephone, doorbell, or fire alarm. They lead deaf people to the source of the noise.
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Medical signal dogs have vastly different responsibilities, depending on the person’s disease. For patients with diabetes, alert dogs recognize a dangerous metabolic state before clinical symptoms develop. For patients with epilepsy, dogs warn patients that a seizure is about to occur.
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Researchers are investigating whether dogs can sniff out various diseases, such as cancer, COVID-19, or bacterial infections. It is likely that they recognize these diseases through volatile organic compounds (VOCs) in exhaled air. Each disease changes individual metabolic steps in the body, which is a topic of research in metabolomics.
Researchers in this field are measuring a positive side effect of the household pet. Clinical studies show that dog owners exhibit less mental stress and are at lower cardiovascular risk than people without a dog.
Sniffing Out COVID
Since the beginning of the pandemic, researchers such as Holger Volk, PhD, chair of small animal diseases at the University of Veterinary Medicine in Hannover, Germany, have been investigating whether dogs can recognize SARS-CoV-2 infections. Following a range of laboratory experiments, they have published the results of a mass screening at a large-scale event.
Eight dogs were trained to detect samples that were positive for chemically inactivated SARS-CoV-2 RT-qPCR. To assess the animals’ performance, the researchers collected real-world data from 2802 attendees at four concerts.
Sweat samples from 2802 participants were presented to the dogs. SARS-CoV-2 specific antigen rapid tests and RT-qPCR tests were then used. The participants’ infection status was not known at the time the samples were taken.
The dogs achieved a diagnostic specificity of 99.93% and a sensitivity of 81.58%. The participants’ vaccination status, whether they had been previously infected with SARS-CoV-2, whether they had chronic diseases, and medications the participants were taking had no effect on the dogs’ performance.
COVID Screening
Researchers also saw a large amount of potential in schools for dogs to detect SARS-CoV-2 infections. The use of tracking dogs is one strategy for a fast, noninvasive, cost-effective, and environmentally friendly COVID-19 screening method.
Experts trained two tracking dogs to recognize the VOC of COVID-19. The canine screening was performed before the actual practice phase in volunteers on the days on which antigen tests were planned in schools. The participants stood 1.5 m away from each other. The dogs, led by the dog handlers, sniffed at their ankles and feet.
After 2 months of training with COVID-19 odor samples in the laboratory, the dogs achieved a sensitivity and specificity of more than 95% for detecting the virus.
Dog Owners Benefit
During the COVID-19 pandemic, dog owners were potentially better protected from depressive moods than people without dogs. This was the conclusion of US researchers who analyzed the results of a survey.
In all, 768 dog owners and 767 potential dog owners who did not have a pet took part in the online study. Potential dog owners were defined as people who did not have a dog at the time of the survey but who showed interest in owning a dog in the future.
Participants completed six tests, including tests regarding depression, anxiety, and happiness. The scientists’ hypothesis was that dogs make their owners feel loved, treasured, and needed, which suppresses stress, anxiety, and depression and triggers or reinforces feelings of happiness.
Dog owners indicated that they had access to much more social support than potential dog owners; their depression scores were also lower than those of the comparator group. However, there were no significant differences between the two groups in the scores for anxiety and satisfaction.
Dogs and Diabetes
Researchers showed that well-trained signal dogs react more sensitively to changes in blood sugar levels of patients with type 1 diabetes than had previously been observed. Therefore, these dogs could improve the quality of life of patients with type 1 diabetes, especially for patients who have not experienced a hypoglycemic attack. These patients could be children or adolescents who have little experience in dealing with the metabolic disease.
The authors investigated 28 dogs and their owners, as well as more than 4000 episodes of hypo- or hyperglycemia. Dogs who had passed through a well-structured training program alerted their owners to 83% of hypoglycemic episodes and 67% of hyperglycemic episodes. Four of the dogs recognized episodes in which blood glucose levels were overly high or low 100% of the time. The median rate for all dogs was 81%.
Nevertheless, even well-trained animals are inferior to continuous glucose measurement.
Urogenital Tract Infections
Urinary tract infections are problematic for patients with neurologic diseases and for the elderly. These patients do not always recognize the symptoms and sometimes seek medical attention too late. Delayed diagnoses can lead to severe infections such as pyelonephritis and life-threatening sepsis. It is here that dogs come into play. They are able to detect bacteriuria.
In a double-blind, case-control validation study, researchers collected daily urine samples from participants for 16 weeks. The dogs were trained to differentiate urine samples that were culturally positive for bacteriuria and from culturally negative control samples.
The samples were collected from 687 people aged from 3 months to 92 years. About 34% of the samples were culturally positive.
Dogs detected urine samples that were positive for 100,000 colony-forming units/mL of Escherichia coli (250 tests; sensitivity, 99.6%; specificity, 91.5%). The diluting of E coli urine with distilled water had no effect on precision at either a concentration of 1% (sensitivity, 100%; specificity, 91.1%) or of 0.1% (sensitivity, 100%; specificity, 93.6%).
The diagnostic precision was similar for Enterococcus (n = 50; sensitivity, 100%; specificity, 93.9%), Klebsiella (n = 50; sensitivity, 100%; specificity, 95.1%) and Staphylococcus aureus (n = 50; sensitivity, 100%; specificity, 96.3%).
The overall sensitivity — taking into account every dog participating in the study — was at or near 100%, and the specificity was over 90%.
Dogs Detect Cancer
In recent years, researchers have demonstrated that dogs can recognize various cancers long before any clinically relevant symptoms develop. The literature contains at least three examples.
First, two sheep dogs were trained to recognize prostate cancer-specific VOC in urine samples. They were tested on 362 patients with prostate cancer (with low risk to metastases) and on 540 healthy control patients.
Dog 1 had a sensitivity of 100% and a specificity of 98.7%. For Dog 2, the study authors reported a sensitivity of 98.6% and a specificity of 97.6%.
A second study showed that dogs could detect bowel cancer. Breath samples and stool samples were the basis of the test.
Each test group comprised one sample from a patient with bowel cancer and four samples from volunteers without cancer. These five samples were allocated randomly and put into five boxes. A Labrador retriever specially trained to recognize the scent of cancer and a dog handler took part in the tests. The dog first smelled a standard breath sample from a patient known to have colorectal cancer, then smelled each sample station and sat down in front of the station in which a cancer scent was found.
The detection sensitivity for breath samples, compared with colonoscopy, was 0.91 for breath samples, and the specificity was 0.99. The authors stated that the detection sensitivity for a dog’s nose was 0.97, and the specificity was 0.99.
The dogs were highly precise at odor recognition, even in the early stages of the cancer. The dogs’ odor recognition was not impaired by smoking, benign colorectal diseases, or inflammatory bowel diseases.
Last but not least, dogs can help to locate melanomata, as shown by another, albeit rather small, study. Dog A detected a melanoma that had been clinically suspected and that was subsequently confirmed on biopsy. In a sixth patient, this dog indicated a melanoma at a skin location for which the initial pathologic examination was negative. A more thorough histopathologic examination of this person then confirmed the suspicion. And for a seventh patient in whom a definitive reaction was neither shown by the dog nor dermatologists, a melanoma was determined through a histopathologic examination.
Dog B searched four of these seven patients; in every case, the responses matched those of dog A.
The objective of another study was to check whether trained dogs could detect an imminent epileptic seizure by smell. The odor samples came from five patients who had different kinds of epilepsy.
Three of the five dogs achieved a sensitivity and specificity of 100%. The other two dogs demonstrated a sensitivity of 67% and a specificity of 95%, which are fairly high values.
The authors saw the results as proof that despite patients’ individual scents, epileptic seizures are associated with distinctive olfactory characteristics. Epileptic seizures are associated with a specific scent that exhibits similar characteristics in different patients.
Now researchers must clarify whether this scent occurs before the seizure and whether patients therefore have time to call for help or take medicine.
Dogs and Longevity
It is not just therapy dogs that are beneficial to the health of their owners. Ordinary, untrained animals also do a lot of good. Owning a dog has long been associated with a lower mortality risk, which may be attributable to a reduction in cardiovascular mortality.
For a systemic overview and meta-analysis, researchers searched for publications that dealt with associations between dog ownership and overall mortality and cardiovascular mortality. They included ten studies that provide data from 3,837,005 participants with an average follow-up time of 10.1 years.
According to these data, owning a dog was associated with a 24% reduction in the risk of overall mortality, compared with not owning a dog (relative risk, 0.76). Particularly for people with previous coronary events, the effects on overall mortality were much larger (relative risk, 0.35).
When scientists restricted their analyses to studies of cardiovascular mortality, dog ownership was associated with a 31% reduction in the risk of cardiovascular death (relative risk, 0.69).
Possible reasons behind the effect incluide increased movement, reduced stress, and reduced loneliness.
Emergency Department Benefits
A 10-minute visit with a therapy dog leads to a clinically significant reduction in pain and anxiety and to an improvement in the well-being of patients who are visiting the emergency department, according to a randomized controlled study.
Pain, anxiety, depression, and well-being were measured in 97 patients (average age, 56 years; 44% women) before, immediately after, and 20 minutes after the visit by the therapy dog using the revised 11-point rating scale of the Edmonton Symptom Assessment System. At these time points, researchers also recorded participants’ blood pressure and heart rate.
The same data were recorded twice at an interval of 30 minutes in 101 control patients (average age, 57 years; 39% women) who were not treated with a therapy dog in the emergency department.
The visit by the therapy dog had a statistically significant, albeit mild, influence on patients’ perception of pain, anxiety, and depression. Participants in the therapy-dog group rated their well-being after the interaction with the dog and its handler significantly higher than the participants in the control group did.
This article was translated from the Medscape German edition.
