Author : Dr. P. D. GUPTA
Former Director Grade Scientist, Centre for Cellular and Molecular Biology, Hyderabad, India
www.daylifenews.in
Those who have pet dogs know that when the owner suffers from some chronic disease. Pet dogs generally change their behavior, because dogs can detect the smell far earlier in the disease’s progress—even while it is still “in initial stages,” This is because dogs can smell between 10,000 and 100,000 times more than us.
If a dog smells cancer, it may act very differently from normal. Some dogs will keep sniffing at you constantly and you may struggle to push your pooch away. Others may lick or even bite at lesions on your body – their way of trying to get rid of the cancer for you. 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.
Dogs are famously known for their sense of smell, that is why they have been trained to detect a dozen human diseases and most recently, COVID-19. Characteristic of a particular disease some metabolic volatile organic compounds (VOCs) are produced during diseased conditions can be exhaled in breath, or sweat, or urine or stool samples and can be identified by dogs to recognize diseases by smell.
Why Dogs?: Dogs are famously known for their sense of smell since ages. Their genetics and physiology make them perfectly suited for sniffing. And for centuries now, humans have taken advantage 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’ noses are powerful enough to detect substances at concentrations of one part per trillion. Dogs inhale up to 300 times per minute in short breaths, meaning that their olfactory cells are constantly supplied with new particles coming out from humans. 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 are most famously known for detecting cancer. They can be trained to sniff out a variety of types of cancers using samples from known cancer patients and people without cancer. Once trained, the dogs were able to detect breast cancer with 88 percent accuracy, and lung cancer with 99 percent accuracy. Dogs can also detect different 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. Dogs can also detect Parkinson’s disease.
Inexpensive way to detect Covid-19 (Corona):
Dogs as a new diagnostic tool could revolutionise our response to corona in the short term, particularly in the months to come, and could impact disease management particularly in high risk events In this second phase of coron out-break . Many sniffer-dog scientists turned their attention to corona. Dogs can be trained to smell samples, most often of sweat, in sterile containers, and to sit or paw the floor when they detect signs of infection. During the last outbreak trials at airports in the United Arab Emirates, Finland and Lebanon were performed using dogs to detect COVID-19 in sweat samples from passengers; these are then checked against conventional tests. Even before disease flare up suggesting that they can spot infection before symptoms start.
In a pilot study at the University of Helsinki, dogs were taught to recognize the previously unknown odour signature of the COVID-19 disease caused by the novel corona virus. 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. .
In India the military trained indigenous dog breeds chippiparai, cocker spaniels to detect Covid19 . The dogs are being trained on specific biomarkers emanating from urine and sweat samples of Covid19 positive patients. The Indian Army said Jaya and Casper(names of the dogs) have been fully trained and and during last corona outbreak they screened 806 transient samples, of which 18 were detected as Covid-19 positive. “It has been inferred that Covid-19 volatile metabolic biomarkers are within the threshold limit of olfactory detection capability of trained dog and can help in quick and real time detection of disease,” 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 COVID19 change our body odour, so there is a very high chance that dogs will be able to detect it. Dogs would be able to screen anyone, including those who are asymptomatic in a fast, effective and noninvasive way.
Researchers working on more conventional viral tests say that initial results from dog groups are intriguing and show promise. But some question whether the process can be scaled up to a level that would allow the animals to make a meaningful impact. Although study after study has shown that dogs can detect disease, it may be a while before they are consistently used in the lab to replace standard testing. Researchers mostly still don’t know exactly what chemical compounds dogs detect to alert to the presence of the disease, and this remains a hurdle both for better training of disease-sniffing dogs and for creating machines that can more accurately detect cancer in the early stages
Knowing more precisely what the dogs are noticing would allow their training to be standardized, but even then the skepticism of the medical community might prevail. Not all doctors would want to rely on a dog to make a diagnosis.
The false positive and negative rates of the standard PCR lab test vary depending on the brand of test used and the timing of the test. The false-negative rate of RT-PCR tests to be 2–33% if the same sample is tested repeatedly. Up to 4% of UK PCR test results could be false positives, according to government documents. Groups need to boost their sample sizes before the wider scientific community can evaluate how useful the dogs might be, agrees James Logan, an infectious disease researcher at the London School of Hygiene & Tropical Medicine who is training and studying COVID-19 dogs.
In conclusion if it is proved with parallel RT-PCR tests, certainly in future it would be a boon to have Dog’s diagnosis for such an infective virus test without much involvement of mankind. (The author has his own study and views)