Diagnosis of Covid-19: Dog competes well with rtPCR

Writer : Dr. P.D. Gupta  

Former Director Grade Scientist, Centre for Cellular and Molecular Biology, Hyderabad (INDIA), Email: pdg2000@hotmail.com, Cell: 080728 91356


Dogs are the most faithful  and best friends of humans. The pet dogs are used in many ways by the owners. Many people keep dogs as pets for safety purposes. Military and police  trained them for forensic purposes such as drug-sniffing and bombs and catching criminals. Earlier programs for medical detection did not exist, however, dogs have great potential in medical fields. It was noticed that Dogs  generally change their behavior when the owner suffers from some chronic disease. Because, with a sense of smell researchers showed that 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.

In a 2006 study, five dogs were trained to detect cancer based on breath samples. Trained dogs are able to detect colorectal cancer from people’s breath and watery stools with high levels of accuracy, even for early stage cancers.  The presence of gut inflammation or noncancerous colorectal disease does not seem to affect dogs’ ability to detect these cancers. Dogs have been trained to detect a dozen human diseases and most recently, COVID-19. 

Photo : courtesy

Dogs have been famously known for their sense of smell since ages. 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, however, they soon become much older than us.  They found that humans and dogs don’t age at the same rate, as dogs age more quickly  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 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. Dogs inhale up to 300 times per minute in short breaths, meaning that their cells for smell   are constantly supplied with new odour particles. Dogs’ sense of smell is so subtle that they can notice the slightest change in human scent caused by a 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 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 disease. 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. 

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. 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 preemptively, before the symptoms get irremediably too severe. Inexpensive way to detect Covid-19: 

Dogs as a new diagnostic tool could revolutionize 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. Many sniffer-dog scientists turned their attention to COVID-19 early in the pandemic. They have trained their canines to smell samples, most often of sweat, in sterile containers, and to sit or paw the floor when they detect signs of infection. Trials at airports in the United Arab Emirates, Finland and Lebanon are using dogs to detect COVID-19 in sweat samples from passengers; these are then checked against conventional tests. According to data presented at the K9 meeting, dogs in Finland and Lebanon have identified cases days before conventional tests picked up the virus, suggesting that they can spot infection before symptoms start. 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 recognize 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 randomized, 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. In India, the military trained indigenous dog breed 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 have been fully trained and Mani is still undergoing training. The two trained canines (Jaya and Casper Fig. 1) were deployed at a transit camp in Delhi where 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 (sic) 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 [9].

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. Along with testing and vaccine research, dogs’ highly sensitive noses may be on the front lines to tackle the worldwide pandemic . Dogs in clinics, not quite yet: But most of these findings have not yet been peer reviewed or published, making it hard for the wider scientific community to evaluate the claims. 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 repeated times. 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, including Storm  . 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 a infective virus test without much involvement of mankind.