Dogs have an acute sense of smell. They have up to 300 million olfactory receptors in their noses, compared to six million in humans, making their smell receptors up 10,000 to 100,000 more powerful than humans. The part of a dog's brain that is devoted to analyzing smells is, proportionally speaking, 40 times greater than humans. Trained sniffer dogs can detect diseases such as malaria, cancer, and even viral infections.
Now, a team of German researchers at the University of Veterinary Medicine Hanover, the German Armed Forces, and the Hannover Medical School revealed that dogs can discriminate between human saliva samples infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and non-infected samples with a 94 percent overall success rate. Their research is published in the journal BMC Infectious Diseases.
Accurate and reliable
To arrive at their findings, the team trained eight detection dogs to sniff out SARS-CoV-2-infected samples for one week. The training aims to hone the smelling power of the dogs to detect saliva or tracheobronchial secretions of infected patients in a randomized, double-blinded, and controlled study.
The trained dogs sniffed the saliva of more than 1,000 people that were either healthy or infected with the virus. The samples of coronavirus disease (COVID-19) patients were distributed at random.
During the study, the dogs achieved an overall average detection rate of 94 percent with 157 correct indications of positive, 792 correct rejections of negative, 33 incorrect indications of negative or incorrect rejections of 30 positive sample presentations.
"These preliminary findings indicate that trained detection dogs can identify respiratory secretion samples from hospitalized and clinically diseased SARS-CoV-2 infected individuals by discriminating between samples from SARS-CoV-2 infected patients and negative controls. This data may form the basis for the reliable screening method of SARS-CoV-2 infected people," the researchers concluded in the study.
The team emphasized that the timely and accurate detection of SARS-CoV-2 infected people is critical for countries to contain the spread of the pandemic. The research findings indicate that dogs can be trained in just about a week to differentiate between samples of people infected and non-infected with SARS-CoV-2.
The researchers believe that dogs can detect infected samples because people who get infected have changes in their metabolic processes.
"We think that the dogs can detect a specific smell of the metabolic changes that occur in those patients," Maren von Koeckritz-Blickwede, a professor at the university, who conducted the study, said in a video.
The team hopes that the method can be used amid the pandemic, to help control the virus spread and reduce the number of cases, which has now topped 16.66 million across 188 countries and territories.
"The current study results are promising, although they should be regarded as preliminary, and suitability for this detection method in the field can only be acquired after further research has been conducted. Our work provides the very first steps of the development of a new SARS-CoV-2 screening method," the researchers said.
Further, the researchers added that in countries with limited access to diagnostic tests, detection dogs could be used for mass detection of people infected with the novel coronavirus.
The use of detection dogs has made its debut in Chile. Police dogs are being trained to identify infected people, even in the earliest stages of the disease.
In England, six dogs are being trained by Medical Detection Dogs in Milton Keynes to sniff out and detect the presence of the virus. Dr. Claire Guest, the charity's co-founder and chief executive, said that the dogs had shown signs that they would be able to detect the virus. She has previously trained dogs to detect the scent of other diseases, such as cancer, Parkinson's disease, and malaria.
The dogs, named Digby, Norman, Jasper, Star, Storm, and Asher, will be trained to smell samples on sterilized socks, stockings, and face masks worn by NHS staff in London. The training team expects about 3,200 samples and will use them for training the dogs.
The team believes that when they train dogs to detect the virus, they can help contain its spread.