Tag Archives: scents

Scent dogs detect coronavirus reliably from skin swabs

Scent dog Silja at the Helsinki-Vantaa airport. (Image: Egil Björkman)

A recent study by the University of Helsinki and Helsinki University Hospital confirmed that scent detection dogs can be taught to identify individuals with a coronavirus infection from skin swabs. In the experimental set-up the accuracy of the dogs in identifying the samples was 92 percent.

The rapid and accurate identification and isolation of patients with coronavirus infection is an important part of global pandemic management. The current diagnosis of coronavirus infection is based on a PCR test that accurately and sensitively identifies coronavirus from other pathogens. However, PCR tests are ill-suited for screening large masses of people because of, among other things, their slow results and high cost.

Researchers from the Faculties of Veterinary Medicine and Medicine at the University of Helsinki and from Helsinki University Hospital jointly designed a triple-blind, randomized, controlled study set-up to test the accuracy of trained scent detection dogs where none of the trio – dog, dog handler or researcher – knew which of the sniffed skin swab samples were positive and which negative. The study also analysed factors potentially interfering with the ability of the dogs to recognize a positive sample.

The three-faceted study has now been published in the journal BMJ Global Health. The study provides valuable information on the use of scent dogs in pandemic control.

Correct identification in over 90 percent of samples; only small differences in accuracy between dogs

In the first phase of the study, the dogs were taught to discriminate the skin swab samples of coronavirus patients from those of volunteers who tested negative. After a training period of several weeks, the dogs moved from the training centre to Helsinki-Vantaa Airport for the next stages of the study.

In the second phase of the study, four trained dogs completed a validation test to prove their discriminatory ability. During the experiment, each dog was presented with a series of 420 samples over a period of seven days. As several parallel samples had been collected from each sample donor, each dog received an identical set of 114 coronavirus patient samples and 306 control samples for sniffing. The coronavirus status of all sample donors had been confirmed by PCR. During each testing day, the dog sniffed 20 sample tracks with three samples each, with the tracks presented in random order.

The dogs recognized the samples correctly 92 percent of the time. While their sensitivity to detect a positive coronavirus sample was 92 percent, their specificity was 91 percent. Only small differences in accuracy were observed between the four dogs. The coronavirus infection being caused by virus variants was the single largest factor contributing to erroneous identification by the dogs.

The study confirms previous reports suggesting that scent dogs can identify individuals with a coronavirus infection.

“Our study set-up was of a high scientific standard. The sample sizes were sufficiently large, and all dogs sniffed an identical set of samples, allowing comparison of their performances. The dogs also had to successfully indicate sample sets containing only negative samples – an important trait when screening individuals. Another significant advantage was that samples were collected from outpatients instead of hospital patients. In addition, the testing was performed under real-life conditions rather than in a laboratory”, says the leader of the DogRisk research group and docent of clinical research in companion animals Anna Hielm-Björkman from the University of Helsinki.

“I was particularly impressed by the fact that dogs performed worse with samples we had collected from patients suffering from a disease caused by a coronavirus variant. The explanation is simple: the dogs had originally been trained with the initial wild-type virus, and thus they did not always identify the variant samples as positive. This reveals their incredible ability of discrimination”, says Anu Kantele, Professor of Infectious Diseases and Chief Physician at the University of Helsinki and Helsinki University Hospital.

Major help from scent dogs at airports and ports

The third phase of the study was conducted by screening passengers and staff at Helsinki-Vantaa Airport in a real-life situation. The scent dogs correctly identified 98.7 percent of the negative samples. The low number of coronavirus-positive samples in real-life testing prevented a proper assessment of the dogs’ performance with positive samples. However, based on positive ‘work motivation samples’ regularly given to the dogs during this part of the study, the performance on the correctly identified positive samples also was evaluated at 98.7 percent. Work motivation samples are naive samples pre-collected from PCR positive patients, but not previously sniffed by dogs. They are provided to the dogs at regular intervals to maintain their interest in the target odour in situations and environments where the proportion of positive samples is otherwise very low.

“Scent dogs can provide an invaluable tool for limiting viral spread during a pandemic, serving for example at air- and seaports. Such a reliable, cheap approach to rapidly screen a vast number of samples or to identify passing virus carriers from a large crowd is of value particularly when the testing capacity with traditional approaches is insufficient”, says Anu Kantele.

“Our research group will continue to study how scent dogs can best help our society. We hope that this newly published study will help to allocate funds for the development of this new ‘tool’. There are many other diseases where research could benefit from the excellent sense of smell that these dogs possess”, says Hielm-Björkman.

The study was conducted with the support of the Finnish Cultural Foundation, Svenska Kulturfonden i Finland, Academy of Finland, Jane and Aatos Erkko Foundation, Finnish Medical Association, Veterinary Hospital Chain Evidensia, Nose Academy, Finavia, Vantaa city and deputy mayor Timo Aronkytö. The research group of Anna Hielm-Björkman has also been supported by private donations through the coronadog fundraising campaign, organized jointly by the Finnish Kennel Club and the University of Helsinki. The dogs were initially trained at the NGO Wise Nose trainings center.

Original article: Kantele A, Paajanen J, Turunen S, Pakkanen S, Mattress A, Itkonen L, Heiskanen E, Lappalainen M, Desquilbet L, Vapalahti O, Hielm-Björkman A. Scent dogs in detection of COVID-19 – triple-blinded randomized trial and operational real -life screening in airport setting . BMJ – Global Health, 2022; 0: e008024. Doi : 10.1136/bmjgh-2021-008024

Source: University of Helsinki

Odorology – the science behind training scent dogs

Dog training for scent tracking

Cisko, one of the police dogs, during a scent detection test. The dog sniffs the reference scent and then smells a series of five jars containing human scents, one of which corresponds to the reference. If the dog recognizes the reference scent it lies down in front of the relevant jar; if the dog does not find a match, then it does not stop or lie down. Credit: © DGPN – SICOP

Odorology is a technique that uses specially-trained dogs to identify human scent. It is used in police investigations to establish that an individual has been at the scene of a crime. However, there is no international norm on how these dogs are trained. At the Centre de recherche en neurosciences de Lyon (CNRS/Université Claude Bernard Lyon 1/Inserm), researchers specializing in scents and their memorization have analyzed data, provided since 2003 by the Division of the Technical and Scientific Police (DTSP, Ecully) on dog performances in scent identification tasks.

Their results show that, at the end of a 24-month training program, the dogs are able to recognize the smell of an individual in 80-90% of cases and never mistake it for that of another. These findings validate the procedures that are currently in use and should convince the international community of the reliability of this method.

Odorology, or the science of smells, is a method of identifying human scents. It has been used in France since 2003 in police investigations to establish that an individual has been present at a crime scene. The method is based on the fact that each person has their own scent and relies on the powerful canine sense of smell (which can be 200 to 10,000 times more sensitive than that of a human being1). It involves a long period of dog training.

This technique consists in using a specially-trained dog to compare a human scent collected from an object found at a crime scene with scents from several people, including that of a suspect or victim. As the results of these tests are of critical importance for investigators, they need to be obtained through viable and reproducible methods. However, there are no internationally recognized norms for the training of these dogs or for their inclusion in investigations—hence the occasional reluctance to treat their evidence as proof. By analyzing results collected since 2003 at the Division of the Technical and Scientific Police (DTSP, Ecully), researchers from the Centre de recherche en neurosciences de Lyon have succeeded in demonstrating the viability of the technique used.

During basic training, the German and Belgian shepherd police dogs must learn to make the link between two scents from the same individual through the completion of increasingly complex tasks. By the end of this training, the dogs are able to carry out identification exercises during which they sniff a reference human scent and then compare it with five different human odors, one of which is the reference scent. When a dog matches the scent in the jar to the reference one (which it shows by lying down in front of the correct jar) it is rewarded with a treat or a game. The human odors may consist of traces collected from an object that someone has touched or of a scent collected directly from a person.

The analysis of the data obtained with the 13 DTSP dogs since 2003 shows that after they have learned the task’s principles, 24 months of regular training is necessary for stable and optimal performances. At the end of the first twelve months, the dogs no longer made any recognition errors, i.e., they did not confuse the scent of one person with that of another. Furthermore, their olfactory sensitivity increased significantly over the training period: on average, after two years, the dogs managed to recognize two scents from the same person in 85% of cases. The remaining 15% of cases in which no match was obtained, were mostly the result of poor scent sampling rather than poor recognition.

The researchers also found that German shepherds were better than Belgian shepherds.

At the end of their basic training, the dogs are able to participate in criminal cases and receive continuing training throughout their lives. In practice, each identification test is carried out by at least two dogs. Additionally, each dog performs at least two tests with the same panel of scents: the collected scent is presented either as a sample to be sniffed at the start of the task, or in one of the jars that the dog sniffs successively. Between 2003 and 2016, odorology was used in 522 cases at the SDPTS and helped to resolve 162 cases.

In these criminal cases, the sampled scents were only a few hours or days old. The researchers now want to study how the dogs perform on older scents. Scent samples can in fact be stored in scent libraries over several years.