Silja, Rele, Kosti and ET are not just any dogs, but experts in detecting drugs, dangerous goods and now also Covid. Three labrador retrievers and a white shepherd between four and eight years old are the protagonists of the research carried out by the University of Helsinki, just published in BMJ Global Health.
Dogs’ noses discriminate odors up to 100,000 times more than humans, and their sense of smell is so developed that it surpasses any device created up to now. For this reason, in a period of pandemic, some studies have been carried out to understand how and if these animals could help humans in the detection of the virus and from the Finnish study the confirmation has arrived: sniffer dogs can be trained in a short time to detect people infected with Covid-19 with a degree of accuracy equal to that of molecular tests (PCR).
“One of our best dogs is Kössi – says Anu Kantele, author of the research and professor of infectious diseases, head physician at the University of Helsinki and the University Hospital of Helsinki – even if he was not part of this team. He is a true talent, collected on a freeway in Malaga, Spain, and brought to Finland. He is a crossbreed, there is no need for a specific breed for this job, all you need is a good nose and a great desire to learn “.
In the spring of 2020, the researchers began working with four dogs, teaching them to recognize SarsCov2. The choice fell on specimens that had already worked successfully in the research of drugs, illicit goods and even cancer. The first step was to make him discriminate the skin swab samples of Coronavirus patients from those of people who tested negative.
420 volunteers were then involved in the study and provided four skin swab samples each. The dogs sniffed skin samples from 114 Sars-CoV2 positive and 306 negative volunteers in test sessions. During each day of testing, each dog sniffed twenty tracks in random order.
The result was 92 percent accuracy in detecting infected subjects. Identification of non-infected people was 91 percent. Of the samples presented, twenty-eight positives were from subjects with no symptoms, only one was identified as negative, and two were not smelled. The absence of symptoms therefore does not appear to influence the identification by the dogs.
The practical test
Then came the field work. Between September 2020 and April 2021 the dogs worked at Helsinki-Vantaa International Airport, Finland, identifying 298 out of 303 positive people and 296 out of 300 negative people. Only three, who tested positive on PCR, were instead indicated by them as negative. . With a further examination, however, one subject was judged negative, one positive and another post-infectious post-infectious at Sars Cov 2. Four cases were instead identified by the dogs as positive while they were negative on the molecular test.
In addition, the researchers presented to Silja, Rele, Kosti and ET an additional 155 samples of people who were positive on the PCR swab test: they identified just under 99%.
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The research also found that dogs are less successful in detecting variants of the virus. This underscores how strong a sniffer dog’s discriminating ability is, but at the same time implies that they should be trained for all variants.
‘Sniffer dogs can provide a valuable tool for limiting viral spread during a pandemic, for example in air and sea ports,’ adds Professor Kantele.
In February of this year, the results of the first Italian multicenter study “C19-screendog”, from the Polytechnic University of Marche, were also presented, which has the same goal of demonstrating how well-trained dogs can detect Sars positive subjects. -Cov2 without resorting to invasive and expensive samples and tests. Also in this case, on 1251 subjects, the detection proved to be correct with a percentage between 98 and 100%.