Published on 05/17/2022 06:00
(credit: Brian Thomas)
Dogs can be trained to detect people infected with the new coronavirus, and they do a very good job of that endeavour. This is what scientists at the University of Helsinki Medical School in Finland guarantee. According to the team, the animals’ performance is equivalent to the efficacy of the PCR test, which is considered the gold standard for diagnosing the cause of COVID-19. Therefore, researchers are betting that they can be trained to help combat the ongoing pandemic and other health crises.
“Dogs can be used both in places with high prevalence of Sars-CoV-2, such as hospitals, for pre-screening of patients and staff, and in low-prevalence settings, such as airports or ports, for pre-screening of passengers. This can save a lot of time and resources,” As the authors of the study, published in the latest issue of the journal BMJ Global Health led by Anu Kantele, note.
Four sniffer dogs took part in the tests that led the Finnish team to propose a new weapon against COVID-19. In the first step, the group submitted 420 volunteers for PCR testing, of whom 114 were positive for the presence of SARS-CoV-2 and 306 were negative. Samples were randomly submitted to each dog over seven laboratory sessions.
Overall, the diagnostic accuracy of all samples detected was 92%. The pooled sensitivity—accuracy of detecting infected subjects—was 92%, and pooled specificity—accuracy of detecting uninfected subjects—was 91%. The PCR accuracy rate can reach 99%.
The four dogs were previously trained to sniff out illegal drugs, dangerous products or cancers. The training to detect the novel coronavirus lasted “weeks,” according to the scientists, and the animals achieved practically similar performance — the animals performed best at 93% for compound sensitivity and 95% for compound specificity, and the worst were 88% and 90%, respectively.
The numbers changed slightly in cases of samples taken from infected people who did not show symptoms of COVID-19 (asymptomatic). There were 28 samples with this profile. Only one was incorrectly identified as negative by the animals, and two were not sniffed, which means that 25 out of 28 (slightly more than 89%) were correctly identified as positive.
The real life
In a second step, dogs were taken to inhale 303 passengers at Helsinki-Vantaa International Airport between September 2020 and April 2021. The PCR result was 98% effective – 296 out of 303 samples. Animals correctly identified samples as negative in 296 of 300 negative (99%) PCR tests and identified three PCR-positive cases as negative.
After reassessment with clinical and serological data, one was considered negative for Sar-CoV-2, the other positive, and the third as potentially postinfectious. Similarly, the dogs indicated four PCR-negative cases that were positive. All were found negative for Sars-CoV-2 on further analysis.
Because the sample of positive cases in real life was small, the scientists gave dogs 155 samples from people who tested positive for the polymerase chain reaction (PCR) test. This time, the animals correctly identified fewer than 99% of them as positive.
It also caught the team’s attention that the dogs were less successful in correctly identifying the alpha variant. This is because they have been trained to detect the wild type, the first version of Sars-CoV-2. But for the study authors, “this shows how good dogs are at distinguishing between different odors.”
“This observation is remarkable because it demonstrates the strong discriminatory power of sniffer dogs. The clear implication is that training samples should cover all epidemiologically relevant variables. Our preliminary observations indicate that dogs predisposed with one type of virus can be retrained within a few hours, to detect variables,” they point out.
Scientists are of the opinion that more studies should be conducted, taking into account, for example, new variants of Sars-CoV-2 and real-life tests with a larger number of infected people. However, the team emphasizes that recent studies have shown dogs’ high ability to detect various organic compounds released by the body’s metabolic processes, including those resulting from bacterial, viral and parasitic infections. They argue that “sniffers may provide a valuable approach for rapid, high-throughput screening of large numbers of people”.
Similarities with children’s diseases
Scientists at the University of California, San Diego School of Medicine have found that COVID-19 and pediatric multisystem inflammatory syndrome, a complication that has affected girls and boys infected with the novel coronavirus, share the same immune response. There are also similarities with Kawasaki disease, an inflammatory disease that has intrigued pediatricians for more than 50 years.
Through genetic analysis, the team identified a set of 166 genes expressed in viral respiratory diseases, including COVID-19. They then found that this same “gene signature” applies to SIM-P disease and Kawasaki disease, suggesting that all cases stem from a similar underlying mechanism: the rapid release of the cytokines IL15/IL15RA, a protein that regulates defense system responses.
explains Jane C. Burns, co-author of the study, published in the journal Nature Communications.
While the work provides a new unifying framework for these diseases, it also identifies some subtle differences. For example, patients with SIM-P had lower platelets and eosinophils, two characteristics that could be measured from routine blood tests.
According to Depachis Sahu, also an author of the study, the findings open doors for new investigations that help develop preventive strategies. “We believe our findings have a high potential to immediately influence clinical trial planning and also shape customer care guidelines.”