Accurately trained sniffer dogs detect airport passengers infected with SARS-CoV-2

Accurately trained sniffer dogs detect airport passengers infected with SARS-CoV-2

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Trained sniffer dogs can accurately detect airport passengers infected with SARS-CoV-2, the virus responsible for COVID-19, according to research published in the journal Open Access. Global Health BMJ.

This method of detection is likely to be particularly valuable, not only in the early stages of a pandemic when other resources are not yet available, but also to help contain an ongoing pandemic, the researchers suggest.

Dogs have an extremely strong sense of smell, and they can pick up scent at levels as low as one part per trillion, far exceeding any available mechanical techniques.

It is believed to be able to detect distinct VOCs that are released during various metabolic processes in the body, including those resulting from bacterial, viral and parasitic infections.

Preliminary data suggests that dogs can be trained within weeks to detect samples from patients infected with COVID-19, with a degree of accuracy comparable to that of a standard PCR nose and throat swab test.

Although this laboratory data is promising, it needs to be replicated in real-life conditions. So researchers trained 4 dogs to sniff out SARS-CoV-2 in the spring of 2020. Each dog was previously trained to sniff out illegal drugs, dangerous goods or cancer.

To test the dogs’ detection skills, 420 volunteers provided four skin swab samples each. Each of the four dogs sniffed skin samples from 114 volunteers who tested positive for SARS-CoV-2 on a PCR swab test and from 306 who tested negative. Samples were randomly presented to each dog over the course of 7 experimental sessions.

Overall, the diagnostic accuracy of all aspirated samples was 92%: the combined sensitivity – accuracy of detecting those with infection – was 92% and the composite specificity – the accuracy of detecting those without infection – was 91%.

Only slight variation was observed between dogs: the best performance was 93% for sensitivity and 95% for specificity. The worst was 88% for sensitivity and 90% for specificity.

About 28 of the positive samples came from people who had no symptoms. Only one was incorrectly identified as negative and two were not sniffed, which means that 25 of 28 (just over 89%) were incorrectly identified as positive: the lack of symptoms did not appear to affect the dogs’ performance.

The four dogs were then operated on to sniff 303 arriving passengers at Helsinki-Vantaa International Airport, Finland, between September 2020 and April 2021. Each passenger also underwent a polymerase chain reaction (PCR) swab test.

PCR and olfactory results matched in 296 out of 303 (98%) real-life samples. Dogs correctly identified samples as negative in 296 of 300 (99%) PCR-negative swab tests and identified three PCR-positive cases as negative.

After reassessment with clinical and serological data, one was judged to be SARS-CoV-2 negative, one SARS-CoV-2 positive, and the other a possible positive post-infection PCR test result.

Similarly, dogs indicated 4 PCR-negative cases that were positive. These have all been judged negative for SARS-CoV-2.

Because the prevalence of SARS-CoV-2 among airport passengers was relatively low (<0.5%), 155 samples from people who tested positive were also submitted for a dog PCR swab test.

Dogs correctly identified just under 99% of them as positive. Had these “spike” samples been included in the real-life study, the dogs’ performance would have reached a sensitivity of 97% and a specificity of 99%.

Based on these results, the researchers then calculated the ratio of true positive results (PPV) and proportion of true negative results (NPV) in two hypothetical scenarios that reflect the prevalence of SARS-2-CoV-2 at 40% and 1%.

For a prevalence of 40%, they estimated a PPV of 88% and an NPV of 94.5%. This means that the information provided by the dog increases the chances of being detected to about 90%.

For a population spread of 1%, on the other hand, they estimated the PPV to be just under 10% and the NPV just under 100%.

In both scenarios, high NPV supports the use of sniffer dogs for screening, with the goal of excluding people who do not need a PCR smear test, the researchers say.

They suggested that: “Dogs could be used in locations with high SARS-CoV-2 prevalence, such as hospitals (for pre-screening of patients and staff), as well as in locations with low prevalence, such as airports or seaports (for pre-screening of passengers).” They say this It can save a lot of time and resources.

Researchers acknowledge that dogs trained to sniff out other substances may mistakenly identify these substances as positive for SARS-CoV-2. They also say that the storage period required for training and serrated samples may also have affected the viability of VOCs.

The main finding was that dogs were less successful in correctly identifying the alpha variant as they had been trained to detect the wild type. But this only shows how good dogs are at distinguishing between different scents, say the researchers.

“This observation is remarkable because it demonstrates the strong discriminatory power of dogs with a scent. The clear implication is that training samples should cover all epidemiologically relevant variants. Our preliminary observations indicate that dogs predisposed with one type of virus can be retrained within a few hours to detect its variants.” “.

Study shows dogs can detect COVID-positive arrivals

more information:
Smell dogs in the detection of COVID-19: a randomized, triple-blind trial and real-life practical screening in airport settings, Global Health BMJ (2022). DOI: 10.1136 / bmjgh-2021-008024

Submitted by the British Medical Journal

the quote: Trained sniffer dogs accurately detect airport passengers infected with SARS-CoV-2 (2022, May 16) Retrieved May 16, 2022 from passengers. programming language

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2022-05-16 22:30:04

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