Sniffer dogs are better at spotting coronavirus-infected people than specialist laboratory tests, researchers claim.
When the dogs were deployed at Helsinki airport in Finland, scientists were left scratching their heads when the animals stopped people who seemed well.
Travellers stopped by the sniffer dogs were given swab tests to see if they were carrying the virus but they all came back negative.
A few days later, however, the same supposedly-negative people told researchers they had come down with symptoms of Covid-19.
Dogs have been used in experiments for years because they are able to pick up on changes in the way people smell that can indicate illness, for example changes in their metabolism that can be caused by cancer.
Although they could not be used as a standalone way of screening people for coronavirus – but could be useful for picking out who should get tested – they can provide scientists with unique insights on how to spot early signs of the disease.
Six sniffer dogs were trialled by the London School of Hygiene and Tropical Medicine earlier this year to see whether they could be used to detect the virus.
The results of the £500,000-study were reported to Health Secretary Matt Hancock in October, but it is unknown whether they will lead to dogs being used officially.
Finnish researchers say dogs are better at detecting Covid-19 infections than PCR tests. Pictured are sniffer dogs Valo (left) and E.T. at Helsinki airport, Finland, where they were being used to sniff out people infected with the virus
Sniffer dogs Miina (left) and Kossi outside Helsinki airport. They were able to detect the virus because the infection causes changes in body odour
The three dogs involved in the Finnish study – named Miina, Kossi and Valo – had a near 100 per cent success rate in detecting the virus, said lead researcher Anna Hielm-Bjorkman.
‘They’re actually finding PCR negatives that are going to be PCR positives in a week’s time,’ she told The Times.
PCR is the type of test that is currently used around the world to diagnose Covid-19 and is considered the ‘gold standard’. It stands for polymerase chain reaction and works by analysing genetic material in a nasal swab to look for signs of the virus.
SNIFFER DOGS AND COVID-19: WHAT YOU NEED TO KNOW
Dogs have an incredible sense of smell which has made them useful in the detection of diseases for decades.
The complex folded structure of their nasal cavity – which results in a huge surface area – is home to over 300million scent receptors compared to 5milllion in a human, according to researchers at London School of Hygiene & Tropical Medicine (LSHTM).
Over the past 10 years, the research group Medical Detection Dogs has published in numerous scientific journals, demonstrating that the dogs’ accuracy in detecting the odour of disease is reliably between 85 and 90 per cent.
And in July, researchers in Germany found trained sniffer dogs can detect the coronavirus in human swab samples with 94 per cent success rate.
LSHTM, in collaboration with Medical Detection Dogs (MDD) and Durham University, have been rigorously testing whether six dogs can detect coronavirus smells through an intensive training programme, which was announced in May.
The researchers collect odour samples from people who are infected with COVID-19, and people who are uninfected. Then, they use those odour samples with six medical detection dogs.
If successful, the clever dogs could be deployed to places like airports within eight to ten weeks after training, the researchers said, where each dog can ‘screen’ 250 people per hour.
Canine scent detectors have been working at Helsinki-Vantaa Airport since 22 September in a pilot study to see if they can speed up the detection of SARs-CoV-2 in the arrivals lounge.
Professor Hielm-Bjorkman added: ‘They [the dogs] are much, much more accurate than any PCR at the moment. PCRs are around 70 per cent. The good dogs never go under 100 per cent.’
The dogs are better at sniffing out the virus because infections trigger a change in body odour, explained Professor James Logan from the London School of Hygiene.
Professor Logan said in March, ahead of trials: ‘Our previous work demonstrated that dogs can detect odours from humans with a malaria infection with extremely high accuracy – above the World Health Organization standards for a diagnostic…
‘We know that other respiratory diseases change our body odour so there is a chance that [Covid-19] does. And if it does dogs will be able to detect it. This new diagnostic tool could revolutionise our response to Covid-19.’
The body changes smell based on gases called volatile organic compounds that are being emitted all the time, and the composition of these is based on chemical reactions that happen inside the body. If someone becomes ill with an infection or disease the chemical makeup of VOCs coming out of the body changes, which is something dogs’ super-sensitive noses can smell.
In the Covid sniffer dogs trial, travellers were asked to dab their skin with a wipe and this was then placed in front of the dog alongside other wipes that were loaded with smells known to not be linked to Covid.
If the dog reacted to the person’s swab – by nudging it or barking at it, for example – it means it detected the coronavirus smell it was trained to detect.
The results of the Finnish study have not yet been published.
The pilot was launched on September 22 by the University of Helsinki, and it took just minutes to train the dogs to pick out people infected with the virus.
Sniffer dogs are already used to warn of epileptic fits, cancer and Parkinson’s disease, but experts hope they could also be deployed to spot coronavirus patients.
But it is lengthy and expensive to train them, and they can accidentally detect people who have recovered from the infection.
In October, health minister Lord James Bethell praised the ‘extremely exciting’ trials of sniffer dogs at the London School of Hygiene.
If approved by ministers, the dogs could be placed in airports to screen up to 250 people every hour for coronavirus.
They would be able to sniff out the carriers who aren’t showing symptoms.
Lord Bethell said: ‘I take my hat off to the School of Tropical Medicine who run an extremely exciting trial…
‘Dogs can be used as a way of screening crowds in places like airports and high-density venues.
‘The validation of that method hasn’t been proven yet, but I am personally extremely hopeful and remain grateful to those involved in the pilot.’
Dogs used to detect Parkinson’s can sniff out the disease ears before people develop symptoms because of changes to the body odour due to switches in the chemistry of cells.
The United Arab Emirates has also been using the method to detect people who have the virus that arrive in the country’s airports.
The lead researcher said it took just minutes to train the dogs to detect the virus, after trials were launched on September 22. Pictured are Valo (left) and E.T.
Sniffer dog Miina is shown above being trained to pick out the virus’ scent
Kossi (left) and Miina snuggle up with one of their trainer’s at Helsinki airport