Sniffer dog trials make case for rapid detection of Covid

A study from the London School of Hygiene & Tropical Medicine (LSHTM) has discovered that dogs can detect Covid-19 on clothing worn by infected people with a 94 per cent accuracy.

The research, which was carried out with medical detection dogs trained to recognise the odour of the novel coronavirus, Sars-CoV-2, has found these dogs can correctly identify the scent immediately, furiously wagging their tails, whining or standing stock still (depending on the trained dog’s disposition) when they catch the scent, while passing by other stands which don’t have the virus.

“The dogs beat PCR tests [the gold standard Covid-19 test] on speed and their diagnosis includes people who are asymptomatic and also people with a low viral load,” Prof James Logan of the LSHTM told reporters. For the study, the six sniffer dogs were guided to three low stands, each holding a fragment of a blue nylon sock beneath a metal grill.

The medical detection dogs used in the UK study came from Dr Claire Guest’s Medical Detection Dogs charity and it took eight to 10 weeks to train them to detect the odour of the virus. These highly skilled canines had previously been trained to detect cancers, diabetes and other diseases such as malaria. Dogs have about 60 times more olfactory receptors in the top of their noses than humans.

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Dr Guest told The Irish Times that a two-dog team could screen a plane load of 300 passengers in half an hour. Those passengers identified as having coronavirus by the sniffer dogs would require a confirmatory PCR test and to quarantine while awaiting the results. But this rapid screening of disembarking passengers would arguably inconvenience far fewer people than requiring everyone to quarantine and undergo PCR tests.

Entrance gates to large concerts and sporting events are other possible locations where sniffer dogs could be used to detect Sars-CoV-2. “We would need to train more dogs for Covid-19 detection and we are currently in discussion with a number of experts in the relevant fields to deploy Covid-19 dogs,” says Dr Guest.

Gundog breeds such as spaniels, retrievers and Labradors make particularly good detection dogs. “They are dogs that absolutely love searching. They are also very friendly and they enjoy working in public places,” says Dr Guest.

Helsinki Airport

Other countries have also been using trained dogs to test people for the virus. Anne Karhio is a Finnish citizen living in Galway who partook in the "Corona dog study" at Helsinki's international airport at Vantaa when she travelled to Finland with her daughter in January.

“We didn’t have a PCR test before departure because it wasn’t compulsory. Everyone was offered one as soon as we got off the plane but the dogs were in the arrivals hall and you could be tested by them if you wanted,” explains Karhio. To partake, she had to rub a wipe against parts of exposed skin and put it into a bag which was then placed in a container for the dog to sniff. “Within a few minutes, I was told no Covid was detected and given a certificate. It was comforting. I still had to go into quarantine and within eight hours, I got back a negative PCR test.”

Karhio says she thinks using sniffer dogs to detect the virus could be a cost effective way to keep track of people coming into countries. “It’s easy, quick and not at all stressful,” she says.

County Clare-based IT worker Michelle Cotter also partook in the corona dog study at Helsinki Airport on arrival from Canada in February 2021. “I already had a negative result from a PCR test before leaving Toronto but it was an additional way to assure myself I was Covid-free and that I didn’t get it on the flight. It gave me peace of mind,” explains Cotter, who says using sniffer dogs could be a low-tech more affordable way of detecting Covid in the developing world. “It’s much less stressful than having a PCR swab,” she adds.

Finland was the first country in Europe (Dubai Airport carried out a similar trial with sniffer dogs) to put dogs to work sniffing out coronavirus. However, Finnish customs authorities have said they won’t employ specially trained sniffer dogs at border points after the Ministry of Social Affairs and Health said there wasn’t enough evidence to support the canines’ ability to detect the virus.

Antigen tests

Meanwhile, a French study in March/April of this year found that dogs are better at detecting Covid-19 in humans than many fast lateral flow antigen tests. That study by France’s national veterinary school and the clinical research unit of Paris’s Necker-Cochin hospital showed dogs were able to detect the presence of the virus with a 97 per cent accuracy. A recent review of 64 studies found that lateral flow (antigen) tests correctly identify about 70 per cent of people infected with the virus who have symptoms and 58 per cent who don’t show any symptoms.

"Dogs would not replace PCR tests which are significantly more reliable than lateral flow tests but they could help identify those people who should undergo a [PCR]test and because the dogs' response is so quick, they could facilitate mass testing in places such as airports, train stations and concert venues," Prof Jean-Marc Treluyer told Agence-France Presse.

Customs authorities in Ireland say they haven't been approached by the Department of Health to use sniffer dogs to detect Covid-19 at border points. And the Dublin Airport Authority says they will facilitate any measures that the Department of Health puts in place but as yet, haven't had any requests for the use of Covid sniffer dogs. – (Additional reporting from The Guardian)