Dogs Can Be Trained to Sniff COVID-19 Infections, Even Asymptomatic Cases: Study

Paris:

According to research published Monday, dogs can be trained to detect more than 90% of Covid-19 infections even when patients are asymptomatic, which the researchers hope would eliminate the need to quarantine new arrivals.

Dogs have also shown that their remarkable sense of smell, which can detect the equivalent of half a teaspoon of sugar in an Olympic-sized swimming pool, can detect diseases such as cancer, malaria, and epilepsy.

In previous research, dogs were shown to be able to detect SARS-CoV-2.

The London School of Tropical Medicine wanted to see whether dogs could detect a distinct odour released by chemical compounds linked to people who are Covid positive but do not show symptoms.

They collected clothing and face mask samples from people who tested positive for moderate or symptomatic SARS-CoV-2 infection.

Sock samples from 200 Covid-19 cases were obtained and organised in lab tests for six dogs who had been conditioned to indicate whether the chemical compound was present or absent.

The dogs had to be trained not to identify "false positives" in order to manipulate their reward system and receive rewards even though no Covid-19 samples were present in a given test. 

"This means that the dog fully understands and gets a reward for a correct negative as well as a correct positive," Claire Guest, a member of the school's Faculty of Infectious and Tropical Diseases, explained the situation. 

In total, the dogs were able to correctly identify 94 to 82 percent of SARS-CoV-2 samples.

The researchers then calculated how well these success rates, when used in conjunction with standard PCR tests, could help detect mild or asymptomatic Covid-19 cases. 

They discovered that screening arrivals at airport terminals with dogs could identify 91 percent of cases, resulting in a 2.24 times lower rate of transmission than using PCR tests alone. 

The authors of the study hoped that it would eventually replace the need for travellers to quarantine, which causes delays in every arrival even though the vast majority are not Covid positive. 

"The key thing is that dogs are significantly quicker than other tests," said co-author James Logan.

"What we're suggesting is that dogs would give the first initial screening, and then those (arrivals) that were indicated as positive would then receive a complimentary PCR test," he added. 

According to the researchers, fewer than 1% of passengers on a plane carrying 300 people were statistically likely to be infected with SARS-CoV-2.

All 300 will be needed to isolate under current quarantine legislation in some countries, causing considerable inconvenience.

However, given the vulnerability of qualified dogs, the paper suggests that a maximum of 35 people on board will be considered optimistic.

A positive PCR result is expected in just about three of these.  

Mick Bailey, a comparative immunology professor at the University of Bristol who was not involved in the study, said, "This is a really important start and could lead to a useful, usable system."

"But there's a lot more validation needs to be done before we could be confident that the dogs can reliably and specifically detect asymptomatic SARS-CoV-2 infection in people in airports and train stations," he added. 

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