Dogs can be trained to detect more than 90% of Covid-19 infections even when patients are asymptomatic, according to a study released Monday, which the authors said could help replace the need to quarantine new arrivals.
Using their remarkable sense of smell – which can scoop up the equivalent of half a teaspoon of sugar in an Olympic-size swimming pool – dogs have already shown that they can sniff out diseases such as cancer, malaria and the like. ‘epilepsy.
Several previous studies have shown proof of concept that dogs can detect SARS-CoV-2.
Researchers at the London School of Tropical Medicine wanted to see if dogs could detect a distinctive odor emitted by chemical compounds associated with a person positive for Covid but not showing symptoms.
They collected samples of clothing and face masks from people who had tested positive for mild or symptomatic SARS-CoV-2.
Sock samples from 200 cases of Covid-19 were collected and placed in lab tests for six dogs that had been trained to indicate the presence or absence of the chemical compound.
Dogs were to be trained not to identify “false positives” in order to hack their reward system and obtain treats even though there were no Covid-19 samples in a given test.
“This means the dog fully understands and gets a reward for a correct negative as well as a correct positive,” said Claire Guest, from the school’s Faculty of Infectious and Tropical Diseases.
Overall, the dogs were able to identify between 94 and 82 percent of the SARS-CoV-2 samples.
The researchers then modeled how effectively these success rates, combined with traditional PCR tests, could help detect mild or asymptomatic Covid-19 cases.
They found that using dogs to filter arrivals at terminals such as airports could detect 91% of cases, which would result in a transmission rate 2.24 times lower than PCR tests alone.
– ‘Important start’ –
The authors of the research, which has not yet been peer reviewed, said they hope it could eventually replace the need for travelers to quarantine – which necessarily disrupts every arrival. even if the vast majority are not positive for Covid.
“The bottom line is that the dogs are significantly faster than the other tests,” said co-author James Logan.
“What we’re suggesting is that the dogs would do the initial screening first, then those (arrived) that were marked positive would then receive a free PCR test. “
The team said that on a plane full of arrivals – around 300 people – less than one percent were statistically likely to carry SARS-CoV-2.
Under current quarantine regulations used by some countries, the 300 would all have to self-isolate, causing significant inconvenience.
But given the sensitivity of the trained dogs, a maximum of 35 people on board would be indicated as positive, according to the newspaper.
Of these, only about 3 are expected to return a positive PCR test.
“This is a really important start and could lead to a useful and usable system,” said Mick Bailey, professor of comparative immunology at the University of Bristol, who was not involved in the research.
“But there is still a long way to go for validation before we can be sure that dogs can reliably and specifically detect asymptomatic SARS-CoV-2 infection in people at airports and train stations. “
© 2021 AFP