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Dogs in Brazil are being trained to sniff out COVID-19 in humans

Sinatra is restless. He circles a sample of cotton while barking, digging and sniffing. He didn’t end up there by chance, and it’s not the first time he has behaved like this, either. Strong and sharp-eyed, the spotted mutt is trained to sniff out traces of the novel coronavirus. Sinatra is an advanced student at what’s effectively a school for “coronavirus sommeliers” here in the Brazilian city of Campo Limpo Paulista, 40 kilometers (25 miles) from São Paulo. He is part of a pair already trained to identify people infected with the virus; another 11 dogs are also being trained.

Dogs are immune to COVID-19, and they have a powerful olfactory system — about 300 million olfactory receptors compared to the 5 millions in humans. They have 40 times the capacity to assimilate odors, and this means that around the world they’re employed by scientists looking for quick and practical methods to identify human hosts of the virus.

Several studies have proved their talent. At Hannover Medical School, Germany, researchers are advancing the testing of sniffer dogs for volatile organic compounds. In other European countries, results from similar research are also promising. In October, a trained pack was photographed at the Helsinki airport in Finland, apparently sniffing for signs of coronavirus infection.

In Brazil, Anísio Francisco Soares is the head researcher for dogs at the Federal Rural University of Pernambuco (UFRPE). He explains how dogs’ sense of smell can help them identify infected individuals: “It is important to remember that the coronavirus is odorless. It is the volatile compounds that evaporate when humans sweat that will give off a certain odor, different from those who are not contaminated,” he says.

Soares coordinates a team of teachers, students and collaborators, working in partnership with the Alfort National Veterinary School in France.

Scientists began their research with the dogs in early April, when the pandemic was picking up pace around the world. “[The research] went through ethical commissions, not only in the human instance, but also in the animal commission,” Soares says. “It was quite trouble-free to get the licenses to train the dogs.”

And despite misinformation to the contrary on social media, dogs don’t contract the coronavirus. “It is important to make it clear, to avoid rumors on Facebook: we don’t put any animals at risk,” Soares says.

Sinatra, one of 13 dogs being trained at a facility near São Paulo to sniff out coronavirus infection in humans. Image courtesy of UFRPE.

While Soares and his team got to work in Pernambuco, in Rio de Janeiro doctors Dominique Grandjean and Clothilde Lecoq Julien were responsible for supplying the canines, including Sinatra, to Jorge Pereira, a dog trainer with a ranch in Campo Limpo Paulista.

Working in partnership with the health department of the municipality of Paudalho, Pernambuco state, Soares says he was surprised by the volunteers’ goodwill in the research. “We asked the staff who felt certain symptoms — fever, chills, cough — to take a cotton ball and rub it for 20 minutes in each armpit,” he says.

With two samples — one destined for the UFRPE lab, the other sent directly to the kennel in Campo Limpo — the procedure was simple: “All the volunteers were tested by the COVID RT-PCR test,” Soares says, referring to what’s considered the gold standard for coronavirus testing, with a 99% effectiveness rate. “Sometimes we even repeated the [cotton ball odor sampling] collection in another opportunity, because the willingness of the participants was such that some even took a shower and sprayed perfume to be part of the experiment … and they shouldn’t!

“It is necessary to follow the protocols, and all the volunteers who collaborated could not be in any kind of COVID treatment. I joke that the smell of the soap interferes, but the smell of the medicine interferes too, whatever medicine it is. We were strict with it, but even so unexpected problems arose.”

With a steady flow of samples going to the dogs, the research was in full swing — until an obstacle popped up. “Things were going well, the tests were advancing with an effectiveness of 90%, and then came Patient number 41,” Soares says. “His RT-PCR test was negative, but the dog barked when in contact with the cotton simple.”

The dog had sniffed out traces of the virus in the simple, and this proved true, Soares says. “Patient 41 had already developed antibodies. In the end, the dog got it right.” He attributes the negative PCR test to the fact that, after 15 days, with the body already creating antibodies, the test is no longer effective. Yet the dog was still able to detect organic compounds associated with the virus in the patient’s sweat.

Sniffer dogs have long been employed by law enforcement, working at airports and border crossings to detect narcotics and weapons. But they are also used in medical detection, used to identify cases of diabetes, malaria and some cancers, including prostate cancer.

For Sinatra and his pack mates, phase two of the coronavirus research will see them deployed from Campo Limpo Paulista to Paudalho, where UFRPE has signed a partnership with the municipal health department.

Anísio Soares says he’s glad about the advances in the research and continues to monitor global developments relating to the pandemic. But he’s also fighting another battle on the home front: the high cost of equipment needed for research. Although their work is being financed by the Brazilian and French universities, the researchers are still stretched for resources, Soares says.

“The equipment is very expensive, there are machines that cost hundreds of thousands of dollars,” he says.

Money is not the only issue that has Soares worried. More than ever, he says, the world needs the expertise of scientists. But the waves of misinformation and negativity that have been generated by the pandemic and various authorities’ responses to it, he says, have effectively thrown trust in science to the dogs.

Banner image of a sniffer dog at Helsinki airport in Finland, courtesy of Finavia.

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