Mei Zheng trained dogs' sense of smell for the COVID-19 test. Netizen: Is there not enough testing reagent?

The College of Veterinary Medicine of the University of Pennsylvania is launching a program to train dogs to be sensitive to smells, so as to screen humans for COVID-19 virus infection at an early stage. Penn Vet, the project leader, said that it is very hoped that the dog's sense of smell will play an important role in early screening.

How can a dog smell COVID-19?

Penn Vet, the project leader, plans to train eight dogs. In the planned three-week period, saliva and urine samples that have been tested positive in COVID-19 will be distinguished from ordinary samples, so as to establish a database to determine whether the dog's nose can recognize COVID-19!

The prospect of this research is uncertain, but if it is successful, it will be of great significance, because the nose smell efficiency of dogs is extremely high, which will greatly increase the efficiency of community communication and detection, and can also be a favorable supplement to the detection system in COVID-19.

Can dogs sniff out COVID-19?

Dogs have as many as 300 million olfactory cells in their noses, while humans have only about 6 million. Their keen sense of smell can distinguish cancer cells from healthy cells. 1989, the British magazine The Lancet published the first report about dogs smelling cancer, which described that two dermatologists spent several minutes every day sniffing a mole on the owner's thigh and tried to bite it off. After examination, it is malignant melanoma. Fortunately, this malignant melanoma did not spread in the early stage, and it can be completely cured by surgical resection!

But the early studies were all case reports and failed to pass the strict double-blind test. Dr Klaus Hackner, a pulmonary physician at krems University Hospital, said that in about 2006, a fairly high-quality double-blind research report was published in the research on dogs sniffing out malignant tumors. In the test, neither the dog nor the researcher knew which one of the samples was cancerous.

Dogs can distinguish 500,000 kinds of smells, while humans can only distinguish 1 10,000 kinds.

After that, quite a few research reports show that trained dogs can detect specific cancers by smelling biological samples such as human respiratory secretions or urine. This is because cancer cells release specific compounds (VOC), which have different smells compared with other cells.

Dogs can smell cancer cells, and the cost may be high.

Some friends may think that dogs can smell cancer cells without cost. In fact, it takes about six months to train a dog who can only smell cancer cells, but it often happens that dogs can accurately distinguish cancerous samples in experimental environment, but in actual tests, this accuracy is obviously reduced, and it may even be meaningless!

Is it "inhuman" to expose dogs directly to high-risk environment?

In order to let the dog accurately distinguish whether it contains the special smell of the virus, it is impossible to take measures such as special masks for dogs between dogs and samples. Therefore, it will be a new topic whether dogs can be infected with COVID-19 if they work directly in high-risk situations!

On March 8, 2020, it was reported that a Hong Kong pet dog, Pomeranian, contracted COVID-19 virus from its owner and died. However, the cause of death of the dog is still unknown because the owner does not allow autopsy on the dog, but it is certain that COVID-19 was infected.

At that time, there was a big discussion about whether pet dogs would become another transmission chain for human beings. Vanessa Barrs, an animal health expert at City University, said that according to the experience during SARS in 2003, cats and dogs do get infected with SARS virus, but cats and dogs don't transmit the virus to humans. There is no evidence that this transmission chain exists.

On April 5th, a tiger in Brooks Zoo was diagnosed with SARS-COV-2 virus. On April 22nd, the Centers for Disease Control and Prevention (CDC) diagnosed that two pet cats were also infected with SARS-COV-2 virus. On April 28th, a pet dog in North Carolina was infected with novel coronavirus virus. According to Hong Kong's past cases, there should be many cases of animals infected with COVID-19 in the world.

However, the CDC said that there is no clear evidence that animals "played an important role" in the spread of COVID-19. "The risk of animals transmitting coronavirus pneumonia-19 to humans is considered to be very low." On the contrary, humans can spread it to animals in some cases.

Therefore, dogs will become high-risk dogs after participating in this work. As for whether these viruses will spread in dogs or cause life-threatening, further research reports may be needed.