Why some animals get Covid and others don’t

Scientists have finally unraveled the mystery of how vulnerable some animals are to coronavirus infection while others are not.

They claim this is due to tiny differences in the molecular structure of their ACE2 receptors, which are found on the surfaces of cells.

ACE2 is common in humans and is found throughout the body, including the lungs. It has been dubbed the ‘gateway’ to the coronavirus.

Many animals have their own version of ACE2, but each species’ version is slightly different in its molecular structure.

These differences, scientists believe, explain why some animals – like cats and cows – get infected, while other species – including pigs and chickens – are immune.

Throughout the pandemic, there have been many cases of animals infected with the coronavirus.

Scientific studies have also analyzed the genomes of various species in which there have been no confirmed cases, but the animal could be infected if exposed.

An article published in October found that dozens of animals that regularly come into close contact with humans are susceptible to infection, for example.

This research by University College London (UCL) found a total of 28 terrestrial species, including gorillas, polar bears and horses.

A separate study published in November by researchers at Dalhousie University in Canada looked at marine mammals and found that at least 15 species of dolphins, seals and whales could be infected.

These two studies worked on hypothetical situations based on pre-existing knowledge of SARS-CoV-2 and the animal genes that make the ACE2 receptor.

The latest research, published today in the journal PLOS Computational Biology, built on these past findings and created computer models of the ACE2 receptor found in 28 animal species.

Researchers at Stanford University found that the receptor was very similar in all of the species analyzed.

The most similar to humans was that of chimpanzees (99.5% similarity) and the most different was that of goldfish (72% similarity).

The researchers then performed computer tests to virtually combine the coronavirus peak with each animal’s ACE2 receptor and predict which bonds would or would not be established at critical times.

In humans, there are a multitude of places where the tip and receptor create an attractive force, physically holding them together.

Many of these occur at a place on the coronavirus peak called the receptor binding domain (RBD).

However, some mutations in the RBD of animals prevent these connections from being made, and therefore the virus cannot attach itself to the ACE2 receptor and infiltrate the cell.

The researchers write in their study that they found “ species known not to be susceptible to infection with SARS-CoV-2 have non-conservative mutations ‘in several places on the ACE2 receptor’ that disrupt key contacts with the viral spike protein ”.

“ Thanks to open data, pre-prints, and free academic software, we have moved from the question of whether tigers can catch Covid-19 to 3D models of protein structures offering a possible explanation as to why it ‘is the case in just a few weeks. Says study author Dr João Rodrigues.

To reduce the risk of infecting domestic and wild animals, including endangered species, he recommended following the guidelines of the World Organization for Animal Health.

Dr Rodrigues added: “ People infected with Covid-19 should limit contact with their pets as well as other animals – including humans. ”