London: Humans, followed by ferrets and, to a lesser extent, cats, civets and dogs are the animals most susceptible to infection by SARS-CoV-2, the virus behind Covid-19 disease, say researchers.
The study, published in the journal PLOS Computational Biology, found that ducks, rats, mice, pigs, and chickens had less or no susceptibility to infection compared to humans.
“Knowing which animals are susceptible to SARS-CoV-2 helps us prevent the accumulation of animal reservoirs from which the coronavirus can re-emerge at a later date,” said study author Luis Serrano, from the Center for Genomic Regulation ( CRG) in Spain.
“Our findings offer a clue as to why minks, which are closely related to the ferret, are being infected by the disease, which is likely to be made worse by their crowded living conditions and close contact with human workers,” Serrano added.
In this article ten species were studied. Five species (humans, cats, ferrets, civets, and dogs) have had documented cases of SARS-CoV-2 infection. There are no reports of infection in the other five species: mice, rats, pigs, chickens, and ducks.
The researchers used computer modeling to test how the coronavirus uses its spike proteins, which protrude from the surface of the virus, to infiltrate the cells of different animals.
The main entry point on the surface of a cell is the ACE2 receptor, which binds to the spike protein through a lock and key mechanism. There are many different variants of ACE2 within human populations and in different species.
ACE2 receptor variants in humans followed by ferrets, cats, dogs, and civets have the highest binding affinities for the viral spike protein, while mice, rats, chickens, and ducks have low binding energy.
However, the binding affinity alone is not sufficient to measure the susceptibility of a cell to infection.
The researchers also tested the “codon adaptation index” of different species, which is the effectiveness of the coronavirus in controlling the machinery of a cell once it has entered.
The more efficient the process, the better the coronavirus will be able to create the proteins it needs to replicate. Humans, chickens and ducks have the highest codon adaptation index, while the other species are less well adapted.
Taking into account both the binding affinity and the codon adaptation index, the researchers conclude that humans, followed by ferrets, cats, civets, and dogs, are the animals most susceptible to coronavirus infection.