Coronavirus CAT-astrophe? : Susceptibility of animals to SARS-CoV-2 poses threat of future COVID-19

With all pathogenic human coronaviruses having animal origins, scientists fear that SARS-CoV-2 could hide in animals and then resurge back in humans in the future, when the pandemic has already substantially subsided.

Already around a year into the pandemic, evolutionary biologist Sophie Gryseels wrote to her colleagues, "It has happened." A wild mink in Utah was reported to have tested positive for SARS-CoV-2.[1] What this implies is that even if the spread of the virus is suppressed, free-roaming or wild animals carrying the virus could pose a problem especially as they are hard to monitor and track. In fact, two farm workers have been reported to have caught the virus from mink in mid-2020.[1] "Not to sound any alarms, but everything we don't want to see with this virus seems to happen," coronavirus researcher Arinjay Banerjee says.[1]

Logistically speaking, it would be difficult to investigate the susceptibility of all animal species to the virus. Hence, Banerjee et al. (2021) proposed a hierarchical scheme: (1) similarity in the virus primary receptor angiotensin-converting enzyme 2 (ACE2); (2) likelihood of the species to come in contact with humans; and (3) reports of SARS-CoV-2 infection, whether natural or experimental, in the species in question (Figure 1).[2]

Figure 1. Hierarchical system for animal species surveillance. For example, ACE2 homology with humans is the highest with non-human primates but since likelihood of human contact is low, it is only recommended to survey high-risk areas such as zoos and wildlife sanctuaries.[2]

Following this scheme, it has been reported that ferrets and cats are highly susceptible to SARS-CoV-2, while dogs have low susceptibility and livestock such as pigs, chickens, cows, and ducks are not susceptible at all.[3] Other animals found to be susceptible are: hamsters, non-human primates, minks, tree shrews, raccoon dogs, fruit bats, and rabbits.[2]

Figure 2. A cat undergoes a swab test as part of a study concerning SARS-CoV-2 in pets.[1]

However, variants of SARS-CoV-2 have been reported independently in the United Kingdom, Brazil, Nigeria, and South Africa. Not only confined to these places, the variants contain a D614G mutation in the spike protein, which enhances infection and transmission rates.[2] "Any change to the virus in people can influence how it affects animals," Gryseels says. Coupled to this, the virus could also mutate while it lurks in animals, which could lead to one of two ways: first, the variant could no longer infect humans, or second, the variant becomes even more infectious to humans.[2]

What we can do is to first duly recognize which animal species are most susceptible to infection. Strict biosecurity measures such as controlled access to farms, wearing personal protective equipment (PPE), and regular disinfection and downtime for animal transport vehicles must also be implemented and maintained.[2] Any detected cases are also reported to the World Organization for Animal Health (OIE) in Paris.[1]

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References

[1] Mallapaty, S. (2021). The search for animals harbouring coronavirus — and why it matters. Nature, 591(7848), 26–28. https://doi.org/10.1038/d41586-021-00531-z

[2] Banerjee, A., Mossman, K., & Baker, M. L. (2021). Zooanthroponotic potential of SARS-CoV-2 and implications of reintroduction into human populations. Cell Host & Microbe, 29(2), 160–164. https://doi.org/10.1016/j.chom.2021.01.004

[3] Shi, J., Wen, Z., Zhong, G., Yang, H., Wang, C., Huang, B., ... & Bu, Z. (2020). Susceptibility of ferrets, cats, dogs, and other domesticated animals to SARS–coronavirus 2. Science, 368(6494), 1016-1020. https://doi.org/10.1126/science.abb7015

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