Pandemic danger to the deep: the risk of marine mammals contracting SARS-CoV-2 from wastewater



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The current COVID-19 pandemic is caused by the SARS-CoV-2 coronavirus that spreads between humans, primarily through respiratory droplets. However, recent studies demonstrate that SARS-CoV-2 is excreted in feces and can survive in water for up to 25 days¹, raising the possibility that wastewater provides a separate mode of spread for this coronavirus.

The current COVID-19 pandemic is caused by the SARS-CoV-2 coronavirus that spreads between humans, primarily through respiratory droplets. However, recent studies demonstrate that SARS-CoV-2 is excreted in feces and can survive in water for up to 25 days, raising the possibility that wastewater provides a separate mode of spread for this coronavirus.

The impact of COVID-19 is not just felt by humans, but the wildlife around us too. SARS-CoV-2 has been shown to infect a wide range of mammals, including ferrets, minks, and cats, sparking greater analysis of the range of species put at risk by this virus^2,3.These infections can occur by direct contact or potentially indirect contact via human sewage and wastewater⁴.

The reason SARS-CoV-2 is able to infect such a wide range of animal species is that the receptor responsible for virus entry, called the angiotensin-converting enzyme 2 (ACE2), is highly conserved among numerous species. Recent studies^5,6 identified the physical mechanisms of ACE2 binding to the viral spike protein of SARS-Cov-2 virus. Cell infection requires “lock-and-key” interactions between the virus and host cell, and this interaction relies on a few specific amino acid residues. As a result, the conservation between ACE2 of different species can predict binding efficiency and thus potential susceptibility.

Using this approach several groups have begun to define the sphere of susceptible species in our environment, which has now been expanded to non-human primates, several species of cats, and in a recent study by Mathavarajah and colleagues⁷ even marine mammals. In the Mathavarajah preprint, they looked at the genome of 35 species of marine mammals and identified 15 species, including beluga whales, sea lions, seals and sea otters that are predicted to be as susceptible (or more so) than humans to SARS-CoV-2 infection. Many of these species are threatened or critically endangered. In the past, these animals have been infected by related coronaviruses that have caused both mild disease as well as life threatening liver and lung damage.

Marine animals might become infected by SARS-CoV-2 through direct contact with humans, although this is not a frequent occurrence, at least in the wild. Mathavarajah and colleagues examined the possibility that coronavirus in untreated sewage via wastewater spillover could be a source of infection. In Alaska, a region that employs lagoon-based settling ponds, their treatment of wastewater could put marine mammals on the coastlines at risk. The analysis by Mathavarajah and colleagues revealed several municipalities that potentially put endangered beluga whales and seal populations at risk of SARS-CoV-2 from wastewater spillover.

So how do we prevent our ocean friends from being put at risk from COVID-19? The authors suggest that we can monitor susceptible mammal populations with innovations such as drone sampling of whale blow hole mucus, and even suggest vaccination of these animals, in particular seals and sea lions, for which vaccines have proven useful in the past. Ultimately, restricting human contact with these endangered marine mammals in aquariums and zoos, and during commercial and recreational fishing, is probably the most important in protecting these majestic animals from coronavirus infection.

References

1. Shutler, J., Zaraska, K., Holding, T. M., Machnik, M., Uppuluri, K., Ashton, I., et al. (2020). Risk of SARS-CoV-2 infection from contaminated water systems. medRxiv, 2020.2006.2017.20133504. doi:10.1101/2020.06.17.20133504
2. Schlottau, K., Rissmann, M., Graaf, A., Schön, J., Sehl, J., Wylezich, C., et al. (2020). SARS-CoV-2 in fruit bats, ferrets, pigs, and chickens: an experimental transmission study. Lancet. 1 (5). E218-E225. https://doi.org/10.1016/S2666-5247(20)30089-6
3. Shi, J., Wen, Z., Zhong, G., Yang, H., Wang, C., Huang, B., et al. (2020). Susceptibility of ferrets, cats, dogs, and other domesticated animals to SARS-coronavirus 2. Science. 368 (6494). 1016-1020. doi:10.1126/science.abb7015
4. Damas, J., Hughes, G. M., Keough, K. C., Painter, C. A., Persky, N. S., Corbo, M., et al. (2020). Broad host range of SARS-CoV-2 predicted by comparative and structural analysis of ACE2 in vertebrates. PNAS. 117 (36). 22311-22322. https://doi.org/10.1073/pnas.2010146117
5. Lan, J., Ge, J., Yu, J. Shan, S., Zhou, H, Fan, S, et al. (2020). Structure of the SARS-CoV-2 spike receptor-binding domain bound to the ACE2 receptor. Nature. 581. 215-220.
6. Yan, R., Zhang, Y., Li, Y., Xia, L., Guo, Y., Zhou, Q. (2020). Structural basis for the recognition of SARS-CoV-2 by full-length human ACE2. Science. 367 (6485). 1444 1448. DOI: 10.1126/science.abb2762
7. Mathavarajah, S., Stoddart, A. K., Gagnon, G. A., Dellaire, G. (2020). Pandemic danger to the deep: the risk of marine mammals contracting SARS-CoV-2 from wastewater. bioRxiv. August 14. doi: https://doi.org/10.1101/2020.08.13.249904.

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