Through a process dubbed “reverse zoonotic transmission”, scientists worry SARS-CoV-2, the coronavirus that causes Covid-19, could jump from humans to marine mammals. Specifically, there are concerns that untreated wastewater could function as a vessel for coronavirus.
Wastewater is known to carry the SARS-CoV-2 virus. In fact, cities around the world are testing wastewater to gauge the extent of local coronavirus outbreaks. Wastewater is often treated before it enters the ocean to kill microbes, like viruses and bacteria. However, untreated wastewater is occasionally released into waterways when treatment plants reach capacity, such as during a heavy rain event. In these situations, wastewater treatment facilities may release wastewater that has not been fully treated. When over-capacity wastewater treatment plants release untreated effluent during the current pandemic, the virus that causes COVID-19 enters marine habitats.
Unlike other marine life, marine mammals are more susceptible to the ‘jumping’ of human diseases due to our comparatively recent divergence evolutionarily. In other words, humans are much more closely related to marine mammals than other ocean dwellers. The genetic similarities between marine mammals and humans make it more likely for an infectious agent, like a virus, to find a shared weakness. For the same reason, scientists are actively researching which mammal the SARS-CoV-2 virus may have come from, while concerns over future infectious ‘jumps’ between wildlife and humans are mounting.
To understand just how susceptible marine mammals – particularly endangered species – may be to infection by SARS-CoV-2, scientists at Dalhousie University searched through genetic data for the key the amino acids that make up the proteins the virus uses to start an infection. Without a good amino acid match, the virus would not be expected to cause an infection.
Based on these amino acid patterns, researchers found that at least 15 marine mammal species are susceptible to infection by the coronavirus SARS-CoV-2. Of these, over half are already at-risk globally.
“Many of these species are threatened or critically endangered,” explains Dr. Graham Dellaire, who led the study. “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.”
Indeed, coronavirus infections have been reported in marine mammals prior to the Covid-19 pandemic. While no infections by the SARS-CoV-2 coronavirus have been documented in marine mammals to date, the results of this research reveal a key susceptibility among marine mammals to infection by the coronavirus that causes Covid-19.
The study specifically identified the risk untreated wastewater in Alaska poses to vulnerable populations of beluga whales and sea otters and identified concerns broadly for marine mammals in waters near developing nations that may not have wastewater treatment facilities in place.
“Monitoring susceptible species in these high-risk areas around the world will be pertinent for protecting wildlife during and post-pandemic,” explains Saby Mathavaraja, a co-author of the study. Marine mammals, like humans, are social creatures, which makes them similarly vulnerable to having infections spread throughout an entire population.
By highlighting these vulnerabilities among marine mammals to infection by the SARS-CoV2 coronavirus, the researchers hope to shape policy decisions regarding wastewater management around the world to help protect at-risk marine mammal species that may be exposed to this coronavirus.
