Some marine mammals carry gene mutations that could make them more susceptible than humans to SARS-CoV-2, the coronavirus at the heart of the ongoing pandemic. If these marine mammals get infected, the results could be devastating\u2014more than half of the species predicted to be susceptible to SARS-CoV-2 are already at risk of extinction.<\/p>\n
Several mammals<\/a>, including cats, dogs, and minks, have been detected with COVID-19, and in April, eight tigers and lions at the Bronx Zoo in New York became sick<\/a>. Graham Dellaire, a pathologist at Dalhousie University in Nova Scotia who is studying how the virus affects other animals, and his colleagues have shown in their latest research<\/a>, which is still under review, that many marine mammals may be at risk, too.<\/p>\n So far, the threat is theoretical\u2014no marine mammals are known to have contracted the virus\u2014but it\u2019s based on research that looks at the genetic susceptibility of various marine mammals to infection by SARS-CoV-2.<\/p>\n To determine that vulnerability, scientists are studying how amenable an animal\u2019s angiotensin-converting enzyme 2 (ACE2) receptors<\/a>\u2014found on cells in the lungs, heart, kidneys, and elsewhere\u2014are to the virus\u2019s spike protein<\/a>. Dellaire likens this spike protein to the teeth on a key, and the animal\u2019s ACE2 receptors to the grooves in the lock. How well they line up determines how easily the virus can penetrate those cells and cause infection. In previous research, for instance, Dellaire showed that a single genetic variation makes cats more susceptible than dogs.<\/p>\n Some marine mammals have ACE2 receptors that bind even more easily with SARS-CoV-2\u2019s spike protein than human receptors. This creates a risky situation, Dellaire says: \u201cIf binding efficiency is high, you don\u2019t need a high viral load to become infected.\u201d<\/p>\n Unlike house cats, or tigers and lions in a zoo, wild marine mammals aren\u2019t often in close contact with people. But their high susceptibility to the SARS-CoV-2 virus means that marine mammals may be at risk from even small amounts of the virus.<\/p>\n Given that potential, Dellaire and his colleagues analyzed ways marine mammals might come into contact with the virus, identifying the greatest potential threat as contaminated, untreated wastewater.<\/p>\n In their paper, the scientists wanted to present a potential case study of how and where wild marine animals might be most at risk of catching COVID-19 because of untreated wastewater spillover. They focused on Alaska, juxtaposing the locations and types of more rudimentary wastewater treatment facilities with known habitats of marine mammals.<\/p>\n \u201cWe looked at coastal regions that have either primary or lagoon-based treatment, which is the worst level of treatment for waste,\u201d Dellaire says. \u201cIf any of those leak, or you have a big rainfall, that raw sewage just goes right into the ocean.\u201d The analysis shows that in Alaska, beluga whales, harbor seals, and sea otters face the greatest potential danger of SARS-CoV-2 infection.<\/p>\n This pathway would not be unprecedented. Previous research, says Tracey Goldstein, a veterinary pathologist at the University of California, Davis, has revealed cases where wastewater runoff has led to marine mammals becoming sick with terrestrial pathogens. Toxoplasma gondii<\/em>, for example, a protozoan parasite that can be shed by feral cats, mountain lions, foxes, and bobcats, has gone on to infect sea otters<\/a> in California. And 10 years ago, a group of elephant seals<\/a> showed antibodies to the H1N1 flu. Since H1N1 is a human virus, Goldstein says one hypothesis for how they contracted it is that they may have encountered wastewater discharged from ships.<\/p>\n Though Dellaire\u2019s research focused on the United States, other new research<\/a>\u2014such as the recent discovery of the SARS-CoV-2 virus in a river in Ecuador\u2014extends the possibility of infection to untreated wastewater in other countries.<\/p>\n