By Jonathan Runstadler and Kaitlin Sawatzki
Over the course of the COVID-19 pandemic, researchers have found coronavirus infections in pet cats and dogs and in multiple zoo animals, including big cats and gorillas. These infections have even happened when staff were using personal protective equipment.
More disturbing, in December the United States Department of Agriculture confirmed the first case of a wild animal infected with SARS-CoV-2, the virus that causes COVID-19. Researchers found an infected wild mink in Utah near a mink farm with its own COVID-19 outbreak.
Are humans transmitting this virus to wildlife? If so, what would this mean for wild animals – and people too?
How Viruses Hop Between Species
When viruses move from one species into another, scientists call it spillover. Thankfully, spillover doesn't occur easily.
To infect a new species, a virus must be able to bind to a protein on a cell and enter the cell while dodging an immune system the virus hasn't encountered before. Then, as a virus works to avoid antibodies and other antiviral attackers, it must replicate at a high enough volume to be transmitted on to the next animal.
This usually means that the more closely related two species are, the more likely they are to share viruses. Chimpanzees, the species most closely related to humans, can catch and get sick from many human viruses. Earlier this month, veterinarians at the San Diego Zoo announced that the zoo's troop of gorillas was infected with SARS–CoV–2. This indicated it is possible for this virus to jump from humans to our close relatives.
Some viruses tend to stay in a single species or in closely related species, while other viruses seem innately more capable of large species jumps. Influenza, for example, can infect a wide variety of animals, from sparrows to whales. Similarly, coronaviruses are known to regularly jump between species.
The question of how many and which species can be infected by SARS-CoV-2 – and which ones might be able to support continued circulation of the virus – is an important one.
Searching for COVID-19 in Wildlife
For human-to-wildlife spillover of SARS-CoV-2 to occur, an animal needs to be exposed to a high-enough viral dose to become infected.
The highest-risk situations are during direct contact with humans, such as a veterinarian's caring for an injured animal. Contact between a sick person and a pet or farm animal also poses a risk, as the domestic animal could act as an intermediate host, eventually passing the virus to a wild animal.
Another way COVID-19 could spill over from humans into animals is through indirect infection, such as through wastewater. COVID-19 and other pathogens can be detected in waste streams, many of which end up dumped, untreated, into environments where wildlife like marine mammals may be exposed. This is thought to be how elephant seals in California became infected with H1N1 influenza during the swine flu pandemic in 2009.
To study whether spillover of SARS-CoV-2 is happening, our team at Tufts is partnering with veterinarians and licensed wildlife rehabilitators across the U.S. to collect samples from and test animals in their care. Through the project, we have tested nearly 300 wild animals from over 20 species. So far, none – from bats to seals to coyotes – have shown any evidence of COVID-19 by swab or antibody tests.
Other researchers have launched targeted surveillance of wild animals in places where captive animals have been infected. The first confirmed infection in a wild mink was found during surveillance near an infected mink farm. It's not yet clear how this wild mink got the coronavirus, but the high density of infected minks and potentially infectious particles from them made it a high-risk location.
Bad for Animals, Bad for Humans
When a virus infects a new species, it sometimes mutates, adapting to infect, replicate and transmit more efficiently in a new animal. This is called host adaptation. When a virus jumps to a new host and begins adapting, the results can be unpredictable.
In late 2020, when SARS-CoV-2 jumped into farmed mink in Denmark, it acquired mutations that were uncommon in humans. Some of these mutations occurred in the part of the virus that most vaccines are designed to recognize. And it didn't just happen once – these mutations independently arose in mink farms multiple times. While it's not yet clear what impact, if any, these mutations may have on human disease or the vaccine, these are signs of host adaptation that could allow novel variants of the virus to persist and reemerge from animal hosts in the future.
Another risk is that SARS-CoV-2 could cause disease in animals. Ecologists are especially concerned about endangered species like the black-footed ferret, which is closely related to minks and thought to be very susceptible to the virus.
Human-to-wildlife spillover has happened before. In the late 20th century, the Ebola virus jumped from humans into great apes and has resulted in devastating consequences for these endangered animals. More recently, a human respiratory virus has been detected in threatened mountain gorilla populations and has caused deaths as well.
But perhaps the biggest risk to humans is that spillover could result in the coronavirus establishing a reservoir in new animals and regions. This could provide opportunities for reintroduction of COVID-19 into humans in the future. This month researchers published a paper showing that this had already happened on a small scale with human–to–mink–to–human transmission on mink farms in Denmark.
While our team has found no evidence of COVID-19 in wild animals in the U.S. at this time, we have seen convincing evidence of regular spillover into dogs and cats and some zoo animals. The discovery of the infected wild mink confirmed our fears. Seeing the first wild animal with natural COVID-19 is alarming, but sadly, not surprising.
Jonathan Runstadler is a professor of infectious disease and global health at the Cummings School of Veterinary Medicine, Tufts University.
Kaitlin Sawatzki is a postdoctoral infectious disease researcher at Tufts University.
Disclosure statements: Jonathan Runstadler receives funding from NIH/NIAID. Kaitlin Sawatzki receives funding from the NIH/NIAID.
Reposted with permission from The Conversation.
- Gorillas in San Diego Test Positive for Coronavirus - EcoWatch ›
- Wildlife Rehabilitators Are Overwhelmed During the Pandemic. In ... ›
- Coronavirus Pandemic Linked to Destruction of Wildlife and World's ... ›
- Utah Mink Becomes First Wild Animal to Test Positive for Coronavirus ›
- Antarctica Wildlife May Be Impacted by COVID-19 ›
To save the planet, we must save the Amazon rainforest. To save the rainforest, we must save its indigenous peoples. And to do that, we must demarcate their land.
A new EarthxTV film special calls for the protection of the Amazon rainforest and the indigenous people that call it home. EarthxTV.org
- Meet the 'Women Warriors' Protecting the Amazon Forest - EcoWatch ›
- Indigenous Tribes Are Using Drones to Protect the Amazon ... ›
- Amazon Rainforest Will Collapse by 2064, New Study Predicts ... ›
- Deforestation in Amazon Skyrockets to 12-Year High Under Bolsonaro ›
- Amazon Rainforest on the Brink of Turning Into a Net Carbon Emitter ... ›
EcoWatch Daily Newsletter
By Anke Rasper
"Today's interim report from the UNFCCC is a red alert for our planet," said UN Secretary General Antonio Guterres.
The report, released Friday, looks at the national climate efforts of 75 states that have already submitted their updated "nationally determined contributions," or NDCs. The countries included in the report are responsible for about 30% of the world's global greenhouse gas emissions.
- World Leaders Fall Short of Meeting Paris Agreement Goal - EcoWatch ›
- UN Climate Change Conference COP26 Delayed to November ... ›
- 5 Years After Paris: How Countries' Climate Policies Match up to ... ›
- Biden Win Puts World 'Within Striking Distance' of 1.5 C Paris Goal ... ›
- Biden Reaffirms Commitment to Rejoining Paris Agreement ... ›
India's New Delhi has been called the "world air pollution capital" for its high concentrations of particulate matter that make it harder for its residents to breathe and see. But one thing has puzzled scientists, according to The Guardian. Why does New Delhi see more blinding smogs than other polluted Asian cities, such as Beijing?
- This Indian Startup Turns Polluted Air Into Climate-Friendly Tiles ... ›
- How to Win the Fight Against Plastic - EcoWatch ›
In a historic move, the Delaware River Basin Commission (DRBC) voted Thursday to ban hydraulic fracking in the region. The ban was supported by all four basin states — New Jersey, Delaware, Pennsylvania and New York — putting a permanent end to hydraulic fracking for natural gas along the 13,539-square-mile basin, The Philadelphia Inquirer reported.
- Appalachian Fracking Boom Was a Jobs Bust, Finds New Report ... ›
- Long-Awaited EPA Study Says Fracking Pollutes Drinking Water ... ›
- Pennsylvania Fracking Water Contamination Much Higher Than ... ›
Colombia is one of the world's largest producers of coffee, and yet also one of the most economically disadvantaged. According to research by the national statistic center DANE, 35% of the population in Columbia lives in monetary poverty, compared to an estimated 11% in the U.S., according to census data. This has led to a housing insecurity issue throughout the country, one which construction company Woodpecker is working hard to solve.
- Kenyan Engineer Recycles Plastic Into Bricks Stronger Than ... ›
- Could IKEA's New Tiny House Help Fight the Climate Crisis ... ›