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How Animal Disease Surveillance Protects Human Health: COVID-19 and Beyond

COVID-19 has been detected in multiple species of animals, including cats, dogs, deer, lions, otters, hippos, manatees, and mink. This has brought into focus how the health of humans is interconnected with the health of animals and our shared environment, and why animal disease surveillance is an important component of measures to protect human health. This video explores what animal surveillance looks like on the ground in an urban area of the US.

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[Voiceover:] This white-tailed deer fawn is only a few days old. It's been caught by wildlife researchers in Schiller Woods, right at the edge of the city of Chicago.

Here, the researchers are putting on a radio collar, which will allow them to track the fawn's location and to assess deer mortality in the larger population. The researchers examine the fawn, assess its age, check for ectoparasites and wounds, and take multiple measurements.

And this year, the fawns are also getting surveyed for SARS-CoV-2, the virus that causes COVID-19 in humans.

Animal disease surveillance like this is a key part of public health. Let's take a closer look at what animal surveillance looks like in an urban area in the US, and the importance of this work in light of the COVID-19 pandemic and beyond.


SARS-CoV-2 infection is what's called a zoonosis, or zoonotic disease, which means that it can be naturally transmitted from animals to humans and vice versa. Currently, the highest infection risks to humans are from other humans, not from animals. However SARS-CoV-2 infection becoming widespread in wildlife raises two potential concerns. The first is that after COVID-19 cases among people have declined, spillover events from animal reservoirs could drive new outbreaks. The second concern is that as the virus evolves in different animal hosts, this could result in the emergence of new variants, which might look very different from any of the variants currently circulating.

Right now there are more questions than answers, and animal surveillance is key to untangling this puzzle.

[Chris Anchor:] My name is Chris Anchor. I'm the wildlife biologist of the Forest Preserve District of Cook County. Cook County is the third largest metropolitan area in North America. There are more than 9 million people that live within 50 miles of the city of Chicago. And, as such, the interface between humans and animals is very profound.

[Voiceover:] This type of urban environment highlights how the health of people is closely connected to the health of animals and our shared environment, a concept known as One Health.

Take turtles; Cook County has several native species of turtles. The wildlife biologists there are currently focusing on soft shell turtles, and collecting measurements, swabs and blood to understand the health of the species. But turtles are also excellent sentinels for environmental contaminants, like microplastics or lead, so studying them can reveal crucial information about changes in the water environment, which we all share.

One Health is also key for understanding emerging infectious diseases. For example, since 2009, the World Health Organization has declared seven Public Health Emergencies of International Concern. All but one of these pathogens are either zoonotic or vector-borne.

And for many diseases, humans are not dead-end hosts. In fact we have been giving our diseases to animals throughout history.

This definitely holds true with COVID-19. A recent study by the US Department of Agriculture looked at past infection with the SARS-CoV-2 virus in wild deer across four US states. SARS-CoV-2 antibodies were detected in a staggering 40% of blood serum samples. Cook County was one of the locations surveyed in that study. Of the 9 Cook County samples tested, 3 were positive.

[Chris Anchor:] It's counterintuitive, but as you move closer into the city, many species of animals, including things like raccoons, skunks opossums, deer, the densities actually get higher. They don't get lower. And that's due to the fact that the environment is so changed and their behaviors are so plastic, they're able to live amongst us and actually exploit underutilized or non-utilized environmental conditions. So it's a fabulous place to look at how disease moves across the landscape.

Oh, yeah. Like Christmas. So these are internal and external fish transmitters. And then here are my turtle transmitters. So...much excitement!

[Voiceover:] Transmitters like these, or the radio collars on the fawns, are examples of radio telemetry, an important tool used by scientists since the 1960s to understand animal behavior.

[Chris Anchor:] We are very interested in how animals come into contact with humans and how they come into contact with other animals, which is typically the weak link if you want to understand how disease moves across the landscape. And through radio telemetry, we're able to understand some of those contact points that were missing.

If you look in the peer reviewed literature, in many cases it's 180 degrees from the reality of what's occurring in an urban environment. Because for 60 years we have been studying animals in the rural, agricultural, wild environment.

[Samantha Plencner:] We, like, set up an outdoor lab in the back of a truck. It works, right?

[Voiceover:] This outdoor lab is getting set up for a baby osprey that lives in Busse woods, just west of O'Hare International Airport. Ospreys are apex predators and almost exclusively fish eaters. They accumulate heavy metals, pesticides, and other chemicals, so just like turtles they can serve as sentinels for environmental contaminants.

In addition to getting measured, tagged, and getting its blood drawn, this baby osprey is also getting swabbed for avian flu.

The blood and tissue samples the wildlife biologists collect may be used to alert public health officials, or in ongoing studies by researchers who collaborate with the forest preserves. Many of the samples simply get logged into freezers and cataloged for future research needs.

This type of ongoing preservation of samples and monitoring of animals allows researchers to find out when a disease first entered the landscape, and to determine how it has mutated over time. More foundationally, it allows them to determine the baseline; or what is normal in different species on this particular landscape. And at baseline, there may be hundreds of pathogens circulating in wildlife, without causing outbreaks of disease in humans.

[Chris Anchor:] There are many things that animals will test positive for, but it does not make them a threat. And that's part of the reason why we go through the process of active surveillance. So we're always looking. We're always looking for that next disease. We're always stocking away blood and tissue from what we presume to be normal animals so we can go back years or decades later to get an understanding of has there been a change over time?

[Voiceover:] Some estimates indicate there may be thousands of pathogens with zoonotic potential--that is pathogens that have not spilled over into humans, but--given the right environmental conditions--could do so.

With global warming, as well continuing deforestation and urban development across the globe, different species of wildlife are likely to come in more and more contact with each other and with humans. And this will potentially greatly increase the likelihood and frequency of spillover events.

So while SARS-CoV-2 circulating in wildlife does raise concerns, the need for increased surveillance as well global cooperation in detecting and understanding spillover events reaches far beyond the COVID-19 pandemic.

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