Americans’ use of animals — whether as food, products, or pets — is enormous, as is the resulting risk to humans from disease spillover, concludes a new report issued by Harvard Law School’s Brooks McCormick Jr. Animal Law & Policy Program.

The paper, which was co-written with experts at New York University, outlines and connects 36 major animal industries in the United States, from factory farming to trade in exotic pets, and estimates the threat each industry poses from zoonotic, or animal-to-human, transfer of disease. It also foregrounds the disconnected patchwork of federal and state laws that govern animal industries, many of which go under- or even unregulated in the U.S., says Ann Linder, research fellow with Harvard’s Animal Law & Policy Program and one of the report’s lead authors.

“We’ve all lived through the COVID-19 pandemic with all of its loss and costs,” she says, adding that the leading consensus about the origins of the pandemic point to transfer of the virus from animals to humans. “It would be the height of hubris for anyone to suggest the practices inside the United States don’t pose a risk, since we use and process more animals here than almost any other country on Earth.”

In an interview with Harvard Law Today, Linder outlined the report’s key findings, shared what most surprised her, and offered a grim assessment of what may happen if the country doesn’t take action. “It’s dangerous,” she says. “I think there’s very good reason to be proactive in trying to take these risks seriously and stop them at the source.”

Harvard Law Today: What goal did you and your team begin with when working on the report?

Ann Linder: Our goal was to shed light on the many ways in which human use of animals drives zoonotic spillover, where pathogens move from animals into humans. We started really narrowly, in the wake of COVID, focused on live animal markets — locations where animals were stored alive and then slaughtered on site to be sold to customers as food. But when we started pulling on those threads, we realized that the scope needed to expand, because even though these are high risk sites for zoonotic transmission, they’re only one part of a larger tangled lattice of animal use and animal trade. From there, we started looking more longitudinally at supply chains that support these markets and interconnections between different forms of animal industry, and it continued to grow from there.

HLT: What’s the most important thing for readers to take away from the report?

Linder: The most important thing that’s come out of this research is that we need to focus on prevention — stopping spillover before it starts. Policymakers too often treat these outbreaks like lightning strikes that can’t be predicted or prevented, but there are clear patterns and throughlines that can be drawn from animal use to outbreak. The bigger, more interesting questions are, what are we going to do about it once we’re able to acknowledge that? And do we have the willpower to do what needs to be done to stop future pandemics?

HLT: Why should Americans be concerned about your findings?

Linder: We’ve all lived through the COVID-19 pandemic with all of its loss and costs. Today, we no longer have to wonder what a large-scale disease outbreak in the United States would look like, and I think it’s safe to say that no one wants to go through that again. At the same time, there’s this quiet consensus within the scientific community that the next pandemic might be far worse than what we just experienced, and that it might happen sooner than we think. And, too often in the U.S., we think of infectious disease as an ‘over there’ problem. But it would be the height of hubris for anyone to suggest the practices inside the United States don’t pose a risk, since we use and process more animals here than almost any other country on Earth. So, I think these findings are deeply relevant to Americans, for all of those reasons.

HLT: What’s the worst-case scenario if we don’t act?

Linder: It’s bad. First, I should say that we are in the middle of the largest avian flu outbreak of all time, which has resulted in the deaths of more than 58 million birds in the U.S. alone. Influenza viruses like this one (H5N1) are an important area to watch for future pandemic risk. There was research done at Stanford around the question of whether an H5N1 outbreak could lead to human extinction — comfortingly, their answer was “probably not.” But their modeling did suggest that an outbreak could cause a loss of human life on a scale not yet seen — one that could stretch into the billions. So, I think there’s very good reason to be proactive in trying to take these risks seriously and stop them at the source.

“There was research done at Stanford around the question of whether an H5N1 outbreak could lead to human extinction … their answer was ‘probably not.’ But their modeling did suggest that an outbreak could cause a loss of human life on a scale not yet seen — one that could stretch into the billions.”

HLT: Let’s turn to the data. Your report mentions that one potential source of information about animals being brought into the U.S. is compiled by the Fish and Wildlife Service, yet the agency has withheld data in recent years. Those involved in other animal industries are also reluctant to share information on their operations. Given those challenges, how did you and your team gather the data used in your report?

Linder: The short answer is that it was difficult. Regarding that Fish and Wildlife data — the Harvard Animal Law & Policy Clinic, along with the Center for Biological Diversity, brought a Freedom of Information Act claim against the Fish and Wildlife Service for failing to release that data, which is really one of the only windows we have into what wild animals are coming into the United States, where they’re going once they get here, and how those animals are being used. While they’ve now agreed to release the data, what they’re providing is heavily redacted and leaves out a lot of critical information, so there are still real gaps in our understanding.

In a broader sense, though, so many of these forms of animal industries that we looked at are lacking in transparency. They ban photography or are closed to journalists. Some of them are closed to the public. Many of them have escaped regulatory scrutiny and operate truly out of the public eye. And for many of those industries, producers have a vested financial interest in keeping it that way. So, there’s a cloud that surrounds many of the industries that we studied — in fact, even some of the image credits in the report are pseudonyms to protect the identity of the people who took them. We relied on white papers and grey literature and scientific literature, but that only takes you so far. From there, we looked at the popular press, but also things like production manuals, or blog posts from producers, and interviews, trying to understand what’s happening within these industries. It was not always easy, much of what we’ve written is a testament to how much we still don’t know. And that understanding is the first step.

HLT: One of the things that might strike readers of the report is the sheer number of ways in which animals are used in the U.S. They are raised or imported for food, for other commercial uses, as pets, and more. Was it challenging to examine such a wide array of practices and industries?

Linder: Absolutely. When we were starting this report on the U.S., we began by making a list of all of the different industries we could think of that relied on and used animals, and that list just kept growing. Three years later, it was still growing. Even in the weeks leading up to releasing this report, we came across industries that we had never heard of before. In the report, we include 36 forms of animal industry, everything from big industries that everyone’s heard of like factory farming, to smaller niche industries, like roadside zoos, captive hunting ranches, and fur farms. This is by no means an extensive list — it’s just a sample of what’s out there.

HLT: What are some of the highest risk industries for zoonotic spillover in the U.S.?

Linder: There are lots of answers to this question, but I’ll give you three that really stood out for various reasons. The first is industrial animal agriculture. We produce about 10 billion land animals for food here in the United States every year, and two of the species that we produce in higher numbers than almost any other — pigs and poultry — also happen to be carriers for influenza viruses. Every expert we spoke to, when asked “What keeps you up at night?” responded that it was influenza viruses. That’s because we think they are the most likely kind of virus to give rise to a large-scale human pandemic. Given the scale of the industry, and the scale of that risk, we should look very closely at industrial animal agriculture.

Others that come to mind include the exotic pet trade. We move a huge amount of wild animals into the United States for use as pets. The exotic pet trade is largely unmonitored. Even trying to get estimates for the size of this industry proved really difficult. It spans all kinds of animals, from primates to sugar gliders, and many are living in American homes, interacting closely with humans.

The third industry I’d mention is fur farming, which combines many different risk factors — including higher risk species like mink, for example, and then raising those animals in high-risk conditions, marked by close confinement. They generally have poor health and welfare. And the farms themselves are almost completely unregulated.

“It would be the height of hubris for anyone to suggest the practices inside the United States don’t pose a risk, since we use and process more animals here than almost any other country on Earth.”

HLT: What findings surprised you most?

Linder: Just how few guardrails exist that focus specifically on disease risk in animals. A lot of the ways in which we regulate animals have nothing to do with disease. For example, with wildlife imports that are coming into the country, we’re only screening them on a conservation basis. In other words, we look at whether the animal is subject to the Endangered Species Act, but not necessarily whether it poses a risk of disease spread to humans. It’s also interesting because oftentimes, the public-facing aspects of these markets appear much more regulated. If I want to bring a cat or a dog into the United States, for example, there are procedures that I have to go through. But if I’m a wildlife importer, and I want to bring in 100 wild animals from South America, I can do that with very little regulatory red tape or health and safety checks of any kind.

HLT: You mentioned that there is no single federal or state entity dedicated to preventing zoonotic disease. Instead, a patchwork of federal and state laws serves this purpose. In your view, what problems does this arrangement cause? Are there any advantages to this approach?

Linder: One of our major findings was that we don’t have a comprehensive regulatory strategy to address zoonotic threats — that instead, we have a lot of different agencies focused on a lot of discrete issues, without a lot of cooperation and information sharing towards a common goal of disease prevention. Part of the reason for that, and why this is so problematic, is that animals are challenging subjects of regulation for a lot of different reasons. They can change status along with a change in use. For example, you might have an animal of the same species that could be used as livestock in one setting, or as a pet in another setting, or as wildlife in a different context. Also, different states have different rules, and don’t always exchange information effectively with each other or with the federal government. Because of this, you have critical information related to health that’s not being shared effectively.

On the flip side, as to whether there are any advantages of this approach: there could be, if each agency was truly able to specialize and we were able to close the daylight between them, such that there aren’t whole industries that fall between the gaps, like fur farming or captive wildlife in general. But right now, there just isn’t sufficient coordination to make that happen. They’re not all operating towards the same guiding principle. They’re all doing their own thing.

HLT: What are the largest regulatory gaps that you found?

Linder: There are whole industries that fly under the radar, and often that happens where you have animals that we might associate with one of those categories, such as livestock or wildlife, acting as if they’re part of another. Fur farming is a good example. There, you have the U.S. Fish and Wildlife Service saying those are captive animals since they’re being raised like livestock, and therefore, outside of our agency’s jurisdiction. But you also have the USDA, which deals with traditional livestock animals, saying essentially the same thing in reverse. That these animals are not livestock, so they are not our problem.

The risks posed by industries that operate in these in-between spaces are something that were borne out in interviews we did with regulators. In some cases, we were asking regulators questions about industries that they didn’t know existed, or first learned of when the animals in those industries began contracting COVID-19.

HLT: And what do you see as the biggest barriers to addressing those issues?

Linder: The most obvious thing we need to do is recognize that our practices here in the U.S. are contributing to global disease risk. I think the lack of information and data is the second step that we need to tackle. People don’t know that many of these industries even exist. We have tried to do some of that groundwork by documenting the different forms of animal industry here in the United States and the risks that are associated along with those practices. But there’s a long way we need to go, for example, to examine and study the risks to individuals who work in those industries, who are interacting with animals closely on a daily basis and are the most at-risk group for zoonotic disease.

HLT: Are there any easy actions we as individuals can take to help reduce the risks you highlighted?

Linder: While zoonotic risk can’t be eliminated, it can be reduced, and we can reduce it in many ways that would scarcely be felt by the public at large. We can do easy things like not buying fur coats, not keeping exotic animals as pets, or avoiding purchasing wildlife products. We can also make practical choices on a daily basis, like consuming more plant-based foods, and working to reduce deforestation and protect habitat, which is critical to limiting spillover events.

HLT: What are the next steps for you and your team?

Linder: We just published one portion of what is a much larger project. Our U.S. report looks at animal industries here inside the States, but we are also looking at 14 other countries as part of a global project that we’ve been working on for the last three years with partners on the ground in each of those countries. We hope to take these 15 country studies and release a synthesis to see what lessons we can learn and how we can reduce risk at a global scale. We hope to get that global report out the door by this fall.

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