In the summer of 1997, I was a newspaper reporter covering the Centers for Disease Control and Prevention, and I heard from a contact at the CDC that a team was headed to Hong Kong to check out an odd case. A 3-year-old boy had died of flu. That was sad, but not notable enough on its own to send premier disease detectives rocketing around the world. What was extraordinary about the boy’s death was its cause: a strain of flu known as H5N1 that had never been seen in humans before, though it was common in birds and had recently killed 4,500 chickens on a Hong Kong farm. By the end of that year, 17 other Hong Kong residents would become infected, five others would die, and to shut down the epidemic, Hong Kong would slaughter every chicken in the territory, 1.4 million of them.
That worked, for a while. But in 2003, H5N1 appeared again. Since then, it has sickened 607 people around the world, killing more than half of them. It has done something else too. H5N1 and the 2009 H1N1 “swine flu” — a much larger epidemic whose toll of illness and death was recently revised sharply upward — introduced to many people the idea that diseases could jump from animals to humans, and be much more dangerous to their new human hosts than to the animals they came from.
Diseases that jump in that manner are called “zoonoses,” and because their effect can be so dramatic, they are the subject of major international tracking projects, not to mention cultural fascination. (For just one example, watch last year’s movie Contagion.) But a new book, “Zoobiquity: What Animals Can Teach Us About Health and the Science of Healing” (Knopf) argues that by viewing animals only as a source of infection, we miss a rich range of illnesses that we have in common with other species and that could broaden our understanding of what affects our health and theirs.
“Zoobiquity” has two authors, UCLA cardiology professor Dr. Barbara Natterson-Horowitz and journalist Kathryn Bowers. For the third installment of Superbug Summer Books, I talked to Dr. Natterson-Horowitz by phone and edited and condensed our chat.
Maryn McKenna: I’ve written about zoonoses for years now — as far as I know, I wrote the first story in the U.S. about H5N1. So I take for granted that different species have similar diseases. But you and your co-author say that isn’t well-known — and when it is recognized, it’s all people know about human-animal connections.
Barbara Natterson Horowitz: When I was in medical school, I remember a few lectures on the intersection between human and animal disease, and all of it had to do with zoonoses. And for many physicians, that’s all they really understand about the connection. Periodically a threatened pandemic pops up: SARS, H1N1. Then all of a sudden there is a brief recognition that animal health connects to human health, but once the pandemic threat quiets down, we don’t think about it. If you ask the average front-line clinical physician how can animals help us understand health, they’ll probably point to the animal lab.
MM: But as you explain, infectious diseases are not the only ones that animals and humans have in common. You mention chronic diseases, such as cancer and obesity. I was surprised — despite being an animal owner — at how broad the range was, particularly in what we would think of as psychological or behavioral problems.
BNH: It turns out that self-injury is very common — in parrots, horses, and a remarkably broad range of species. Some dogs, when they’re stressed, they’ll lick at their paw. They lick and lick and their fur comes off, and they continue to lick and the skin breaks down. It’s painful for the animal, but they continue to do it. What are they doing? They’re grooming. Animals groom for a variety of practical reasons, but also for self-soothing. if you frame self-injury in that way, it actually offers this broadened perspective that can be useful for humans.
There’s a similar situation with substance-seeking. It turns out naturalists have been observing what appears to be substance-seeking behavior in a wide variety of animals: birds, bighorn sheep, wallabies in Tasmania. Is there meaning for human patients? I think there is the potential to help destigmatize addiction — addicts and substance abusers continue to be horribly stigmatized medically. Beyond that, I think it leads us to look at the evolutionary biology that underlies addiction, and gives us a broader frame for asking why these reward circuits exist.
MM: You’re arguing that disease isn’t a thing that animals do to us, but a condition that our species share and that we can learn from.
BNH: What we are taught about zoonoses is that animals are giving us diseases, which is such an incomplete representation of the ecology of disease. It’s as though animals are the enemy. But zoonoses are bidirectional: There are things we give animals also. For instance, eco-tourists pose a risk to native fauna. There are cases of great apes, for example, in Africa who acquired human viruses. I suppose if I could wave a magic wand, via this book, what I would want is to broaden our appreciation of our interconnectedness to the complexity of the microbial world, and how marvelous and yet vulnerable that ecology is.
MM: While I was reporting my last book, I talked to a number of physicians whose patients acquired antibiotic-resistant bacteria from farm animals and from pets. So I’m surprised that there isn’t more awareness of this commonality.
BNH: Well, veterinarians know. Some of the feedback I’ve gotten from vets is, “Everybody knows that animals get the same diseases that humans do. How could you be writing a book about something so obvious?” And I don’t know how to break it to them, but 99.9 percent of the physicians that I know, clinical rank-and-file people who take care of patients, are shocked to hear this. I was in our hospital cafeteria, talking to an oncologist at the salad bar, and said: “Did you know that jaguars and other big cats have a pretty high incidence of breast and ovarian cancers?” And he didn’t.
From their first days in school, veterinarians study comparatively: You learn cardiology, not just about a four-chambered heart, but about a reptilian heart, and a fish heart. In fact, they have a joke: “What do you call a veterinarian who treats only one species? A physician.”
MM: To help spread this awareness, you founded a conference about species-spanning medicine; you’re holding the second one next September. Do you have the sense awareness is growing, of the need to take this broader view?
BNH: There is the One Health Initiative, which has been working on this. Veterinarians have really taken the lead with One Health, but there are not enough physicians involved, especially physicians who are not infectious-disease specialists. The reality is, there is a bias against veterinary medicine amongst physicians — in fact, as we were working on this book, I heard from colleagues who wondered why I was “spending all this time with animals” when I have a wonderful career in human medicine.
In order to make any kind of real change, we have to show that this broadened perspective matters. We have to not just say it’s important, because there are a billion things that are important for medical students to learn. Not all questions in medicine are going to be answered through reductionistic approaches. There is potential for the opposite approach, a very broadly spanning perspective, to be helpful for obesity, cancer, addiction, suicide, sexuality — key human medical concerns.
This is the third in an intermittent series I’m running this summer about books I like and think you should take a look at. Some of the books will be directly related to this blog’s core topics. Others, I just think are cool. You can find my picks at #SBSBooks.
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