An Epidemic of Absence: A New Way of Understanding Allergies and Autoimmune Diseases - Softcover

Über die Autorin bzw. den Autor

Moises Velasquez-Manoff covered science and the environment for The Christian Science Monitor, and his work has appeared in The New York Times Magazine, The Chicago Tribune, and Slate, among other publications. He graduated from the Columbia Graduate School of Journalism’s Master of Arts program, with a concentration in science writing.

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An Epidemic of Absence

CHAPTER 1

Meet Your Parasites

Mother, it is no gain, thy bondage of finery, if it keep one shut off from the healthful dust of the earth, if it rob one of the right of entrance to the great fair of common human life.1

—Rabindranath Tagore,
Bengali poet and Nobel laureate

One chilly November morning, I head south from San Diego in a bottom-tier rental car. The standard journalistic paraphernalia—a digital recorder, camera, notepad, and pencils—accompany me in the passenger seat, as well as directions to my meeting point: the last exit before Mexico. I also have a printout of my recent blood work, proof that I’m not anemic, not infected with hepatitis or HIV—that I’m healthy enough for the coming experiment.

As I drive, the radio announcer conducts a gruesome tally of the most recent violence in Tijuana, where I’m headed: two bodies hung from a bridge, a third decapitated, a fourth shot. More than this terrible, ongoing brutality, however, parasites occupy my mind—worms that migrate through flesh, burst into lungs, crawl down throats, and latch on to tender insides. Any traveler might fret over acquiring such hangers-on while abroad. But I’m heading to Mexico precisely to obtain not just one, but a colony. Today in Tijuana I’ll deliberately introduce the hookworm Necator americanus—the American murderer—into my body.

And for this dubious honor, I’ll pay handsomely—a onetime fee of $2,300. If I receive twenty of the microscopic larvae, that’s $115 apiece for a parasite that, in the early decades of the twentieth century, was considered a scourge on the American south. Some worried—without condescension, I should add—that hookworm was making southerners dim-witted and lazy, that it was socially and economically retarding half the country. And photos of poor, worm-ridden country folk from the time—followed by their robust health after deworming—clearly show the dire costs of necatoriasis, or hookworm disease: jutting collarbones, dull eyes, and listless expressions on wan faces. They appear as if consumed from the inside.

Hookworm has mostly disappeared from the U.S., the result of protracted eradication efforts in the early twentieth century. But in the usually poor, tropical countries where it’s still endemic, it can cause anemia, stunt growth, halt menstruation, and even retard mental development in growing children. Between 576 million and 740 million people carry the parasite. And for all the aforementioned reasons, public-health types consider worm infections a “neglected tropical disease.” Helminths, as they’re called, are not as obviously fatal as malaria, say, but their constant drag on vitality is insidious. The parasites keep children from learning in school. They prevent parents from working. Some argue that they contribute to the self-reinforcing cycles of poor health and poverty that plague entire nations.

So why am I considering acquiring this terrible creature? Scientists have two minds about parasites these days. Some consider them evil incarnate, but others note that while the above-mentioned horrors are sometimes true, the majority of humans infected with parasites today—upward of 1.2 billion people, or somewhere between one-fifth and one-sixth of humanity—host worms with few apparent symptoms. This camp has begun to suspect that worms may, in fact, confer some benefits on their human hosts.

As early as the 1960s, by which time hookworm had been largely eradicated in the U.S., scientists puzzled over the lack of symptoms in some. “Well-nourished persons often harbor helminths without apparent damage,” remarked one physician in 1969.2 “One may question the wisdom of treating such infections, especially with chemotherapeutic agents with toxic qualities.”

Decades of plumbing the mechanisms that allow one creature to persist within another, a clear violation of the self-versus-nonself rules thought to govern immune functioning, has taught immunologists much not only about how wily worms really are, but also about how the human immune system actually works. Parasites like hookworm were ubiquitous during our evolution. Might our bodies anticipate their presence in some respects, require it even? And might some of the more curious ailments of modernity result partly from their absence?

That brings me to my motive: A large and growing body of science indicates that parasites may prevent allergic and autoimmune diseases. And I’ve got both.

*   *   *

When I was eleven, my hair began falling out. My grandmother first noticed it. I was visiting my grandparents at their beach house that summer when, one afternoon, she called me over, examined the back of my head, and proclaimed that I had a nickel-sized bald spot. Then we all promptly forgot about it. With the sand, waves, and sun beckoning, it just didn’t seem that important.

But by the time school started a few months later, the bald patch had grown. A dermatologist diagnosed alopecia areata, an autoimmune disorder. My immune system, normally tasked with protecting against invaders, had inexplicably mistaken friend for foe, and attacked my hair follicles. Scientists didn’t know what, exactly, triggered alopecia, but stress was thought to play a role. And at first glance, that made sense. My parents were in the middle of a messy, drawn-out divorce. I was also beginning at a new junior high school that fall; I had, it seemed, much to worry about.

I also had other, better-known immune-mediated problems. I suffered from fairly severe asthma as a child, and food allergies to peanuts, sesame, and eggs. (Only the egg allergy eventually disappeared.) At least once yearly, usually during seasons of high pollen count, my wheezing became so severe that my lips and fingernails turned blue, and my parents had to rush me to the emergency room. There, doctors misted me with bronchodilators, or, during severe attacks, pumped me full of immune-suppressing steroids.

“Aha!” said the dermatologist when he learned of these other conditions. There was a correlation among allergies, asthma, and alopecia, he explained. No one was sure why or what it meant, but having an allergic disease like asthma increased one’s chances of developing alopecia.

Years later, I would learn that the co-occurrence of these two disorders was likely evidence of a single, root malfunction. But at age eleven, I accepted on faith that where one problem arose, so, probably, would others. So what to do? Given my age and the relatively small size of the bald spot, the doctor recommended watching and waiting. Alopecia usually corrected itself in time, he said. So we waited.

In a month, another bald spot appeared, on the right side of my head. Then one on the left. Seemingly overnight, a large one opened up just above the middle of my forehead. As more hairless patches appeared, the pace at which new ones emerged accelerated. Every morning, my mother combed and gelled my hair into place to hide the growing expanse of denuded skin; but soon, concealing my bare scalp became nearly impossible. The spots began to converge. I was going bald.

We returned to the dermatologist. This time, he had a less upbeat assessment. The more the disease progressed, he noted, the less likely recovery. The odds worked like...