Enterobiasis

To learn about grisly parasites that have afflicted North and South Americans for millennia, researchers are studying the mummified remains of people the parasites killed.

IN A DUSTY STORAGE ROOM TURNED MAUSOLEUM IN THE CHILEAN CITY OF Arica, Bernardo Arriaza gazes down at the body of another dead child. It's an austral autumn afternoon during the Third World Congress on Mummy Studies, and Arriaza is making the most of a few stolen hours away from the conference room. In shadows cast by rows of shelving, the young physical anthropologist from the University of Nevada closes one box and opens another. Inside, a mummified child stares out through a crumbling, mask of bluish gray clay. Its eyes are open, its round mouth agape, and bundles of sticks, reeds, and ash bulge from its narrow chest. Arriaza slips the lid back on and glances up at shelves filled with other small gray boxes. "There are a lot of children," he says.

The mummies in this room were exhumed from the sands of the Atacama Desert, one of the driest places on Earth; all were members of the Chinchorro, a coastal people who fished northern Chilean waters from 5500 to 500 B.C. The Chinchorro mummies include the oldest ever deliberately created, which go back 7,000 years, millennia before the Egyptians conceived of such a notion. Eviscerated, dried, stuffed, covered in colored clay, and fitted with wigs, many look more like modern art than human beings. The Chinchorro so loved their dead, it seems, that they were reluctant to part with them. They kept them nearby, continually repainting and touching up their work. "They did not separate death from life," says Arriaza.

The people who crafted such immortality always had plenty of work. Despite ocean waters teeming with fish and lands free of modern pollutants, the Chinchorro were plagued with mysterious ailments. According to one study, a quarter of their children perished before reaching their first birthday. More than a third suffered from infections that eroded their leg bones. And one in every five Chinchorro women was stricken with bones so porous that her vertebrae splintered from the weight of her own flesh. The average Chinchorro lived just 25 years.

PRECISELY WHAT WEAKENED AND killed the Chinchorro is a question that fascinates Arriaza and his colleague Karl Reinhard, an archeoparasitologist at the University of Nebraska at Lincoln. For decades, says Reinhard, scientists regarded the ancient Americas as a healthy, parasite-free paradise. Of the dozens of parasites that rampaged through the Old World--armies of flukes that burrowed through lungs and livers, knots of writhing roundworms that blocked intestines and gobbled undigested food, masses of protozoans that invaded nerve tissues and poisoned cells--few were thought to have accompanied humans to the New World. Most parasitic species, it was thought, evolved only after people domesticated livestock, greened farmlands with irrigation, and crowded together in cities, events that took place long after Ice Age Asian hunters set off for the New World. The few parasites that had learned to infect those prehistoric migrants were deemed too delicate to have survived the long, frozen trek across Beringia, the land bridge that joined northeastern Siberia and Alaska during the last ice age. Few researchers gave any thought to potential New World parasites. "So as late as 1981," marvels Reinhard, "parasitologists in general believed that the New World was essentially flee of human parasite disease, with the exception of enterobiasis," an infection caused by pinworms.

But in recent years, Reinhard and others have shown that these assumptions were mistaken. While examining human remains, including the mummies of ancient seal hunters in Alaska, prehistoric cave painters in southern Texas, and Inca corn farmers in Peru, they have detected a host of parasites throughout the ancient New World. Some, says Reinhard, weathered the Beringian cold; others, native to the Americas, assailed humans as they encroached on new forests and coastlines. And the diseases they spawned took a high toll. In the Arctic, for example, hunters perished from heart failure as armies of tiny nematodes invaded their muscles. In the Great Basin of the United States, thorny-headed worms pierced the intestinal walls of foragers. And in the South American Andes, protozoans ulcerated and rotted farmers' throats, mouths, and lips. "The hard data of paleopathology show that many people were as sick as dogs," says Reinhard.

Such findings "really give you a window into the lives of these people," says John Hawdon, a parasitologist at the Medical Helminthology Laboratory at Yale. "Ritual life has always been an important thing in archeology, but the health of a people is just as important because it determines a lot about how they interacted with each other. One could argue that the Aztecs performed many human sacrifices because of protein deficiencies and malnourishment. And who knows what caused that? Hookworms could have been involved." Moreover, the implications extend far beyond archeology. By charting the rise and spread of parasites in the New World, Reinhard and others are now shedding light on both the evolution of these pathogens and the origins of ancient plagues such as Chagas' disease, which currently infects an estimated 370,000 Americans and 16 to 18 million inhabitants of Central and South America. And this, emphasizes Reinhard, is only the beginning. "If we look at the research questions of the past, it was `Can we find the worms?' But in the future, our questions are going to relate to the influence of climate change on the parasites and how this archeological evidence of emergent and reemergent disease can contribute to our understanding of emerging diseases today."

Reinhard comes by his work honestly. As a child, he was fascinated by the spectacle of a massive parasitic worm under glass in the laboratory of his epidemiologist father. "My father thought that Native Americans in Alaska had inherited resistance to tuberculosis and other diseases, which meant the diseases were there before the Europeans arrived," says Reinhard. And if bacteria had broken the cold barrier, why not parasites as well?

As a fledgling parasitologist at Northern Arizona University, Reinhard began looking for ways to test the notion. Fortunately, archeological sites commonly contain an informative leftover: desiccated human feces, or coprolites. He set to work analyzing hundreds of samples from Anasazi settlements in Arizona and New Mexico, rehydrating them and examining them under high-powered microscopes. Among bits of undigested corn and squash, he noticed the tiny mummified larvae and eggs of four parasites: roundworms; pinworms; tapeworms, whose poisonous excretions in heavy infestations leave their hosts dizzy, nauseated, and even delirious; and wireworms, whose random migrations through intestines can scar tissue so badly that little food passes through. "As one of my professors used to say, it's like replacing the intestine with PVC piping," says Reinhard.

Reinhard suspected, however, that his coprolite analysis didn't tell the whole story. Some parasites neither inhabit the human intestine nor cast their eggs into it. Moreover, excavated feces offered few clues to the prevalence of diseases. A collection from a site could represent a few sick individuals or a cross section of the community. Studying mummies, he decided, would give him a clearer picture, since their tissues were an archive of disease.

Mummies were once surprisingly abundant in North America. In the Aleutian Islands, ancient families dried and stuffed the bodies of prominent men, then placed them in caves heated by volcanic vents where the living could consult them as oracles. In the American Southwest, the cliff-dwelling Anasazi occasionally eviscerated and preserved their dead. And in southern Texas, Arizona, Kentucky, and Tennessee, native societies interred their dead in dry caves, and hundreds of these bodies escaped water and decay. Researchers and ranchers in the mesquite and creosote desert of the Lower Pecos in Texas exhumed nearly 150 mummies from caves painted with shamans, panthers, and snakes.

With the help of colleagues, Reinhard obtained samples from three American mummies at the University of Arizona, and he examined them for signs of parasitic disease. But in the 1980s, studying North American mummies was rapidly becoming politically and legally difficult as Native American activists began to demand that museums return to them all human remains that they considered ancestral. In South America, however, there was no local opposition to studies of the dead, and when archeologists started to unearth hundreds of prehistoric mummies in the Atacama Desert, Reinhard headed south to do his fieldwork. Today, thousands of coprolites and nearly 250 mummies later, he has proved that America's prehistoric hunters and farmers were plagued by parasites. Of 16 species that he and other researchers have found, including protozoans, tapeworms, roundworms, flukes, and thorny-headed worms, 11 were almost certainly native parasites that humans encountered for the first time as they intruded on strange new environments in the Americas. The rest were probably old-world species that survived humanity's frozen northern trek. Some, like Ascaris lumbricoides, the large roundworm, evolved eggs that could endure the extreme cold. Others, such as Trichuris trichiura, the human whipworm, eked out an existence in the migrants' heated winter homes.

One species, however, the hookworm, perplexes parasitologists. A tropical and subtropical species that currently ventures no farther north than southern Japan, Ancylostoma duodenale is largely a parasite of the agricultural poor, infecting hundreds of millions of people around the world. The worm latches onto the human intestine with two sharp hooks, takes a mouthful of tissue, dissolves it with enzymes, and slurps up blood from ruptured capillaries. In a heavy infestation of a hundred or more worms, a person can lose nearly a pint of blood every two days, suffering severe anemia and iron deficiency. "And if kids get anemia young," says Hawdon, "they are mentally handicapped for the rest of their lives." Without medical treatment, heart failure and death follow. Hookworms currently kill 50,000 people worldwide every year.

"Kids tend to be the vector," says Hawdon, "because they essentially defecate anywhere." Once passed from the host, A. duodenale eggs hatch into larvae within 48 hours. After feeding in the feces and undergoing a series of molts, they migrate to the top of the soil. There the tiny worms stand on their tails, weaving back and forth like an army of microscopic vipers as an unsuspecting human walks by. The lucky ones crawl onto their new host's skin, slipping into tiny cracks or wriggling down hair follicles. They enter blood capillaries, swim to the lungs, make their way up the bronchi to the throat, and are swallowed and propelled to their final destination, the small intestine.

But A. duodenale has one critical weakness, says Reinhard. To survive outside the human body, its eggs and larvae need moisture, shade, and a minimum temperature of 59 degrees. Just how such a hothouse flower accompanied Ice Age migrants is still far from clear. But Hawdon, an expert on hookworms, suggests that the worm escaped the fatal cold entirely by hypobiosis, a form of arrested development.

In parts of India, he notes, A. duodenale larvae that infect humans at the beginning of the dry season soon go into a quiescent state. They awaken months later when the monsoon rains arrive, wetting the soil and preventing the parasite's eggs from drying out. Something similar, argues Hawdon, most likely occurred in the Arctic: A. duodenale could have slumbered through the icy days of winter. In A. caninum, a hookworm species that parasitizes dogs, larvae emerge from their sleep when their female host becomes pregnant. "They migrate into the mammary glands and are transmitted into the milk," says Hawdon, and then into nursing puppies. The parasites, barely challenged by the puppies' naive immune systems, have no trouble establishing themselves.

SO FAR, NOTES HAWDON, NO ONE HAS EVER DETECTED hookworm larvae in human breast milk. But he and others have come up with other circumstantial evidence. "There's epidemiological data from China where very young infants, under six months or so, became infected with A. duodenale. And this is at an age when they would not normally be exposed to contaminated soil, which is where people generally pick up hookworm."

The parasites that humans carried with them on their Arctic wanderings may have been horrible, but the worms and protozoans the migrants encountered in American forests and oceans were far worse--as Reinhard discovered when he examined a 1,150-year-old mummy, the body of a man 35 to 45 years old, exhumed from the northern fringe of the Chihuahuan Desert, near the Texas-Mexico border. A local rancher discovered the mummy one Sunday in 1937, brought it home, and put it on the spare bed in his son's room. The mummy has long troubled Reinhard. On his first visit to the ranch a decade ago, Reinhard asked one of his companions, a prominent Texas archeologist, about the mummy's suspected cause of death. She pointed to a badly abscessed tooth. But as Reinhard scanned the body, he could see dark brown intestines so packed with mummified food that they filled the man's entire pelvic girdle. To Reinhard, it looked as if the man had not had a bowel movement for months before his death. "That mass of food haunted me for years after," he says. "I couldn't put it out of my mind."

Last April, the parasitologist went back to study it thoroughly. While an average mummified human had a large intestine just over an inch in diameter and generally held less than a third of an ounce of fecal matter, this mummy had an intestine four inches wide that contained 38 ounces of mummified food. This food occupied nearly a cubic foot of space in the man's pelvic girdle, crowding out the kidneys and the bladder and jamming up against the spine. "There was so much pressure from the food that there is actually an indentation in the colon from the bones of the spine," says Reinhard. "And this man must never have been able to urinate either. He had no body functions. What a horrible way to die."

Medical researchers have dubbed this painful condition megacolon. And as Reinhard explains, there are two chief causes. Children inherit the condition as part of a rare congenital disorder called Hirschsprung's disease. But adults may develop it as a result of Chagas' disease, a massive infection by a parasitic protozoan known as Trypanosoma cruzi. "The parasite attacks the nerves of the colon, and peristalsis, the normal contraction of the intestines, becomes disrupted and after a while stops," says Reinhard. "And then the intestine fills with food, the muscles of the intestinal wall lose their tonus, and the intestine becomes incredibly enlarged. The individual who is infected eventually dies, often of blood poisoning, after several months of not being able to defecate."

Chagas' is an insect-borne disease that today kills some 43,000 people annually in the Americas. It is transmitted by several members of the reduviid family, popularly known as kissing bugs. Fond of hiding in the crevices of poorly built walls, they emerge at night to seek blood. Almost any mammal will do, from guinea pigs to humans. Lured by body heat, the insects crawl onto sleepers' faces and quench their thirst, defecating as they drink. The waste is saturated with T. cruzi, and people who scratch or rub a bite risk sweeping the feces into the sore, or into their mouths or eyes. Once inside the human body, the tiny single-celled parasites swiftly spread to local lymph nodes, often triggering an acute infection. But the most serious trouble generally comes two decades or so later, when the tiny invaders have had time to storm nerve cells. More than a quarter of T. cruzi victims will develop severe cardiac disorders, often culminating in death: 1 in 17 will develop megacolon or megaesophagus.

Today most physicians view T. cruzi as a parasite of Latin America, where it thrives in villages of mud-brick houses. But as Reinhard points out, it is no stranger to North America. While the rancher's mummy is the oldest known case of T. cruzi in the United States, it is certainly not the only one. Medical authorities estimate that as many as 370,000 Latin American immigrants are infected. Moreover, physicians have reported several homegrown cases of Chagas' disease in the southern United States, a region that is home to at least 17 species and subspecies of kissing bugs. In Texas alone, state epidemiologists have gathered records on at least six endemic cases, the most recent diagnosed just last year. And this probably represents only a small fraction of actual cases. Although a survey conducted in Texas in the late 1970s revealed the protozoan swimming in the blood of 2.4 percent of 500 longtime residents living in the Rio Grande Valley, Chagas' disease is frequently overlooked when physicians diagnose heart disorders.

Moreover, T. cruzi is a parasite with a future in the United States. Epidemiologists are particularly concerned about blood-borne transmission. But a few researchers wonder about the potential breeding ground for T. cruzi in transient communities known as colonias that have sprung up along the southern borders of Texas, New Mexico, and Arizona. There, kissing bugs fly into the makeshift houses through open unscreened windows. Inside they find walls riddled with the cracks and crevices they love. "Every year," says Kate Hendricks, an epidemiologist at the Texas Department of Health, "we try to recruit officers from the Epidemic Intelligence Service of the Centers for Disease Control, and I tell them I'd like them to work on Chagas' disease, but I've never gotten one to do it."

With neither a vaccine nor a cure to offer once the infection is well established, health officials are now trying to combat the plague in Latin America by improving housing conditions and stamping out the vector with insecticides. But opponents of the plan point out that similar tactics failed in the 1960s with another major insect-borne disease, malaria. As researchers sprayed houses and mosquito breeding grounds, they spawned strains immune to insecticides. Fearing that something similar could happen with Chagas', opponents suggest that the best defense is more knowledge about the murky origins of the protozoan and its spread.

Studies of mummies, says Reinhard, supply several critical new clues. Using molecular probes to search for the DNA of T. cruzi in tissue samples from 27 mummies in the region, Felipe Guhl of the University of the Andes, in Bogota, Colombia, and his associates found the protozoan in 11 of 25 tissue samples well enough preserved for testing. The oldest dated to 4,000 years ago. The emergence of T. cruzi at that time, says Reinhard, is telling. Some 4,000 to 5,000 years ago, Andean societies embarked on one of the world's great agricultural revolutions. Sowing manioc, potatoes, and corn along the rivers that flowed year-round from the nearby Andes, Atacama families settled in hamlets and built houses with walls of reed-lined adobe. Inside they tended broods of domesticated guinea pigs.

And as they reinvented themselves as farmers, says Reinhard, kissing bugs and T. cruzi were waiting. The new houses served as reduviid incubators, filled with food. "In a study done in a later site in the Moquegua Valley of Peru," notes Reinhard, "Juan Rofes found an average of 15 guinea pigs per house. That's a great potential source for disease. If you have 15 guinea pigs and a family of seven people in a house, that gives you 22 hosts for the kissing bug to transfer the disease."

Nor was T. cruzi the only indigenous menace to attack ancient Americans. Along the Arctic coast, families who dined on the raw meat of polar bears became infected with Trichinella nativa, a potentially fatal roundworm that caused pneumonia, encephalitis, meningitis, brain damage, and heart failure. In what is now Utah and Nevada, hunters who snacked on camel crickets were soon infested with Moniliformis clarki, a thorny-headed worm that caused severe intestinal pain. And in South America, freshwater-crab eaters were plagued with Paragonimus mexicanus, a lung fluke that sometimes fatally invaded human heart and brain tissue.

But few societies in the ancient Americas carried as many parasites in their bodies as the Chinchorro of Chile, whose children perished so young and whose morticians were kept so busy. Reinhard's studies are yielding important clues to their misery. While poring over feces from nearly two dozen Chinchorro accidentally mummified by the desert heat, Reinhard spied the tiny translucent eggs of Diphyllobothrium pacificum, an intestinal tapeworm that can grow as long as 16 feet. A common parasite of sea lions, D. pacificum enters the ocean when one of its hosts defecates into the water. From there it climbs back up the food chain, infecting crustaceans, crustacean-eating fish, and finally fish-loving sea lions and humans. Although cooking, drying, and other methods of food preparation can kill parasites, including D. pacificum, many cultures prefer their food raw.

Today, on the coasts of Chile and Peru, where people consume a lot of infected seafood, the worm does serious harm. Outcompeting its human hosts for vitamin [B.sub.12] when it randomly chooses to attach high in the intestine, D. pacificum can trigger an insidious condition known as pernicious anemia. Those left untreated produce defective red blood cells and are soon stricken with porous bones, weakness, and finally death.

TO WHAT DEGREE THE ANCIENT CHINCHORRO SUFFERED this extreme form of anemia is still not entirely clear. But Reinhard's studies show that the early coastal dwellers relied extensively on fish for their survival: at least 32 percent of the food in their bowels at the time of death was fish. And new evidence from a University of Nevada team suggests that the early Chinchorro knew pernicious anemia well. Twenty-five percent of more than 300 skeletons revealed traces of two bone diseases caused by this anemia. To Reinhard, it seems possible that sea lion tapeworms drained the life from the Chinchorro.

Reinhard's studies of the worm are also helping pave the way for a new theory of parasite evolution. For years, he explains, researchers assumed that the goal of all parasites was to become specialists finely tuned to the physiology of just one host. To pull off this feat, reasoned researchers, parasites needed two things: a populous host spread over a broad area, and enough time to evolve these specializations--1,000 to 2,000 years. But in his studies of D. pacificum, says Reinhard, he detected no sign of such adaptations, even though the worm had clearly enjoyed at least 10,000 years of contact with a bountiful supply of human hosts spread along the Chilean and Peruvian coasts.

In the mid-1990s, says Reinhard, parasitologists at the University of Nebraska began promoting a new model, based on data with modern parasites. "They argued that there are two very different and mutually exclusive methods for parasites to establish and survive in hosts. The first is for parasites to become specialists. And the second is for a parasite to become morphologically and physiologically diverse so it can inhabit a lot of different animals." To Reinhard, D. pacificum clearly fitted the latter scheme, as did all but one of the other parasites known to have evolved in the New World. "So D. pacificum has been an important temporal indication of a new paradigm to parasitology," says Reinhard. "This specialist-generalist paradigm is more valid than we thought in the past."

The tapeworm may also have led an even earlier people to an idea that still haunts us. Surrounded by the slowly crumbling bodies of the Chinchorro in Arica, Bernardo Arriaza muses over the silent dead and the reasoning that gave rise to the world's first mummies. It is possible, he says, that the Chinchorro sculpted, painted, and preserved their dead as a way of staking claim to the land of their ancestors. And it is also possible that they went to such lengths to create human shrines that could be petitioned for divine assistance. Or the earliest mummies may reflect something far more elemental and enduring--the inconsolable grief of a parent. The earliest known Chinchorro mummies, after all, are those of children.

As a scientist, Arriaza has little evidence to settle the matter one way or another. But as a person, he can't help being moved by all the mummified children. "It's the emotion of love that's represented in these," he says finally, shaking his head. "Taking all this care to mummify infants and even a little fetus. That is very, very touching. It's hard to distance yourself. It's not just an artifact. It was a human being they were trying to preserve."

HEATHER PRINGLE

("The Sickness of Mummies," page 74) is a freelance writer in Vancouver, British Columbia, who specializes in archeology. "The people at the mummy congress had some of the world's best anecdotes," she says. "A French researcher told of a Romanera mummy found in France in the fifties. The body was so perfectly preserved, she said, that when the scientists pulled out the tongue, it snapped immediately back into place. Amazed villagers deemed it a saint and began stealing its teeth as relics." Pringle is the author of In Search of Ancient North America. She wrote about the origins of cash in October.

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