When Justin arrived at the hospital, he already had parasites in his brain. The nurses gave him injections of melarsoprol for three days, and the medicine wiped out a fair number of the trypanosomes in his brain and spine. But as a result, his brain and spine had been flooded with scraps of dead parasite tissue, driving his immune cells from a torpor to a frenzy. They shot out blasts of poisons, which scorched Justin’s brain. The inflammation they triggered was squeezing it like a vise.
Now Richer prescribed steroids for Justin to try to bring the swelling down. Justin whimpered remotely as the needleful of steroids went into his arm, his eyes closed as if he were deep in a bad dream. If he was lucky, the steroids would take pressure off his brain. The next day would telclass="underline" either he would be better or he would be dead.
Before I arrived at Justin’s bedside, I had been traveling with Richer for a few days, watching her at work. We had gone to villages where her staff was spinning blood in centrifuges, looking for the signature of the parasite. We had driven for hours to get to another clinic of hers, where people were getting spinal taps to see if the trypanosomes were on their way to the brain. We had made the rounds of the Tambura hospital, seeing other patients: little children who had to be held down for injections as they screamed, old women bearing up silently as the medicine burned into their veins, a man made so crazy by the medicine that he had taken to attacking people and needed to be tied to a post. And from time to time—and now, as I looked at Justin—I tried to see the parasites inside them. It brought to mind that old movie Fantastic Voyage, in which Raquel Welch and her fellow crewmates climb into a submarine that is then squinched down to microscopic size. They are injected into a vein in a diplomat’s body so that they can travel through his circulatory system to his brain and save him from a life-threatening wound. I had to enter that world, made of underground rivers, where the currents of blood follow ever-smaller branches of arteries until they pass back around into the veins, joining up to larger veins until they reach the surging heart. Red blood cells bounced and rolled along, squeezing through capillaries and then rebounding to their original puck shapes. White blood cells used their lobes to crawl into the vessels through lymphatic ducts, like doorways disguised as bookshelves in a house. And among them traveled the trypanosomes. I have looked at trypanosomes under a microscope in a Nairobi laboratory, and they are quite beautiful. Their name comes from trypanon, the Greek word for an augur. They are about twice as long as a red blood cell, silvery under a microscope. Their bodies are flat, like a strip, but as they swim they spin like drill bits.
Parasitologists who spend enough time looking at trypanosomes in laboratories tend to fall in love with them. In an otherwise sober scientific paper, I came across this sentence: “Trypanosoma brucei has many enchanting features that have made this parasite the darling of experimental biologists.” Parasitologists watch the trypanosomes as carefully as an ornithologist watches ospreys, while the parasites gulp glucose, while they evade the pursuit of immune cells by tossing off their coat and putting on a new one, while they transform themselves into new forms that can survive in the gut of a fly and then transform back into a form perfectly adapted for human hosts.
Trypanosomes are only one of many parasites inside the people of southern Sudan. If you could travel Fantastic Voyage–style through their skin, you would probably come across marble-sized nodules where you’d float past coiled worms as long as snakes and as thin as threads. Called Onchocerca volvulus, these animals, male and female, spend their ten-year-long lives in these nodules, making thousands of babies. The babies leave them and travel within the skin, in the hope that they’ll get taken up in the bite of a black fly. In the black fly’s gut they can mature to their next stage, and the insect can then inject them in the skin of a new host, where they will form a nodule of their own. As the babies swim through a victim’s skin they can trigger a violent attack from the immune system. Rather than kill the parasite, though, the immune system puts a rash of leopard spots on the skin of its host. The rash can get so itchy that people may scratch themselves to death. When the worms wander through the outer layer of the eyes, the immune system’s scarring can leave a person blind. Since their larvae are aquatic, black flies tend to stay around water, and the disease has thus earned the name river blindness. There are some places in Africa where river blindness has claimed the eyes of just about every person over forty.
Then there are Tambura’s guinea worms: two-foot-long creatures that escape their hosts by punching a blister through the leg and crawling out over the course of a few days. Then there are filarial worms that cause elephantiasis, which can make a scrotum swell up until it can fill a wheelbarrow. Then there are tapeworms: eyeless, mouthless creatures that live in the intestines, stretching as long as sixty feet, made up of thousands of segments, each with its own male and female sex organs. There are leaf-shaped flukes in the liver and the blood. There are single-celled parasites that cause malaria, invading blood cells and exploding them with a fresh new generation hungry for cells of their own. Stay long enough in Tambura, and people around you turn transparent and become glittering constellations of parasites.
Tambura is not as freakish as it might seem. It’s just a place where you can find parasites thriving in humans with particular ease. Most people on Earth carry parasites, even if you set aside bacteria and viruses. Over 1.4 billion people carry the snakelike roundworm Ascaris lumbricoides in their intestines; almost 1.3 billion carry blood-sucking hookworms; 1 billion have whipworm. Two or three million die of malaria a year. And many of these parasites are on the rise, not the wane. Richer may be slowing down the spread of sleeping sickness in her little patch of Sudan, but around her it seems to be spreading. It may kill three hundred thousand people a year; it probably kills more people in the Democratic Republic of Congo than AIDS. Parasitically speaking, New York is actually more freakish than Tambura. And if you step back and survey our evolution from an apelike ancestor 5 million years ago, the past century of parasite-free living that some humans have enjoyed is a fleeting reprieve.
I checked in on Justin the following day. He was propped up on his side, eating broth from a bowl. His back was lazily curved along the bed as he ate; his eyes were no longer swollen; his neck was supple again; his nose was clear. He was still exhausted and was far more interested in eating than in talking to strangers. But it was good to see that the fleeting reprieve included him as well.
Visiting places like Tambura, I began to think of the human body as a barely explored island of life, home to creatures unlike anything in the outside world. But when I remembered that we are just one species out of millions on this planet, the island swelled up to a continent, a planet.
A few months after my trip to Sudan, on a night that wavered between muggy and rainy, I walked through a Costa Rican jungle. I held a butterfly net in my hand, and the pockets of my raincoat spilled over with plastic bags. The headlamp on my brow cast a slanted oval on the path in front of me, which a spider crossed twenty feet ahead. Its eight eyes glinted together like a single diamond chip. A giant solitary wasp crawled slowly into its burrow on the side of the path to hide from my glare. The only light beyond my lamp came from distant lightning and the fireflies that glowed for long slow flashes in the trees overhead. The grass gave off the rank odor of jaguar urine.