With his dark hair, burnt-sienna skin, and flashing teeth, he looked like an actor off the set of Lawrence of Arabia.
In fact, he was a career military man far from home. Major Ali Al Rahim was a Saudi Arabian pilot assigned to two years of elite training at an air base in southern California. He was pleased with his posting, but he had a problem: unrelenting cramps and diarrhea. "Could it be the food?" he wondered. Some days after lunch he shuttled from flight lab to lavatory nearly every hour.
The major's gut had plagued him for years, but never like this. After seeing the base medic, he began taking anti-motility drugs. But the problems didn't go away, so he returned to the clinic time and again. Then he showed up one day with a tender belly and a bloody stool.
That's when an official request went forth. Would the Saudi consul OKa visit with Mark Griffin, a top gastroenterologist at the university hospital where I work? Yes, the answer came back. One week later, Mark performed Major Al Rahim's colonoscopy. The next day, I was paged.
"Claire, you won't believe it when you see this guy's biopsies," Mark said. "At first when I 'scoped him, I thought his mucosa was a dead ringer for ulcerative colitis: hemorrhagic, cobblestoned, eroded. Forget that. Under the microscope, he's loaded with worms."
Worms--including roundworms, tapeworms, and flukes--hold a special place among the human body's invaders. For one thing, they're big, measuring anywhere from one quarter of an inch to more than three feet. They also exploit nature, sometimes using intermediate hosts like fish and snails to further their life cycles. And once they've made their way into a host, many species have sex and lay eggs.
When I looked at the major's biopsies, I could see male and female worms entwined in the intestinal tissue. Deposited nearby were rust-brown worm eggs with lateral spines. With a little imagination, the eggs looked like human heads with beaked noses pointed sideways.
To a parasitologist like me, that profile is the hallmark of just one species: Schistosoma mansoni.
The biopsies offered living proof: Major Al Rahim was infected with a strain of fluke that, together with four related species, constitutes the world's most deadly worm scourge. Currently, there are some 200 million people with schistosomiasis worldwide. And because water development projects such as dams and irrigation systems actually aid schistosomes' spread, the number of infected people in developing countries may rise in coming decades.
Freshwater is the prime milieu of schistosomes. Consider the fate of schistosome eggs passed in stool. If an infected human defecates in or near freshwater, the eggs rupture, releasing embryos. Propelled by microscopic beating hairs called cilia, the embryos home like stealth bombs to freshwater snails. Once invaded, the snails transform into parasite hatcheries that over the ensuing weeks produce thousands of fork-tailed baby schistosomes. The newborns, called cercariae, have up to 48 hours to penetrate human skin or die trying.
Now picture life in the tropics, where schistosomes thrive. Countless human pastimes--bathing, fishing, washing clothes--entail water contact. If cercariae are nearby, they can breach the skin in just three to five minutes, no cut or crack required. They then pierce capillaries and bodysurf the bloodstream to reach their beachhead: the veins lacing the human bladder and gut.
Adult schistosomes measure a quarter to three quarters of an inch long. Most dwell in humans for five to 10 years, although a hardy few survive two or three decades. Whether short- or long-lived, they copulate nonstop once settled into their venous burrows. Except, that is, when the female fluke briefly detaches from the male's vertical cleft (the "schist") to lay eggs. A mature, partnered S. mansoni
female deposits 100 to 300 eggs per day.
In considering Major Al Rahim's case, schistosome eggs were my real worry. Like buckshot, they scatter through the abdomen and pelvis, sometimes also lodging in the lungs, brain, and spinal cord. Surrounding each egg are pinpoints of inflammation that eventually coalesce into scars. When a human has been infected with schistosomes for years, the end result can be pain, blood-tinged urine, diarrhea, a swollen liver and spleen, and--in the worst case scenario--dilated esophageal veins called varices that can spurt like oil wells.
With Major Al Rahim's heavy worm load, I figured his tissue egg counts were astronomical. Any complication was possible. And so I took extra care performing his physical examination.
"Does it hurt here?" I asked when I got to his lower abdomen. The major answered with a wince as I pressed right over his inflamed colon. Then my fingers came upon the fleshy peninsula of an enlarged liver extending below his ribs on the right. Inwardly, I grimaced. The evidence for advanced inflammation of the liver and spleen--the chronic immune response to the schistosome eggs--was growing stronger.
"First we'll do a baseline abdominal CT scan," I told the major, "then we'll order up your pills."
In most parts of the world affected by schistosomiasis, X rays and scans have little place in managing the disease. The best use of limited health care resources in such settings is simply mass treatment. Every six to 12 months, for example, groups of Egyptian schoolchildren in the Nile delta receive praziquantel, a safe and effective antihelminthic drug given by mouth.
Our technology-rich health care system in the United States, however, operates differently. When we're treating patients with exotic ailments, high-tech resources can sometimes teach us new lessons about old diseases.
That was my reasoning when I sent Major Al Rahim for a full scan of his intra-abdominal organs. As I'd expected, his liver was diffusely scarred and his spleen was twice the normal size. Left untreated, his illness could easily progress within a few years to full-blown esophageal varices and fatal hemorrhage. Because the major could be assigned anywhere around the world, I worried where he might be when the dam broke.
I treated the major with two courses of praziquantel, and months later I repeated his scan. Much to my amazement, his swollen organs looked normal. For the first time in nearly a year, he said, his diarrhea and cramps were gone.
Finally he could focus full attention on his military assignment. And yes, he assured me, he would continue taking praziquantel over the next several years to wipe out the final traces of the worms.
At that point, my job was done. But one nagging question remained. How on Earth, I asked, did Major Al Rahim pick up schistosomiasis in the first place? After all, he had grown up in a desert.
"Yes, of course," the major said, with a grin, "the earth was dry most of the year. But, remember, my home was also an oasis. When the waters came, like any boy, naturally I splashed and played."
Ah, yes. Mystery solved.
Find an overview--and gripping images--of all stages of the schistosome life cycle at the University of Cambridge's Web site: www.path.cam.ac,uk/~tjs16/home-page.html