For the children of Gwagwalada, the river that runs alongside their town is a choice destination. Never mind that their parents forbid them to play in the water, never mind that the water is infested with tiny flatworms that take up residence in their intestines.
There is nothing much to do, after all, in this area to the west of Abuja, Nigeria’s capital city, nor a better way to stay cool when the temperature soars.
But on a hot day in November, in the low-slung buildings of a government school in Gwagwalada, dozens of students told aid workers they had fevers, blood in their stool or urine and abdominal and body pains — the symptoms of an illness called schistosomiasis, or bilharzia.
The students who reported symptoms, and those who did not, all received doses of a drug called praziquantel that treats the illness. This strategy — called mass drug administration — is endorsed by the World Health Organization for any region where more than one in five residents has schistosomiasis.
Gwagwalada more than meets the W.H.O. criteria. When children return to the river to swim, and adults turn to it as a water supply, “they cannot really avoid contact and reinfection,” said Amadou Garba Djirmay, who oversees the schistosomiasis program at the W.H.O.
“The main strategy is this treatment to really cure the majority of them,” he said.
Thought to affect 200 million people globally, schistosomiasis is considered one of the most important parasitic infections worldwide, second only to malaria. Yet it is still what is called a neglected tropical disease, meaning that it attracts nowhere near the funding or the attention that killers like malaria do.
Campaigns to identify and treat schistosomiasis worldwide face formidable hurdles. Praziquantel is not consistently available, and it can have unpleasant side effects, like a bitter taste that may cause gagging or vomiting. Swallowing the pill whole after a meal minimizes the side effects, but many affected families cannot afford regular meals and do not have access to clean water.
It is also unclear how schistosomiasis will fare when the money available for global health is greatly reduced. The Trump administration’s budget for 2026 eliminates support for neglected tropical diseases and sharply cuts funds for many others.Schistosomiasis is so little known that many doctors in Nigeria do not recognize its symptoms, said Louise K. Makau Barasa, a senior director at the End Fund, a nonprofit organization focused on neglected diseases.
“It’s really a visibility problem,” she said.
In 2014, before the drugs to treat schistosomiasis were distributed en masse, the prevalence in Gwagwalada was 52 percent. It dropped to about 39 percent in 2024, but rose in some other areas.
The river in Gwagwalada is speckled with tiny freshwater snails that harbor the larvae of parasitic worms called schistosomes. Fork-tailed larvae released from the snails penetrate children’s skin as they bathe, swim or frolic in the water. The larvae travel to their bowels, where they mature into half-inch-long adult worms.
The adult worms produce eggs that become established in various tissues of the body — including, in rare cases, the eyes.
At the school on that November day, Rinpan Ishaya, an aid worker with the nonprofit group HANDS, abruptly stopped talking to look closely at the face of a student, Mohammed Aliyu, a socially awkward 11-year-old.
“Look at his eyes,” Mr. Ishaya said.
They looked pale, stiff and bulgy. In a barely audible voice, Mohammed said yes, his eyes were often itchy and he sometimes felt some odd movements around them.
Mohammed had previously had a case of schistosomiasis. He is not much of a talker. He had felt a burning sensation when he urinated and had blood in his urine and stool for almost three years before his mother, Amina Aliyu, realized that there was a serious problem, and then only because he was constantly scratching his eyes.
“Some people are slow,” she said of her son, matter-of-factly.
Children in Nigeria contend with many types of worms. They may lose their vision because of a roundworm, carried by flies, that causes river blindness, or their limbs may swell because of tiny parasitic worms, or helminths, spread by mosquitoes. More than half of Nigerian children harbor helminths acquired from soil infested with the worms’ eggs.
Soil-transmitted helminths can cause anemia, weight loss and stunted growth, but they are generally not fatal. Schistosomiasis leads to many of the same problems, but left untreated, it can seriously damage the liver and intestines, cause infertility and lead to bladder cancer.
Praziquantel is often distributed with mebendazole, a treatment for soil-transmitted helminths, because some children may harbor more than one type of worm. Mass drug administration by schools and communities is hotly contested in the case of some other worms, but much less so for schistosomiasis.
When Mohammed complained about his eyes, Ms. Aliyu took him to several doctors, who examined him and gave him eyeglasses. She grew up in a small village where most people she knew, including her brothers, had the illness at some point, she said. But she now lived in a neat home in the city, with marble floors and clean water. It did not occur to her that her son could have the same disease again. “I was very surprised,” she said.
At the school, the volunteers dispensed one to five tablets of praziquantel, based on a child’s height. Only about 60 percent of the 644 enrolled students were at school that day, so the others would still need to be treated, either at Gwagwalada’s sole clinic, which serves 50,000 people, or by volunteers who go home to home.
The clinic’s volunteers help run campaigns year round — measles in the hot season, diarrhea in the rainy season and schistosomiasis in the dry season, from October to March.
The Gwagwalada program has not been immediately affected by the Trump administration’s cuts to foreign aid, said Sam Macintosh, a vice president for the End Fund. But, he said, “we know the same health systems that we support are stretched much further now, and we are likely to see a bigger impact on programs in 2026.”
Without clean water and other changes to accompany the treatment programs, the effectiveness of the drugs is already limited.
Perhaps the biggest hurdle, though, is to change people’s behavior. Baseera Salinhu has had repeated bouts of schistosomiasis over the last six years. The third of five children, Baseera’s disease was diagnosed and treated three years ago at the community health center.
Last year, when the normally voluble girl again turned quiet and began complaining of nausea and blood in her urine, her mother, Halimatu Salihu, recognized the signs. The symptoms seemed especially severe in that round, but her mother had neither the money nor the time to take her to the clinic.
She was relieved when Baseera brought home a consent form for praziquantel from school, and was so impressed with the pills she sought them out from the community health center as a preventive measure for herself.
Baseera is once again seeing urine in her blood, but she is back at the river with her friends. “She doesn’t listen,” her mother said.
Apoorva Mandavilli reports on science and global health for The Times, with a focus on infectious diseases and pandemics and the public health agencies that try to manage them.
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