In 2009, the Centers for Disease Control and Prevention (CDC) received a plea from officials in Uganda: Could the agency investigate a mysterious head-nodding disease spreading among more than 3,000 young people there? Healthy children would suddenly begin to nod their heads uncontrollably, sometimes falling into a trancelike state. The incidents seemed to be triggered by food, so eating was a struggle for the victims; some were dying of malnutrition as a result.
“We saw families lock their children in their homes or tie them to trees to prevent them from injuring themselves while the family was working,” says the CDC’s Scott Dowell, an infectious disease specialist charged with finding the cause.
Examining the children with brain scans, Dowell determined the spells were seizures like those seen in epilepsy. But what was the cause? Blood and urine tests ruled out hundreds of viruses, as well as hepatitis E, measles, heavy-metal poisoning, tainted bush meat, and vitamin B12 deficiency.
In August, the World Health Organization and the CDC cosponsored a four-day conference in Uganda’s capital, Kampala, to identify new lines of research. One clue is that sufferers of a disease called river blindness are much more likely to have nodding syndrome as well. That cast suspicion on Onchocerca volvulus, a parasitic worm transmitted by black flies that breed in sub-Saharan rivers (among other places). The worm’s larvae can trigger damage in the eyes, leading to river blindness if untreated.
Autopsies could determine directly whether they also cause brain damage in nodding disease sufferers, the CDC says. Infection with O. volvulus may be just one of the triggers, Dowell adds. He suspects that vitamin B6 deficiency, known to cause a severe form of epilepsy, might contribute as well.