Peer reviewed research news

Is a parasitic worm the solution to the mystery and misery of nodding syndrome?

A debilitating form of children’s epilepsy may be caused by an autoimmune response triggered by infection with a parasitic worm, suggests a new study published this week in Science Translational Medicine

The exact cause of Nodding syndrome, which is characterised by neurological deterioration, stunted growth, seizures and the nodding of the head, has long been a mystery. The condition is found mostly in children between five and 15 years old in areas of Tanzania, Uganda and South Sudan.

It was first identified in the 1960’s and little is known about the exact cause or the true number of children affected by the disease. Previous studies have suggested an epidemiological association with Onchocerca volvulus, the parasitic worm that causes onchocerciasis also known as river blindness.


A microfilarial Onchocerca volvulus larvae – Photo credit: CDC/Dr Lee Moore

The parasite is carried by black flies and clusters of Nodding syndrome cases have been found in areas where these insects live and transmit onchocerciasis . Yet, there is still little evidence that the worms themselves were capable of invading the human nervous system and causing the symptoms associated with Nodding syndrome.

The researchers at the U.S. National Institute of Neurological Disorders and Stroke had a theory that nodding syndrome may be an autoimmune-mediated disease, where the body attacks its own healthy cells and tissues, triggered when the worm infects a person.

They compared serum samples from patients in Uganda with Nodding syndrome and healthy controls who lived in the same village.

The researchers found that people with Nodding syndrome were more likely to have high levels of auto antibodies to leiomodin-1, a protein found in the human brain, than the control group. They also found these antibodies in the cerebrospinal fluid of those with Nodding syndrome.

On further investigation in the laboratory, the study team discovered that these antibodies were neurotoxic when they were introduced to healthy neurons, in other words they were attacking healthy human tissue.

The researchers also found that the same antibodies found in patients also attached to proteins from the parasitic worm.

These proteins were shown to be structurally very similar to leiomodin-1 in humans, suggesting that the worm itself could be molecularly mimicking the hosts to avoid detection by the host’s immune system.

According to the researchers, these results suggest that the immune system creates antibodies to fight off the parasite, but as they also bind to leiomodin-1, the person’s own immune system will attack brain cells that contain that protein, which may then cause the symptoms of Nodding syndrome.

“These results may ultimately provide a diagnostic test, which can help identify individuals at risk for developing Nodding syndrome,” said Dr Tory Johnson, the lead author of the study.

The clinical director of the NIH’s National Institute of Neurological Disorders and Stroke, Avindra Nath, M.D. said: “The findings also suggest that therapies targeting the immune system may be effective treatments against this disorder and possibly other forms of epilepsy.”

He added: “Another huge implication of the study is that exterminating black flies and getting rid of the parasite should top the disorder from occurring.”

Johnson TP et al. Nodding syndrome as an autoimmune reaction to Onchocerca volvulus. Science Translational Medicine. February 15, 2017.

The OZ’s news cheat sheet

What’s this about ? Don’t tell me to go and read the article it’s been a long day.

Researchers have found more evidence to support a link between the disease called river blindness and a devastating neurological condition in children known as Nodding syndrome. Essentially, they think that our own immune system incorrectly attacks our nervous system when we are infected with the worm. The research suggests that the worm has a similar protein to one found in our brains so our immune system scores a spectacular own goal when it produces antibodies to fight the parasite.

Didn’t we know this already?

No. That said, the researchers do not claim to be the first to link river blindness and nodding syndrome.

Will this directly affect me?

It’s unlikely at this stage, even if you do live, work or visit the affected regions in Tanzania, Uganda and The Republic of South Sudan.  It will take lots of time and research and development before they can start rolling out a treatment but this work may lead to a diagnostic test in the future.

Why are you bothering to tell me then?

Well you looked bored and I bet you didn’t know what Nodding syndrome was without looking it up.

Ok, of course you knew what it was. As you know, it’s a horrible condition that causes disability and death and it doesn’t get talked about much.  It’s exciting that something is being done to find out the cause and develop a treatment.

If you’re interested you can read more about Nodding syndrome, river blindness or just check out the original journal article.