Cause of mysterious ‘nodding syndrome’ may have been discovered


In parts of Eastern Africa children in some communities have been afflicted by a mysterious condition. When given food or experiencing bouts of cold weather, they are struck by a strange form of epilepsy that makes the children uncontrollably nod their heads. Known as ‘nodding syndrome, the condition eventually gets worse, with the children suffering more severe seizures leading to disability and occasionally death.

Over a 23 year period from 1990 to 2013, thousands of children suddenly came down with the condition in South Sudan and Uganda, leading a team of researchers to start investigating the cause of the syndrome. It turns out that this strange form of epilepsy may be down to a parasitic worm common in the region, and the cause of another prevalent disease.

Known scientifically as Onchocerca volvulus, the nematode worm is usually associated with the neglected tropical disease, river blindness. Found mainly in sub-Saharan Africa, it is thought that up to 120 million people are at risk from the disease, which is spread by the bite of the black fly in which the worm spends half its life cycle. It tends to cause severe itching of the skin, development of bumps under the skin, and can eventually lead to a thickening of the cornea that causes blindness.

Now, in a new paper published in Science Translational Medicine, researchers suggest that it could also be responsible for nodding syndrome, by over-stimulating the immune system that then attacks the neurons. They are careful to note that they have not proven that this is the case, but they found evidence that those with the syndrome were much more likely to have a particular antibody that targets a protein called leiomodin-1.

This protein is found in smooth muscle and thyroid cells, but it is also present in brain tissue and the nervous system. But more importantly, it also closely resembles other proteins typically found on the surface of O. volvulus nematodes. The researchers suspect that the immune system may have originally been launching an attack against the worm, but then got confused and mistook the proteins on the body’s own neurons for the parasite.

The cases closely resemble another situation seen in Tanzania, where in the 1960s doctors suggested that children experiencing epileptic seizures and nodding symptoms may well have been related to the presence of river blindness.

This means that the mysterious nodding illness could, in theory, be easily treated by ridding the children of the nematodes, which should also stop the seizures. There has been a push for the treatment of river blindness to be expanded, which is achieved using the drug ivermectin, something that non-government organisation, the Carter Centre is now working towards.

This story was sourced from the IFL Science website.


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