Hundreds of children in northern Uganda have been affected by a rare and unexplained "nodding disease" that causes seizures, physical and mental stunting and at times leads to blindness and even death.
Previously reported in Southern Sudan, its cause is being investigated, according to the Ugandan health ministry. Researchers, Sébastien Pion, Michel Boussinesq and Christoph Kaiser answer questions about the disease:
QUESTION: Is the nodding disease or syndrome a form of epilepsy?
ANSWER: The head nodding syndrome (HN) has been extensively documented in a recent article by Dr Andrea Winkler and colleagues. According to these authors, to date HN is not mentioned in any clinical classification and whether this represents a seizure disorder remains unclear.
If HN is not an epileptic phenomenon, it might be a non-epileptic movement disorder which could be caused by the same underlying brain disorder causing epilepsy in most patients with HN.
In the study of Kaiser et al. from West Uganda, HN was understood as "non-classified" seizure. Because HN has so far exclusively been reported from Onchocerciasis endemic areas, the common causative agent for both phenomena may well be Onchocerca volvulus. [Onchocerciasis is often called river blindness]
Q: Why is it reported so much among children - could it mean that those afflicted die before adulthood?
A: To our knowledge, the life expectancy of people suffering from HN has not been assessed. We have been able to evaluate that the life expectancy of epileptic people living either in Central Cameroon or west Uganda was dramatically reduced compared to non-epileptic matched controls.
Since the clinical expression of HN syndrome is similar to an active form of epilepsy, it is very likely that HN is a major cause of mortality among the afflicted young people.
Q: Why might food be a trigger for the symptoms to present?
A: Cold may also act as a trigger. We do not have any answer to this point. Neurologists may have some explanations.
Q: Why did previous studies fail to find a strong statistical link between Onchocerciasis and epilepsy (in 2004 and even in 2008)?
A: The study of Winkler et al was possibly limited because it was performed in an area where ivermectin [anti-parasitic] control programmes have been conducted over several years. A clinical study such as the (excellent) study of Winkler et al. does not allow much statistical conclusions.
More case control studies with an appropriate design are needed, especially from areas not yet covered by ivermectin treatment. Possibly such studies could be performed in Northern Uganda and Southern Sudan.
There are probably many more patients suffering from this devastating disease in other highly endemic areas of Onchocerca volvulus throughout sub-Saharan Africa.
More research and publications of other kind will be helpful to bring to light the suffering of these patients. We also think that much of this suffering can be prevented because Onchocerciasis can be controlled and possibly even be eradicated.