Nodding syndrome and epilepsy in onchocerciasis endemic regions: comparing preliminary observations from South Sudan and the Democratic Republic of the Congo with data from Uganda

Abstract

BackgroundNodding syndrome (NS) is an epilepsy disorder occurring in children in South Sudan, northern Uganda and Tanzania. The etiology of NS is unknown, but epidemiological studies demonstrate an association between NS and onchocerciasis.MethodsBetween November 2013 and July 2015 we visited onchocerciasis endemic regions in South Sudan, Uganda, and the Democratic Republic of the Congo (DRC) to assess the epilepsy situation. In South Sudan we interviewed patients and affected families, health officials, colleagues and healthcare workers, and performed a small household survey to estimate the epilepsy prevalence in the village of Mvolo, Western Equatoria State. Most information from Uganda was collected through discussions with colleagues and a review of published literature and reports. In the Bas-Uélé district of the DRC, we visited the villages of Liguga, Titule and Dingila, interviewed patients with epilepsy and family members and conducted a preliminary entomological assessment.ResultsIn South Sudan there is an ongoing NS and epilepsy epidemic in the Western Equatoria state that started around 1990. A survey of 22 households in Mvolo revealed that 28 out of 168 (16.7 %) children suffered from NS or another form of epilepsy. Thirteen (59 %) households had at least one child, and nine (41 %) households at least two children with NS or another form of epilepsy. In northern Uganda, an NS and epilepsy epidemic started around 2000. The occurrence of new NS cases has been in decline since 2008 and no new NS cases were officially reported in 2013. The decline in NS cases coincided with the bi-annual distribution of ivermectin and the treatment of blackfly-breeding rivers with larvicides. In Bas-Uélé district in the DRC, epilepsy appears to be endemic with cases clustered in villages close to blackfly-infested, rapid-flowing rivers. The majority of epilepsy cases in Liguga, Dingila and Titule presented with generalized (tonic–clonic) seizures without nodding, but with mental retardation. In Titule, an epilepsy prevalence of 2.3 % was documented. The only anthropophilic species of blackfly collected in the region belonged to the Simulium damnosum complex.ConclusionBlackflies may play a key role in the transmission of an etiological agent that either directly or indirectly cause, not only NS, but also other forms of epilepsy in onchocerciasis endemic regions.

Nodding Syndrome in Onchocerciasis Endemic Areas

“…In a study in Cameroon, the prevalence of epilepsy and the community microfilarial load (the geometric mean number of Onchocerca volvulus (OV) microfilariae per skin snip among adults aged 20 years and over in the community) were closely related, and microfilarial loads in patients with epilepsy were significantly higher than in controls [3]. In villages in onchocerciasis endemic regions in the Democratic Republic of the Congo, we observed a prevalence of epilepsy of >2% [4], while prevalence in nonendemic African regions is <1% [5].…”

“…In Mvolo, a village in South Sudan, we found that one in six children suffered from OAE and 50% of the families had at least one child with OAE [4]. Children are the social security of the family in these regions, therefore, having one or more affected children in the family has a huge impact on the family income and status.…”

Onchocerciasis‐associated epilepsy: From recent epidemiological and clinical findings to policy implications

“…In this situation, because children with OAE will become adults and very few new children will develop OAE, the highest prevalence of epilepsy will be observed among the age group between 20 and 30 years and not among the 10‐ to 20‐year age group before the introduction of CDTi . In most places in Africa, epilepsy is associated with increased mortality because children with epilepsy often die at a young age from drowning, burn injuries, status epilepticus (itself due to lack of access to anti‐epileptic treatment), or neglect, malnourishment, or infections …”

“…Most patients with OAE present with generalized primarily tonic‐clonic seizures, clinically not different from seizures of another etiology. The main differences between OAE and other forms of epilepsy are the time of onset, between the ages of 3 and 18 years (mean age 8–12 years), the fact that persons with epilepsy live in villages with high Ov transmission, and the fact siblings in the family often are also affected by epilepsy . The reason why some children present with generalized tonic‐clonic seizures without other symptoms and others present with NS or features of Nakalanga syndrome is not clear.…”

“…Indeed, if we consider that the onchocerciasis infection is poorly controlled in 30% of the 37 million people infected, and that 1% of those develop epilepsy (equivalent to the approximate excess prevalence of epilepsy over nononchocerciasis areas), the number of OAE cases could be more than 100,000 . In Mvolo, a village in South Sudan, one in six children suffer from epilepsy and at least 50% of the families have at least one child with epilepsy . Untreated OAE may lead to further cognitive and physical decline due to uncontrolled seizures and possibly neglect .…”