Blackflies are the vectors that transmit the parasitic worm Onchocerca volvulus. This worm causes onchocerciasis or river blindness. A high prevalence of Nodding syndrome (NS) and other forms of epilepsy has been observed in onchocerciasis endemic regions in Africa for decades. Recent epidemiological studies suggest that O. volvulus is the trigger causing the seizures, which appear in previously healthy children between the ages of 3 and 18 years.
Blackflies breed in the proximity of rapid flowing rivers. Onchocerciasis-associated epilepic disorders or onchocerciasis-associated epilepsy (OAE) is therefore clustered in villages close to blackfly-breeding rivers and is therefore referred to as river epilepsy.
Persons with OAE present with a wide spectrum of seizures including atonic neck seizures (nodding), but also absences and most frequently generalized tonic-clonic seizures. Often individuals with OAE also present with intellectual disabilities and psychiatric disorders and occasionally with severe stunting with delayed or absent external signs of sexual development.
OAE is a major public health problem in many onchocerciasis endemic regions with high ongoing onchocerciasis transmission e.g. in the Democratic Republic of the Congo, Cameroon, Uganda, South Sudan, Tanzania, and the Central African Republic. It occurs in remote rural areas in Africa and involves very poor populations, often in zones where the health system is very weak and where there has been war or where there is instability. OAE is associated with severe socio-economic consequences for families. Communities often believe that people with epilepsy are possessed by evil spirits and therefore entire families may become stigmatized. Many affected children are deprived from education and quality patient care. Caretakers are left desperate and living in fear of leaving their affected children alone because some children wander away, disappear and die as a result of uncontrolled seizures that lead to drowning or burning.
NS was first documented in the United Republic of Tanzania in the 1960s, then later in the Republic of South Sudan in the 1990s and in northern Uganda in 2007. Only a relatively small number of persons with OAE present with NS. It should be considered as only one of the clinical manifestations of OAE.
OAE could be prevented by strengthening onchocerciasis elimination programs.