Epidemiology and clinical characteristics of onchocerciasis-associated epilepsy
23 September 2020
UAntwerp online - - - - -
Joseph Siewe Fodjo
Em. Prof. R. Colebunders and Prof. A. Njamnshi
PhD defence Joseph Siewe Fodjo - Faculty of Medicine and Health Sciences
Epilepsy is a brain disorder characterized by repeated unprovoked seizures, currently affecting over 50 million individuals globally. There is a disproportionate geographical repartition of epilepsy, with 80% of cases living in low- and middle-income countries including sub-Saharan Africa. Among other reasons, infections of the central nervous system are responsible for the substantially greater burden of epilepsy in sub-Saharan Africa. Previous studies have found a high prevalence of epilepsy in areas with a high transmission of Onchocerca volvulus, the parasite that causes onchocerciasis (river blindness), although this has not yet been investigated in detail. Given the limited knowledge regarding the association between epilepsy and onchocerciasis, the NSETHIO research group (University of Antwerp, Belgium) conducted several epilepsy surveys across African villages affected differently by onchocerciasis.
Our studies confirmed that villages with high onchocerciasis transmission also have a high burden of epilepsy. Furthermore, we found that the implementation of interventions to control onchocerciasis resulted in a drastic reduction of epilepsy prevalence and incidence. A wide clinical spectrum of epilepsy was encountered in the surveyed villages, with some patients presenting with generalized seizures, focal seizures, absences, nodding syndrome (head nodding seizures associated with cognitive impairment and stunting), and/or Nakalanga syndrome (severe growth retardation, delayed sexual development, cognitive impairment and sometimes deformities). Persons with epilepsy were most often clustered in villages or households closest to the breeding sites of the blackfly insects which transmit O. volvulus. Our findings lead us to conclude that the different epileptic conditions encountered in the study villages are most likely onchocerciasis-related, and all fall under the umbrella of onchocerciasis-associated epilepsy (OAE). Sadly, OAE cases mostly occurred in remote, poverty-confronted communities with limited access to healthcare.
OAE currently causes a significant disease burden in villages with high onchocerciasis transmission. Fortunately, OAE is preventable by strengthening onchocerciasis elimination programs by ensuring frequent mass drug administration of the drug ivermectin to treat onchocerciasis-infected persons, and/or by destroying blackfly breeding sites to prevent the transmission of the parasite. We recommend that scientists and health decision-makers should urgently enlist OAE on their agenda so as to prioritize research and interventions aimed at treating and preventing OAE in onchocerciasis foci.