Onchocerciasis-associated epilepsy and biomarkers

There is increasing international recognition that onchocerciasis-associated epilepsy (OAE) is an important public health problem in onchocerciasis-endemic areas where onchocerciasis elimination programmes were either absent or functioning sub-optimally [1].In several recent population-based studies, it was shown that OAE (which includes the nodding syndrome (NS)) is preventable by strengthening onchocerciasis elimination efforts [2][3][4][5].However, the pathogenesis of OAE remains to be elucidated [6].So far, little was known about the immunological processes associated with OAE.In a recent PNTD paper, Arndts et al. [7] describe the immune profile (cytokine, chemokine, and immunoglobulin levels) of persons with epilepsy including NS that were examined at the Mahenge epilepsy clinic in Tanzania between November 2014 and April 2015.Profiles of persons with epilepsy were compared with profiles of individuals without neurological disorders residing in the same endemic area.In all study participants, skin snips were collected and tested for Onchocerca volvulus presence using PCR.Study participants were classified into three groups: Persons with epilepsy (including NS)-O.volvulus PCR-negative, persons with epilepsy (including NS)-O.volvulus PCR-positive, and controls without neurological disorders-O.volvulus PCR-negative.Cytokines, most chemokines, and three neurodegeneration markers were comparable between O. volvulus infected and uninfected participants with epilepsy.However, elevated eosinophil percentages with increased eosinophilic cationic protein (ECP) and antigen-specific IgG levels were observed within the O. volvulus-positive epilepsy/ NS group.In addition, the highest levels of the O. volvulus-related metabolic product (NATOG) were found in O. volvulus-positive NS persons.We applaud the efforts of Arndts and collaborators to investigate an extensive panel of immunological markers in persons with epilepsy including NS.However, we recommend caution in drawing conclusions from their findings, since their study lacked a crucial group for comparison: onchocerciasis-infected individuals without any epileptic disorder.Moreover, they should have categorised the epilepsy/NS group into persons with OAE including NS and persons with other types of epilepsy to investigate whether they can be distinguished based on immune profile.Mahenge area is an onchocerciasis-endemic area with a high prevalence of epilepsy, up to 3.5% in certain rural villages (8) with a high proportion of them (77.9%)meeting the criteria for OAE (9).In 2014-15, when the samples were collected at the Mahenge epilepsy clinic, most rural villages had no health facilities nor a constant supply of anti-seizure medication.Therefore, in order to obtain anti-seizure medication persons with epilepsy had to attend the