Persons with onchocerciasis‐associated epilepsy and nodding seizures have a more severe form of epilepsy with more cognitive impairment and higher levels of Onchocerca volvulus infection

Abstract

Following previous reports of very high epilepsy prevalence in the onchocerciasis-endemic villages in Maridi County, South Sudan, a study was conducted to investigate the association between the level of Onchocerca volvulus infection, epilepsy, and related outcomes. Methods. In December 2018, persons with epilepsy (PWE) were recruited from villages where an epilepsy prevalence of 4.4% (range: 3.5-11.9%) was documented. We enrolled 318 participants from whom two skin snips were taken for microscopic detection of O. volvulus microfilariae (mf). Seizure history was obtained for all PWE and their degree of disability assessed using the modified Rankin scale.Results. Almost all (84.9%) PWE had detectable mf in their skin snips. Onchocerciasis-infected PWE experienced nodding seizures more often than uninfected PWE (p=0.034). Moreover, persons with nodding seizures

Onchocerca volvulus and epilepsy: A comprehensive review using the Bradford Hill criteria for causation

“…Based on a meta-analysis of 8 population-based epilepsy surveys performed in 7 different countries, Pion and colleagues [5] calculated that, on average, the prevalence of epilepsy increased by 0.4% for each 10% increase in onchocerciasis prevalence. A higher microfilarial density was found to be associated with NS, a more severe form of OAE [84].…”

“…Hence, the different clinical presentations of OAE (NS, Nakalanga syndrome, and other forms of epilepsy) may be related to the age at which children become infected with O. volvulus and their microfilarial density. In a recent study in South Sudan, persons with NS were found to have more disabilities and to have higher microfilarial densities than persons with other forms of OAE [84]. In areas where Onchocerca ochengi is endemic among cattle, humans when bitten by O. ochengiinfected blackflies may develop some immunity toward O. volvulus [85,86], and therefore, in such areas, children may develop lower O. volvulus microfilarial loads and consequently less NS and Nakalanga which are characterized by high microfilarial densities.…”

Effect of Ivermectin Treatment on the Frequency of Seizures in Persons with Epilepsy Infected with Onchocerca volvulus

“…This could be due to the higher pre-ivermectin mf density among PWE in Maridi, which was probably due to the prolonged CDTI interruption in South Sudan. High mf densities have been shown to be associated with more severe forms of OAE, with more seizures and disabilities [ 20 ]. In a recent randomised trial among people infected with O. volvulus who are also PWE, seizure freedom was more often observed in the last 4 months of a one year trial in those who received two or three doses of ivermectin compared to only one dose [ 11 ].…”

Case Report: Nakalanga Syndrome Revisited: Long-Term Follow-Up of a Patient Living in Western Uganda, 1994–2018

“…18 With regard to nodding syndrome, increasing evidence supporting a causal relation with onchocerciasis was gathered from several areas: 1) A positive correlation between onchocerciasis endemicity level and prevalence of nodding syndrome was demonstrated in the Itwara area 13 and in the Mahenge focus of southern Tanzania 26,27 ; 2) Case-control studies consistently found a positive association between O. volvulus infection status and nodding syndrome [28][29][30] ; 3) As for Nakalanga syndrome, in the Itwara focus, no new cases of nodding syndrome were found after elimination of onchocerciasis by community-directed treatment with ivermectin and vector control 18 ; 4) A recent study from southern Sudan demonstrated that patients with nodding syndrome had higher microfilarial counts in skin biopsy, more frequent seizures, and more severe cognitive disability than persons with other forms of epilepsy. 31 Additional evidence that O. volvulus can damage the brain originated from numerous epidemiological studies on the relationship between onchocerciasis and epilepsy at large. These demonstrated that throughout the endemic areas of sub-Sahara Africa, epilepsy prevalence increases at an exponential rate with that of onchocerciasis, 32 that there is a robust positive association between O. volvulus infection status and epilepsy, 33,34 and that the risk of a young individual exposed to onchocerciasis of developing epilepsy is increasing with infection intensity.…”