Onchocerciasis-associated epilepsy in the Democratic Republic of Congo: Clinical description and relationship with microfilarial density

Background High epilepsy prevalence and incidence were observed in onchocerciasis-endemic villages in the Democratic Republic of Congo (DRC). We investigated the clinical characteristics of onchocerciasis-associated epilepsy (OAE), and the relationship between seizure severity and microfilarial density. Methods In October 2017, ivermectin-naive persons with epilepsy (PWE) were recruited from onchocerciasis-endemic areas in the Logo health zone in the DRC. Additional PWE were enrolled in the Aketi health zone, where ivermectin had been distributed annually for 14 years. Past medical history, clinical characteristics and skin snips for Onchocerca volvulus detection were obtained from participants. Bivariate and multivariable analyses were used to investigate associations with microfilarial density. Results Of the 420 PWE in the Logo health zone, 392 were skin snipped (36.5% positive). Generalized motor seizures were most frequent (392 PWE, 93.3%), and nodding seizures were reported in 32 (7.6%) participants. Twelve PWE (3.1%) presented Nakalanga features. Sixty-three (44.1%) skin snip-positive PWE had a family history of epilepsy, compared to only 82 (32.9%) skin snip-negative PWE (p = 0.027). Eighty-one onchocerciasis-infected PWE were recruited in the Aketi health zone. Positive correlations between seizure frequency and microfilarial density were observed in Logo (Spearman-rho = 0.175; p<0.001) and Aketi (Spearman-rho = 0.249; p = 0.029). In the multivariable model adjusted for age, gender, and previous treatment, high seizure frequency was associated with increasing microfilarial density in Aketi (p = 0.025) but not in Logo (p = 0.148). Conclusion In onchocerciasis-endemic regions in the DRC, a wide spectrum of seizures was observed. The occurrence of Nodding seizures and Nakalanga features, as well as an association between seizure severity and O. volvulus microfilarial density suggest a high OAE prevalence in the study villages. Trial registration ClinicalTrials.gov NCT03052998. Author summary Several epidemiological surveys suggest that onchocerciasis (a disease resulting from an infection with the parasite Onchocerca volvulus) is a cause of epilepsy. We conducted a study to describe the clinical characteristics of persons with epilepsy (PWE) living in onchocerciasis-endemic villages in the Democratic Republic of Congo. In some study sites, the frequency of seizures increased with increasing number of O. volvulus microfilariae detected in the skin snips of participants. A wide spectrum of seizures was observed, including generalized tonic-clonic seizures, absence seizures, and focal seizures. Growth retardation and household clustering of PWE were common. Specific clinical presentations such as nodding seizures and Nakalanga features were encountered. These results suggest a high prevalence of onchocerciasis-associated epilepsy (OAE) in the study villages.