ObjectiveWe sought to evaluate the relationship between onchocerciasis prevalence and that of epilepsy using available data collected at community level.DesignWe conducted a systematic review and meta-regression of available data.Data SourcesElectronic and paper records on subject area ever produced up to February 2008.Review MethodsWe searched for population-based studies reporting on the prevalence of epilepsy in communities for which onchocerciasis prevalence was available or could be estimated. Two authors independently assessed eligibility and study quality and extracted data. The estimation of point prevalence of onchocerciasis was standardized across studies using appropriate correction factors. Variation in epilepsy prevalence was then analyzed as a function of onchocerciasis endemicity using random-effect logistic models.ResultsEight studies from west (Benin and Nigeria), central (Cameroon and Central African Republic) and east Africa (Uganda, Tanzania and Burundi) met the criteria for inclusion and analysis. Ninety-one communities with a total population of 79,270 individuals screened for epilepsy were included in the analysis. The prevalence of epilepsy ranged from 0 to 8.7% whereas that of onchocerciasis ranged from 5.2 to 100%. Variation in epilepsy prevalence was consistent with a logistic function of onchocerciasis prevalence, with epilepsy prevalence being increased, on average, by 0.4% for each 10% increase in onchocerciasis prevalence.ConclusionThese results give further evidence that onchocerciasis is associated with epilepsy and that the disease burden of onchocerciasis might have to be re-estimated by taking into account this relationship.

ObjectiveA systematic review and meta-analysis of all available case-control studies on the relationship between onchocerciasis and epilepsy. Because age and level of onchocerciasis endemicity in the area of residence are major determinants for infection, an additional analysis was performed, restricted to studies achieving control of these confounding factors.Data sourcesMedical databases, the “African Neurology Database, Institute of Neuroepidemiology and Tropical Neurology, Limoges,” reference lists of relevant articles, commercial search engines, up to May 2012.MethodsWe searched for studies examining infection status with Onchocerca volvulus in persons with epilepsy (PWE) and without epilepsy (PWOE) providing data suitable for the calculation of pooled odds ratios (ORp) and/or standardized mean differences (SMD) using random-effects models.ResultsEleven studies providing data of qualitative skin biopsies for diagnosis of onchocerciasis were identified. Combined analysis on the total sample of 876 PWE and 4712 PWOE resulted in an ORp of 2.49 (95% confidence interval (95%CI): 1.61–3.86, p<0.001). When this analysis was restricted to those studies achieving control for age, residence and sex (367 PWE, 624 PWOE), an ORp of 1.29 (95% CI: 0.93–1.79; p = 0.139) was found. Presence of nodules for diagnosis of onchocerciasis was analyzed in four studies (225 PWE, 189 PWOE; ORp 1.74; 95%CI: 0.94–3.20; p<0.076), including two studies of the restricted analysis (106 PWE, 106 PWOE; ORp 2.81; 95%CI: 1.57–5.00; p<0.001). One study examined quantitative microfilariae counts in patients without preceding microfilaricidal treatment and demonstrated significantly higher counts in PWE than in PWOE.InterpretationOur results strengthen the hypothesis that, in onchocerciasis foci, epilepsy and infection with O. volvulus are associated. Analysis of indicators giving information on infection intensity, namely nodule palpation and quantitative microfilaria count in untreated patients, support the hypothesis that intensity of infection with O. volvulus is involved in the etiology of epilepsy.

Mortality from epilepsy was investigated in a rural area of West Uganda where epilepsy is found to be closely linked to onchocerciasis. Thirty-three female and 28 male patients (age range 4-58 years, median 15 years) were identified in a population-wide prevalence survey and were followed from June 1994 to March 2001 (observation period 3,929 person-months). Patients had continuing access to antiepileptic drug (AED) treatment with phenobarbital. Eighteen patients died during the period of observation, corresponding to a standardised mortality ratio (SMR) of 7.2 (95% CI 4.4-11.6; P<0.0001). Adherence to treatment was considered good in 36 of 56 patients receiving regular AEDs, with a SMR of 7.4 in this group compared with a SMR of 8.0 for those 20 patients considered poorly adherent. These findings show high mortality in patients with onchocerciasis-associated epilepsy despite regular AED treatment. Epilepsy appears to have a dramatic impact on this community with high Onchocerca volvulus infestation. If the suspected causal relationship between epilepsy and infection with O. volvulus could be confirmed, this would further underline the importance of sustained control efforts against onchocerciasis.

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Nakalanga syndrome is a condition that was described in Uganda and various other African countries decades ago. Its features include growth retardation, physical deformities, endocrine dysfunction, mental impairment, and epilepsy, amongst others. Its cause remains obscure. Nodding syndrome is a neurological disorder with some features in common with Nakalanga syndrome, which has been described mainly in Uganda, South Sudan, and Tanzania. It has been considered an encephalopathy affecting children who, besides head nodding attacks, can also present with stunted growth, delayed puberty, and mental impairment, amongst other symptoms. Despite active research over the last years on the pathogenesis of Nodding syndrome, to date, no convincing single cause of Nodding syndrome has been reported. In this review, by means of a thorough literature search, we compare features of both disorders. We conclude that Nakalanga and Nodding syndromes are closely related and may represent the same condition. Our findings may provide new directions in research on the cause underlying this neurological disorder.

In February 1987, 322 Sudanese school children were diagnosed for Schistosoma mansoni infection and treated randomly with praziquantel (either 20 mg/kg or 40 mg/kg body weight). A followup of these subjects was carried out in January 1989. This treatment resulted in a substantial reduction of egg output. Patients underwent complete abdominal ultrasonography and periportal fibrosis of the liver was graded into three degrees of severity. The proportion of patients with periportal fibrosis decreased from 36.6% in February 1987 to 21.7% in January 1989. At the time of followup, higher grades of periportal fibrosis (grades II and III) were encountered in only 4.3% and 0.3% of these patients, respectively, compared with 21.1% and 5.9%, respectively, before therapy. This was paralleled by a significant decrease in hepatomegaly from 10.9% to 7% of the patients. In contrast, the rate of splenomegaly showed a slight increase during the period of observation. The different dosage regimens of praziquantel did not result in a significantly different reversibility of periportal fibrosis or a decrease in egg excretion. The reversibility of specific liver lesions 23 months after antischistosomal therapy with praziquantel was substantial. The improvement was greater at 23 months than that obtained seven months after treatment.

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