Association Between Onchocerciasis and Epilepsy in the Itwara Hyperendemic Focus, West Uganda: Controlling for Time and Intensity of Exposure

Abstract

In 38 pairs of epilepsy patients and controls matched for time and intensity of exposure to transmission of onchocerciasis, the presence of microfilariae in the skin of epilepsy patients was found insignificantly elevated compared with controls (odds ratio = 1.68; 95% confidence interval [CI] = 0.60–4.57; P = 0.31). This difference was more pronounced when detection of subcutaneous nodules was used as indication of infection with Onchocerca volvulus (odds ratio = 2.77; 95% CI = 0.92–8.33; P = 0.065). These findings from a patient group of limited size suggest that intensity of infection may play a substantial role in the development of onchocerciasis-associated epilepsy. Our results are in contrast to the results of two other independent studies from the identical endemic area; one case concluded a significant positive correlation between onchocerciasis and epilepsy, and the other case concluded a clearly negative correlation. Studies with a greater sample size are needed to confirm this possible relationship.

Case-control Studies on the Relationship between Onchocerciasis and Epilepsy: Systematic Review and Meta-analysis

“…Out of these records, 16 articles, medical theses and abstracts representing 11 studies were found to include a control group for the investigation of a relationship between onchocerciasis and epilepsy [18], [20], [29]–[42]. Two records, each representing an additional eligible study [43], [44], and one unpublished congress abstract [45] containing relevant information about one of the above-mentioned studies were identified in other sources.…”

“…Among these studies, heterogeneity in ORs was significant (Cochrane's Q test: p<0.001) and yielded an I 2 value of 65.7%. Data on the prevalence of nodules in PWE and PWOE was provided in four studies [20], [39], [40], [44] from which we calculated a pooled OR of 1.74 (95%CI: 0.94–3.20, p = 0.076) (Table 2). Between-studies heterogeneity was not significant (p = 0.093) and I 2 was assessed as 53.3%.…”

“…When looked at more closely, the most extreme results included in this review originated from two studies carried out in the same endemic area in Western Uganda with a time interval of only one year [18], [19]. The discrepancy between the results of these studies was most likely due to shortcomings in study design and the selection of comparison groups [20].…”

Nodding Syndrome, Western Uganda, 1994

“…11 This parish of 4,743 inhabitants is situated in the Itwara onchocerciasis focus, with a prevalence of microfilaria (mf) carriers ranging from 15% to 85% in the 10-20 years age group of its 13 villages in 1994. 11 A detailed description of the epidemiology of onchocerciasis and epilepsy in Kabende parish can be found in our previous publications, [11][12][13][14] and detailed maps of the entire Itwara focus are presented by Garms and others. 15 All patients who were registered in the survey underwent a thorough clinical assessment.…”

In Response: A Call for More Case-Controlled Studies on Onchocerciasis and Epilepsy

“…Unfortunately, in this publication, the number of subcutaneous nodules was communicated only for the complete sample but not separately for patients and controls 4. In view of the intriguing consistency between the above-mentioned investigations from Cameroon2 and Uganda,3 it would be of interest to know the exact result of nodule palpations carried out in the Central African Republic by Druet-Cabanac and others 4…”