The Prevalence of Epilepsy Follows the Distribution of Onchocerciasis in a West Ugandan Focus

Introduction In comparison with figures from industrialized countries, higher prevalences of epilepsy have been reported in studies from developing countries (1). Apart from neurocystocercosis due to Taenia solium, which is of relevance in some regions, little is known about specific causes to explain this difference (2). In Kabarole district, West Uganda, a high frequency of patients with epilepsy has been observed (3), and in one study this was related to the occurrence of onchocerciasis (4). However, this preliminary investigation has been criticized for a number of shortcomings (5). Epidemiological data from a population of 4700 living in a neighbouring subcounty of the same endemic focus are presented in this article. Materials and methods The study was carried out in the Kabende parish of Kabarole district, West Uganda, during the period March-June 1994. According to a government census, the parish had 4389 inhabitants in 1992. Its eastern boundary is formed by the Sogohi river, a habitat of Simulium neavei flies, the local vector for onchocerciasis (6). Towards the west, the parish is adjacent to the West Ugandan rift valley. Vegetation in the western parish consists mainly of grass and agricultural plantations, and no significant transmission of Onchocerca volvulus has been found along the small rivers towards the rift valley. People in Kabende are subsistence farmers and also earn income from work in a nearby tea plantation. A complete house-to-house census was carried out, assessing the population of each village and the age, sex, and ethnicity of inhabitants, as well as the duration of residence of the households. This was performed by elected representatives of the 12 villages of Kabende after the investigations had been discussed with them and community leaders. During the census, each household was asked if they had any cases of epilepsy, using the term for this condition in the local language without further specification. All persons thus identified were invited to present themselves at a nearby health centre for examination, together with an informant who had observed the seizures. Those who did not come to the health centre during the first two months of the study were met at a central location of their village or were visited at their homes. Patients who presented themselves directly at the health centre without having been registered as epileptic during the census were confirmed as inhabitants of the study area by use of the census list that had been compiled. A full medical history was obtained for the description, onset, and course of seizures, as well as for other illnesses and the patient's development. All interviews were conducted by a native Rutoro speaker (GA or CM), together with a doctor trained in paediatric neurology (CK). All patients also underwent a complete physical and neurological examination. Active epilepsy was defined as two or more afebrile seizures during the previous 2 years, not related to alcohol use, drug intake, or acute illness (7, 8). Crude prevalences of epilepsy were calculated based on the number of confirmed cases found by means of the examinations described above. When appropriate, these rates were also standardized by adjustment to the age distribution of a standard world population (9, 10). A serum sample was taken from patients who gave their consent. Serum samples were stored at -20[degrees]C and screened for T. solium antibodies by indirect immunofluorescence (IFT) at the Institute for Medical Parasitology, University of Bonn, Germany. Sera positive by IFT were examined additionally for Echinococcus spp. by an indirect haemagglutination assay (IHA). After completion of the epilepsy investigation, a skin-snip survey for detection of microfilariae (mf) of O. volvulus was carried out in all the study villages. One village was considered as two for this purpose, because of its size and geographical heterogeneity (villages Nos. …