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Ways to mitigate the public health problem caused by onchocerciasis-associated epilepsy

Onchocerciasis, known as river blindness, is a neglected tropical diseases caused by a filarial worm Onchocerca volvulus (O. volvulus) and is transmitted by blackflies through the repeated bites of the genus Simulium. In onchocerciasis-endemic areas mainly in sub-Saharan Africa, a high epilepsy prevalence of 2−8% has been documented, which is considerably higher than the median prevalence of epilepsy in Africa of 1.4%. Recent data suggest that onchocerciasis is linked with epilepsy, so-called onchocerciasis-associated epilepsy (OAE). OAE affect children between 3 to 18 years. OAE affected children present, in addition to epilepsy, often cognitive impairment, severe stunting and delayed puberty. This PhD research aimed to better understand the link between onchocerciasis and epilepsy and to investigate ways to mitigate the public health impact caused by OAE. Despite many years of onchocerciasis elimination efforts with mass drug administration of ivermectin treatment, there is still high ongoing onchocerciasis transmission in certain areas. We found that a higher intensity of O. volvulus infection was associated with a lower parasitological ivermectin response. Moreover, our findings suggest that the high ongoing onchocerciasis transmission in certain areas may be the consequence of sub-optimal functioning of the onchocerciasis-elimination programme. We demonstrated that onchocerciasis antibody positivity among 6-10-year-old children (a proxy for ongoing O. volvulus transmission), epilepsy prevalence and incidence, and ivermectin therapeutic coverage in an onchocerciasis endemic area could be used to identify areas where onchocerciasis-elimination programmes need to be strengthened or introduced. We also showed that a community-based epilepsy treatment programme in an onchocerciasis endemic areas in Ituri, in the Democratic Republic of Congo was able to positively change the communities’ perceptions and attitudes towards persons with epilepsy and empowered the local health care workers to manage epileptic seizures. Our studies show that the current high prevalence of OAE is a consequence of sub-optimal performance of onchocerciasis-elimination programmes. Onchocerciasis elimination programs should prioritize their efforts towards onchocerciasis-endemic regions with a high epilepsy prevalence and incidence.

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