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Pediatric Oncall Journal

Onchocerciasis endemicity and childhood epilepsy in rural Cameroon 01/15/2024 00:00:00

Onchocerciasis endemicity and childhood epilepsy in rural Cameroon

Siewe Fodjo JN1,2,3, Njamnshi WY1,3,4, Ngarka L1,4,5, Njamnshi AK1,4,5.
1Brain Research Africa Initiative (BRAIN), Geneva, Switzerland & Yaoundé, Cameroon,
2Global Health Institute, University of Antwerp, Antwerp, Belgium,
3Department of Health Operations Research, Ministry of Public Health, Yaoundé, Cameroon,
4Neuroscience Lab, Faculty of Medicine & Biomedical Sciences, The University of Yaoundé I, Yaoundé, Cameroon,
5Deparment of Neurology & Clinical Neuroscience, Yaoundé Central Hospital, Yaoundé, Cameroon.

Dr. Joseph Siewe Fodjo, BRAIN Cameroon, Yaounde, 0000, CAMEROON.
Onchocerciasis, Epilepsy, Cameroon.
We read with interest Enyama et al.’s paper describing persons with epilepsy (PWE) in Ntui from the clinical and management perspectives.1 While their title is emphatic on the endemicity of onchocerciasis in the study site, regrettably little is discussed regarding its association with epilepsy. We recently conducted door-to-door surveys in the same Ntui health district and found that epilepsy prevalence ranged from 3.5-5.1% in the study villages, with epilepsy and onchocerciasis correlating positively.2 Furthermore, two cohort studies conducted by our group have confirmed the association between these two conditions in the Mbam-Sanaga valley (Cameroon), with a clear temporality and dose-effect: infection with Onchocerca volvulus occurring first and exposed/infected individuals developing epilepsy later in a parasitic load-dependent fashion.3,4 Analysis of available evidence on onchocerciasis and epilepsy using the Bradford Hill criteria strongly supports a causal role of onchocerciasis in epilepsy development, in what is now known as “onchocerciasis-associated epilepsy” (OAE).5
It is likely that over 90% of epilepsy cases encountered in the Mbam area (Cameroon) are associated with onchocerciasis, with reports of typical phenotypic presentations of OAE like the nodding syndrome and Nakalanga syndrome.2,6 The findings of Enyama et al.,1 showing that other risk factors for childhood epilepsy such as prolonged labour (15% of PWE) and resuscitation at birth (7.5%) are rather infrequent in this area, confirm the argument we have put forward for the important role of onchocerciasis for epilepsy prevalence in these areas. The occurrence of epilepsy in another member of the same nuclear family was common (84.1%) in the Enyama et al. study1 and could be erroneously interpreted as a genetic trait in favour of familial epilepsy. A more plausible explanation would be that several cases occur in the same household due to the proximity of their residence to blackfly breeding sites thereby increasing the risk for all individuals in that household of acquiring O. volvulus infection and potentially developing OAE depending on the intensity of the environmental exposure and consequent microfilarial load. This is supported by the inverse relationship between epilepsy prevalence and distance from the river (blackfly breeding sites) observed in Ntui2 and the household clustering of PWE which has been reported in several onchocerciasis-endemic settings.7,8 In Maridi (South Sudan), villages/households close to blackfly breeding sites were most affected by epilepsy, even among immigrants with no previous personal/ancestral history of epilepsy.8
To address the epilepsy problem in onchocerciasis-endemic rural areas, a comprehensive approach integrating components from both epilepsy care and interventions against a predominant risk factor – onchocerciasis is required.9 Community-based strategies for PWE follow-up and general public sensitization will help to reduce the epilepsy treatment gap and facilitate the social rehabilitation of affected children, including school attendance. Beyond optimising therapeutic coverage during the annual community-directed treatment with ivermectin, alternative strategies for onchocerciasis prevention must be instituted to accelerate elimination prospects; for instance, the “slash and clear” vector control intervention which we recently implemented in Ntui (Mbam), with the aim of breaking the O. volvulus transmission cycle and ultimately reducing OAE incidence in the at-risk communities.10

Compliance with Ethical Standards
Funding None
Conflict of Interest None
  1. Enyama D, Koum DCK, Tounde BT, Njinkui DN, Mapoure YN. Challenges in the Management of Childhood Epilepsy in a Rural Area with Endemic Onchocerciasis in Cameroon. Pediatr Oncall. 2024;21(2). doi:10.7199/ped.oncall.2024.19.  [CrossRef]
  2. Ngarka L, Siewe Fodjo JN, Ambomatei C, et al. Epidemiology of epilepsy and relationship with onchocerciasis prevalence in villages of the Ntui Health District of Cameroon. Epilepsy Behav. 2023;142:109184. doi:10.1016/j.yebeh.2023.109184.  [CrossRef]  [PubMed]  [PMC free article]
  3. Chesnais CB, Nana-Djeunga HC, Njamnshi AK, et al. The temporal relationship between onchocerciasis and epilepsy: a population-based cohort study. Lancet Infect Dis. 2018;18(11):1278-1286. doi:10.1016/S1473-3099(18)30425-0.  [CrossRef]  [PubMed]
  4. Chesnais CB, Bizet C, Campillo JT, et al. A second population-based cohort study in Cameroon confirms the temporal relationship between onchocerciasis and epilepsy. Open Forum Infect Dis. Published online June 2, 2020:ofaa206. doi:10.1093/ofid/ofaa206.  [CrossRef]  [PubMed]  [PMC free article]
  5. Colebunders R, Njamnshi AK, Menon S, et al. Onchocerca volvulus and epilepsy: A comprehensive review using the Bradford Hill criteria for causation. Bennuru S, ed. PLoS Negl Trop Dis. 2021;15(1):e0008965. doi:10.1371/journal.pntd.0008965.  [CrossRef]  [PubMed]  [PMC free article]
  6. Siewe Fodjo JN, Ngarka L, Tatah G, et al. Clinical presentations of onchocerciasis-associated epilepsy (OAE) in Cameroon. Epilepsy Behav. 2019;90:70-78. doi:10.1016/j.yebeh.2018.11.008.  [CrossRef]  [PubMed]
  7. Lenaerts E, Mandro M, Mukendi D, et al. High prevalence of epilepsy in onchocerciasis endemic health areas in Democratic Republic of the Congo. Infect Dis Poverty. 2018;7(1). doi:10.1186/s40249-018-0452-1.  [CrossRef]  [PubMed]  [PMC free article]
  8. Colebunders R, Carter JY, Olore PC, et al. High prevalence of onchocerciasis-associated epilepsy in villages in Maridi County, Republic of South Sudan: A community-based survey. Seizure. 2018;63:93-101. doi:10.1016/j.seizure.2018.11.004.  [CrossRef]  [PubMed]  [PMC free article]
  9. Siewe Fodjo JN, Dekker MCJ, Idro R, et al. Comprehensive management of epilepsy in onchocerciasis-endemic areas: lessons learnt from community-based surveys. Infect Dis Poverty. 2019;8(1). doi:10.1186/s40249-019-0523-y.  [CrossRef]  [PubMed]  [PMC free article]
  10. Fodjo JNS, Vieri MK, Ngarka L, et al. 'Slash and clear' vector control for onchocerciasis elimination and epilepsy prevention: a protocol of a cluster randomised trial in Cameroonian villages. BMJ Open. 2021;11(9):e050341. doi:10.1136/bmjopen-2021-050341.  [CrossRef]  [PubMed]  [PMC free article]


Cite this article as:
JN S F, WY N, L N, AK N. Onchocerciasis endemicity and childhood epilepsy in rural Cameroon. Pediatr Oncall J. 2024;21. doi: 10.7199/ped.oncall.2024.13
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