Research Article: From river blindness to river epilepsy: Implications for onchocerciasis elimination programmes

Date Published: July 18, 2019

Publisher: Public Library of Science

Author(s): Robert Colebunders, Joseph Nelson Siewe Fodjo, Adrian Hopkins, An Hotterbeekx, Thomson L. Lakwo, Akili Kalinga, Makoy Yibi Logora, Maria-Gloria Basáñez, Marc P. Hübner. http://doi.org/10.1371/journal.pntd.0007407

Abstract: None

Partial Text: Current onchocerciasis elimination programmes do not include identification and management of onchocerciasis-associated epilepsy (OAE) in their strategies. Creating awareness about OAE will increase community-directed treatment with ivermectin (CDTI) adherence, particularly in areas of high prevalence, while motivating funders and stakeholders not to relent their efforts in the fight against onchocerciasis. Strengthening onchocerciasis elimination efforts should be prioritised wherever epilepsy prevalence is high in order to reduce OAE-related morbidity and mortality. In such areas, alternative treatment strategies including biannual CDTI, ground larviciding of blackfly breeding sites, and/or treatment with moxidectin should be considered. Addressing the OAE disease burden in these generally remote onchocerciasis-endemic regions confronted with poverty, weak healthcare infrastructures, and insecurity goes beyond current onchocerciasis elimination plans. New strategies with appropriate budgets are required. A morbidity management and disease prevention (MMDP) strategy, fully integrated into the health system, must be developed by multidisciplinary working groups involving neglected tropical disease (NTD) and epilepsy specialists, advocacy experts, and persons from affected communities. ‘River epilepsy’ needs to be urgently recognised and placed in the international development and NTD agendas.

The possibility of an association between onchocerciasis (river blindness) and epilepsy (leading to the term ‘river epilepsy’; https://en.ird.fr/the-media-centre/scientific-newssheets/onchocercosis-or-river-epilepsy) has been suggested for a long time [1], but this link has not yet been fully embraced by the scientific community and stakeholders involved in onchocerciasis control. Consequently, intervention programmes targeting elimination of onchocerciasis as a public health problem do not take into account OAE. Table 1 summarises the OAE criteria [2].

There is increasing epidemiological evidence that onchocerciasis is, directly or indirectly, a cause of epilepsy [2]. The strongest evidence to date was recently obtained in a retrospective cohort study conducted in the Mbam valley in Cameroon, which showed that the risk of developing epilepsy later in life was positively associated with skin microfilarial density in early childhood, demonstrating not only a temporal directionality from Onchocerca volvulus infection to subsequent epilepsy but also a strong dose–response relationship [3].

Regardless of opinions on causality, OAE is an important neglected public health problem, placing a large burden on patients and their caretakers. It has been estimated that in 2015, c. 381,000 people could be affected by OAE across all onchocerciasis-endemic areas [7]. Moreover, OAE may increase onchocerciasis-related mortality among children and adolescents. In a 25-year follow-up study of 295,909 individuals in the Onchocerciasis Control Programme (OCP) in West Africa, not only did the relative risk of mortality increase with skin microfilarial density but also, for a given density, this risk was statistically significantly higher in individuals younger than 20 years than in those aged above 20 [8]. Although this needs further investigation, this excess mortality under 20 years could be due, at least in part, to the consequences of epileptic seizures associated with onchocerciasis; indeed, children usually develop OAE at a peak age of 8–11 years [2], while river blindness generally occurs after the age of 20 [9]. Onchodermatitis may develop earlier, but it is not a fatal condition.

Major progress has been made concerning the control of onchocerciasis, initially by the OCP (1974–2002) and subsequently by the African Programme for Onchocerciasis Control (APOC, 1995–2015) and the Onchocerciasis Elimination Program for the Americas (OEPA, 1993–ongoing) [14]. New cases of blindness and severe skin disease are rare except in conflict zones, where instability has had a detrimental impact on programmes’ performance, and in areas of difficult access [15]. CDTI has indeed been very successful in many areas, and since 2010, the paradigm of onchocerciasis control has shifted to that of elimination [16].

Current onchocerciasis elimination strategies need to be revised and retargeted, taking OAE into account. As onchocerciasis-related blindness is gradually disappearing, it has been more difficult to maintain interest and financial support for CDTI programmes. If the 2025 elimination goals are to be met, ivermectin coverage must be increased, and people should be encouraged to continue taking the drug. Creating awareness and community engagement about OAE is paramount for increasing adherence to CDTI and for policy makers in the health sector to strengthen their onchocerciasis elimination strategies [4,20].

Although some countries have strategies for controlling epilepsy, these are rarely implemented outside of large cities and certainly not in the more remote onchocerciasis-endemic areas. Local epilepsy management must, therefore, depend on local nonphysician staff such as nurses working at primary healthcare facilities or community workers; this strategy is currently being encouraged by the Mental Health Gap Action Programme (mhGAP) of WHO (https://apps.who.int/iris/bitstream/handle/10665/250239/9789241549790-eng.pdf;jsessionid=6010FA3D98E95B3003B61D3C30184F0C?sequence=1), targeted to nonspecialized healthcare providers working at first- and second-level healthcare facilities. These personnel would need to be trained in case identification and simple management protocols. Follow-up could easily be undertaken by CDDs. These CDDs can also be engaged for sensitisation at the community level to enhance antiepileptic treatment adherence by PWE, and their treatment reports would facilitate regular reordering of the necessary supplies. These extra duties could be included in CDD retraining sessions at relatively little extra cost.

These examples illustrate the importance of i) investigating and documenting epilepsy in onchocerciasis meso- and hyperendemic foci, ii) channelling these findings through NOECs to the Ministries of Health and appropriate authorities, iii) establishing collaborations between NTD and mental health programmes, and iv) leveraging additional resources necessary to treat PWE and strengthen existing onchocerciasis elimination programmes (Fig 1).

In onchocerciasis-endemic foci, it is common to find households in which several children present with epilepsy, especially in families residing and/or farming in land close to blackfly breeding sites. Intense exposure to O. volvulus-infected vectors likely puts the children in those households at an increased risk of developing OAE [2,3]. The household clustering of PWE has led communities and local healthcare workers to wrongly believe that epilepsy is contagious and transmissible by direct contact, hence increasing stigma. Therefore, educating communities and health professionals about OAE will reduce stigma and motivate people to take ivermectin [23].

Table 2 summarises some challenges and opportunities regarding the recognition of OAE as a public health problem.

It has been stated that ‘in Africa, onchocerciasis has been eliminated as a public health problem across the length and breadth of the continent’ [14]. This may be true of river blindness, but it is certainly not for ‘river epilepsy’. In order to eliminate onchocerciasis and associated morbidity and mortality, OAE must be tackled. Existing onchocerciasis elimination frameworks cannot address the OAE burden because this requires a multidisciplinary approach and collaboration between NTD programmes, mental health programmes, local communities and funding bodies, and integration into the health system. Increasing OAE awareness, strengthening onchocerciasis elimination strategies, and developing MMDP plans are pivotal in curbing OAE. Ultimately, OAE needs to be put on the international development and NTD agendas as soon as possible. ‘River epilepsy’ must be recognised and eliminated.

Source:

http://doi.org/10.1371/journal.pntd.0007407