Onchocerciasis and River Epilepsy in 2022

A special issue of Pathogens (ISSN 2076-0817). This special issue belongs to the section "Parasitic Pathogens".

Deadline for manuscript submissions: closed (31 December 2022) | Viewed by 8343

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Laboratory of Embryology & Biotechnology, Université Libre de Bruxelles, Gosselies, Belgium
Interests: onchocerciasis; parasite biology; nematodes
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Dear Colleagues,

Onchocerciasis-associated morbidity, and more specifically, onchocerciasis-associated epilepsy (OAE), is a major neglected public health problem in many remote areas of Africa with high transmission rates or where control and elimination programmes based on mass drug administration (MDA) of ivermectin may be weaker or have only started more recently. It is estimated that in Africa, there are approximately 300,000 persons with OAE, which could have been prevented through improved onchocerciasis elimination efforts.

Despite strong epidemiological evidence that O. volvulus is able to trigger seizures, the pathophysiological mechanism of how this may happen remains obscure. Direct invasion of parasites in the central nervous system seems unlikely since no O. volvulus microfilariae or DNA could be detected in the cerebrospinal fluid of persons with OAE, nor in brain samples from persons who died of OAE. It has been suggested that neurotoxic cross-reacting O. volvulus antibodies may play a role, but this has not been confirmed. O. volvulus releases a wide range of excretory/secretory products (ESPs) into the host environment. However, very little is known about the function of these ESP. A better knowledge of the biology of O. volvulus seems to be critical to elucidate the pathophysiology of OAE.

For this Special Issue of Pathogens, we invite you to submit research articles, review articles, short notes, as well as communications that could contribute to a better understanding of the link between onchocerciasis and epilepsy. This includes papers about the epidemiological and clinical aspects of OAE, potential pathophysiological mechanisms, basic research about O. volvulus, and, very importantly, research about how to prevent and treat river epilepsy. We look forward to your contribution.

Prof. Dr. Robert Colebunders
Prof. Dr. Jacob Souopgui
Guest Editors

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Keywords

  • onchocerciasis
  • epilepsy
  • pathogenesis
  • epidemiology
  • ivermectin

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Published Papers (3 papers)

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Research

10 pages, 1130 KiB  
Article
High Prevalence of Glaucoma among Patients in an Onchocerciasis Endemic Area (Mahenge, Tanzania)
by Juliet Otiti-Sengeri, Blair Andrew Omaido, Dan Bhwana, Damalie Nakanjako, Malik Missiru, Musa Muwonge, Luis-Jorge Amaral, Bruno P. Mmbando and Robert Colebunders
Pathogens 2022, 11(9), 1046; https://doi.org/10.3390/pathogens11091046 - 14 Sep 2022
Cited by 1 | Viewed by 1901
Abstract
Onchocerciasis is known to cause skin lesions and blindness, but there is also epidemiological evidence that onchocerciasis is associated with epilepsy, including nodding syndrome. We carried out ocular exams in persons with epilepsy in Mahenge, an onchocerciasis endemic area with a high prevalence [...] Read more.
Onchocerciasis is known to cause skin lesions and blindness, but there is also epidemiological evidence that onchocerciasis is associated with epilepsy, including nodding syndrome. We carried out ocular exams in persons with epilepsy in Mahenge, an onchocerciasis endemic area with a high prevalence of epilepsy in Tanzania. We recruited 278 consecutive persons with epilepsy attending the epilepsy clinic at Mahenge hospital and satellite clinics in rural villages. They underwent a general physical and a detailed ocular examination and were tested for onchocerciasis Ov16 IgG4 antibodies. Glaucoma was defined by a raised intraocular pressure above 21 mmHg with evidence of typical glaucomatous disc changes in one or both eyes. Among the 278 participants, median age 27 (IQR 21–38) years, 55.4% were female; 151/210 (71.9%) (95% CI: 65.3–77.9) were Ov16 positive. The most frequent ophthalmic lesions were glaucoma (33.1%), vitreous opacities (6.5%) and cataracts (2.9%). In multivariate analysis, glaucoma (adjusted IRR = 1.46; 95% CI: 1.24–1.70) and age (adjusted IRR = 1.01; 95% CI: 1.01–1.02) were significantly associated with onchocerciasis. In conclusion, a high prevalence of glaucoma was observed among Ov16 positive persons with epilepsy. Persons with epilepsy with O. volvulus infection should undergo screening for glaucoma to prevent one of the causes of preventable blindness. Full article
(This article belongs to the Special Issue Onchocerciasis and River Epilepsy in 2022)
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17 pages, 1868 KiB  
Article
The Prevalence of Onchocerciasis-Associated Epilepsy in Mundri West and East Counties, South Sudan: A Door-to-Door Survey
by Stephen Raimon Jada, Alfred Dusabimana, Gasim Abd-Elfarag, Samuel Okaro, Nele Brusselaers, Jane Y. Carter, Makoy Yibi Logora, Jacopo Mattia Rovarini, Charles R. Newton and Robert Colebunders
Pathogens 2022, 11(4), 396; https://doi.org/10.3390/pathogens11040396 - 24 Mar 2022
Cited by 15 | Viewed by 3161
Abstract
A two-phase survey of epilepsy was conducted in selected villages in Mundri West and East Counties (26 June–8 July, 2021), an onchocerciasis-endemic area in Western Equatoria State in South Sudan. In the first phase, households were visited by a trained research team to [...] Read more.
A two-phase survey of epilepsy was conducted in selected villages in Mundri West and East Counties (26 June–8 July, 2021), an onchocerciasis-endemic area in Western Equatoria State in South Sudan. In the first phase, households were visited by a trained research team to identify persons suspected to have epilepsy. In the second phase, persons suspected to have epilepsy were interviewed and examined by a clinician to confirm the diagnosis. A total of 364 households agreed to participate in the survey, amounting to 2588 individuals. The epilepsy screening questionnaire identified 91 (3.5%) persons with suspected epilepsy, of whom the diagnosis of epilepsy was confirmed by a clinician in 86 (94.5%). The overall prevalence of confirmed epilepsy was 3.3% (95% CI: 2.7–4.1%), and of nodding syndrome was 0.9% (95% CI: 0.6–1.4%). In 61 (16.8%) households there was at least one person with epilepsy. Only 1212 (46.9%) of 2583 people took ivermectin during the last distribution round in 2021. The annual epilepsy incidence was 77.3/100,000 (95% CI: 9.4–278.9/100,000) and the annual epilepsy mortality was 251.2/100,000 (95% CI: 133.8–428.7/100,000). In conclusion, a high prevalence and incidence of epilepsy was observed in villages in Mundri. Urgent action is needed to prevent children from developing onchocerciasis-associated epilepsy by strengthening the local onchocerciasis-elimination programme. Full article
(This article belongs to the Special Issue Onchocerciasis and River Epilepsy in 2022)
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16 pages, 1671 KiB  
Article
Surveillance for Onchocerciasis-Associated Epilepsy and OV16 IgG4 Testing of Children 6–10 Years Old Should Be Used to Identify Areas Where Onchocerciasis Elimination Programs Need Strengthening
by Alfred Dusabimana, Joseph Nelson Siewe Fodjo, Michel Mandro Ndahura, Bruno P. Mmbando, Stephen Raimon Jada, Annelies Boven, Eric De Smet, Tony Ukety, Alfred K. Njamnshi, Anne Laudisoit, Steven Abrams and Robert Colebunders
Pathogens 2022, 11(3), 281; https://doi.org/10.3390/pathogens11030281 - 23 Feb 2022
Cited by 7 | Viewed by 2633 | Correction
Abstract
To eliminate onchocerciasis-associated morbidity, it is important to identify areas where there is still high ongoing Onchocerca volvulus transmission. Between 2015 and 2021, door-to-door surveys were conducted in onchocerciasis-endemic villages in Cameroon, the Democratic Republic of Congo (DRC), Nigeria, South Sudan, and Tanzania [...] Read more.
To eliminate onchocerciasis-associated morbidity, it is important to identify areas where there is still high ongoing Onchocerca volvulus transmission. Between 2015 and 2021, door-to-door surveys were conducted in onchocerciasis-endemic villages in Cameroon, the Democratic Republic of Congo (DRC), Nigeria, South Sudan, and Tanzania to determine epilepsy prevalence and incidence, type of epilepsy and ivermectin therapeutic coverage. Moreover, children aged between six and 10 years were tested for anti-Onchocerca antibodies using the Ov16 IgG4 rapid diagnostic test (RDT). A mixed-effect binary logistic regression analysis was used to assess significantly associated variables of Ov16 antibody seroprevalence. A high prevalence and incidence of epilepsy was found to be associated with a high Ov16 antibody seroprevalence among 6–10-year-old children, except in the Logo health zone, DRC. The low Ov16 antibody seroprevalence among young children in the Logo health zone, despite a high prevalence of epilepsy, may be explained by a recent decrease in O. volvulus transmission because of a decline in the Simulium vector population as a result of deforestation. In the Central African Republic, a new focus of O. volvulus transmission was detected based on the high Ov16 IgG4 seropositivity among children and the detecting of nodding syndrome cases, a phenotypic form of onchocerciasis-associated epilepsy (OAE). In conclusion, Ov16 IgG4 RDT testing of 6–10-year-old children is a cheap and rapid method to determine the level of ongoing O. volvulus transmission and to assess, together with surveillance for OAE, the performance of onchocerciasis elimination programs. Full article
(This article belongs to the Special Issue Onchocerciasis and River Epilepsy in 2022)
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