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Lakwo TL, Alinda P, Jada SR, Tionga M, Marcello CDR, War DGD, Colebunders R. Mvolo County, an Onchocerciasis Endemic Area in Western Equatoria State, South Sudan: An Entomological Study to Prepare for a "Slash and Clear" Community-Based Vector Control Intervention. Res Rep Trop Med 2024; 15:59-71. [PMID: 38895129 PMCID: PMC11184223 DOI: 10.2147/rrtm.s464874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Accepted: 05/17/2024] [Indexed: 06/21/2024] Open
Abstract
Background Mvolo in Western Equatoria of South Sudan has been a hotspot for Onchocerca volvulus transmission since the 1940s. In Mvolo onchocerciasis is a disease of public health importance, associated with onchocerciasis-associated epilepsy including nodding syndrome. Methods We conducted an entomological study to map the breeding sites of blackflies (Simulium damnosum, sensu lato) on the river Naam, to allow the removal of vegetation from vector breeding sites, the "slash and clear". Three blackfly catching sites were established along the river. Focus group discussions were also conducted to assess the willingness of the communities to support the "slash and clear" intervention and the semi-annual distribution of ivermectin. Results A total of 2466 female S. damnosum s.l. were caught in 14×11h (06.00-15.00) catches. The highest biting density of 4210.25 flies/month/h and monthly biting rate (MBR) of 11,482.25 bites/man/month were observed in November 2023. Biting density and MBR reduced to zero in the intervention site by April 2024. While the mean parity rate was 31% (CI: 0.2976±0.9176). Two diurnal biting peaks were observed, one from 9:00-10:00 (at the bridge site) and a prominent one from 14:00-15:00 in the two catching sites in Mvolo. Along the river Naam, only one site was found productive for S. damnosum s.l.; and the larvae and adults were morphologically associated with the anthropophilic S. damnosum. The "slash and clear" intervention was implemented at Dogoyabolu along the river Naam. Communities expressed willingness to support a "slash and clear" intervention and the semi-annual distribution of ivermectin. Conclusion S. damnosum active breeding was identified along the river Naam in a stretch of 3-5 km close to human settlements. Highest blackfly biting density was 4210.25 flies/month/h, and two fly biting peaks were observed. A community "slash and clear" vector control was implemented, and will be prospectively monitored.
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Affiliation(s)
| | - Peter Alinda
- Ministry of Health, Vector Control Division, Kampala, Uganda
| | | | | | | | - Deng Gai Dual War
- Ministry of Health, National Malaria Control Program, Juba, South Sudan
| | - Robert Colebunders
- Global Health Institute, University of Antwerp, Antwerp, Belgium
- Department of Tropical Disease Pathology, Liverpool School of Tropical Medicine, Liverpool, UK
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Hadermann A, Jada SR, Amaral LJ, Colebunders R, Bol YY, Siewe Fodjo JN. Rapid diagnostic testing for onchocerciasis in Maridi (South Sudan) before and after improving elimination strategies: a repeated cross-sectional survey. OPEN RESEARCH EUROPE 2024; 3:206. [PMID: 38617116 PMCID: PMC11016167 DOI: 10.12688/openreseurope.16093.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Accepted: 02/29/2024] [Indexed: 04/16/2024]
Abstract
Background Maridi County is an onchocerciasis-endemic area in South Sudan. Annual community-directed treatment with ivermectin (CDTi) was instituted in Maridi since the early 2000s, but with low coverage. In 2021, the CDTi programme was strengthened to a six-monthly programme. Additionally, the community-based vector control strategy "Slash and Clear" has been implemented since 2019 at the Maridi Dam, the only blackfly breeding site in the area. This study assessed the effect of these reinforced onchocerciasis elimination interventions on the Onchocerca volvulus seroprevalence among young children, an indicator of ongoing transmission. Methods Baseline and follow-up serosurveys were conducted in Maridi in 2019 (prior to strengthening onchocerciasis elimination efforts) and 2023, respectively. During both surveys, children aged three to nine years were recruited from five study sites situated at different distances from the Maridi Dam. Ov16 antibodies were detected via rapid diagnostic tests (RDTs) using whole blood obtained by finger-pricking the participants. Baseline and follow-up Ov16 prevalence rates were calculated and compared. Results In 2019, the Ov16 seroprevalence among children aged three to nine years was 24.5% compared to 30.6% in 2023 (p=0.22). Both surveys found a particularly high Ov16 seroprevalence in the study site closest to the Maridi Dam (35.0% in 2019 and 44.0% in 2023, p=0.52). The Ov16 seroprevalence had a non-significant decreasing trend in the three-year-old children, from 12.5% (3/24) in 2019 to 8.8% (3/34) in 2023 (p=0.65). Conclusion The persistent Ov16 RDT seropositivity among three-year-old children in 2023 indicates ongoing O. volvulus transmission. Therefore, further strengthening of the onchocerciasis elimination programme is required. The study highlights the utility of RDTs in monitoring onchocerciasis transmission in highly endemic settings.
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Affiliation(s)
- Amber Hadermann
- Global Health Institute, University of Antwerp, Antwerp, Flanders, 2610, Belgium
| | | | - Luís-Jorge Amaral
- Global Health Institute, University of Antwerp, Antwerp, Flanders, 2610, Belgium
| | - Robert Colebunders
- Global Health Institute, University of Antwerp, Antwerp, Flanders, 2610, Belgium
| | - Yak Yak Bol
- Neglected Tropical Diseases Programme, Ministry of Health, Juba, South Sudan
| | - Joseph N Siewe Fodjo
- Global Health Institute, University of Antwerp, Antwerp, Flanders, 2610, Belgium
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Jacob B, Michael E, Unnasch TR. Community-Directed Vector Control to Accelerate Onchocerciasis Elimination. Pathogens 2024; 13:268. [PMID: 38535611 PMCID: PMC10975871 DOI: 10.3390/pathogens13030268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Revised: 03/11/2024] [Accepted: 03/16/2024] [Indexed: 04/01/2024] Open
Abstract
Onchocerciasis, or river blindness, has historically been one of the most important causes of blindness worldwide, and a major cause of socio-economic disruption, particularly in sub-Saharan Africa. Its importance as a cause of morbidity and an impediment to economic development in some of the poorest countries in the world motivated the international community to implement several programs to control or eliminate this scourge. Initially, these involved reducing transmission of the causative agent Onchocerca volvulus through controlling the vector population. When ivermectin was found to be a very effective drug for treating onchocerciasis, the strategy shifted to mass drug administration (MDA) of endemic communities. In some countries, both vector control and ivermectin MDA have been used together. However, traditional vector control methods involve treating rivers in which the black fly vectors breed with insecticides, a process which is expensive, requires trained personnel to administer, and can be ecologically harmful. In this review, we discuss recent research into alternatives to riverine insecticide treatment, which are inexpensive, ecologically less harmful, and can be implemented by the affected communities themselves. These can dramatically reduce vector densities and, when combined with ivermectin MDA, can accelerate the time to elimination when compared to MDA alone.
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Affiliation(s)
| | | | - Thomas R. Unnasch
- Center for Global Health Infectious Disease Research, College of Public Health, University of South Florida, 3720 Spectrum Blvd, Suite 304, Tampa, FL 33612, USA; (B.J.); (E.M.)
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Amaral LJ, Jada SR, Ndjanfa AK, Carter JY, Abd-Elfarag G, Okaro S, Logora MY, Bol YY, Lakwo T, Fodjo JNS, Colebunders R. Impact of annual community-directed treatment with ivermectin on the incidence of epilepsy in Mvolo, a two-year prospective study. PLoS Negl Trop Dis 2024; 18:e0012059. [PMID: 38512994 PMCID: PMC10986994 DOI: 10.1371/journal.pntd.0012059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 04/02/2024] [Accepted: 03/08/2024] [Indexed: 03/23/2024] Open
Abstract
OBJECTIVES The potential impact of cumulative community-directed treatment with ivermectin (CDTI) on epilepsy epidemiology in Mvolo County, South Sudan, an onchocerciasis-endemic area with high epilepsy prevalence, was investigated. Annual CDTI was introduced in 2002 in Mvolo, with interruptions in 2016 and 2020. METHODS Comprehensive house-to-house surveys in Mvolo (June 2020 and 2022) identified cases of epilepsy, including probable nodding syndrome (pNS). Community workers screened households in selected sites for suspected epilepsy, and medical doctors confirmed the diagnosis and determined the year of seizure onset. The incidence of epilepsy, including pNS, was analysed using 95% confidence intervals (CIs). Data on ivermectin intake and onchocerciasis-associated manifestations (itching and blindness) were collected. RESULTS The surveys covered 15,755 (2020) and 15,092 (2022) individuals, identifying 809 (5.2%, 95% CI: 4.8-5.5%) and 672 (4.5%, 95% CI: 4.1-4.8%) epilepsy cases, respectively. Each survey reported that a third of the surveyed population experienced skin itching, and 3% were blind. Epilepsy incidence per 100,000 person-years gradually declined, from 326.5 (95% CI: 266.8-399.1) in 2013-2015 to 96.6 (95% CI: 65.5-141.7) in 2019-2021. Similarly, pNS incidence per 100,000 person-years decreased from 151.7 (95% CI: 112.7-203.4) to 27.0 (95% CI: 12.5-55.5). Coverage of CDTI was suboptimal, reaching only 64.0% of participants in 2019 and falling to 24.1% in 2021 following an interruption in 2020 due to COVID-19 restrictions. Additionally, while 99.4% of cases had active epilepsy in 2022, less than a quarter of these had access to antiseizure medication. CONCLUSIONS The observed decrease in epilepsy incidence despite suboptimal CDTI coverage highlights the potential impact of onchocerciasis control efforts and underscores the need to strengthen these efforts in Mvolo County and across South Sudan. As a proactive measure, Mvolo and neighbouring counties are transitioning to biannual CDTI. Furthermore, the substantial epilepsy treatment gap in Mvolo should be addressed.
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Affiliation(s)
| | | | | | | | - Gasim Abd-Elfarag
- Amref Health Africa, South Sudan
- Access for Humanity, Juba, South Sudan
- School of Public Health, University of Juba, Juba, South Sudan
| | | | - Makoy Yibi Logora
- Neglected Tropical Diseases Unit, Ministry of Health, Juba, South Sudan
| | - Yak Yak Bol
- Neglected Tropical Diseases Unit, Ministry of Health, Juba, South Sudan
| | - Thomson Lakwo
- Vector Control Division, Ministry of Health, Kampala, Uganda
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Doherty M, Grant JR, Pilotte N, Bennuru S, Fischer K, Fischer PU, Lustigman S, Nutman TB, Pfarr K, Hoerauf A, Unnasch TR, Hassan HK, Wanji S, Lammie PJ, Ottesen E, Mackenzie C, Williams SA. Optimized strategy for real-time qPCR detection of Onchocerca volvulus DNA in pooled Simulium sp. blackfly vectors. PLoS Negl Trop Dis 2023; 17:e0011815. [PMID: 38096317 PMCID: PMC10754622 DOI: 10.1371/journal.pntd.0011815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Revised: 12/28/2023] [Accepted: 11/22/2023] [Indexed: 12/30/2023] Open
Abstract
BACKGROUND Onchocerca volvulus is a filarial parasite that is a major cause of dermatitis and blindness in endemic regions primarily in sub-Saharan Africa. Widespread efforts to control the disease caused by O. volvulus infection (onchocerciasis) began in 1974 and in recent years, following successful elimination of transmission in much of the Americas, the focus of efforts in Africa has moved from control to the more challenging goal of elimination of transmission in all endemic countries. Mass drug administration (MDA) with ivermectin has reached more than 150 million people and elimination of transmission has been confirmed in four South American countries, with at least two African countries having now stopped MDA as they approach verification of elimination. It is essential that accurate data for active transmission are used to assist in making the critical decision to stop MDA, since missing low levels of transmission and infection can lead to continued spread or recrudescence of the disease. METHODOLOGY/PRINCIPAL FINDINGS Current World Health Organization guidelines for MDA stopping decisions and post-treatment surveillance include screening pools of the Simulium blackfly vector for the presence of O. volvulus larvae using a PCR-ELISA-based molecular technique. In this study, we address the potential of an updated, practical, standardized molecular diagnostic tool with increased sensitivity and species-specificity by comparing several candidate qPCR assays. When paired with heat-stable reagents, a qPCR assay with a mitochondrial DNA target (OvND5) was found to be more sensitive and species-specific than an O150 qPCR, which targets a non-protein coding repetitive DNA sequence. The OvND5 assay detected 19/20 pools of 100 blackfly heads spiked with a single L3, compared to 16/20 for the O150 qPCR assay. CONCLUSIONS/SIGNIFICANCE Given the improved sensitivity, species-specificity and resistance to PCR inhibitors, we identified OvND5 as the optimal target for field sample detection. All reagents for this assay can be shipped at room temperature with no loss of activity. The qPCR protocol we propose is also simpler, faster, and more cost-effective than the current end-point molecular assays.
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Affiliation(s)
- Mary Doherty
- Department of Biological Sciences, Smith College, Northampton, Massachusetts, United States of America
| | - Jessica R. Grant
- Department of Biological Sciences, Smith College, Northampton, Massachusetts, United States of America
| | - Nils Pilotte
- Department of Biological Sciences, Quinnipiac University, Hamden, Connecticut, United States of America
| | - Sasisekhar Bennuru
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland, United States of America
| | - Kerstin Fischer
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Peter U. Fischer
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Sara Lustigman
- Laboratory of Molecular Parasitology, Lindsley F. Kimball Research Institute, New York Blood Center, New York, New York, United States of America
| | - Thomas B. Nutman
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland, United States of America
| | - Kenneth Pfarr
- Institute of Medical Microbiology, Immunology and Parasitology, University Hospital Bonn, Bonn, Germany
- German Center for Infection Research (DZIF), Partner-Site Bonn-Cologne, Bonn, Germany
| | - Achim Hoerauf
- Institute of Medical Microbiology, Immunology and Parasitology, University Hospital Bonn, Bonn, Germany
- German Center for Infection Research (DZIF), Partner-Site Bonn-Cologne, Bonn, Germany
| | - Thomas R. Unnasch
- Center for Global Health Infectious Disease Research, University of South Florida, Tampa, Florida, United States of America
| | - Hassan K. Hassan
- Center for Global Health Infectious Disease Research, University of South Florida, Tampa, Florida, United States of America
| | - Samuel Wanji
- Parasite and Vectors Research Unit, Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
- Research Foundation in Tropical Diseases and the Environment, Buea, Cameroon
| | - Patrick J. Lammie
- NTD-SC, Task Force for Global Health, Atlanta, Georgia, United States of America
| | - Eric Ottesen
- NTD-SC, Task Force for Global Health, Atlanta, Georgia, United States of America
| | - Charles Mackenzie
- NTD-SC, Task Force for Global Health, Atlanta, Georgia, United States of America
- RLMF, The END Fund, New York, New York, United States of America
| | - Steven A. Williams
- Department of Biological Sciences, Smith College, Northampton, Massachusetts, United States of America
- Molecular and Cellular Biology Program, University of Massachusetts, Amherst, Massachusetts, United States of America
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Jada SR, Amaral LJ, Lakwo T, Carter JY, Rovarini J, Bol YY, Logora MY, Hadermann A, Hopkins A, Fodjo JNS, Colebunders R. Effect of onchocerciasis elimination measures on the incidence of epilepsy in Maridi, South Sudan: a 3-year longitudinal, prospective, population-based study. Lancet Glob Health 2023; 11:e1260-e1268. [PMID: 37474232 DOI: 10.1016/s2214-109x(23)00248-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Revised: 05/15/2023] [Accepted: 05/19/2023] [Indexed: 07/22/2023]
Abstract
BACKGROUND High onchocerciasis transmission predisposes endemic communities to a high epilepsy burden. The 4·4% epilepsy prevalence documented in 2018 in Maridi, South Sudan, prompted the strengthening of onchocerciasis elimination measures. Community-directed treatment with ivermectin was implemented annually in 2017, 2018, and 2019, interrupted in 2020, and re-implemented biannually in 2021. We aimed to assess the effect of these interventions, along with slash and clear vector control on the incidence of epilepsy, including nodding syndrome. METHODS In this longitudinal, prospective, population-based study, we did a two-stage house-to-house epilepsy survey before (May 10-30, 2018) and after (March 9-19, 2022) the strengthening of onchocerciasis elimination interventions in South Sudan. Strengthening also included the implementation of a community-based slash and clear vector control method that we initiated in 2019 at the Maridi dam (the main blackfly breeding site). Eight sites were surveyed near the Maridi dam and inclusion required residence in one of these sites. All household residents were first screened by community workers, followed by confirmation of the epilepsy diagnosis by trained clinicians. The primary outcome was epilepsy incidence, including nodding syndrome, which was assessed via self-reported new-onset epilepsy in the previous 4 years of each survey, confirmed by clinician assessment. FINDINGS The preintervention survey included 17 652 people of whom 736 had epilepsy (315 female and 421 male), and the post-intervention survey included 14 402 people of whom 586 had epilepsy (275 female and 311 male). When biannual community-directed treatment with ivermectin was initiated in 2021, the intervention's coverage rose by 15·7% (95% CI 14·6-16·8); although only 56·6% of the population took ivermectin in 2021. Between 2018 and 2022, epilepsy incidence decreased from 348·8 (307·2-395·8) to 41·7 (22·6-75·0) per 100 000 person-years. Similarly, the incidence of nodding syndrome decreased from 154·7 (127·6-187·3) to 10·4 (2·7-33·2) per 100 000 person-years. The identified risk factors for epilepsy were: living closer to the Maridi dam, being aged between 6 and 40 years, not taking ivermectin, and being male. INTERPRETATION In onchocerciasis-endemic areas with high epilepsy prevalence, strengthening onchocerciasis elimination interventions can decrease the incidence of epilepsy, including nodding syndrome. Additional efforts are needed to increase community-directed treatment with ivermectin coverage and sustain blackfly control in Maridi. FUNDING Research for Health in Humanitarian Crisis, European Research Council, Research Foundation-Flanders, Research Foundation-Flanders, the Italian Agency for Development Cooperation, and La Caixa Foundation.
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Affiliation(s)
| | | | - Thomson Lakwo
- Division of Vector Borne and Neglected Tropical Diseases Control, Ministry of Health, Kampala, Uganda
| | | | - Jacopo Rovarini
- Global Health Institute, University of Antwerp, Antwerp, Belgium
| | - Yak Yak Bol
- Neglected Tropical Diseases Unit, Ministry of Health, Juba, South Sudan
| | - Makoy Yibi Logora
- Neglected Tropical Diseases Unit, Ministry of Health, Juba, South Sudan
| | - Amber Hadermann
- Global Health Institute, University of Antwerp, Antwerp, Belgium
| | - Adrian Hopkins
- The Onchocerciasis Elimination Advisory Committee, Juba, South Sudan
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Eyang-Assengone ER, Makouloutou-Nzassi P, Mbou-Boutambe C, Bangueboussa F, Atsame J, Boundenga L. Status of Onchocerciasis Elimination in Gabon and Challenges: A Systematic Review. Microorganisms 2023; 11:1946. [PMID: 37630506 PMCID: PMC10458829 DOI: 10.3390/microorganisms11081946] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 07/19/2023] [Accepted: 07/26/2023] [Indexed: 08/27/2023] Open
Abstract
Control and treatment programs (CDTI) have been set up nationally in all endemic countries to overcome the impact of onchocerciasis on the affected populations. However, Gabon must still succeed in setting up real onchocerciasis control programs. Here, various database articles have been used to provide the scientific community with a summary document showing the mapping of this disease in Gabon. The articles dealing with onchocerciasis, animal reservoirs, surveillance, and elimination were analyzed. Results showed that little research has been performed. Most studies are concentrated in one region (The area of Lastourville). In addition, we observed that the distribution of the disease varies significantly across the country. Indeed, specific environments present a hyper-endemicity of the disease, while others are meso and hypo-endemic. So, we found some departments with a prevalence ranging from 0% to over 20%; within them, villages had infection levels comprising 10% to 60%, indicating potential hotspots. Vectors activities were studied in some areas. This paper showed the challenges encountered in the country to eliminate this disease. One solution is a deeper understanding of the disease's bioecology to establish effective health policies to eliminate onchocerciasis in Gabon effectively.
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Affiliation(s)
- Elsa-Rush Eyang-Assengone
- Unité de Recherche en Ecologie de la Santé (URES), Centre Interdisciplinaire de Recherches Médicales de Franceville (CIRMF), Franceville BP 769, Gabon; (P.M.-N.); (C.M.-B.); (F.B.)
| | - Patrice Makouloutou-Nzassi
- Unité de Recherche en Ecologie de la Santé (URES), Centre Interdisciplinaire de Recherches Médicales de Franceville (CIRMF), Franceville BP 769, Gabon; (P.M.-N.); (C.M.-B.); (F.B.)
- Département de Biologie et Ecologie Animale, Institut de Recherche en Ecologie Tropicale (IRET/CENAREST), Libreville BP 13354, Gabon
| | - Clark Mbou-Boutambe
- Unité de Recherche en Ecologie de la Santé (URES), Centre Interdisciplinaire de Recherches Médicales de Franceville (CIRMF), Franceville BP 769, Gabon; (P.M.-N.); (C.M.-B.); (F.B.)
| | - Félicien Bangueboussa
- Unité de Recherche en Ecologie de la Santé (URES), Centre Interdisciplinaire de Recherches Médicales de Franceville (CIRMF), Franceville BP 769, Gabon; (P.M.-N.); (C.M.-B.); (F.B.)
| | - Julienne Atsame
- Programme de Lutte Contre les Maladies Parasitaires, Ministère de la Santé du Gabon, Libreville BP 2434, Gabon;
| | - Larson Boundenga
- Unité de Recherche en Ecologie de la Santé (URES), Centre Interdisciplinaire de Recherches Médicales de Franceville (CIRMF), Franceville BP 769, Gabon; (P.M.-N.); (C.M.-B.); (F.B.)
- Département d’anthropologie, Université de Durham, South Road, Durham DH1 3LE, UK
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Amaral LJ, Bhwana D, Mhina AD, Mmbando BP, Colebunders R. Nodding syndrome, a case-control study in Mahenge, Tanzania: Onchocerca volvulus and not Mansonella perstans as a risk factor. PLoS Negl Trop Dis 2023; 17:e0011434. [PMID: 37339148 DOI: 10.1371/journal.pntd.0011434] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Accepted: 06/05/2023] [Indexed: 06/22/2023] Open
Abstract
BACKGROUND Nodding syndrome (NS) has been consistently associated with onchocerciasis. Nevertheless, a positive association between NS and a Mansonella perstans infection was found in South Sudan. We aimed to determine whether the latter parasite could be a risk factor for NS in Mahenge. METHODS Cases of epilepsy were identified in villages affected by NS in Mahenge, Tanzania, and matched with controls without epilepsy of the same sex, age and village. We examined blood films of cases and controls to identify M. perstans infections. The participants were also asked for sociodemographic and epilepsy information, examined for palpable onchocercal nodules and onchocerciasis-related skin lesions and tested for anti-Onchocerca volvulus antibodies (Ov16 IgG4) by ELISA. Clinical characteristics of cases and controls, O. volvulus exposure status and relevant sociodemographic variables were assessed by a conditional logistic regression model for NS and epilepsy status matched for age, sex and village. RESULTS A total of 113 epilepsy cases and 132 controls were enrolled, of which, respectively, 56 (49.6%) and 64 (48.5%) were men. The median age in cases and controls was 28.0 (IQR: 22.0-35.0) and 27.0 (IQR: 21.0-33.3) years. Of the persons with epilepsy, 43 (38.1%) met the probable NS criteria and 106 (93.8%) had onchocerciasis-associated epilepsy (OAE). M. perstans infection was absent in all participants, while Ov16 seroprevalence was positively associated with probable NS (odds ratio (OR): 5.05, 95%CI: 1.79-14.27) and overall epilepsy (OR: 2.03, 95%CI: 1-07-3.86). Moreover, onchocerciasis-related skin manifestations were only found in the cases (n = 7, p = 0.0040), including persons with probable NS (n = 4, p = 0.0033). Residing longer in the village and having a family history of seizures were positively correlated with Ov16 status and made persons at higher odds for epilepsy, including probable NS. CONCLUSION In contrast to O. volvulus, M. perstans is most likely not endemic to Mahenge and, therefore, cannot be a co-factor for NS in the area. Hence, this filaria is unlikely to be the primary and sole causal factor in the development of NS. The main risk factor for NS remains onchocerciasis.
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Affiliation(s)
| | - Dan Bhwana
- National Institute of Medical Research, Tanga, Tanzania
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Bhattacharyya S, Vinkeles Melchers NVS, Siewe Fodjo JN, Vutha A, Coffeng LE, Logora MY, Colebunders R, Stolk WA. Onchocerciasis-associated epilepsy in Maridi, South Sudan: Modelling and exploring the impact of control measures against river blindness. PLoS Negl Trop Dis 2023; 17:e0011320. [PMID: 37235598 DOI: 10.1371/journal.pntd.0011320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Accepted: 04/19/2023] [Indexed: 05/28/2023] Open
Abstract
BACKGROUND Onchocerciasis, also known as "river blindness", is caused by the bite of infected female blackflies (genus Simuliidae) that transmit the parasite Onchocerca volvulus. A high onchocerciasis microfarial load increases the risk to develop epilepsy in children between the ages of 3 and 18 years. In resource-limited settings in Africa where onchocerciasis has been poorly controlled, high numbers of onchocerciasis-associated epilepsy (OAE) are reported. We use mathematical modeling to predict the impact of onchocerciasis control strategies on the incidence and prevalence of OAE. METHODOLOGY We developed an OAE model within the well-established mathematical modelling framework ONCHOSIM. Using Latin-Hypercube Sampling (LHS), and grid search technique, we quantified transmission and disease parameters using OAE data from Maridi County, an onchocerciasis endemic area, in southern Republic of South Sudan. Using ONCHOSIM, we predicted the impact of ivermectin mass drug administration (MDA) and vector control on the epidemiology of OAE in Maridi. PRINCIPAL FINDINGS The model estimated an OAE prevalence of 4.1% in Maridi County, close to the 3.7% OAE prevalence reported in field studies. The OAE incidence is expected to rapidly decrease by >50% within the first five years of implementing annual MDA with good coverage (≥70%). With vector control at a high efficacy level (around 80% reduction of blackfly biting rates) as the sole strategy, the reduction is slower, requiring about 10 years to halve the OAE incidence. Increasing the efficacy levels of vector control, and implementing vector control simultaneously with MDA, yielded better results in preventing new cases of OAE. CONCLUSIONS/SIGNIFICANCES Our modeling study demonstrates that intensifying onchocerciasis eradication efforts could substantially reduce OAE incidence and prevalence in endemic foci. Our model may be useful for optimizing OAE control strategies.
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Affiliation(s)
- Samit Bhattacharyya
- Department of Mathematics, School of Natural Sciences, Shiv Nadar Institution of Eminence, Dadri, Uttar Pradesh, India
- Global Health Institute, University of Antwerp, Antwerp, Belgium
| | | | | | - Amit Vutha
- Department of Mathematics, Ohio State University, Columbus, Ohio, United States of America
| | - Luc E Coffeng
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Makoy Y Logora
- National Neglected Tropical Disease Programme, Ministry of Health South Sudan, Juba, South Sudan
| | | | - Wilma A Stolk
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
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Van Cutsem G, Siewe Fodjo JN, Dekker MCJ, Amaral LJ, Njamnshi AK, Colebunders R. Case definitions for onchocerciasis-associated epilepsy and nodding syndrome: A focused review. Seizure 2023; 107:132-135. [PMID: 37023626 DOI: 10.1016/j.seizure.2023.03.024] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 03/28/2023] [Accepted: 03/31/2023] [Indexed: 04/03/2023] Open
Abstract
Onchocerciasis-associated epilepsy (OAE) is an important but neglected public health problem in onchocerciasis-endemic areas with insufficient or inadequate onchocerciasis control. Hence, there is a need for an internationally accepted, easy-to-use epidemiological case definition of OAE to identify areas of high Onchocerca volvulus transmission and disease burden requiring treatment and prevention interventions. By including OAE as a manifestation of onchocerciasis, we will considerably improve the accuracy of the overall onchocerciasis disease burden, which is currently underestimated. Hopefully, this will lead to increased interest and funding for onchocerciasis research and control interventions, notably the implementation of more effective elimination measures and treatment and support for affected individuals and their families.
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Hadermann A, Amaral LJ, Van Cutsem G, Siewe Fodjo JN, Colebunders R. Onchocerciasis-associated epilepsy: an update and future perspectives. Trends Parasitol 2023; 39:126-138. [PMID: 36528471 DOI: 10.1016/j.pt.2022.11.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 11/22/2022] [Accepted: 11/24/2022] [Indexed: 12/23/2022]
Abstract
Onchocerciasis-associated epilepsy (OAE) is an important neglected public health problem in areas with high ongoing onchocerciasis transmission. The risk that children in such areas develop epilepsy is related to their Onchocerca volvulus microfilarial (mf) load. Before the implementation of mass treatment with ivermectin, microfilariae were detected in cerebrospinal fluid (CSF). More recently, neither O. volvulus microfilariae nor DNA were detected in CSF or brain tissue; however, these samples were obtained years after seizure onset. It is possible that during fever-induced increased blood-brain barrier permeability, microfilariae enter the brain and, upon dying, cause an inflammatory reaction inducing seizures. Including OAE in the onchocerciasis disease burden estimation may mobilise extra resources for onchocerciasis disease elimination and treatment/care of OAE-affected persons/families.
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Affiliation(s)
- Amber Hadermann
- Global Health Institute, University of Antwerp, Antwerp, Belgium
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Tirados I, Thomsen E, Worrall E, Koala L, Melachio TT, Basáñez MG. Vector control and entomological capacity for onchocerciasis elimination. Trends Parasitol 2022; 38:591-604. [DOI: 10.1016/j.pt.2022.03.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Revised: 02/17/2022] [Accepted: 03/08/2022] [Indexed: 11/24/2022]
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Community perception of epilepsy and its treatment in onchocerciasis-endemic villages of Maridi county, western equatoria state, South Sudan. Epilepsy Behav 2022; 127:108537. [PMID: 35026562 DOI: 10.1016/j.yebeh.2021.108537] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 12/27/2021] [Accepted: 12/27/2021] [Indexed: 12/13/2022]
Abstract
OBJECTIVE To assess the community's perception of epilepsy and its treatment in onchocerciasis-endemic villages of Maridi County, Western Equatoria State, South Sudan. The study was conducted prior to the setting up of a community-based intervention to manage the important disease burden caused by onchocerciasis-associated epilepsy in these villages. METHOD Five focus group discussions (FGD) were conducted with community leaders and with persons with epilepsy (PWE) and their families between November and December 2019. RESULTS Villages close to the Maridi dam were considered to be most affected by epilepsy. Misconceptions about the cause and treatment of epilepsy were identified. Most people believed that epilepsy is caused by bad spirits and is contagious, transmitted through saliva, air, and contact with PWE. Very few participants were aware of the link between onchocerciasis and epilepsy. Persons with epilepsy are restricted in their day-to-day activities and children with epilepsy are often denied going to school. Persons with epilepsy are stigmatized and seen as unfit for marriage. Most participants considered both traditional and medical treatment as ineffective. Uninterrupted anti-seizure treatment continuously was unaffordable for most families with one or more PWE. CONCLUSION There is a need to establish a comprehensive epilepsy treatment program which addresses misconceptions about epilepsy and reduces epilepsy-related stigma. Explaining the link between onchocerciasis and epilepsy could lead to a reduction in epilepsy-related stigma.
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