A Novel Biplex Onchocerca volvulus Rapid Diagnostic Test Evaluated Among 3- to 9-Year-Old Children in Maridi, South SudanHadermann, Jada, Lubbers
et alDiagnostics (Basel) (2025) 15 (5)
Abstract: Background: Point-of-care diagnostic tests are essential for confirming Onchocerca volvulus transmission in remote, resource-limited, onchocerciasis-endemic communities. In Maridi, South Sudan, we field-tested a novel "biplex A" rapid diagnostic test (RDT) developed by Drugs & Diagnostics for Tropical Diseases (DDTD), San Diego, California. Methods: In February 2023, children aged 3-9 years were recruited from study sites at different distances from the Maridi Dam, a known blackfly breeding site. O. volvulus antibodies were detected using the DDTD biplex A RDT, which detects antibodies to Ov16 and OvOC3261 at test line 1 and to Ov33.3 and OvOC10469 at test line 2, along with the commercially available Ov16 SD Bioline RDT. Both tests were performed on whole blood obtained via finger prick. The feasibility and acceptability of the DDTD biplex A RDT were assessed, and its results were compared with those of the Ov16 SD Bioline RDT. Results: A total of 239 children participated in the study. The anti-Ov16 seroprevalence detected by the Ov16 SD Bioline RDT was 30.2% (72/239), with the highest prevalence observed in children living closest to the Maridi Dam (p < 0.001). Testing with the DDTD biplex A RDT was determined to be feasible, acceptable, and easy to use in a field setting. The DDTD biplex A RDT test line 1 (anti-Ov16 and anti-OvOC3261) was positive in 35.1% (84/239) of children, while test line 2 (anti-Ov33.3 and anti-OvOC10469) was positive in 18.4% (44/239). Both lines were simultaneously visible in 15.5% (37/239). Conclusions: The DDTD biplex A RDT prototype was user-friendly and practical for field deployment. However, additional research is needed to evaluate its performance relative to the commercially available Ov16 SD Bioline RDT. The high anti-Ov16 seroprevalence that was observed underscores the ongoing O. volvulus transmission near the Maridi Dam. Strengthening the onchocerciasis elimination program in Maridi should be prioritized as a critical public health intervention.
Pregnant Women, a Potential Reservoir for Onchocerca volvulus? A Cross Sectional Study in Maridi County, South SudanTrevisan, Hadermann, Jada
et alJ Epidemiol Glob Health (2025) 15 (1), 14
Abstract: Onchocerciasis, a neglected tropical disease (NTD) caused by Onchocerca volvulus, is hyperendemic in many parts of Africa, including South Sudan. Pregnant women may be a parasite reservoir as they are not included in routine ivermectin (IVM) treatments due to unassessed drug safety. In our study we determined the proportion of pregnant women infected with Onchocerca volvulus and assessed the knowledge and practices on IVM use during pregnancy.A hospital-based cross-sectional study was conducted in 2023 at Maridi hospital in Maridi County, an onchocerciasis endemic area in South Sudan. All pregnant or one-week post-partum women willing to participate were interviewed, clinically examined, tested with the Ov16 Bioline rapid diagnostic test (RDT) and skin snipped for O. volvulus detection. A total of 317 women aged between 14 and 44 years participated in the study [median age: 23 years (IQR: 19-29)]. Of 290 women who were tested, 179 (61.7%) were Ov16 RDT positive (SD Bioline). Of the 162 women skin snipped, 51 (31.5%) were positive for O. volvulus microfilarial worm following microscopic examination. The microfilaridemia (skin parasite load) ranged between one microfilaria per skin snip (1mf/ss) and 300 mf/ss with a mean value of value of 12.4 (sd: ± 49.1) mf/ss. Most pregnant women (87.8% (274/312)) knew that it was not advised to take IVM during pregnancy. Out of 309 women, 54 (17.5%) had never taken IVM, and 6.4% (16/251) inadvertently took IVM during pregnancy. Of the 16 women who took IVM during pregnancy, 50% (8/16) knew that they were pregnant. Out of 248 women with children, 9 (3.6%) had children suffering from epilepsy; two of them had two children with epilepsy. No abnormalities were reported in the children of the women who took IVM.Our study is the first to investigate the prevalence and level of O. volvulus infection among pregnant women in onchocerciasis-endemic areas in Africa. Our results showed a high infection rate of O. volvulus among pregnant women, which may pose a risk for adverse materno-foetal outcomes. Pregnant women in South Sudan are a reservoir for parasite transmission. A clinical trial evaluating the potential beneficial effect of treating O. volvulus infected pregnant women with IVM should be considered, as our preliminary results and the literature suggest that IVM intake might not affect the newborn.© 2025. The Author(s).
Onchocerciasis is not a major cause of blindness in two endemic villages in Sierra LeoneKargbo-Labour, Redwood-Sawyerr, Conteh
et alBMC Res Notes (2025) 18 (1), 21
Abstract: Sierra Leone, a country where onchocerciasis is endemic in 14 of the 16 districts, was the focus of our investigation. Despite 17 rounds of annual ivermectin treatment since 2005, a report circulated by a local politician indicated an increase in cases of suspected onchocerciasis-related vision impairment in two villages (Mangobo and Petifu) in Tonkolili district. In response, the National Neglected Tropical Disease Program conducted a comprehensive investigation. Ophthalmological, parasitological, and serological tests were conducted using standard procedures to determine the relationship between self-reported vision loss and onchocerciasis in adults. In addition, serological tests were carried out on children aged 5 to 9 years to assess the recent status of exposure to onchocerciasis in the two villages.Reported vision loss in 37 patients was mainly due to cataracts (35.1%), allergic conjunctivitis (18.9%), refractive error (10.8%), and other conditions not related to onchocerciasis. There were 40.7% of all adults (N = 54) tested and 29.0% of 31 persons with self-reported vision loss who were positive for Ov-16 IgG4 antibodies, suggesting a history of exposure to onchocerciasis. However, otoscopic eye examinations and microscopic skin snip tests were all negative for Onchocerca volvulus microfilariae, indicating no active or low-intensity infection among adults and a low or zero risk of serious ocular morbidity in the two villages. Onchocerciasis may no longer be a major cause of blindness in these two villages. Apparently, 4.6% of 153 children aged 5 to 9 years tested positive for Ov-16 IgG4 antibodies, suggesting that onchocerciasis transmission is likely still ongoing in the two villages. The data presented here suggest that more annual rounds of mass treatment with ivermectin with high coverage are needed to eliminate onchocerciasis transmission in this area.© 2024. The Author(s).
Approaching onchocerciasis elimination in Equatorial Guinea: Near zero transmission and public health implicationNcogo, Hernández-González, Ta-Tang
et alInfect Dis Poverty (2024) 13 (1), 86
Abstract: Onchocerciasis and lymphatic filariasis (LF) are endemic in Equatorial Guinea with notable variations in disease incidence between island and mainland regions. Historically, efforts to control and map these diseases were concentrated in Bioko Island, where loiasis is absent, allowing for targeted onchocerciasis interruption strategies. With the cessation of onchocerciasis transmission on Bioko and no reported cases on Annobon island, assessing the transmission status in the previously unaddressed mainland region has become imperative. Mapping efforts in mainland Equatorial Guinea have proven low to moderate level of transmission for LF and onchocerciasis, although the results so far have not been very conclusive. The current study aims to update the prevalence estimates for onchocerciasis and LF in mainland Equatorial Guinea using various diagnostic techniques.This is the first cross-sectional study carried out to estimate the prevalence of onchocerciasis and LF in the mainland area of Equatorial Guinea, from September to December 2019, based on the combination of skin snip biopsies, thick blood smears, laboratory serological tests (ELISA tests for the detection of IgG4 antibodies against Onchocerca volvulus recombinant antigen Ov16 and Wuchereria bancrofti recombinant antigen Wb123) and molecular laboratory tests. Frequencies and prevalence rates, along with 95% confidence intervals for interval estimation of a binomial proportion, were computed.The overall onchocerciasis seroprevalence calculated for the study was 0.3% (95% CI: 0.1 to 0.5%). Microscopic examination of skin biopsies from the eight individuals seropositive for Ov16, out of the 3951 individuals initially tested, revealed no O. volvulus microfilariae. However, DNA extracted from one skin snip was successfully amplified, with subsequent sequencing confirming the presence of O. volvulus. Among the 3951 individuals, 182 were found to have anti-Wb123 antibodies, suggesting exposure to W. bancrofti, with an estimated seroprevalence of 4.6% (95% CI: 4.0 to 5.3%). Microscopy and Filaria-real time-PCR (F-RT-PCR) analysis for W. bancrofti were negative across all samples.The findings indicate that onchocerciasis may no longer constitutes a public health problem in Equatorial Guinea, positioning the country on the verge of achieving elimination. Additionally, the mapped prevalence of LF will facilitate the formulation of national strategies aimed at eradicating filariases countrywide.© 2024. The Author(s).
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