ORCID Profile
0000-0002-1494-3101
Current Organisation
Wageningen University & Research
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Publisher: Springer Science and Business Media LLC
Date: 19-09-2018
Publisher: Public Library of Science (PLoS)
Date: 11-06-2021
DOI: 10.1371/JOURNAL.PNTD.0009489
Abstract: Onchocerciasis (river-blindness) in Africa is targeted for elimination through mass drug administration (MDA) with ivermectin. Onchocerciasis may cause various types of skin and eye disease. Predicting the impact of MDA on onchocercal morbidity is useful for future policy development. Here, we introduce a new disease module within the established ONCHOSIM model to predict trends over time in prevalence of onchocercal morbidity. We developed novel generic model concepts for development of symptoms due to cumulative exposure to dead microfilariae, accommodating both reversible (acute) and irreversible (chronic) symptoms. The model was calibrated to reproduce pre-control age patterns and associations between prevalences of infection, eye disease, and various types of skin disease as observed in a large set of population-based studies. We then used the new disease module to predict the impact of MDA on morbidity prevalence over a 30-year time frame for various scenarios. ONCHOSIM reproduced observed age-patterns in disease and community-level associations between infection and disease reasonably well. For highly endemic settings with 30 years of annual MDA at 60% coverage, the model predicted a 70% to 89% reduction in prevalence of chronic morbidity. This relative decline was similar with higher MDA coverage and only somewhat higher for settings with lower pre-control endemicity. The decline in prevalence was lowest for mild depigmentation and visual impairment. The prevalence of acute clinical manifestations (severe itch, reactive skin disease) declined by 95% to 100% after 30 years of annual MDA, regardless of pre-control endemicity. We present generic model concepts for predicting trends in acute and chronic symptoms due to history of exposure to parasitic worm infections, and apply this to onchocerciasis. Our predictions suggest that onchocercal morbidity, in particular chronic manifestations, will remain a public health concern in many epidemiological settings in Africa, even after 30 years of MDA.
Publisher: Public Library of Science (PLoS)
Date: 26-07-2021
DOI: 10.1371/JOURNAL.PNTD.0009604
Abstract: Onchocerciasis (“river blindness”) can cause severe morbidity, including vision loss and various skin manifestations, and is targeted for elimination using ivermectin mass drug administration (MDA). We calculated the number of people with Onchocerca volvulus infection and onchocercal skin and eye disease as well as disability-adjusted life years (DALYs) lost from 1990 through to 2030 in areas formerly covered by the African Programme for Onchocerciasis Control. Per MDA implementation unit, we collated data on the pre-control distribution of microfilariae (mf) prevalence and the history of control. Next, we predicted trends in infection and morbidity over time using the ONCHOSIM simulation model. DALY estimates were calculated using disability weights from the Global Burden of Disease Study. In 1990, prior to MDA implementation, the total population at risk was 79.8 million with 26.0 million (32.5%) mf-positive in iduals, of whom 17.5 million (21.9%) had some form of onchocercal skin or eye disease (2.5 million DALYs lost). By 2030, the total population was predicted to increase to 236.1 million, while the number of mf-positive cases (about 6.8 million, 2.9%), people with skin or eye morbidity (4.2 million, 1.8%), and DALYs lost (0.7 million) were predicted to decline. MDA has had a remarkable impact on the onchocerciasis burden in countries previously under the APOC mandate. In the few countries where we predict continued transmission between now and 2030, intensified MDA could be combined with local vector control efforts, or the introduction of new drugs for mopping up residual cases of infection and morbidity.
Publisher: SAGE Publications
Date: 09-01-2020
Abstract: Informed by goal-setting/self-regulatory theories, we tested the mediating role of career-related effort (i.e., goal striving) in the relationships between career-related indecision (i.e., goal ambiguity) and career-related stress (i.e., affect) and perceived employability (i.e., career-related attitude) and examined the effect of financial distress as a moderator in these direct and indirect relationships. Using a s le of 202 young adults ( M age = 19.8 years, 81.7% female), we found career indecision was related negatively to effort and perceived employability and positively to stress, with effort mediating between indecision and both stress and perceived employability. However, financial distress influenced these relationships. The associations between career indecision and effort and perceived employability were more negative and the associations between career indecision and stress were more positive when financial distress was higher. The study contributes by identifying how financial distress affects the relationships between career indecision, effort, and other career variables.
Location: Tanzania, United Republic of
Location: United Kingdom of Great Britain and Northern Ireland
Location: Netherlands
No related grants have been discovered for Natalie VS Vinkeles Melchers.