Publications
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Colebunders R, Siewe Fodjo JN, Hopkins A, et al., 2019, From river blindness to river epilepsy: Implications for onchocerciasis elimination programmes., PLoS Negl Trop Dis, Vol: 13, Pages: e0007407-e0007407
Turner HC, Walker M, Pion SDS, et al., 2019, Economic evaluations of onchocerciasis interventions: a systematic review and research needs, TROPICAL MEDICINE & INTERNATIONAL HEALTH, Vol: 24, Pages: 788-816, ISSN: 1360-2276
Grillet ME, Hernandez-Villena JV, Llewellyn MS, et al., 2019, Venezuela's humanitarian crisis, resurgence of vector-borne diseases, and implications for spillover in the region, LANCET INFECTIOUS DISEASES, Vol: 19, Pages: E149-E161, ISSN: 1473-3099
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Dixon MA, Braae UC, Winskill P, et al., 2019, Strategies for tackling Taenia solium taeniosis/cysticercosis: A systematic review and comparison of transmission models, including an assessment of the wider Taeniidae family transmission models, PLoS Neglected Tropical Diseases, Vol: 13, ISSN: 1935-2727
BackgroundThe cestode Taenia solium causes the neglected (zoonotic) tropical disease cysticercosis, a leading cause of preventable epilepsy in endemic low and middle-income countries. Transmission models can inform current scaling-up of control efforts by helping to identify, validate and optimise control and elimination strategies as proposed by the World Health Organization (WHO).Methodology/Principal findingsA systematic literature search was conducted using the PRISMA approach to identify and compare existing T. solium transmission models, and related Taeniidae infection transmission models. In total, 28 modelling papers were identified, of which four modelled T. solium exclusively. Different modelling approaches for T. solium included deterministic, Reed-Frost, individual-based, decision-tree, and conceptual frameworks. Simulated interventions across models agreed on the importance of coverage for impactful effectiveness to be achieved.Other Taeniidae infection transmission models comprised force-of-infection (FoI), population-based (mainly Echinococcus granulosus) and individual-based (mainly E. multilocularis) modelling approaches. Spatial structure has also been incorporated (E. multilocularis and Taenia ovis) in recognition of spatial aggregation of parasite eggs in the environment and movement of wild animal host populations.Conclusions/SignificanceGaps identified from examining the wider Taeniidae family models highlighted the potential role of FoI modelling to inform model parameterisation, as well as the need for spatial modelling and suitable structuring of interventions as key areas for future T. solium model development. We conclude that working with field partners to address data gaps and conducting cross-model validation with baseline and longitudinal data will be critical to building consensus-led and epidemiological setting-appropriate intervention strategies to help fulfil the WHO targets.
Cucunuba Perez Z, Nouvellet P, Peterson J, et al., 2018, Complementary paths to chagas disease elimination: the impact of combining vector control with aetiological treatment, Clinical Infectious Diseases, Vol: 66, Pages: S293-S300, ISSN: 1058-4838
Background:The World Health Organization’s 2020 goals for Chagas disease are (1) interrupting vector-borne intradomiciliary transmission and (2) having all infected people under care in endemic countries. Insecticide spraying has proved efficacious for reaching the first goal, but active transmission remains in several regions. For the second, treatment has mostly been restricted to recently infected patients, who comprise only a small proportion of all infected individuals.Methods:We extended our previous dynamic transmission model to simulate a domestic Chagas disease transmission cycle and examined the effects of both vector control and etiological treatment on achieving the operational criterion proposed by the Pan American Health Organization for intradomiciliary, vectorial transmission interruption (ie, <2% seroprevalence in children <5 years of age).Results:Depending on endemicity, an antivectorial intervention that decreases vector density by 90% annually would achieve the transmission interruption criterion in 2–3 years (low endemicity) to >30 years (high endemicity). When this strategy is combined with annual etiological treatment in 10% of the infected human population, the seroprevalence criterion would be achieved, respectively, in 1 and 11 years.Conclusions:Combining highly effective vector control with etiological (trypanocidal) treatment in humans would substantially reduce time to transmission interruption as well as infection incidence and prevalence. However, the success of vector control may depend on prevailing vector species. It will be crucial to improve the coverage of screening programs, the performance of diagnostic tests, the proportion of people treated, and the efficacy of trypanocidal drugs. While screening and access can be incremented as part of strengthening the health systems response, improving diagnostics performance and drug efficacy will require further research.
Verver S, Walker M, Kim YE, et al., 2018, How can onchocerciasis elimination in Africa be accelerated? Modelling the impact of increased ivermectin treatment frequency and complementary vector control, Clinical Infectious Diseases, Vol: 66, Pages: S267-S274, ISSN: 1058-4838
Background:Great strides have been made toward onchocerciasis elimination by mass drug administration (MDA) of ivermectin. Focusing on MDA-eligible areas, we investigated where the elimination goal can be achieved by 2025 by continuation of current practice (annual MDA with ivermectin) and where intensification or additional vector control is required. We did not consider areas hypoendemic for onchocerciasis with loiasis coendemicity where MDA is contraindicated.Methods:We used 2 previously published mathematical models, ONCHOSIM and EPIONCHO, to simulate future trends in microfilarial prevalence for 80 different settings (defined by precontrol endemicity and past MDA frequency and coverage) under different future treatment scenarios (annual, biannual, or quarterly MDA with different treatment coverage through 2025, with or without vector control strategies), assessing for each strategy whether it eventually leads to elimination.Results:Areas with 40%–50% precontrol microfilarial prevalence and ≥10 years of annual MDA may achieve elimination with a further 7 years of annual MDA, if not achieved already, according to both models. For most areas with 70%–80% precontrol prevalence, ONCHOSIM predicts that either annual or biannual MDA is sufficient to achieve elimination by 2025, whereas EPIONCHO predicts that elimination will not be achieved even with complementary vector control.Conclusions:Whether elimination will be reached by 2025 depends on precontrol endemicity, control history, and strategies chosen from now until 2025. Biannual or quarterly MDA will accelerate progress toward elimination but cannot guarantee it by 2025 in high-endemicity areas. Long-term concomitant MDA and vector control for high-endemicity areas might be useful.
Routledge I, Walker M, Cheke R, et al., 2018, Modelling the impact of larviciding on the population dynamics and biting rates of Simulium damnosum s.l.: implications for vector control as a complementary strategy for onchocerciasis elimination in Africa, Parasites & Vectors, Vol: 11, Pages: 1-16, ISSN: 1756-3305
Background:In 2012, the World Health Organization set goals for the elimination of onchocerciasis transmission by 2020 in selected African countries. Epidemiological data and mathematical modelling have indicated that elimination may not be achieved with annual ivermectin distribution in all endemic foci. Complementary and alternative treatment strategies (ATS), including vector control, will be necessary. Implementation of vector control will require that the ecology and population dynamics of Simuliumdamnosum sensu latobe carefully considered.Methods:We adapted our previous SIMuliid POPulation dynamics (SIMPOP) model to explore the impact of larvicidal insecticides on S.damnosums.l.biting rates in different ecological contexts and to identify how frequently and for how long vector control should be continued to sustain substantive reductions in vector biting. SIMPOP was fitted to data from large-scale aerial larviciding trials in savannah sites (Ghana) and small-scale ground larviciding trials in forest areas (Cameroon). The model was validated against independent data from Burkina Faso/Côte d’Ivoire (savannah) and Bioko (forest). Scenario analysis explored the effects of ecological and programmatic factors such as pre-control daily biting rate (DBR) and larviciding scheme design on reductions and resurgences in biting rates.Results: The estimated efficacy of large-scale aerial larviciding in the savannah was greater than that of ground-based larviciding in the forest. Small changes in larvicidal efficacy can have large impacts on intervention success. At 93% larvicidal efficacy (a realistic value based on field trials), 10 consecutive weekly larvicidal treatments would reduce DBRs by 96% (e.g. from 400 to 16bites/person/day). At 70% efficacy, and for 10 weekly applications, the DBRwould decrease by 67% (e.g. from 400 to 132bites/person/day). Larviciding is more likely to succeed in areas with lower water temperatures and where blackfly species have lo
Zain SNM, Basanez M-G, 2018, Collaborate or Collapse: Capacity Building in Zoonotic and Neglected Tropical Disease Modelling, TRENDS IN PARASITOLOGY, Vol: 34, Pages: 356-+, ISSN: 1471-4922
Whittaker C, Walker M, Pion SDS, et al., 2018, Loa loa: More Than Meets the Eye?, TRENDS IN PARASITOLOGY, Vol: 34, Pages: 261-262, ISSN: 1471-4922
Whittaker C, Walker M, Pion SDS, et al., 2018, The population biology and transmission dynamics of Loa loa, Trends in Parasitology, Vol: 34, Pages: 335-350, ISSN: 1471-5007
Endemic to Central Africa, loiasis – or African eye worm (caused by the filarial nematode Loa loa) – affects more than 10 million people. Despite causing ocular and systemic symptoms, it has typically been considered a benign condition, only of public health relevance because it impedes mass drug administration-based interventions against onchocerciasis and lymphatic filariasis in co-endemic areas. Recent research has challenged this conception, demonstrating excess mortality associated with high levels of infection, implying that loiasis warrants attention as an intrinsic public health problem. This review summarises available information on the key parasitological, entomological, and epidemiological characteristics of the infection and argues for the mobilisation of resources to control the disease, and the development of a mathematical transmission model to guide deployment of interventions.
Colebunders R, Basanez M-G, Siling K, et al., 2018, From river blindness control to elimination: bridge over troubled water, INFECTIOUS DISEASES OF POVERTY, Vol: 7, ISSN: 2095-5162
BackgroundAn estimated 25 million people are currently infected with onchocerciasis (a parasitic infection caused by the filarial nematode Onchocerca volvulus and transmitted by Simulium vectors), and 99% of these are in sub-Saharan Africa. The African Programme for Onchocerciasis Control closed in December 2015 and the World Health Organization has established a new structure, the Expanded Special Project for the Elimination of Neglected Tropical Diseases for the coordination of technical support for activities focused on five neglected tropical diseases in Africa, including onchocerciasis elimination.AimsIn this paper we argue that despite the delineation of a reasonably well-defined elimination strategy, its implementation will present particular difficulties in practice. We aim to highlight these in an attempt to ensure that they are well understood and that effective plans can be laid to solve them by the countries concerned and their international partners.ConclusionsA specific concern is the burden of disease caused by onchocerciasis-associated epilepsy in hyperendemic zones situated in countries experiencing difficulties in strengthening their onchocerciasis control programmes. These difficulties should be identified and programmes supported during the transition from morbidity control to interruption of transmission and elimination.
Colebunders R, Mandro M, Njamnshi AK, et al., 2018, Report of the first international workshop on onchocerciasis-associated epilepsy, Infectious Diseases of Poverty, Vol: 7, ISSN: 2095-5162
Background:Recently, several epidemiological studies performed in Onchocerca volvulus-endemic regions have suggested that onchocerciasis-associated epilepsy (OAE) may constitute an important but neglected public health problem in many countries where onchocerciasis is still endemic.Main text:On October 12–14th 2017, the first international workshop on onchocerciasis-associated epilepsy (OAE) was held in Antwerp, Belgium. The workshop was attended by 79 participants from 20 different countries. Recent research findings strongly suggest that O. volvulus is an important contributor to epilepsy, particularly in meso- and hyperendemic areas for onchocerciasis. Infection with O. volvulus is associated with a spectrum of epileptic seizures, mainly generalised tonic-clonic seizures but also atonic neck seizures (nodding), and stunted growth. OAE is characterised by an onset of seizures between the ages of 3–18 years. Multidisciplinary working groups discussed topics such as how to 1) strengthen the evidence for an association between onchocerciasis and epilepsy, 2) determine the burden of disease caused by OAE, 3) prevent OAE, 4) improve the treatment/care for persons with OAE and affected families, 5) identify the pathophysiological mechanism of OAE, and 6) deal with misconceptions, stigma, discrimination and gender violence associated with OAE.An OAE Alliance was created to increase awareness about OAE and its public health importance, stimulate research and disseminate research findings, and create partnerships between OAE researchers, communities, advocacy groups, ministries of health, non-governmental organisations, the pharmaceutical industry and funding organizations.Conclusions:Although the exact pathophysiological mechanism underlying OAE remains unknown, there is increasing evidence that by controlling and eliminating onchocerciasis, OAE will also disappear. Therefore, OAE constitutes an additional argument for strengthening onchocerciasis elimination
Cano J, Basáñez M-G, O'Hanlon SJ, et al., 2018, Identifying co-endemic areas for major filarial infections in sub-Saharan Africa: seeking synergies and preventing severe adverse events during mass drug administration campaigns, Parasites & Vectors, Vol: 11, Pages: 70-70, ISSN: 1756-3305
BACKGROUND: Onchocerciasis and lymphatic filariasis (LF) are major filarial infections targeted for elimination in most endemic sub-Saharan Africa (SSA) countries by 2020/2025. The current control strategies are built upon community-directed mass administration of ivermectin (CDTI) for onchocerciasis, and ivermectin plus albendazole for LF, with evidence pointing towards the potential for novel drug regimens. When distributing microfilaricides however, considerable care is needed to minimise the risk of severe adverse events (SAEs) in areas that are co-endemic for onchocerciasis or LF and loiasis. This work aims to combine previously published predictive risk maps for onchocerciasis, LF and loiasis to (i) explore the scale of spatial heterogeneity in co-distributions, (ii) delineate target populations for different treatment strategies, and (iii) quantify populations at risk of SAEs across the continent. METHODS: Geographical co-endemicity of filarial infections prior to the implementation of large-scale mass treatment interventions was analysed by combining a contemporary LF endemicity map with predictive prevalence maps of onchocerciasis and loiasis. Potential treatment strategies were geographically delineated according to the level of co-endemicity and estimated transmission intensity. RESULTS: In total, an estimated 251 million people live in areas of LF and/or onchocerciasis transmission in SSA, based on 2015 population estimates. Of these, 96 million live in areas co-endemic for both LF and onchocerciasis, providing opportunities for integrated control programmes, and 83 million live in LF-monoendemic areas potentially targetable for the novel ivermectin-diethylcarbamazine-albendazole (IDA) triple therapy. Only 4% of the at-risk population live in areas co-endemic with high loiasis transmission, representing up to 1.2 million individuals at high risk of experiencing SAEs if treated with ivermectin. In these areas, alternative treatment strategies should be ex
Veriegh F, Basanez M-G, Baidoo P, et al., 2018, GEO-STATISTICAL ANALYSIS OF CONTINUAL ONCHOCERCIASIS TRANSMISSION IN AND AROUND AREAS RECEIVING BI-ANNUAL IVERMECTIN TREATMENT REGIMENS, 67th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTHM), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 36-37, ISSN: 0002-9637
Buell K, Whittaker C, Chesnais C, et al., 2018, FROM INFECTION TO DISEASE IN LOIASIS: A SYSTEMATIC REVIEW OF CLINICO-EPIDEMIOLOGICAL CASE REPORTS, 67th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTHM), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 385-385, ISSN: 0002-9637
Nouvellet P, Cucunuba Z, Rodriguez-Barraquer I, et al., 2018, CHARACTERIZATION OF POPULATION EXPOSURE (SEROPREVALENCE) TO ARBOVIRUSES AFTER RECENT OUTBREAKS IN COLOMBIA: DENGUE, CHIKUNGUNYA AND ZIKA, 67th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTHM), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 296-296, ISSN: 0002-9637
Whittaker C, Walker M, Pion S, et al., 2018, EVALUATING THE IMPACT OF ANTHELMINTIC-BASED INTERVENTION STRATEGIES FOR CONTROLLING <it>LOA LOA</it>: A MATHEMATICAL MODELLING STUDY USING EPILOA, 67th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTHM), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 16-16, ISSN: 0002-9637
Dixon M, Braae U, Winskill P, et al., 2018, TOWARDS THE DESIGN AND OPTIMIZATION OF INTERVENTION STRATEGIES AGAINST <it>TAENIA SOLIUM</it> TAENIOSIS/CYSTICERCOSIS BY MULTI-MODEL COMPARISON, 67th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTHM), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 151-151, ISSN: 0002-9637
Halder J, Prociuk D, Nouvellet P, et al., 2018, DECREASING THE IMPACT OF CHAGAS DISEASE THROUGH MODELLING: THE DICTUM FRAMEWORK FOR RETRIEVING, COLLATING, AND ANALYSING SEROSURVEY DATA FOR CHAGAS DISEASE ACROSS LATIN AMERICA, 67th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTHM), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 625-625, ISSN: 0002-9637
Jewell P, Abraham A, Schmidt V, et al., 2018, TREATMENT OF INDIVIDUALS LIVING WITH NEUROCYSTICERCOSIS AND HIV/AIDS: A SCOPING REVIEW, 67th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTHM), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 151-151, ISSN: 0002-9637
Assoum M, Ortu G, Basanez M-G, et al., 2017, Spatiotemporal distribution and population at risk of soil-transmitted helminth infections following an eight-year school-based deworming programme in Burundi, 2007-2014, Parasites & Vectors, Vol: 10, ISSN: 1756-3305
Background: Investigating the effect of successive annual deworming rounds on the spatiotemporal distribution ofinfection prevalence and numbers at risk for soil-transmitted helminths (STHs) can help identify communitiesnearing elimination and those needing further interventions. In this study, we aim to quantify the impact ofan 8-year mass drug administration (MDA) programme (from 2007 to 2014) on the spatiotemporal distribution ofprevalence of STH infections and to estimate the number of school-aged children infected with STHs in Burundi.Methods: During annual longitudinal school-based surveys in Burundi between 2007 and 2011, STH infection andanthropometric data for a total of 40,656 children were collected; these data were supplemented with data froma national survey conducted in 2014. Bayesian model based geostatistics (MBG) were used to generate predictiveprevalence maps for each STH species and year. The numbers of children at-risk of infection per district between2008 and 2014 were estimated as the product of the predictive prevalence maps and population density maps.Results: Overall, the degree of spatial clustering of STH infections decreased between 2008 and 2011; in 2014 thegeographical clusters of all STH infections reappeared. The reduction in prevalence was small for Ascaris lumbricoidesand Trichuris trichiura in the centre and central north of the country. Our predictive prevalence maps for hookwormindicate a reduction in prevalence along the periphery of the country. The predicted number of children infected withany STH species decreased substantially between 2007 and 2011, but in 2014 there was an increase in the predictednumber of children infected with A. lumbricoides and T. trichiura. In 2014, the districts with the highest predictednumber of children infected with A. lumbricoides, T. trichiura and hookworms were Kibuye district (n = 128,903),Mabayi district (n = 35,302) and Kiremba (n = 87,511), respectively.Conclusions: While the MDA programme
Walker M, Stolk WA, Dixon M, et al., 2017, ELIMINATION OF ONCHOCERCIASIS WITH IVERMECTIN: A VALIDATION OF THE EPIONCHO AND ONCHOSIM MODELS USING DATA FROM MALI AND SENEGAL, 65th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 154-154, ISSN: 0002-9637
Pearson I, Halder JB, Basanez M-G, et al., 2017, THE EFFICACY OF PREVENTATIVE CHEMOTHERAPY DRUGS FOR THE TREATMENT OF LYMPHATIC FILARIASIS: A SYSTEMATIC REVIEW AND MODEL-BASED META-ANALYSIS, 65th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 344-345, ISSN: 0002-9637
Cucunuba ZM, Sicuri E, Diaz D, et al., 2017, ESTIMATING THE COSTS AND COST-EFFECTIVENESS OF EARLY DIAGNOSIS AND TREATMENT OF CHAGAS DISEASE IN COLOMBIA, 65th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 364-364, ISSN: 0002-9637
Halder JB, Jule AM, Vaillant M, et al., 2017, SYSTEMATIC REVIEW AND META-ANALYSIS OF SOIL-TRANSMITTED HELMINTH TREATMENT EFFICACY STUDIES AND THE CASE FOR SHARING INDIVIDUAL PATIENT DATA, 65th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 542-542, ISSN: 0002-9637
Walker M, Halder JB, Awadzi K, et al., 2017, DEFINING AND DETECTING SUBOPTIMAL RESPONSES TO IVERMECTIN IN PATIENTS WITH ONCHOCERCIASIS, 65th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 344-344, ISSN: 0002-9637
Deol AK, French MD, Walker M, et al., 2017, COMMUNITY-WIDE PATTERNS OF INFECTION AFTER MORE THAN TEN YEARS OF PREVENTIVE CHEMOTHERAPY FOR SCHISTOSOMIASIS AND SOIL-TRANSMITTED HELMINTH INFECTION IN UGANDA: ARE WE READY TO MOVE BEYOND MORBIDITY CONTROL?, 65th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 558-558, ISSN: 0002-9637
Cucunuba Z, Nouvellet P, Okuwoga O, et al., 2017, PROGRESSION AND MORTALITY RATES FOR MODELLING THE BURDEN OF CHAGAS DISEASE, 65th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 206-207, ISSN: 0002-9637
Assoum M, Magalhaes RS, Ortu G, et al., 2017, PREDICTING INFECTION DISTRIBUTION AND BURDEN OF DISEASE USING SPATIOTEMPORAL MODELS FOLLOWING A SEVEN YEAR MASS DRUG ADMINISTRATION PROGRAM AND LONGITUDINAL STUDY IN BURUNDI: 2008-2014, 65th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 543-543, ISSN: 0002-9637
Jule AM, Halder JB, Vaillant M, et al., 2017, SYSTEMATIC REVIEW OF ANTISCHISTOSOMAL TREATMENT EFFICACY STUDIES AND THE SIGNIFICANCE OF INDIVIDUALLEVEL PARTICIPANT DATA FOR META-ANALYSES, 65th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 371-371, ISSN: 0002-9637
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