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@article{Hamley:2019:10.1371/journal.pntd.0007557,
author = {Hamley, JID and Milton, P and Walker, M and Basáñez, M-G},
doi = {10.1371/journal.pntd.0007557},
journal = {PLoS Neglected Tropical Diseases},
pages = {e0007557--e0007557},
title = {Modelling exposure heterogeneity and density dependence in onchocerciasis using a novel individual-based transmission model, EPIONCHO-IBM: Implications for elimination and data needs},
url = {http://dx.doi.org/10.1371/journal.pntd.0007557},
volume = {13},
year = {2019}
}

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TY  - JOUR
AB  - BackgroundDensity dependence in helminth establishment and heterogeneity in exposure to infection are known to drive resilience to interventions based on mass drug administration (MDA). However, the interaction between these processes is poorly understood. We developed a novel individual-based model for onchocerciasis transmission, EPIONCHO-IBM, which accounts for both processes. We fit the model to pre-intervention epidemiological data and explore parasite dynamics during MDA with ivermectin.Methodology/Principal findingsDensity dependence and heterogeneity in exposure to blackfly (vector) bites were estimated by fitting the model to matched pre-intervention microfilarial prevalence, microfilarial intensity and vector biting rate data from savannah areas of Cameroon and Côte d’Ivoire/Burkina Faso using Latin hypercube sampling. Transmission dynamics during 25 years of annual and biannual ivermectin MDA were investigated. Density dependence in parasite establishment within humans was estimated for different levels of (fixed) exposure heterogeneity to understand how parametric uncertainty may influence treatment dynamics. Stronger overdispersion in exposure to blackfly bites results in the estimation of stronger density-dependent parasite establishment within humans, consequently increasing resilience to MDA. For all levels of exposure heterogeneity tested, the model predicts a departure from the functional forms for density dependence assumed in the deterministic version of the model.Conclusions/SignificanceThis is the first, stochastic model of onchocerciasis, that accounts for and estimates density-dependent parasite establishment in humans alongside exposure heterogeneity. Capturing the interaction between these processes is fundamental to our understanding of resilience to MDA interventions. Given that uncertainty in these processes results in very different treatment dynamics, collecting data on exposure heterogeneity would be essential for improvin
AU  - Hamley,JID
AU  - Milton,P
AU  - Walker,M
AU  - Basáñez,M-G
DO  - 10.1371/journal.pntd.0007557
EP  - 0007557
PY  - 2019///
SN  - 1935-2727
SP  - 0007557
TI  - Modelling exposure heterogeneity and density dependence in onchocerciasis using a novel individual-based transmission model, EPIONCHO-IBM: Implications for elimination and data needs
T2  - PLoS Neglected Tropical Diseases
UR  - http://dx.doi.org/10.1371/journal.pntd.0007557
UR  - https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0007557
UR  - http://hdl.handle.net/10044/1/75612
VL  - 13
ER  -

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