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Potential effects of warmer worms and vectors on onchocerciasis transmission in West Africa

Potential effects of warmer worms and vectors on onchocerciasis transmission in West Africa

Cheke, Robert A. ORCID: 0000-0002-7437-1934, Basáñez, Maria-Gloria, Perry, Malorie, White, Michale T., Garms, Rolf, Obuobie, E., Lamberton, Poppy H.L., Young, Stephen, Osei-Atweneboana, Mike Y., Intsiful, Joseph, Shen, Mingwang, Boakye, Daniel A. and Wilson, Michael D. (2015) Potential effects of warmer worms and vectors on onchocerciasis transmission in West Africa. Philosophical Transactions B, 370 (1665):20130559. ISSN 0962-8436 (Print), 1471-2970 (Online) (doi:

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Development times of eggs, larvae and pupae of vectors of onchocerciasis (Simulium spp.) and of Onchocerca volvulus larvae within the adult females of the vectors decrease with increasing temperature. At and above 25C,the parasite could reach its infective stage in less than 7 days when vectors could transmit after only two gonotrophic cycles. After incorporating exponential functions for vector development into a novel blackfly population model, it was predicted that fly numbers in Liberia and Ghana would peak at air temperatures of 29C and 34C, about 3C and 7C above current monthly averages, respectively; parous rates of forest flies (Liberia) would peak at 298C and of savannah flies (Ghana) at 308C. Small temperature increases (less than 28C) might lead to changes in geographical distributions of different vector taxa. When the new model was linked to an existing framework for the population dynamics of onchocerciasis in humans and vectors, transmission rates and worm loads were projected to increase with temperature to at least 338C. By contrast, analyses of field data on forest flies in Liberia and savannah flies in Ghana, in relation to regional climate change predictions, suggested, on the basis of simple regressions, that 13–41% decreases in fly numbers would be expected between the present and before 2040. Further research is needed to reconcile these conflicting conclusions.

Item Type: Article
Additional Information: [1] Copyright: (C) 2015 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License, which permits unrestricted use, provided the original author and source are credited. [2] Cite this article: Cheke RA et al. 2015 Potential effects of warmer worms and vectors on onchocerciasis transmission in West Africa. Phil. Trans. R. Soc. B 370: 20130559. [3] Funding statement: The part of this study dealing with Ghana was conducted as part of a project entitled ‘Ecohealth approach to the control of onchocerciasis in the Volta Basin of Ghana’ (no. 104270–017), supported by the Climate Change Adaptation in Africa (CCAA) programme, a joint initiative of Canada’s International Development ResearchCentre (IDRC) and theUK Department for International Development (DfID). The Liberian climate change work was part of a study to prepare Liberia’s first Climate Change and Vulnerability Assessment National Communication to the United Nations Framework Convention on Climate Change (UNFCCC), supported by the Global Environment Fund of the United Nations Environment Programme (GEF-UNEP). M.G.B., R.A.C., P.H.L.L., M.Y.O.-A. and M.D.W. acknowledge funding from the Wellcome Trust (grant nos. 085133/Z/08/Z and 092677/Z/10/Z), and M.G.B., M.Y.O.-A. and R.A.C. from a Leverhulme Trust– Royal Society Capacity Building Africa Award. [4] Published in Philosophical Transactions B, 05 April 2015; volume 370, issue 1665. Theme issue ‘Climate change and vector-borne diseases of humans’ compiled and edited by Paul E. Parham, Joanna Waldock, George K. Christophides and Edwin Michael
Uncontrolled Keywords: simulium damnosum complex, onchocerca volvulus, temperature, rainfall, river discharges, mathematical models
Subjects: S Agriculture > S Agriculture (General)
S Agriculture > SF Animal culture
Faculty / School / Research Centre / Research Group: Faculty of Engineering & Science
Faculty of Engineering & Science > Natural Resources Institute
Faculty of Engineering & Science > Natural Resources Institute > Agriculture, Health & Environment Department
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Last Modified: 12 May 2020 11:01

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