title: Potential effects of warmer worms and vectors on onchocerciasis transmission in West Africa.
abstract: 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 25°C, 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 29°C and 34°C, about 3°C and 7°C above current monthly averages, respectively; parous rates of forest flies (Liberia) would peak at 29°C and of savannah flies (Ghana) at 30°C. Small temperature increases (less than 2°C) 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 33°C. 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.
authors: Agriculture, Health and Environment Department, Natural Resources Institute, University of Greenwich at Medway, Central Avenue, Chatham Maritime, Kent ME4 4TB, UK Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, St Mary's Campus, Norfolk Place, London W2 1PG, UK r.a.cheke@greenwich.ac.uk.
authors: Robert A
authors: RA
authors: Cheke
authors: Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, St Mary's Campus, Norfolk Place, London W2 1PG, UK.
authors: Maria-Gloria
authors: MG
authors: Basáñez
authors: Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, St Mary's Campus, Norfolk Place, London W2 1PG, UK.
authors: Malorie
authors: M
authors: Perry
authors: Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, St Mary's Campus, Norfolk Place, London W2 1PG, UK.
authors: Michael T
authors: MT
authors: White
authors: Bernhard Nocht Institute for Tropical Medicine, Bernhard-Nocht-Strasse 74, Hamburg 20359, Germany.
authors: Rolf
authors: R
authors: Garms
authors: Water Research Institute, Council for Scientific and Industrial Research, PO Box M32, Accra, Ghana.
authors: Emmanuel
authors: E
authors: Obuobie
authors: Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, St Mary's Campus, Norfolk Place, London W2 1PG, UK.
authors: Poppy H L
authors: PH
authors: Lamberton
authors: Agriculture, Health and Environment Department, Natural Resources Institute, University of Greenwich at Medway, Central Avenue, Chatham Maritime, Kent ME4 4TB, UK.
authors: Stephen
authors: S
authors: Young
authors: Water Research Institute, Council for Scientific and Industrial Research, PO Box M32, Accra, Ghana.
authors: Mike Y
authors: MY
authors: Osei-Atweneboana
authors: Regional Institute for Population Studies, University of Ghana, PO Box LG 97, Legon, Accra, Ghana.
authors: Joseph
authors: J
authors: Intsiful
authors: Department of Applied Mathematics, Xi'an Jiaotong University, Xi'an 710049, People's Republic of China.
authors: Mingwang
authors: M
authors: Shen
authors: Noguchi Memorial Institute for Medical Research, University of Ghana, PO Box LG 581, Legon, Accra, Ghana.
authors: Daniel A
authors: DA
authors: Boakye
authors: Noguchi Memorial Institute for Medical Research, University of Ghana, PO Box LG 581, Legon, Accra, Ghana.
authors: Michael D
authors: MD
authors: Wilson
mesh_terms: D000354:Africa, Western / Q000453:epidemiology; D000818:Animals; D057231:Climate Change; D005260:Female; D006801:Humans; D007303:Insect Vectors / Q000502:physiology*; D007814:Larva / Q000254:growth & development; D008954:Models, Biological; D017181:Onchocerca volvulus / Q000502:physiology*; D009855:Onchocerciasis / Q000635:transmission*; D010063:Ovum / Q000254:growth & development; D011679:Pupa / Q000254:growth & development; D012843:Simuliidae / Q000254:growth & development*; D013696:Temperature
keywords: Onchocerca volvulus; Simulium damnosum complex; mathematical models; rainfall; river discharges; temperature