• Parasitology / Volume 139 / Issue 01 / January 2012, pp 14-25
  • Copyright © Cambridge University Press 2011. The online version of this article is published within an Open Access environment subject to the conditions of the Creative Commons Attribution-NonCommercial-ShareAlike licence <>. The written permission of Cambridge University Press must be obtained for commercial re-use.
  • DOI: (About DOI), Published online: 14 October 2011

Research Article

Regime shifts and heterogeneous trends in malaria time series from Western Kenya Highlands


a1 Graduate School of Environmental Sciences and Global Center of Excellence Program on Integrated Field Environmental Science, Hokkaido University, Sapporo, Japan

a2 Programa de Investigación en Enfermedades Tropicales, Escuela de Medicina Veterinaria, Universidad Nacional, Heredia, Costa Rica

a3 Institute of Tropical Medicine (NEKKEN) and Global Center of Excellence Program on Tropical and Emergent Infectious Diseases, Nagasaki University, Nagasaki, Japan


Large malaria epidemics in the East African highlands during the mid and late 1990s kindled a stream of research on the role that global warming might have on malaria transmission. Most of the inferences using temporal information have been derived from a malaria incidence time series from Kericho. Here, we report a detailed analysis of 5 monthly time series, between 15 and 41 years long, from West Kenya encompassing an altitudinal gradient along Lake Victoria basin. We found decreasing, but heterogeneous, malaria trends since the late 1980s at low altitudes (<1600 m), and the early 2000s at high altitudes (>1600 m). Regime shifts were present in 3 of the series and were synchronous in the 2 time series from high altitudes. At low altitude, regime shifts were associated with a shift from increasing to decreasing malaria transmission, as well as a decrease in variability. At higher altitudes, regime shifts reflected an increase in malaria transmission variability. The heterogeneity in malaria trends probably reflects the multitude of factors that can drive malaria transmission and highlights the need for both spatially and temporally fine-grained data to make sound inferences about the impacts of climate change and control/elimination interventions on malaria transmission.

(Online publication October 14 2011)


c1 Corresponding author: Graduate School of Environmental Sciences, Hokkaido University, Suite A701, Kita-10, Nishi-5, Kita-Ku, Sapporo, Hokkai-do, 060-0810 Japan. Tel: +81 11 706 2267. Fax: +81 11 706 4954. E-mail: