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MALARIA AND RAINFALL

Saturday, 26th of May 2012

• MALARIA AND RAINFALL

       Expand+Journal of Infectious Diseasesjid.oxfordjournals.org

J Infect Dis. (2012) 205 (12): 1885-1891. doi: 10.1093/infdis/jis289 First published online: April 5, 2012

 

Indian Ocean Dipole and Rainfall Drive a Moran Effect in East Africa Malaria Transmission

1.   Luis Fernando Chaves1,2, Akiko Satake1, Masahiro Hashizume3 and Noboru Minakawa3

+ Author Affiliations

1.    ¹Graduate School of Environmental Sciences and Global Center of Excellence Program on Integrated Field Environmental Science, Hokkaido University, Sapporo

2.    ²Programa de Investigación en Enfermedades Tropicales, Escuela de Medicina Veterinaria, Universidad Nacional, Heredia, Costa Rica

3.    ³Institute of Tropical Medicine (NEKKEN) and Global Center of Excellence Program on Tropical and Emergent Infectious Diseases, Nagasaki University, Japan

1.    Correspondence: Luis Fernando Chaves, Lic, MSc, PhD, Graduate School of Environmental Sciences, Hokkaido University, Rm A701 5-chome, Kita 10-jo Nishi, Kita-ku, Sapporo 060-0810, Hokkaido, Japan (lchaves@ees.hokudai.ac.jp).

Abstract below; full text available to JID subscribers

Background. Patterns of concerted fluctuation in populations—synchrony—can reveal impacts of climatic variability on disease dynamics. We examined whether malaria transmission has been synchronous in an area with a common rainfall regime and sensitive to the Indian Ocean Dipole (IOD), a global climatic phenomenon affecting weather patterns in East Africa.

Methods. We studied malaria synchrony in 5 15-year long (1984–1999) monthly time series that encompass an altitudinal gradient, approximately 1000 m to 2000 m, along Lake Victoria basin. We quantified the association patterns between rainfall and malaria time series at different altitudes and across the altitudinal gradient encompassed by the study locations.

Results. We found a positive seasonal association of rainfall with malaria, which decreased with altitude. By contrast, IOD and interannual rainfall impacts on interannual disease cycles increased with altitude. Our analysis revealed a nondecaying synchrony of similar magnitude in both malaria and rainfall, as expected under a Moran effect, supporting a role for climatic variability on malaria epidemic frequency, which might reflect rainfall-mediated changes in mosquito abundance.

Conclusions. Synchronous malaria epidemics call for the integration of knowledge on the forcing of malaria transmission by environmental variability to develop robust malaria control and elimination programs.