Temperature and population density determine reservoir regions of seasonal persistence in highland malaria

Amir S. Siraj, Menno J. Bouma, Mauricio Santos-Vega, Asnakew K. Yeshiwondim, Dale S. Rothman, Damtew Yadeta, Paul C. Sutton, Mercedes Pascual

Research output: Contribution to journalArticlepeer-review

Abstract

A better understanding of malaria persistence in highly seasonal environments such as highlands and desert fringes requires identifying the factors behind the spatial reservoir of the pathogen in the low season. In these ‘unstable’ malaria regions, such reservoirs play a critical role by allowing persistence during the low transmission season and therefore, between seasonal outbreaks. In the highlands of East Africa, the most populated epidemic regions in Africa, temperature is expected to be intimately connected to where in space the disease is able to persist because of pronounced altitudinal gradients. Here, we explore other environmental and demographic factors that may contribute to malaria’s highland reservoir. We use an extensive spatio-temporal dataset of confirmed monthly Plasmodium falciparum cases from 1995 to 2005 that finely resolves space in an Ethiopian highland. With a Bayesian approach for parameter estimation and a generalized linear mixed model that includes a spatially structured randomeffect, we demonstrate that population density is important to disease persistence during the low transmission season. This population effect is not accounted for in typical models for the transmission dynamics of the disease, but is consistent in part with a more complex functional form of the force of infection proposed by theory for vector-borne infections, only during the low season as we discuss. As malaria risk usually decreases in more urban environments with increased human densities, the opposite counterintuitive finding identifies novel control targets during the low transmission season in African highlands.

Original languageEnglish (US)
Article number20151383
JournalProceedings of the Royal Society B: Biological Sciences
Volume282
Issue number1820
DOIs
StatePublished - Dec 2 2015

Keywords

  • Malaria
  • Persistence
  • Reservoir

ASJC Scopus subject areas

  • General Biochemistry, Genetics and Molecular Biology
  • General Immunology and Microbiology
  • General Environmental Science
  • General Agricultural and Biological Sciences

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