Environmental limits of Rift Valley fever revealed using ecoepidemiological mechanistic models

Giovanni Lo Iacono*, Andrew A. Cunningham, Bernard Bett, Delia Grace, David W. Redding, James L.N. Wood

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)

Abstract

Vector-borne diseases (VBDs) of humans and domestic animals are a significant component of the global burden of disease and a key driver of poverty. The transmission cycles of VBDs are often strongly mediated by the ecological requirements of the vectors, resulting in complex transmission dynamics, including intermittent epidemics and an unclear link between environmental conditions and disease persistence. An important broader concern is the extent to which theoretical models are reliable at forecasting VBDs; infection dynamics can be complex, and the resulting systems are highly unstable. Here, we examine these problems in detail using a case study of Rift Valley fever (RVF), a high-burden disease endemic to Africa. We develop an ecoepidemiological, compartmental, mathematical model coupled to the dynamics of ambient temperature and water availability and apply it to a realistic setting using empirical environmental data from Kenya. Importantly, we identify the range of seasonally varying ambient temperatures and water-body availability that leads to either the extinction of mosquito populations and/or RVF (nonpersistent regimens) or the establishment of long-term mosquito populations and consequently, the endemicity of the RVF infection (persistent regimens). Instabilities arise when the range of the environmental variables overlaps with the threshold of persistence. The model captures the intermittent nature of RVF occurrence, which is explained as low-level circulation under the threshold of detection, with intermittent emergence sometimes after long periods. Using the approach developed here opens up the ability to improve predictions of the emergence and behaviors of epidemics of many other important VBDs.

Original languageEnglish
Pages (from-to)E7448-E7456
JournalProceedings of the National Academy of Sciences of the United States of America
Volume115
Issue number31
DOIs
Publication statusPublished - 31 Jul 2018

Bibliographical note

Funding Information:
We thank Dr. Erasmus Zu Ermgassen for his help during the preliminary stages of the work. This work was mainly conducted within the Dynamic Drivers of Disease in Africa Consortium, Natural Environment Research Council (NERC) Project NE-J001570-1, which was funded with support from the Ecosystem Services for Poverty Alleviation (ESPA) program. The ESPA program is funded by the Department for International Development, the Economic and Social Research Council, and the NERC. The work was partially supported by the National Institute for Health Research (NIHR) Health Protection Research Unit in Environmental Change and Health at the London School of Hygiene and Tropical Medicine in partnership with Public Health England (PHE) and in collaboration with the University of Exeter, University College London, and the Met Office. A.A.C. and J.L.N.W. are also supported by European Union FP7 Project ANTIGONE (Contract 278976). A.A.C. was supported by a Royal Society Wolfson Research Merit Award. J.L.N.W. is supported by the Alborada Trust. D.W.R. is supported by a Medical Research Council UK Research and Innovation/Rutherford Fellowship (MR/R02491X/1). The views expressed are those of the author(s) and not necessarily those of the National Health Service, the NIHR, the Department of Health, or PHE.

Funding Information:
ACKNOWLEDGMENTS. We thank Dr. Erasmus Zu Ermgassen for his help during the preliminary stages of the work. This work was mainly conducted within the Dynamic Drivers of Disease in Africa Consortium, Natural Environment Research Council (NERC) Project NE-J001570-1, which was funded with support from the Ecosystem Services for Poverty Alleviation (ESPA) program. The ESPA program is funded by the Department for International Development, the Economic and Social Research Council, and the NERC. The work was partially supported by the National Institute for Health Research (NIHR) Health Protection Research Unit in Environmental Change and Health at the London School of Hygiene and Tropical Medicine in partnership with Public Health England (PHE) and in collaboration with the University of Exeter, University College London, and the Met Office. A.A.C. and J.L.N.W. are also supported by European Union FP7 Project ANTIGONE (Contract 278976). A.A.C. was supported by a Royal Society Wolfson Research Merit Award. J.L.N.W. is supported by the Alborada Trust. D.W.R. is supported by a Medical Research Council UK Research and Innovation/Rutherford Fellowship (MR/R02491X/1). The views expressed are those of the author(s) and not necessarily those of the National Health Service, the NIHR, the Department of Health, or PHE.

Publisher Copyright:
© 2018 National Academy of Sciences. All rights reserved.

Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.

Keywords

  • Cross-species transmission
  • Floquet analysis
  • Stability analysis
  • Vector-borne diseases
  • Zoonosis

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