Selected wetland soil properties correlate to Rift Valley fever livestock mortalities reported in 2009-10 in central South Africa

PLoS One. 2020 May 18;15(5):e0232481. doi: 10.1371/journal.pone.0232481. eCollection 2020.

Abstract

Outbreaks of Rift Valley fever have devastating impacts on ruminants, humans, as well as on regional and national economies. Although numerous studies on the impact and outbreak of Rift Valley fever exist, relatively little is known about the role of environmental factors, especially soil, on the aestivation of the virus. This study thus selected 22 sites for study in central South Africa, known to be the recurrent epicenter of widespread Rift Valley fever outbreaks in Southern Africa. Soils were described, sampled and analyzed in detail at each site. Of all the soil variables analyzed for, only eight (cation exchange capacity, exchangeable Ca2+, exchangeable K+, exchangeable Mg2+, soluble Ca2+, medium sand, As, and Br) were statistically identified to be potential indicators of sites with reported Rift Valley fever mortalities, as reported for the 2009-2010 Rift Valley fever outbreak. Four soil characteristics (exchangeable K+, exchangeable Mg2+, medium sand, and Br) were subsequently included in a discriminant function that could potentially be used to predict sites that had reported Rift Valley fever-associated mortalities in livestock. This study therefore constitutes an initial attempt to predict sites prone to Rift Valley fever livestock mortality from soil properties and thus serves as a basis for broader research on the interaction between soil, mosquitoes and Rift Valley fever virus. Future research should include other environmental components such as vegetation, climate, and water properties as well as correlating soil properties with floodwater Aedes spp. abundance and Rift Valley fever virus prevalence.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Aedes / virology
  • Animals
  • Disease Outbreaks / veterinary*
  • Humans
  • Livestock
  • Metals / analysis
  • Mosquito Vectors / virology
  • Rift Valley Fever / mortality*
  • Rift Valley Fever / transmission
  • Rift Valley Fever / virology
  • Rift Valley fever virus / pathogenicity
  • Risk Factors
  • Soil / chemistry
  • South Africa / epidemiology
  • Wetlands
  • Zoonoses / mortality

Substances

  • Metals
  • Soil

Grants and funding

WBK, MKR and JTP are thankful to the U.S. Department of Defense, Defense Threat Reduction Agency's Biological Threat Reduction Program for funding. Grant number: HDTRA1-14-1-0029. URL: https://www.dtra.mil/Mission/Mission- irectorates/Cooperative-Threat-Reduction/#. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The project depicted is sponsored by the U.S. Department of Defense, Defense Threat Reduction Agency. The content of the information does not necessarily reflect the position or the policy of the federal government, and no official endorsement should be inferred. Claudia Cordel is affiliated with ExecuVet Veterinary Clinical and Scientific Consulting a private consulting company hired through the funding received by the listed funders. ExecuVet Veterinary Clinical and Scientific Consulting provided support in the form of salaries for authors CC, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific role of this author is articulated in the ‘author contributions’ section.