Rift Valley fever risk map model and seroprevalence in selected wild ungulates and camels from Kenya

PLoS One. 2013 Jun 28;8(6):e66626. doi: 10.1371/journal.pone.0066626. Print 2013.

Abstract

Since the first isolation of Rift Valley fever virus (RVFV) in the 1930s, there have been multiple epizootics and epidemics in animals and humans in sub-Saharan Africa. Prospective climate-based models have recently been developed that flag areas at risk of RVFV transmission in endemic regions based on key environmental indicators that precede Rift Valley fever (RVF) epizootics and epidemics. Although the timing and locations of human case data from the 2006-2007 RVF outbreak in Kenya have been compared to risk zones flagged by the model, seroprevalence of RVF antibodies in wildlife has not yet been analyzed in light of temporal and spatial predictions of RVF activity. Primarily wild ungulate serum samples from periods before, during, and after the 2006-2007 RVF epizootic were analyzed for the presence of RVFV IgM and/or IgG antibody. Results show an increase in RVF seropositivity from samples collected in 2007 (31.8%), compared to antibody prevalence observed from 2000-2006 (3.3%). After the epizootic, average RVF seropositivity diminished to 5% in samples collected from 2008-2009. Overlaying maps of modeled RVF risk assessments with sampling locations indicated positive RVF serology in several species of wild ungulate in or near areas flagged as being at risk for RVF. Our results establish the need to continue and expand sero-surveillance of wildlife species Kenya and elsewhere in the Horn of Africa to further calibrate and improve the RVF risk model, and better understand the dynamics of RVFV transmission.

Publication types

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

MeSH terms

  • Animals
  • Animals, Wild / virology
  • Antibodies, Viral / blood
  • Artiodactyla / virology
  • Camelus / virology*
  • Disease Outbreaks*
  • Epidemiological Monitoring
  • Humans
  • Kenya / epidemiology
  • Prevalence
  • Rift Valley Fever / blood
  • Rift Valley Fever / epidemiology
  • Rift Valley Fever / veterinary*
  • Rift Valley fever virus / immunology*
  • Risk
  • Seroepidemiologic Studies

Substances

  • Antibodies, Viral

Grants and funding

We are indebted to the International Atomic Energy Agency (IAEA) for the initial funding of this study. This project was also support in part by the US Department of Agriculture, Agricultural Research Service Project #58-5430-005-00D through an interagency agreement with the Science and Technology Directorate of the U.S. Department of Homeland Security under Award Number HSHQDC-07-00982. The Department of Defense-Armed Forces Health Surveillance Center, Division of GEIS Operations and the United States Department of Agriculture -Agricultural Research Service supported the RVF Monitoring and Risk Mapping project. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.