Wild ungulates as disseminators of Shiga toxin-producing Escherichia coli in urban areas

PLoS One. 2013 Dec 11;8(12):e81512. doi: 10.1371/journal.pone.0081512. eCollection 2013.

Abstract

Background: In 2008, children playing on a soccer field in Colorado were sickened with a strain of Shiga toxin-producing Escherichia coli (STEC) O157:H7, which was ultimately linked to feces from wild Rocky Mountain elk. We addressed whether wild cervids were a potential source of STEC infections in humans and whether STEC was ubiquitous throughout wild cervid populations in Colorado.

Methodology/principal findings: We collected 483 fecal samples from Rocky Mountain elk and mule deer in urban and non-urban areas. Samples testing positive for STEC were higher in urban (11.0%) than non-urban (1.6%) areas. Elk fecal samples in urban areas had a much higher probability of containing STEC, which increased in both urban and non-urban areas as maximum daily temperature increased. Of the STEC-positive samples, 25% contained stx1 strains, 34.3% contained stx2, and 13% contained both stx1 and stx2. Additionally, eaeA genes were detected in 54.1% of the positive samples. Serotypes O103, and O146 were found in elk and deer feces, which also have the potential to cause human illness.

Conclusions/significance: The high incidence of stx2 strains combined with eaeA and E-hyl genes that we found in wild cervid feces is associated with severe human disease, such as hemolytic uremic syndrome. This is of concern because there is a very close physical interface between elk and humans in urban areas that we sampled. In addition, we found a strong relationship between ambient temperature and incidence of STEC in elk feces, suggesting a higher incidence of STEC in elk feces in public areas on warmer days, which in turn may increase the likelihood that people will come in contact with infected feces. These concerns also have implications to other urban areas where high densities of coexisting wild cervids and humans interact on a regular basis.

MeSH terms

  • Adhesins, Bacterial / genetics
  • Animals
  • Child
  • Cities
  • Colorado / epidemiology
  • Deer / microbiology*
  • Disease Reservoirs*
  • Escherichia coli Infections / epidemiology
  • Escherichia coli Infections / microbiology
  • Escherichia coli Infections / transmission*
  • Escherichia coli Infections / veterinary*
  • Escherichia coli O157 / genetics
  • Escherichia coli O157 / isolation & purification*
  • Escherichia coli Proteins / genetics
  • Feces / microbiology
  • Female
  • Gene Expression
  • Humans
  • Male
  • Polymerase Chain Reaction
  • Seasons
  • Serotyping
  • Shiga Toxin 1 / genetics
  • Shiga Toxin 2 / genetics
  • Shiga-Toxigenic Escherichia coli / genetics
  • Shiga-Toxigenic Escherichia coli / isolation & purification*
  • Temperature
  • Trees

Substances

  • Adhesins, Bacterial
  • Escherichia coli Proteins
  • Shiga Toxin 1
  • Shiga Toxin 2
  • eaeA protein, E coli

Grant support

This study was funded by the United States Department of Agriculture. The manuscript was reviewed for general policy statements committing the USDA to action, but otherwise the findings were independently developed by the authors.