Abstract
Illnesses such as hemorrhagic colitis (HC) and hemolytic uremic syndrome (HUS) caused by Shiga toxin-producing Escherichia coli (STEC) remain a health concern in the United States and throughout the world. Although the majority of STEC cases have been linked to undercooked ground beef and contaminated fruits and vegetables, companion animals can also be a source of transmission, specifically dogs and horses (21). This is of particular concern to immunocompromised individuals, elderly and children. Cattle, and other ruminant animals, are known carriers of STEC (4). To date, most STEC research has focused on cattle due to their link to numerous outbreaks as a result of contaminated ground beef, water, fruits and vegetables. Non-ruminant animals such as horses, dogs and birds have also been implicated as carriers of STEC, but at a lower prevalence than ruminant animals (7). There is currently no information in the literature on the prevalence of STEC in horses. The purpose of this study was to develop an assay system for the evaluation of pathogenic bacteria in horse feces and on horse hides and then to evaluate the prevalence of STEC in the equine population in the Sacramento Valley by evaluating both fecal and hide-swab samples. Methods were successfully developed to sample equine feces and hide samples and to isolate the DNA from each sample type to determine the presence of the Shiga toxin genes stx1 and stx2 as a measure of STEC prevalence. The horses sampled in this study were placed in one of two groups: those that interact with ruminant animals and those with no ruminant interaction. One hundred fifty-six horses were sampled in the greater Sacramento Valley between June 2008 and September 2009: 78 ruminant-interacting and 78 non ruminant-interacting. Of the 156 horses sampled, 4 (2.6%) were positive for stx2, all of which interacted with ruminants. Therefore, of the ruminant-interacting group, 4 of 78 (5.1%) were positive for stx2 and of the non- ruminant-interacting group, 0 of 78 (0.0%) were positive for either stx1 or stx2. None of the 156 horses sampled were positive for stx1.