This is the first study to attempt to establish an apparent prevalence of these conditions in racing sled dogs and to attempt to define a causative etiology. The mushing community has been strongly suspicious of an infectious etiology for the occurrence of diarrhea, with recent concern focused on Clostridium spp. and leading to inappropriate use of crude vaccines. However, this study did not identify any association between Clostridium perfringens or Clostridium difficile or their respective toxins and the occurrence of diarrhea or fecal blood in racing sled dogs.