1. Pathobiology Department, College of Veterinary Medicine, Auburn University, Auburn, AL 36832, USA
2. Large Animal Clinical Sciences, School of Veterinary Medicine and Biomedical Sciences, Texas A&M, College Station, TX 77843, USA
3. Hagyard Equine Medical Institute, Lexington, KY 40511, USA
4. College of Sciences and Mathematics, Auburn University, Auburn, AL 36849, USA