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Oklahoma State University
Center for Veterinary Health Sciences

Healthy Animals - Healthy People

Todd Holbrook

Department of Veterinary Clinical Sciences, Veterinary Medical Hospital
Todd Holbrook DVM, Diplomate ACVIM, ACVSMR
Professor and June Jacobs Endowed Chair in Equine Medicine
Equine Section Chief

Contact Information

About Dr. Holbrook

Dr. Todd Holbrook recieved his undergraduate, veterinary, and specialty training at the University of Georgia. From 1994-1995, he was a temporary Assistant Professor in the ambulatory section of the Department of Large Animal Medicine at the University of Georgia. and subsequently owned a large animal practice in Northeast Georgia. He left ambulatory practice in 2002 to join the Equine Medicine Faculty at Oklahoma State University. Dr Holbrook is a Large Animal Diplomate of the American College of Veterinary Internal Medicine and the American College of Veterinary Sports Medicine and Rehabilitation, his special interests in equine medicine include infectious disease, gastrointestinal disease, and sports medicine. He is actively involved in the sport of endurance, and has provided veterinary care at numerous competitions, nationally, and internationally.


“Characterization of a Novel Tick Transmitted Ehrlichia sp. Infection in Horses”

Previous work from our laboratory documented a high prevalence of tick infestations in horses with pasture access in central Oklahoma. Amblyomma americanum was the predominant tick species represented and was present on over 95% of horses infested. Of notable concern was the relatively high (24.7%) prevalence of antibodies reactive to Ehrlichia sp. In horses with heavy tick burdens. Species specific serum ELISA and indirect IFA for antibodies reactive to known species of Ehrlichia as well as Ehrlichia specific PCR testing in whole blood on a subset of horses failed to confirm the identity of Ehrlichia sp.

Project Objectives:

  1.  Develop a natural exposure model to characterize the infection dynamics of tick‐borne Ehrlichia sp. infection in horses.
  2.  Document the clinical, clinicopathologic, and serologic consequences of tick‐borne Ehrlichia sp. infection in horses.
  3. Utilize molecular and culture techniques to identify a novel tick‐borne Ehrlichia sp. that infects horses in central Oklahoma.

PI: Todd C. Holbrook

CO-Investigators: Brian Herrin and Susan Little. 

Professional Affiliations

American College of Veterinary Internal Medicine
American College of Veterinary Sports Medicine and Rehabilitation
American Association of Equine Practitioners
National Reining Horse Association
American Quarter Horse Association