Thousands of horses enter the United States each year for a variety of reasons, and those arriving via air or ocean must go through a USDA Animal and Plant Health Inspection Service (APHIS) quarantine center to reduce the risk of spreading infectious diseases.

A veterinarian examines each horse when it arrives and throughout the quarantine period. Before a horse can be cleared for release from the quarantine center, he must be held there for a specified period of time, be clinically healthy, officially test negative for several diseases, and have three nonelevated temperatures (less than 101.5°F) recorded for the 24 hours immediately prior to release. USDA:APHIS:Veterinary Services officials completed a study in which they summarized the prevalence of elevated temperature among imported horses and determined risk factors for its occurrence.

"Above-normal body temperature can be the result of a true fever—most often caused by an infection—inflammation, hyperthermia because of heat stress, drug reactions, allergies, tumors, or other causes," explained Josie Traub-Dargatz, DVM, MS, Dipl. ACVIM, a professor of equine medicine and epidemiology at Colorado State University, during a presentation at the 2011 American Association of Equine Practitioners convention, held Nov. 18-22 in San Antonio, Texas.

"Other risk factors, such as age, breed, previous experience with air travel, disposition, and location in the cargo area might explain an increased risk for occurrence of elevated body temperature," she added.

To analyze elevated temperature incidence among imported horses, Traub-Dargatz and co-author Barbara Bis