Originally published on TheHorse.com
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 Bischoff, MA, DVM, an APHIS veterinary analyst based in Fort Collins, Colo., examined the records of 4,720 horses imported to the United States through one of the three USDA equine quarantine facilities during one calendar year:
Because many factors varied by location, the team used separate data analysis models for each import center, Traub-Dargatz noted.
The majority of the 2,062 horses that arrived at the NYAIC in 2008 were imported from Europe, with the most common countries of origin being Germany (32.4%); the Netherlands (22.2%); and England (17.8%).
Key findings from the New York data included:
In 2008 the MAIC was a destination for 1,600 horses from South American nations, the U.S. Virgin Islands, Europe, and Australasia, with 75% of the horses originating from Argentina or the Netherlands.
Key findings from the Miami review included:
The majority of the horses arriving in LA in 2009 originated from Europe, followed by Australia and New Zealand.
Key findings from the Los Angeles review included:
What Does it All Mean?
"This U.S. study showed some clear associations within each import center between the occurrence of elevation in body temperature and risk factors, such as age and breed," Traub-Dargatz explained.
One association the veterinarians found was more elevated temperature records among younger horses than older horses at all three import centers.
Traub-Dargatz suggested it's possible that younger horses could be at higher risk for developing elevated temperatures due to lack of experience with air transport and/or susceptibility to transport stress.
"It's also possible that the normal body temperature for some of these younger animals is about the 101.5°F (38.6°F) defined as elevated for this report," she said.
Also, Traub-Dargatz noted that "Friesians were at greater risk than other breeds for elevated temperatures at both LA-AIC and NYAIC; no Friesians were imported through MAIC." She added that further details related to why certain breeds seem more likely to develop an elevated body temperature were outside the scope of this particular study.
Additionally, "The prevalence of elevated temperatures among horses in quarantine varied by center, and there seemed to be an influence of center not described by the available data," Traub-Dargatz noted, adding that there were likely additional factors not reviewed in the current study that influenced the elevated temperatures in some of the horses.
Finally, Traub-Dargatz briefly discussed a condition called psychological stress-induced rise in core temperature (PSRCT) that has been described in the literature: "It seems possible that some of the elevated body temperatures experienced by imported horses on arrival at the import center, particularly those that resolved without treatment or with a single dose of NSAID, represent a form of PRSCT."
Although the current study yielded a host of information about the prevalence of elevated body temperature in imported horses, there is much left to learn: "Analysis of the existing data identified several factors associated with risk of an elevation in temperature," Traub-Dargatz concluded, noting that additional research is needed to precisely pinpoint the cause of and treatments for these elevated temperatures among imported horses.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.