United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

Veterinary Services 

Centers for Epidemiology and Animal Health March 2011 

_________________________________________________________________________________________________________________________ 

Highlights: Demographic 

Characteristics and Prevalence 

of Elevated Temperature among 

Horses Quarantined at the Three 

Air/Ocean Import Facilities in the 

United States

A report has recently been made available on the 

National Animal Health Monitoring System Web site: 

http://www.aphis.usda.gov/animal_health/nahms/equine/

index.shtml. The following are highlights from the report. 

Introduction 

The objectives of a study conducted by USDA Animal 

and Plant Health Inspection Service (APHIS) Veterinary 

Services (VS) were to determine the annual prevalence 

of elevated temperatures for horses1

 imported by air or 

ocean to the three USDA animal import centers during a 

12-month period2

, determine risk factors for elevated 

temperatures, and compare prevalence of elevated 

temperatures across centers. 

The importation of horses into the United States is 

regulated by USDA–APHIS–VS. Horses arriving by air or 

ocean, other than those arriving for special events such 

as the World Equestrian Games, are quarantined at the 

New York Animal Import Center (NYAIC) in Newburgh, 

NY; the Miami Animal Import Center (MAIC) in Miami, 

FL; or the Los Angeles Animal Import Center (LA-AIC)3

in Los Angeles, CA. 

Fever is important in the diagnosis of disease in 

domestic animals; therefore, the body temperature of 

quarantined horses is monitored in order to facilitate 

prompt treatment interventions, if appropriate. Horses 

being imported into the United States, except those from 

Canada, must remain under USDA quarantine for a 

minimum of 42 hours, and must have three nonelevated 

temperatures recorded for the 24-hour period 

immediately prior to release to complete USDA 

quarantine. During quarantine, horses are observed for 

clinical signs of disease and a physical examination is 

 

1

 For this report, the term “horse” will be used to refer to horses and 

other equids. 

2

 Calendar year (CY) 2008 for NYAIC and MAIC, CY 2009 for LA-AIC. 

3

 LA-AIC import quarantine is a privately operated facility (Jet Pets, 

Inc.) with oversight by USDA–APHIS–VS.

generally performed every 12 hours. For this study, an 

elevated temperature was defined as greater than 

101.5°F. 

Above-normal body temperature can be the result of 

a true fever (most often due to an infection), 

inflammation, hyperthermia due to heat stress, drug 

reactions, allergies, tumors, or other causes. Factors 

that might be associated with an increased risk for 

occurrence of elevated body temperature include age, 

breed, gender, disposition, previous air travel, location in 

the jet stall, and location of the jet stall in the cargo area 

of the plane. 

Findings 

All import centers 

The prevalence of elevated temperature varied by import 

center: 12.0 percent for LA-AIC,11.4 percent for NYAIC, 

and 6.6 percent for MAIC. An initial univariable model 

with center as the only factor showed that the 

prevalence of elevated temperature was significantly 

lower for MAIC than for LA-AIC (p<0.0001) or NYAIC 

(p<0.0001) and was not different between 

LA-AIC and NYAIC (p=0.6). Some of the difference may 

be explained by the variation in types of horses imported 

into each center, duration of transport, and type of 

transportation. 

No Friesian horses were imported through the MAIC 

during the study period and a lower percentage of 

horses imported through MAIC were 4 years of age or 

less. Since young age was determined to be a risk factor 

for elevated temperature across all three centers and the 

Friesian breed was more likely to have an elevated 
United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

temperature than the other breed categories, the 

population characteristics may partially explain the 

difference. However, the difference in prevalence 

between centers could not be fully explained by the data 

available for analysis; likely other factors contributed to 

the observed differences. 

The majority of elevated temperatures occurred 

within 12 hours of arrival to an import center, typically as 

a single occurrence, and usually as a low-grade 

elevation—greater than 101.5°F but less than 102.5°F. 

These findings suggest that occurrences of elevated 

temperature later in the quarantine period, high 

temperatures (greater than 102.5°F), or repeated 

elevations in temperature should be considered less 

common events.

Percentage distribution of horses and prevalence of horses that had elevated temperatures by breed, age, and 

region of origin, and by center 

Center 

LA-AIC MAIC NYAIC 

Percent 

Elevated Temp 

Prevalence Percent 

Elevated Temp 

Prevalence Percent 

Elevated Temp 

Prevalence 

Breed

Friesian 4.2 40.0 0.0 2.5 19.6 

Other breeds 24.2 13.7 26.3 9.0 10.3 13.7 

Thoroughbred/ 

other hot-bloods 24.1 16.9 37.1 7.9 22.5 6.7 

Warmblood 47.5 6.2 36.6 3.6 64.7 12.4 

Total 100.0 100.0 100.0 

Age (years) 

1 yr or less 6.0 60.9 2.3 25.0 6.3 26.2 

2 to 4 25.3 17.6 20.5 11.9 29.8 10.0 

5 to 9 47.1 6.4 62.6 5.0 46.1 11.4 

10 or more 21.6 4.0 14.6 3.9 17.8 9.0 

Total 100.0 100.0 100.0 

Region of Origin

Australia/NZ 18.7 4.0 0.0 0.7 0.0 

Middle East 1.7 11.1 0.0 1.3 11.1 

Europe 76.6 13.9 37.5 3.9 95.1 11.8 

Americas* 2.2 17.4 62.5 8.4 0.9 0.0 

Asia 0.8 0.0 0.0 2.0 4.9 

Total 100.0 100.0 100.0 

*Mexico, Central and South America (Argentina, Brazil, Cayman Islands, Chile, Costa Rica, Dominican Republic, Equador, El Salvador, Guatemala, 

Mexico, Panama, Peru, The Bahamas, Turks and Caicos Islands, Uruguay, and Venezuela).

 
United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

New York Animal Import Center 

Of the 2,062 horses quarantined at the NYAIC in 

2008, 236 (11.4 percent) had at least 1 elevated 

temperature from the time of arrival at NYAIC until 

release. Of the horses with an elevated temperature, 

26.3 percent had more than one elevated temperature 

and 34.3 percent had a high temperature (i.e., their 

highest temperature was greater than 102.5°F). An 

interaction between breed and age was detected, so the 

possibility of a breed effect within each age category 

was investigated. In the 2- to 4-year age group, a 

Friesian was three times more likely to have an elevated 

temperature than a Warmblood; a Thoroughbred/other 

hot-blooded horse was less likely to have an elevated 

temperature than was a Warmblood. In the 5- to-9-year 

age group, significantly more Warmbloods had elevated 

temperatures than did horses in the “other breeds” and 

Thoroughbred/other hot-blooded breed categories. 

Horses 1 year of age or less had the highest prevalence 

(26.1 percent) of elevated temperatures. Prevalence of 

elevated temperatures in other age categories was 

between 10 and 11 percent. 

Miami Animal Import Center 

Of the 1,600 horses in quarantine at MAIC in 2008, 

106 (6.6 percent) had at least 1 elevated temperature 

during quarantine. A vast majority of these elevated 

temperatures occurred on day 1 of quarantine. The risk 

factors for elevated temperature for horses at MAIC 

were age and gender. Horses 1 year or less were most 

likely to have one or more elevated temperatures 

compared to other age groups. Intact males were more 

likely than females or castrated males to have an 

elevated temperature. None of the risk factors was 

significantly associated with the time at which the first 

elevation in temperature occurred, because almost all 

horses (93.4 percent) had their first high temperatures at 

arrival.

Los Angeles-Animal Import Center 

Of the 1,058 horses that arrived at LA-AIC in 2009, 

127 horses (12 percent) had at least 1 elevated 

temperature. Although the majority of the imported 

horses were between 5 and 9 years old, those younger 

than 1 year had a higher risk of an elevated temperature. 

The effect of breed varied by region of origin; a Friesian 

from Europe was 3.8 times more likely to have an 

elevated temperature than a Thoroughbred/other hotblooded horse from Europe. Horses coming from 

Australia/New Zealand and categorized as “other” breed 

were least likely to have an elevated temperature 

compared to the Thoroughbreds/other hot-blooded 

breed horses. Females were significantly more likely 

(2.05 times) to have an elevated temperature than a 

castrated male. 

Discussion 

Fever is important in the diagnosis of disease in 

domestic animals. The body temperature of animals at 

risk of developing disease is monitored in order to detect 

disease and allow for initiation of prompt treatment 

interventions. Body temperature is regulated by the 

hypothalamus, which receives input from internal and 

external thermoreceptors. Fever is a form of 

hyperthermia where the hypothalamic temperature point 

is set higher than normal, but heat loss and heat gain 

are still maintained. 

Transport is stressful to horses. Potential stressors 

include isolation from herd mates, forced proximity to 

unfamiliar or aggressive horses, novel or threatening 

surroundings, exposure to new pathogens, lack of 

normal activity patterns, forced adoption of an abnormal 

posture, extremes in temperature and humidity, noise, 

and water and feed deprivation. 

There are references in the literature to a 

psychological stress-induced rise in core temperature 

(PSRCT) in humans and animals. Additionally, transport 

could result in a predisposition to infection due to some 

or all of these factors. It seems possible that some of the 

elevated temperatures experienced by imported horses 

upon arrival at the import center could represent a form 

of PSRCT. Further investigation to rule out other causes 

of elevated temperatures would be necessary to prove 

this hypothesis. 

Summary 

The prevalence of elevated temperatures varied by 

center: MAIC had a significantly lower prevalence while 

LA-AIC and NYAIC had a similar prevalence. The 

majority of elevated temperatures occurred within 

12 hours of arrival to an import center, typically as a 

single event, and usually as a low-grade elevation, i.e., 

greater than 101.5°F but less than 102.5°F. Only 

34.3 percent of the horses at NYAIC, 13.2 percent at 

MAIC, and 15 percent at LA-AIC had a temperature 

greater than 102.5°F. 

These findings suggest that occurrences of an 

elevated temperature later in the quarantine period, high 

temperatures (greater than 102.5F), or repeated 

elevations in temperature should be considered less 

common events. 

The data included in this report summarize records 

for 4,720 horses. This appears to represent the largest 

number of records for horses shipped by air to be 

evaluated for prevalence of an elevated body 

temperature. Analysis of the existing data identified 

several factors associated with risk of an elevation in 

temperature. Additional research is necessary to 

determine more definitively the causes of and potential 

interventions for elevated temperatures among imported 

horses. 

 
United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

____________________ 

For more information, contact: 

USDA–APHIS–VS–CEAH 

NRRC Building B, M.S. 2E7 

2150 Centre Avenue 

Fort Collins, CO 80526-8117 

970.494.7000 

E-mail: NAHMS@aphis.usda.gov 

http://nahms.aphis.usda.gov 

#616.0311 

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