2019 Equine Infectious Anemia Cases 

in the United States 

January 1– December 31, 2019 

This document summarizes State reporting of equine infectious anemia (EIA) cases in the United States 

during 2019. State animal health officials report EIA testing and case information to APHIS Veterinary 

Services (VS) through the National Animal Health Reporting System (NAHRS). The NAHRS is an online 

reporting tool enabling States to submit animal disease information to VS through the Internet with 

assurance of secure data transfer and information confidentiality. For States that did not use NAHRS, 

APHIS-VS requested EIA information by e-mail and recorded the data in the NAHRS database. 

Reporting of EIA testing is summarized on a calendar-year basis. During 2019, a total of 1,151,584 EIA 

tests were conducted, resulting in detection of 89 positive horses (Table 1.) These results compared to 

1,187,536 tests and 51 positives in 2018. Figure 1 displays a map depicting reported numbers of horses 

and premises testing positive for EIA in 2019. Figure 2 presents a summary of EIA testing from 2000-

2019. Historical data and additional information on EIA are available online at 

https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/animal-disease-information/equine/eia

Table 1. Test results reported for equine infectious anemia in the United States, 2019 

State Tests Performed Positive Horses Positive Premises 

Alabama 10418 1 1 

Alaska 01 0 0 

Arizona 7553 1 1 

Arkansas 35318 2 1 

California 24690 0 0 

Colorado 22491 0 0 

Connecticut 1650 0 0 

Delaware 3572 0 0 

Florida 110473 7 2 

Georgia 37793 6 3 

Hawaii 272 0 0 

Idaho 10612 1 1 

Illinois 17074 1 1 

Indiana 26063 1 1 

Iowa 19560 10 1 

Kansas 15532 1 1 

Kentucky 54028 0 0 

 

1 All samples are sent to out-of-State laboratories and Alaska does not receive notification of the number of tests performed at 

these laboratories. 

Animal and Plant 

Health Inspection 

Service 

Veterinary 

Services 

April 2020 
2019 Summary of Equine Infectious Anemia Cases in the United States 

USDA-APHIS-VS 2 

State Tests Performed Positive Horses Positive Premises 

Louisiana 27719 3 3 

Maine 1929 0 0 

Maryland 24939 0 0 

Massachusetts 13227 0 0 

Michigan 31776 0 0 

Minnesota 22757 1 1 

Mississippi 21586 0 0 

Missouri 55452 0 0 

Montana 5388 0 0 

Nebraska 7200 0 0 

Nevada 8799 0 0 

New Hampshire 14439 0 0 

New Jersey 19157 0 0 

New Mexico 17228 1 1 

New York 38215 0 0 

North Carolina 25045 0 0 

North Dakota 7452 0 0 

Ohio 46729 0 0 

Oklahoma 55767 1 1 

Oregon 6993 0 0 

Pennsylvania 30541 0 0 

Rhode Island 1657 0 0 

South Carolina 37124 0 0 

South Dakota 9033 0 0 

Tennessee 28286 5 2 

Texas 91978 45 16 

Utah 6529 0 0 

Vermont 3787 0 0 

Virginia 30987 0 0 

Washington 5511 0 0 

West Virginia 8221 0 0 

Wisconsin 35243 2 1 

Wyoming 13580 0 0 

Puerto Rico 180 0 0 

U.S. Virgin Islands 31 0 0 

U.S. Totals 1,151,584 89 38
2019 Summary of Equine Infectious Anemia Cases in the United States 

USDA-APHIS-VS 3 

Figure 1. Reported numbers of horses and premises testing positive for EIA, 2019 
2019 Summary of Equine Infectious Anemia Cases in the United States 

USDA-APHIS-VS 4 

Figure 2. Reported numbers of EIA tests and positive cases in the United States, 2000-2019 

Although the current prevalence of EIA in the U.S. equine population remains very low, at an estimated 

national prevalence of around 0.004 percent, the epidemiology of EIA-positive cases has shifted in 

recent years. The majority of EIA cases were previously found to occur from natural transmission by 

biting fly vectors in untested and under-tested populations. Now, increasing cases of iatrogenic 

transmission are being identified. 

In 2019, at least 75 of the 89 confirmed cases of EIA were found in Quarter Horse racehorses with 

iatrogenic transmission either suspected or confirmed as the route of infection. Iatrogenic transmission 

in this population is occurring through unhygienic practices by horse trainers and owners. Practices 

include re-use of needles, syringes, and IV sets; administration of blood transfusions from untested 

donor horses; use of illegal blood products from other countries; and infectious blood contamination of 

multi-dose drug vials. Some of the iatrogenic transmission cases in the Quarter Horse racehorse 

population are found in horses participating in unsanctioned racing. However, there are also recognized 

crossover cases between unsanctioned and sanctioned racing in some parts of the United States. Cases 

in sanctioned Quarter Horse racehorses with no obvious connection to unsanctioned racing have been 

identified as well. Frequently, EIA-positive cases in this emerging high-risk population are found in 

clusters, indicative of a horse trainer or owner repeatedly using unhygienic practices that cause disease 

spread to multiple horses. These cases are preventable by good hygienic practices and basic biosecurity 

measures. Thus, increased education and outreach to trainers and owners of Quarter Horse racehorses 

is needed to mitigate the continued spread of EIA. 

0

500

1000

1500

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Number of Tests x 1000 Number of Test-positive Horses