Equine Infectious Anemia

Equine Health Alert

Equine Infectious Anemia Updates:

NEW: EIA Quarantine in Kern County

December 30, 2022: A 9–year–old Quarter Horse stallion residing in Kern County was confirmed positive for Equine Infectious Anemia (EIA). The stallion has been quarantined on premises with four (4) additional exposed horses on the property. Epidemiological tracing is ongoing, but transmission is suspected to be iatrogenic and exposure limited to a subset of an unsanctioned racing population.

RELEASED: EIA Quarantine in Los Angeles

December 13, 2022: A confirmed EIA positive horse must be euthanized or quarantined for life 200 yards away from any EIA negative equid as per USDA EIA program rules. Humane euthanasia was elected for this case and the EIA positive horse was euthanized on December 13th. As there were no additional horses on the premises, the quarantine was released.

November 14, 2022: A 7–year–old Quarter Horse gelding residing in Los Angeles County was confirmed positive for Equine Infectious Anemia (EIA). The gelding has been quarantined on premises with no additional exposed horses on the property.

EIA Quarantine in Kern County

September 12, 2022: A confirmed EIA positive horse must be euthanized or quarantined for life 200 yards away from any EIA negative equid as per USDA EIA program rules. Lifetime quarantine was elected for these cases.

August 25, 2022: On August 25th, two racing Quarter Horse geldings, a 3-year-old and a 4-year-old, were confirmed positive for Equine Infectious Anemia (EIA). The two geldings are the only horses on their home premises in Kern County and have been placed under quarantine. Epidemiological tracing is ongoing.

RELEASED: EIA Quarantine in Riverside County

October 19, 2022: The pregnant mare on the premises tested negative on her sixty (60) day retest. Quarantine on this premises has been released.

August 15, 2022: A confirmed EIA positive horse must be euthanized or quarantined for life 200 yards away from any EIA negative equid as per USDA EIA program rules. Humane euthanasia was elected for this case and the EIA positive horse was euthanized on August 15th. The pregnant mare on the premises will remain under quarantine until her sixty (60) day retest.

August 1, 2022: On August 1st, a 4-year-old racing Quarter Horse gelding was confirmed positive for EIA following testing to return to the racetrack. Exposure was very likely iatrogenic through reuse of contaminated needles. The gelding and one additional pregnant mare at the index premises have been quarantined. The mare was tested and confirmed negative for EIA, and will be retested in sixty (60) days. Epidemiological tracing is ongoing.

RELEASED: EIA Quarantine in Santa Clara County

June 20, 2022: A confirmed EIA positive horse must be euthanized or quarantined for life 200 yards away from any EIA negative equid as per USDA EIA program rules. Humane euthanasia was elected for this case and the EIA positive horse was euthanized on June 20th. As there were no additional horses on the premises, the quarantine was released.

June 9, 2022: On June 9th, a 4-year-old racing Quarter Horse mare was confirmed positive for Equine Infectious Anemia (EIA). The mare was temporarily residing in Merced County when she was tested and was moved back to her home premises in Santa Clara County before EIA test results were received. The mare was the only horse on both premises and has been quarantined at the Santa Clara County premises.

RELEASED: EIA Quarantine in Merced County

June 24, 2022: A confirmed EIA positive horse must be euthanized or quarantined for life 200 yards away from any EIA negative equid as per USDA EIA program rules. Humane euthanasia was elected for this case and the EIA positive horse was euthanized on June 24th. As there were no additional horses on the premises, the quarantine was released.

May 27, 2022: On May 26th, a 4-year-old Quarter Horse gelding in Merced County was confirmed positive for Equine Infectious Anemia (EIA). The gelding was tested for returning to a racetrack and originated from the premises in Tulare County with recently confirmed EIA cases. Transmission was most likely iatrogenic. The gelding has been quarantined at his home premises with no additional exposed horses on the property.

EIA Quarantines in Riverside and Tulare Counties

October 19, 2022: The pregnant mare on the premises tested negative on her sixty (60) day retest. Quarantine on this premises has been released.

August 3, 2022: The remaining horses on the Tulare County premises tested negative on their sixty (60) day recheck. Quarantine on this premises has been released.

June 29, 2022: The remaining horses on the Riverside County premises tested negative on their sixty (60) day recheck. Quarantine on this premises has been released.

May 24, 2022: A confirmed EIA positive horse must be euthanized or quarantined for life 200 yards away from any EIA negative equid as per USDA EIA program rules. Humane euthanasia was elected for these cases and the 24 (twenty-four) EIA positive horses on the Tulare County premises were euthanized on June 24th.

May 13,2022: Twenty-four (24) of the thirty-six (36) horses on the Tulare County premises were confirmed positive for EIA. The remaining twelve (12) horses on the Tulare County premise will remain quarantined until their sixty (60) day retest.

May 4, 2022: On May 2, 2022, a 3-year-old Quarter Horse stallion was confirmed positive for Equine Infectious Anemia (EIA) while residing in Riverside County. The stallion originated from a premises in Tulare County and was being tested for interstate movement to enter a racetrack. The investigation led to the quarantine and testing of twenty-seven (27) exposed horses at the Riverside County premises on May 4th, and thirty-six (36) horses at the Tulare County premises. All horses on the Riverside County premises tested negative but will remain quarantined until retested in sixty (60) days. Testing is pending for the horses on the Tulare County premises. This horse has no known direct links to the previous San Bernardino County EIA cases. Transmission was most likely iatrogenic through reuse of contaminated intravenous equipment. CDFA staff continue the investigation to determine if any additional horses were exposed.

RELEASED: EIA Quarantine in San Bernardino County

June 10, 2022: The remaining eleven (11) horses on the premises tested negative on their sixty (60) day recheck. Quarantine on this premises was released on June 10th.

April 7, 2022: Two (2) additional horses from the home premises in San Bernardino County tested positive on March 25th on their sixty (60) day recheck. These two positive horses were euthanized on April 7th. The remaining elven (11) horses on the premises will continue to be quarantined until their next recheck test in sixty (60) days' time.

January 18, 2022: A confirmed EIA positive horse must be euthanized or quarantined for life 200 yards away from any EIA negative equid as per USDA EIA program rules. Humane euthanasia was elected for these six (6) cases and the EIA positive horses were euthanized on January 18th.

January 13, 2022: On January 3, 2022, a 5-year-old Quarter Horse gelding with a racing history was confirmed positive for Equine Infectious Anemia (EIA) while residing in Arizona. The gelding originated from a premises in San Bernardino County. The investigation led to the quarantine and testing of nineteen (19) exposed horses, and six (6) of those were confirmed positive for EIA on January 13, 2022. Transmission was most likely iatrogenic through contaminated intravenous equipment. The remaining horses on the San Bernardino County premises will remain quarantined until they are retested in sixty (60) days. CDFA staff continue the investigation to determine if any additional horses were exposed.

The Equine Infectious Anemia (EIA) virus belongs to the family Retroviridae. This group of viruses includes human immunodeficiency virus (HIV), the immunodeficiency viruses of apes and monkeys (SIV), goats (CAEV), cats (FIV) and cattle (BIV). The virus persists in the horse’s white blood cells, and in the plasma (non-cellular portion of the blood) during febrile episodes. The amount of virus in the infected animal’s blood varies. Stress due to racing, heavy exercise, transport or illness due to other causes may elevate the amount of virus in the blood.

EIA virus is an enveloped virus, does not persist in the environment and is easily killed by most common disinfectants. The virus is viable (infective) for up to 96 hours on contaminated needles. The virus stays viable in the mouthparts of a biting fly for less than four (4) hours. Thus, horses in close contact with an infected horse are at risk of infection via fly bite.

Natural transmission occurs when a deer or horse fly bites and consumes a blood meal from an infected horse and transfers the virus via its mouthparts to another horse. Additionally, pregnant mares may pass the virus to the foal in utero or through the milk. Stallions can infect mares at breeding.

People can introduce virus to a naïve horse through the use of infected blood or blood products, or through the use of blood contaminated equipment such as needles, syringes, surgical instruments, dental equipment, tattooing equipment, or any other equipment.

Clinical Signs

Clinical signs can vary widely. Most infected horses are asymptomatic, showing no signs of disease. Acutely infected animals may develop a fever, go off feed or die suddenly. A chronically infected equine may develop non-specific signs such as weight loss, weakness, anemia and swelling of the legs, chest and abdomen. Stress or immunosuppression can lead to recrudescence of disease or to increased levels of viremia.

Diagnosis & Treatment

A serologic (blood) test confirms the diagnosis of EIA. The two most commonly used serologic tests are the agar gel immunodiffusion (AGID), commonly known as the “Coggins” Test, and the enzyme-linked immunosorbent assay (ELISA). A positive test indicates the presence of EIA specific antibodies. The ELISA test can detect antibodies earlier than the Coggins test. As the ELISA test may produce false positive results, the confirmatory test for EIA is the AGID test. Only USDA-approved laboratories can perform EIA testing in the United States.

There is no known treatment for EIA. Infected horses become lifelong carriers and pose a risk of infection to other horses.  Therefore, if a horse is confirmed to be positive for EIA, management options are limited to:

  1. Euthanasia
  2. Lifetime quarantine, with permanent isolation at a minimum of 200 yards from all other horses. Positive horses must be permanently identified (tattoo, brand or microchip).

An epidemiologic investigation will be performed to determine the movement history of the infected equine and to identify other exposed horses or equids. Exposed equines will be quarantined and tested, and be subject to a retest 45-60 days after the removal of the EIA positive horse. Quarantine will remain in effect until negative retest results are received.

Prevention and Control

There is no approved vaccine for EIA in the United States. In order to prevent infection, follow these guidelines:

  • Practice good fly control by regular mucking of stalls, proper disposal of manure away from horse stabling areas and use of fly sprays or natural predators to minimize fly presence.
  • Use a sterile needle and syringe for all injections or treatments.
  • Disinfect any surgical or dental equipment thoroughly between horses. Remove all debris and blood with soap and water before disinfection.
  • Only administer commercially licensed blood products.
  • Use a sterile needle each time when puncturing a multi-dose medication bottle. Consult a veterinarian to demonstrate how to use sterile technique when drawing up medications.
  • Require proof of a recent negative Coggins test at time of purchase or for new horses entering the premises. Require an EIA test for horses which have spent time at a premises where EIA-positive horses have been identified.
  • Only participate in events that require evidence of a negative Coggins test for every horse entering the event to prevent disease introduction and spread.
  • Separate horses with fevers, reduced feed intake and/or lethargy from your other horses and contact your veterinarian.

Contact Us

CDFA Animal Health and Food Safety Services,
Animal Health Branch

1220 N Street
Sacramento, California 95814
Phone: 916-900-5002
Fax: 916-900-5333
Email: ahbfeedback@cdfa.ca.gov
Our offices are open 8:00 AM to 5:00 PM Pacific Time.