What Is a Coggins Test?

A Coggins test is a blood test to identify if a horse is a carrier of Equine Infectious Anemia, a viral disease found in horses. A negative Coggins test is required for all travel between states and at most equine facilities.

Many horse owners have heard of a Coggins test, but some do not know what the test evaluates and why it is so important for the horse industry. A Coggins test is a blood test used to identify the presence of antibodies for equine infectious anemia, a potentially fatal disease with no current treatment available. There are multiple tests to detect if a horse has EIA antibodies, but the Coggins test is the most popular and well known among horse industry professionals.

Performing a Coggins Test

To perform a Coggins test, a licensed veterinarian must draw blood from the horse and send it to an accredited lab for analysis. The lab will conduct a test to detect the EIA antibody (a protein that allows the body to recognize the EIA virus; this will only be present if the horse has had the EIA virus). They will then provide either a positive (antibody is present) or a negative (antibody is not present) test result back to the veterinarian, who will share it with the horse owner. These results, often referred to as Coggins papers, will then be available as either a paper or an electronic certificate and should be kept with the horse’s health records. The test results expire one year from the testing date.

The following information is generally found on all Coggins tests (see an example on the following page):

  • Owner information: Owner name, address, phone number
  • Stable information: Point of contact, address, phone number
  • Veterinarian Information: Name, clinic, accreditation number, address
  • Horse’s Identifiable Information: Name, barn name, breed registration number, breed, sex, color, age, permanent identification (microchip, tattoo), pictures or drawings of all markings accompanied with a narrative description of markings
  • Equine Infectious Anemia (EIA) Test Information: Type, lab that preformed the test, reason for testing, date received, date reported, and result

Obtaining a negative Coggins test is important to ensure that EIA is not spread to other horses. Lack of a vaccine or treatment for EIA makes testing crucial for preventing spread by ensuring carriers are not moved or allowed in close proximity with other horses.

What is Equine Infectious Anemia?

Equine infectious anemia is a bloodborne viral disease that can affect all equids. This virus is of great concern for the horse industry and there is currently no treatment or vaccine for it.

Horses with EIA have varying symptoms and prognoses. Acute symptoms often include a fever, disorientation, and weight loss. Rapid death has also been reported for some horses with EIA.

Most often, horses with EIA are asymptomatic carriers—showing no signs or symptoms—which is one of the reasons testing is so important. Horses positive for EIA are lifelong carriers and pose a risk to any other horse they may be around. Therefore, EIA carriers must either be permanently quarantined and kept at least 200 yards away from other horses or euthanized.

Transmission of EIA

EIA is most often transmitted by biting flies; tabanids (horse and deer flies) are considered the most significant transmitters. Biting flies transmit EIA by taking a blood meal from an EIA carrier and then transmitting that infected blood to a noninfected horse. Since it is relatively impossible to eliminate blood-sucking insects around horses, there is always the potential of a horse contracting EIA (and other bloodborne diseases) when in the vicinity of an infected horse. Other modes of transmission of EIA include the use of contaminated equipment, such as used needles and syringes; mare-to-foal transmission in utero; and through natural breeding of mares and stallions.

Reducing the Spread of Equine Infectious Anemia

Obtaining a negative Coggins test ensures that the horse does not have the antibody for EIA at the time of testing. However, you are encouraged to continue implementing biosecurity measures in addition to the annual test. Since EIA is primarily transmitted by flies, employing fly management strategies can help reduce the likelihood of infection. Horse owners are encouraged to use an integrated pest management (IPM) system, which uses multiple, targeted strategies to reduce fly populations.

Prioritizing horse health and sanitation can also help reduce spread. Always use a sterile needle when giving your horse an injection. If using a multidose vaccine bottle, use a sterile needle every time you puncture the bottle. Require proof of a negative Coggins test for horses coming onto your farm and/or interacting with your horse. Quarantine new horses entering the premises for at least 14 days after arrival, evaluating them for signs of illness during that time. Require proof of a negative Coggins test for horses you are considering buying or breeding. The American Association of Equine Practitioners also recommends that horse owners only participate in shows that require a negative Coggins test.

It is always recommended that horse owners regularly evaluate their horses for signs of illness. If you suspect your horse has contracted EIA or any other virus, separate them from other horses to reduce the chances of transmission and contact a veterinarian immediately.

Horse Shows and Other Equine Facilities

Many horse shows and facilities require that a negative Coggins test be provided for the horse to enter the premises or participate in the event. It is encouraged that all horse shows and facilities require proof of a negative Coggins test from competitors upon entry. Similarly, horse owners are encouraged to only participate at shows that have this requirement. Horses that are being sold, entering sales, or newly purchased should also be required to have a current negative Coggins test.


Obtaining a Coggins test annually is imperative to reduce the risk of EIA transmission. As most carriers of EIA are asymptomatic, testing can help identify carriers and prevent transmission to other horses. Anytime you plan to travel with your horse, make sure you explore documentation requirements for that state, facility, and event before departing. Additionally, make sure that a current negative Coggins test is available for any horse you plan to purchase or sell.