What Is a Coggins Test and Why Does My Horse Need It?

Updated September 9, 2024 | Reviewed by: Liz Schatz, DVM
vet drawing blood from a horse's neck
Photo courtesy of Alana Harrison Photography.

What is a Coggins Test for Horses?

A Coggins test is a critical blood test used to detect Equine Infectious Anemia (EIA), a potentially fatal viral disease in horses, ponies, mules, and donkeys. Developed by and named after Dr. Leroy Coggins in the 1970s, the test is vital for preventing the spread of this disease among the equine population.

How a Coggins test is performed

The test is performed by a USDA-accredited veterinarian who draws a small blood sample from a horse with a needle and syringe. This sample is sent to a USDA-approved laboratory, where it is analyzed for antibodies against the EIA virus.

Results of these tests are usually available within a few days, and your veterinarian will inform you of whether your horse has tested positive or negative for EIA.

Understanding Equine Infectious Anemia

EIA, commonly known as "swamp fever," poses a serious threat to horses. It is caused by a retrovirus that can lead to serious illness or death. The virus can be easily transmitted from one horse to another through the bite of blood-feeding flies, such as horseflies and deerflies. This means that even horses showing no signs of illness can spread the virus to others, leading to outbreaks that can devastate entire stables or herds.

A horse infected with EIA remains a carrier for life, even if they show no symptoms. The EIA virus can flare up at any time, especially when a horse is under stress, further complicating their health and increasing the risk of transmission to others. Since there is no cure or vaccine for EIA, understanding and preventing the disease through regular testing is essential.

The impact and symptoms of EIA on horses

EIA can manifest in various ways, ranging from mild symptoms to severe, life-threatening conditions. Common signs of this disease include:

  • Fever
  • Depression
  • Anemia
  • Weight loss or lack of an appetite
  • Jaundice (yellow coloration of the mucous membranes)
  • Rapid heart rate and respiratory rate
  • Swelling due to edema (particularly in the legs and lower abdomen)
  • Muscle weakness
  • Blood in the manure, nasal bleeding, or red to purple spots on mucous membranes

Some horses may show acute symptoms that appear suddenly and severely, while others may exhibit milder, chronic symptoms that persist over time. In severe cases, the disease can cause sudden death.

Transmission of EIA in horses

EIA is primarily spread through blood-to-blood contact, making it highly transmissible under certain conditions. The most common method of transmission is through blood-feeding insects such as horseflies, deerflies, and stable flies.

People can cause the virus to spread by using contaminated needles or medical instruments on multiple horses. Preventive measures, including insect control and regular Coggins testing, are vital to reducing the risk of transmission and protecting the equine population.

Thankfully, EIA infections are rare in the US, as the UDSA’s Animal and Plant Health Inspection Service estimates that about 0.004 percent of the country’s horse population are infected each year. However, rates do vary around the globe. The EIA virus can be killed by common disinfectants, like bleach or alcohol, and can’t survive in the environment (like in soil or water sources).

What Happens if a Horse Tests Positive on a Coggins Test?

A positive result on a Coggins test indicates that a horse has been exposed to the EIA virus and is likely infected. In most cases, a second test will be submitted to confirm this infection. Then, steps must be taken to prevent the spread of the virus, including:

  • Quarantine: An infected horse must be quarantined immediately to prevent transmission of the disease. This involves isolating the horse in a designated area at least 200 yards away from noninfected horses. You must ensure that no equipment, feed, or handlers move between the infected horse and healthy horses without proper biosecurity protocols.
  • Reporting: EIA is a reportable disease, meaning that a positive test result must by law be reported to local or state veterinary authorities. These officials will typically take over management of the case, ensuring that biosecurity measures are in place and advising on the next steps.

What you choose to do after a positive Coggins test is not just a matter of personal choice; it is also governed by legal and ethical considerations. Horse owners are faced with two options:

  1. Lifetime quarantine: In some cases, a horse infected with the EIA virus may be allowed to live out their life in strict isolation. This option requires dedicated facilities as the infected horse will remain a lifelong carrier of the virus.
  2. Humane euthanasia: While difficult, euthanasia is often recommended or required by local laws to protect the broader horse population, as there is no cure for EIA and the disease is highly transmissible.

Cost of Coggins Tests

The cost of a Coggins test typically ranges from $20 to $50, depending on your location and your veterinarian's fees (exam, blood draw, and lab analysis). Despite the expense, the test is essential for your horse's health and gives you peace of mind knowing they’re free of this disease. A negative Coggins is also generally necessary for interstate and international shipping.

How Long is a Horse’s Coggins Test Result Valid?

A grey horse being loaded onto a horse trailer.

A Coggins test result is valid for one year from the date of testing. Horse owners must renew this test annually to comply with legal and health requirements. In some cases, such as transport across state lines or abroad, the validity period may be shorter. Some states or countries require a test within the last six months, or even within 30 to 90 days of travel.

Annual testing helps in monitoring for new infections and protecting other equids, particularly in environments where horses are in close contact, such as boarding facilities or competitions.

Allowing a Coggins test to expire can result in legal penalties, fines, or restrictions on a horse’s movement, and may prevent entry to shows, events, or facilities.

Horse owner resources:

SmartPak strongly encourages you to consult your veterinarian regarding specific questions about your horse's health. This information is not intended to diagnose or treat any disease, and is purely educational.