Investigation into EIA-positive horse in Colorado continues

The Colorado Department of Agriculture’s State Veterinarian’s Office is continuing their investigation into a Weld County horse that tested positive for Equine Infectious Anemia in late August. With the help of records from CDA’s Brands Division and Rocky Mountain Regional Animal Health Laboratory, the State Veterinarian’s Office has determined that approximately 240 horses have been on the quarantined premises during the same time as the index positive animal. Approximately 100 of these horses were sent to 20 other states across the country and steps are being taken to locate, quarantine, and re-test those horses. At this time, no other horses have tested positive for EIA.

“We are working to locate approximately 140 horses that went to different premises across Colorado. We are asking horse owners to contact us if they purchased horses in Weld County between July 18 to Aug. 20,” said State Veterinarian, Dr. Keith Roehr. “We will work with owners to see if their horses came from the quarantined property. This is an important step in the disease investigation.”

So far, the investigation has resulted in:

The index premises in Weld County is under a quarantine order; two associated premises are also under hold orders. There is no cure or treatment for EIA. Therefore, horse that tested positive in the index case has been euthanized.

Fifteen premises are under hold orders in nine Colorado counties: Adams, Arapahoe, Crowley, Delta, Douglas, El Paso, Mesa, Montrose, and Weld.

Thirty-seven exposed horses have been located in Colorado.

The Quarantine and Hold orders will remain in place until the exposed horses on the premises test negative at the 60-day re-test. This re-test date is 60 days from the last known date of exposure to the positive horse. A quarantine is issued to a location that housed an EIA-infected horse. A hold order is issued when horses had contact with an infected horse but have not tested positive for EIA and are being held for re-testing. Both, quarantine and hold orders, include movement restrictions.

CDA is actively monitoring and working to ensure compliance with the quarantine of the index premises and the hold orders issued for premises with exposed horses. The Department does have the legal authority to pursue civil fines against those who violate a quarantine, hold orders, or animal health requirement rules. Due to state laws and regulations, CDA is limited by the details that can be shared regarding individual operations under investigation, quarantine, or hold orders.

FAQs about Equine Infectious Anemia

What is Equine Infectious Anemia?

Equine Infectious Anemia is a viral disease spread by bloodsucking insects, inappropriate use of needles, or other equipment used between susceptible equine animals such as horses, mules and donkeys. Horses may not appear to have any symptoms of the disease, although it also can cause high fever, weakness, weight loss, an enlarged spleen, anemia, weak pulse and even death.

How is it spread?

It is spread most commonly through blood by biting flies such as horse flies and deer flies.

What happens to an infected horse?

There is no cure for the disease, so animals which test positive or are infected have to be quarantined for life or euthanized.

Is there a danger to people?

No. The disease can only be spread to horses, mules and donkeys.

Is the disease common?

Sign up for HPJ Insights

Our weekly newsletter delivers the latest news straight to your inbox including breaking news, our exclusive columns and much more.

No. There has only been a small number of cases in the United States, although the disease exists in other parts of the world. A map of cases from the year 2017 is available at

How is the disease controlled?

Equine Infectious Anemia is a disease for which horses must be tested annually before they can be transported across state lines. The test for EIA is commonly called a Coggins Test.

For more information about the EIA cases in Colorado visit