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Equine Infectious Anemia Horse Investigation Update from the State Vet

The Colorado State Veterinarian’s Office at CDA has continued to work to trace and test horses involved in the EIA Incident in the State of Colorado.

As of 09/27/2018:

  • Only one confirmed positive horse in Colorado (index case)
  • The index premises in Weld County is under a quarantine order; two associated premises are under hold orders. The 124 exposed horses under quarantine on the index premises tested negative for EIA on 09/10/2018; they will be re-tested on or after 10/19/2018 (sixty days after last exposure to the positive horse).
  • 138 exposed horses have been located in Colorado (out of approximately 152 we expect to be in the state)
  • 61 premises are under hold orders in 24 Colorado counties: Adams, Arapahoe, Archuleta, Boulder, Costilla, Crowley, Delta, Douglas, Eagle, Elbert, El Paso, Fremont, Gilpin, Gunnison, Huerfano, Jefferson, Larimer, Mesa, Moffat, Montrose, Morgan, Phillips, Sedgwick, and Weld.
    Five premises have been released from hold after the 60-day re-tests were completed for all exposed horse(s) on those premises and found to be negative.
  • 72 exposed horses have been positively identified in 12 other states (out of approximately 83 we expect to be out-of-state): Arizona, Idaho, Kentucky, Louisiana, Maine, Missouri, Nebraska, Nevada, Oklahoma, Tennessee, Texas, and Wyoming.

Re-testing of Exposed Horses under Hold Orders:

Many of the exposed horses will be eligible for their final 60-day EIA re-test over the next three weeks. We have informed owners of exposed horses to work with their veterinarians to get the re-testing done after the date stated on their Hold Orders. The date varies depending on the last date that their horse was exposed to the EIA-positive horse. At this time only the exposed horses need to be tested, not all of the horses on the premises under the Hold Order.

Once we receive the negative 60-day EIA re-test results, CDA will release the Hold Order as quickly as possible so please notify our office with the results. If you have any questions, please call the State Veterinarian’s Office at 303-869-9130 or email

We appreciate your collaborative work in completing the necessary testing in this EIA incident.

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