The Colorado Department of Agriculture’s State Veterinarian’s Office is announcing a confirmation of a horse in Adams County positive for both Equine Infectious Anemia (EIA) and Equine Piroplasmosis. The initial positive was identified on December 8 during routine testing for movement, underscoring the necessity of Coggins testing for transport requirements. Confirmatory testing was completed at the USDA’s National Veterinary Services Laboratory (NVSL) on December 23, 2025.
The premises where the horse resides has been placed under quarantine, and the initial positive horse was euthanized. Additional tracing and testing are underway for 13 other horses which were exposed to EIA, with follow-up testing identifying four cohort horses with positive results for EIA (one), Piroplasmosis (two), or co-infections (one). The investigation is ongoing.
The likely route of transmission was identified as human-caused, with the trainer citing the reuse of an intravenous (IV) set between horses. This case is associated with a high-risk group of animals used in unsanctioned or bushtrack racing, reflecting a concerning trend of iatrogenic spread of EIA across the United States (e.g., reusing needles, IV sets, drug bottles, etc.).
“These unfortunate cases serve as a critical reminder of the importance of routine testing and strict biosecurity protocols in our equine community,” said Dr. Maggie Baldwin, Colorado State Veterinarian. “While the risk to the general equine population remains low at this time, this human-caused transmission highlights that simple sanitary measures, such as using single-use needles and syringes, are vital to prevent the devastating spread of these diseases.”
Information for Veterinarians
The current case, as well as the recent outbreak associated with a Texas veterinary hospital, are reminders of the critical need to adhere to sanitary protocols. Veterinarians are urged to:
- Review Sanitary Practices: Take time to review the need for strict sanitary practices with all staff, including the requirements of not sharing syringes, needles, tack, or other equipment between equine patients.
- Annual EIA Testing is Critical: These cases emphasize the necessity of annual EIA testing.
- Accurate VS Form 10-11 Completion: Ensure all information on the VS Form 10-11 (Coggins form) is accurate and complete. Please always:
- Put the physical address of the horse in Box 7 (stable/market address).
- Include the correct owner information, including a phone number, for follow-up by state or federal officials.
- Scan horses for a microchip and include that number on the form.
- Check for a lip tattoo and include that on the form.
- Indicate a brand in the markings section if one exists.
- Ensure digital pictures are clear, showing the horse from ear tips to hooves, and that animals are not wearing any blankets, boots, or tack (other than a halter).
Information for the Public
While the current risk to the general equine population in Colorado is considered low, the public should be aware of essential prevention methods and disease facts:
- Annual Testing: Annual EIA testing is strongly recommended for all horses.
- Movement Requirements: A negative EIA test (Coggins) and a Certificate of Veterinary Inspection (health certificate) are required to cross state lines in the United States.
- Event Requirements: The CDA strongly recommends that all equestrian shows, rodeos, fairs, and other equine events require a negative EIA test for entry, even if horses have not crossed state lines, to further safeguard the equine population.
About Equine Infectious Anemia (EIA)
EIA is a viral disease spread by large biting insects or the inappropriate use of needles or other equipment. There is no cure. Infected horses must be quarantined for life or euthanized. Clinical signs, which may not always be present, can include high fever, weakness, weight loss, an enlarged spleen, anemia, weak pulse, and death.
About Equine Piroplasmosis (EP)
EP is a tick-borne or blood-borne protozoal disease. While the natural tick-borne transmission is not known to exist in the continental U.S., iatrogenic transmission can occur from imported or transported infected horses. Transmission within the U.S. is known to occur through the reuse of needles, syringes, or intravenous tubing. Clinical signs often occur in the first 10-30 days and can include reduced appetite, weakness, fever, anemia, jaundice, and weight loss. Horses that survive become chronic lifelong carriers. Treatment protocols are available, but if EP coincides with EIA infection, euthanasia is recommended.
For additional information on EIA and EP, please visit the USDA Equine Disease website. EIA and EP are reportable diseases in Colorado. Visit the CDA website for guidance on reportable diseases.