Equine Infectious Anemia
On December 8th, 2025, a horse in Adams County had a presumptive diagnosis of Equine Infecious Anemia. This was confirmed by a second laboratory on December 23rd, 2025. The initial positive test was found on routine testing (Coggin’s) for interstate movement. The premises in which this horse resided were placed under quarantine. The initial horse was euthanized, and there have been four more horses on the premises that have a presumptive positive diagnosis.
What is Equine Infectious Anemia?
Equine infectious anemia, also known as EIA, is a blood borne infectious disease spread by the virus Lentivirus equinfane. There is no treatment and no vaccines for this disease. All equid species are susceptible to the virus, but horses and ponies are more likely to develop clinical signs of the disease. Horses that become infected with EIA remain lifelong carriers. Disease is spread from horse to horse through mechanical transmission of blood feeding insects or by iatrogenic (i.e. reusing needles or things that touch blood) transmission. Since horses that were infected are lifelong carriers, they must be strictly quarantined away from other horses and insects or be euthanized.
This disease is commonly diagnosed on regular testing for interstate travel but can often be missed due to relatively vague clinical signs. It typically starts with an initial phase of fever and depression. This is followed by a longer period of recurring episodes of fever, depression, anemia, icterus, epistaxis, edema, muscle weakness. In most cases, episodes subside within a year and they become carriers. In some horses they may continue to have recurrent episodes.
As there is no safe and effective disease for EIA, it’s important to prevent the disease. Annual testing of all horses is recommended, and required with interstate travel. Its important to not cause iatrogenic spread of the disease. New, sterile needles, syringes, and IV sets should be used for every animal. Between horses, dental, tattoo, surgical equipment, lip chains, and bits should all be disinfected. All debris and blood should be removed before disinfection. Additionally, practice good fly control to prevent the amount of blood feeding insects. Fortunately there aren't many biting insects at this time of year in Colorado to spread the disease further.
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