Test Horses Annually for Equine Infectious Anemia
Following a rash of positive equine infectious anemia (EIA) tests in racing Quarter Horses in California, a Louisiana State University AgCenter equine specialist is encouraging owners to test horses for the disease annually.

Neely Walker, MS, PhD, said it is critical that horse owners follow regulations when it comes to EIA testing.

An infectious viral disease that affects horses, mules, donkeys, and zebras, EIA is also known as swamp fever. There is currently no effective treatment or vaccine for EIA. The survival rate of horses infected with EIA is high, Walker said, but those animals can threaten the health of their offspring and other horses. As a result, EIA-positive horses must be euthanized or, if permitted, placed in lifelong quarantine.

The virus is typically transmitted from one horse to another by blood-sucking insects. Many epidemics of EIA have also been linked to the reuse of hypodermic needles or nonsterile surgical equipment, Walker said.

Walker said EIA can present itself in three different degrees of infectiousness: acute, chronic, and inapparent.

“Most horses are inapparent carriers of EIA and appear normal, displaying no clinical abnormalities associated with infection,” Walker said. “However, they are lifelong carriers of the virus.”

The acute form of EIA is the most damaging and is difficult to diagnose. This form often occurs seven to 30 days after the first exposure to the virus and can cause fever and hemorrhaging on the mucus membranes, Walker said.

If the horse survives the acute stage of EIA, it could develop chronic symptoms such as fever, small patches of hemorrhages on the mucus membranes, depression, weight loss, anemia, and swelling of the legs and abdomen.

Diagnosis of the virus was not possible until the 1970s, when Leroy Coggins developed a test, which became known as the Coggins test. Today’s tests can produce results in less than one hour.

“Accurate testing allows timely identification of infected animals and removal of those animals from herds, potentially preventing the spread of the disease,” Walker said.

In Louisiana, all horses are required to have a Coggins test performed annually. Foals must be tested no later than one year after being born.

Animals that test positive for EIA in Louisiana must be euthanized or sold for slaughter only. All animals located within 200 yards of an animal with EIA are subject to quarantine and require a negative test before a quarantine release will be issued.