Equine Infectious Aneanemia

Equine Infectious Aneanemia (EIA) is tested for routinely with the Coggins test. The procedure is standard throughout the country. A veterinarian draws a blood sample and fills out forms to accurately identify the horse. Most states and all countries require a negative test withing the last 6 to 12 months as a requirement for crossing the borders.

EIA is caused by a retrovirus, a virus in the same class as HIV, which causes AIDS. But it affects only horses, mules, donkeys, and exotic equine species..not humans. Actual cases of EIA are uncommon. More cases are reported in southern states because of the longer insect vector season; insects appear to be the predominant source of transmission. Transmission is blood-borne. Insects, such as horseflies and deer flies, are the usual carriers due to their feeding bahibs. The flies usually begin feeding on one horse; then, as they are quivered off, will feed on the next, thus spreading the disease. Other modes of transmission are unsterilized hypodermic needles, uncleaned tooth floats, shared tack, and close contact.

The disease is characterized by the sudden onset of a high fever coupled with obvious depression. Within hours, temperatures can soar from 100 degrees Farenheit to 105 or even 107. The horse becomes severely depressed, drips with sweat, and breathes shallow, rapid breaths. This occurs when the virus is reproducing.

As the disease progresses, the horse loses weight in spite of good appetite. Fluid settles in his extremities, giving his legs a swollen appearance. Weakness causes stumbling or sometimes leads to hind-limb paralysis. Gums become pale to yellow, pulse becomes weak, and heart arrthymias occur. In a chronic case, a horse's red blood count drops and the animal becomes anemic. Thirty to fourth percent of all horses affect die.

Treatment is supportive only; there is no vaccine and positive horses remain infected for life. EIA can affect horses in symptomatic, chronic, and unapparent forms. The symptomatic horse runs a scalding fever, is exstemely depressed, loses his appetite, and usually dies. The chronically infected animal suffers recurrent bouts of clinical symptoms, particularly during periods of stress.

The unapparent carrier (an infected horse who has no symptoms) is most commonly diagnosed. This horse shows no outward signs, but is infective to other horses. Unapparent carriers can convert to more clinical forms of the disease.

A horse who tests positive to EIA is reported to the state department of agriculture. A state veterinarian then prefoms a second Coggins test to confirm the diagnosis. Since most horses with positive test are unapparent carriers, the horse will likely be completely asymptomatic. Studies show that bloodsucking flies rarely travel farther then 200 yards from the original host..therefore infected animals need to be quarantined this distance form the nearest equine.

An owner will be offered three options for a contaminated animal. The first and most common is euthenasia; the horse will be destroyed. The second will spare the animal's life...however, he will live in isolation and be permanently identified with a tattoo or brand on the left shoulder or neck. He must be stabled no closer then the 200 yards mentioned from any other equine and must be behind insect vector-proof sheilds during warm weather when insects are more active. The third option is slaughter.

The consequences of not testing for EIA could be extreme. Horses should be tested annually and any new horses coming on and off a farm or ranch should be tested and maintained in clean, isolated stalls.