KNOXVILLE, Tenn. — At a time of year when horses normally get an enormous amount of positive attention, the Tennessee state veterinarian’s office released the negative news of four confirmed cases of Equine Infectious Anemia (EIA) in the western part of the state.

According to information from the Tennessee Department of Agriculture (TDA), four horses stabled at three locations in Henderson County recently tested positive for EIA. A second round of screening confirmed the positive results. State officials are testing additional horses that stabled with or live near the infected horses.

State Veterinarian Dr. Charles Hatcher said, in a press release, early detection and containment are critical to preventing the spread. He also said this disease is taken seriously.

Dr. Carla Sommardahl, an equine internal medicine specialist and a clinical associate professor at the University of Tennessee College of Veterinary Medicine, said EIA – which is commonly called “swamp fever” or “horse malaria” – is a virus that can lead to destruction of platelets, red blood cells and inflammation in many of the organs in a horse’s body.

“The virus invades the white blood cells, monocytes and macrophages, and causes a lifelong infection within the spleen, liver and other tissues,” she explained. “The virus is spread from horse to horse by biting, blood-sucking flies such as the horsefly and deerfly.”

She also said the virus can be passed from dam to foal through the placenta, through natural breeding as a venereal disease and by any transfer of blood from an infected horse to an uninfected horse through the use of dirty needles or other equipment.

For those horses that get the virus, options are few. Either the animal will have to be in quarantine for the remainder of its life or will have to be euthanized. Sommardahl pointed out clinical signs of EIA can vary and may be an acute form of the disease that can include a sudden high fever, lethargy, anemia and low blood platelets – or a more chronic form with intermittent fever, weight loss, edema in the legs and lower abdomen and anemia.

“Initially the horse’s immune system may be able to stop the virus and the horse will go through periods showing no symptoms but can still spread the virus,” she said. “These animals serve as inapparent carriers. The horse will then have reoccurring episodes that can lead to chronic debilitation.”

The keys to stopping the spread of EIA are detection and isolation. Sommardahl said control of the disease is through testing of horses to identify carriers of the virus. The Coggins test, developed in 1970, is used as the standard diagnostic to detect antibodies in the blood against the virus, according to Sommardahl.

“This testing is part of a federal and state program to control this disease,” she said. “The Coggins test is commonly required when moving horses within and among states.” She also said it is recommended horses get a yearly test for EIA beginning at 6 months of age.

The USDA offers many recommendations for keeping horses safe from the disease, including:

•Use disposable syringes and needles; follow the rule of “one horse, one needle”

•Clean and sterilize all instruments thoroughly after each use

•Keep stables and immediate facilities clean and sanitary – remove manure and debris promptly, and ensure the area is well drained

•Implement insect controls; avoid habitats favorable to insect survival

•Do not commingle infected and healthy animals, and do not breed EIA-positive horses

•Isolate all new horses, mules and asses brought to the premises until they have been tested for EIA

•Obtain the required certification of negative EIA test status for horse shows, county fairs, racetracks and other places where many animals are brought together

•Abide by state laws that govern EIA – the major regulatory actions to control EIA are carried out by the states (contact your veterinarian or state veterinarian for testing requirements in your state)

The TDA noted Tennessee normally experiences a few cases of EIA each year.

For more information, contact the state veterinarian’s office at 615-837-5120.