Equi

Equine Infectious Anemia (EIA), also known as swamp fever, is a viral disease affecting horses, mules, and donkeys. The disease is caused by a virus of the family Retroviridae and is transmitted primarily through blood-feeding insects, notably horseflies and deerflies. EIA is characterized by fever, anemia, jaundice, swelling in the limbs, and occasionally death. There is no vaccine or cure for EIA, making prevention through management and testing practices crucial.

Transmission

EIA is transmitted through the transfer of blood by biting insects such as horseflies and deerflies. The virus can also be spread through the use of contaminated needles, surgical instruments, and through blood transfusions. Vertical transmission from mare to foal is possible, though less common.

Symptoms

Symptoms of EIA can vary from acute, subacute to chronic, depending on the stage of the disease:

• Acute: High fever, severe anemia, and death in severe cases.
• Subacute: Milder symptoms including intermittent fever and weight loss.
• Chronic: Recurrent fever, weight loss, anemia, and swelling in the limbs.

Some horses may become asymptomatic carriers, showing no visible symptoms but capable of spreading the virus.

Diagnosis

Diagnosis of EIA is primarily through blood tests, with the Coggins test being the most widely used method. This test detects antibodies to the EIA virus, indicating exposure. Positive horses are usually required to be either euthanized or permanently quarantined and branded to prevent the spread of the disease.

Prevention and Control

Prevention focuses on controlling biting insects, testing new and existing horses, and implementing biosecurity measures:

• Use of insect repellents and management practices to reduce insect populations.
• Regular testing of horses through the Coggins test.
• Quarantine of new or returning horses until they have been tested.
• Sanitization of equipment and avoiding the use of shared needles.

Legal and Ethical Considerations

In many countries, there are legal requirements for testing horses for EIA, especially before travel or sale. The euthanasia or lifelong quarantine of positive horses raises ethical considerations, balancing animal welfare with the need to control the disease.

See Also

• Horse health
• Viral diseases in animals
• Retroviridae