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Medical Index
First Posted: Feb 8, 2007
Mar 11, 2016

Equine Infectious Anemia or Swamp Fever

Update: ..."'The equine infectious anemia virus is similar in many ways to the human immunodeficiency virus (HIV), the cause of AIDS in people,' says Robert Mealey, DVM, PhD, Dipl. ACVIM, associate professor of immunology and infectious diseases at Washington State University's College of Veterinary Medicine.

For example, both viruses:

  • Are lentiviruses, a viral variety known for persistent infections resulting in slow, progressive disease;
  • Are retroviruses (RNA viruses that replicate as part of the host cell's DNA); and
  • Cause lifelong infections.

Just like HIV in humans, EIA can spread insidiously from one horse to another--developing subtly and gradually enough to be well-established before becoming apparent. And also like HIV, we do not want a retrovirus running rampant in the equine community. Infections are not preventable by vaccination, can go undetected, and are incurable.

However, 'unlike HIV, which eventually destroys the immune system resulting in fatal disease, most horses infected with EIAV do not die from the infection,' notes Mealey. 'Instead, their immune systems are able to keep the virus at low levels, and they live their lives persistently infected yet otherwise normal.'" .. Keeping Tabe on EIA

Referenced from "Wikipedia"

Equine Infectious Anemia or Equine Infectious Anemia (EIA), is caused by a retrovirus and transmitted by bloodsucking insects. The virus is endemic in the Americas, parts of Europe, the Middle and Far East, Russia, and South Africa. EIA can be transmitted through blood, saliva, milk, urine, and body secretions. Transmission is usually through blood-sucking insects, such as the horse-fly and deer-fly. Contaminated surgical equipment and recycled needles and syringes can also transmit the disease. Mares can transmit the disease to their foals via the placenta. The risk of transmitting the disease is greatest when an infected horse is ill, as the blood levels of the disease are high enough to infect the blood-feeding insects.

Stages of EIA

Acute: The acute form is a sudden onset of the disease at full-force. Symptoms include high fever, anemia (due to the breakdown of red blood cells), weakness, swelling of the lower abdomen and legs, weak pulse, and irregular heartbeat. The horse may die suddenly. Mortality rate is high.

Subacute: A slower, less severe progression of the disease. Symptoms include recurrent fever, weight loss, an enlarged spleen (felt during a rectal examination), anemia, and swelling of the lower chest, abdominal wall, penile sheath, scrotum, and legs.

Chronic: Horse tires easily and is unsuitable for work. May have a recurrent fever and anemia, may relapse to the subacute or acute form even several years after the original attack.

A horse may also not appear to have any symptoms, yet still tests positive for EIA antibodies. This horse can still pass on the disease.

EIA may cause abortion in pregnant mares. This may occur at any time during the pregnancy if there is a relapse when the virus enters the blood. Most infected mares will abort, however, some give birth to healthy foals.

Prevention and Treatment of EIA

Currently, there is no vaccine for EIA. The virus can be variable, which makes it hard to produce one. Do not reuse syringes and needles. Currently in the United States, all horses that test positive must be reported to federal authorities by the testing laboratory. Options for the horse include sending the horse to a recognized research facility, branding the horse and quarantining it at least 200 yards from other horses for the rest of its life, and euthanizing the horse. EIA-positive horses are infected for life. The danger that they may spread the disease, even if they are not showing any clinical signs, is enough of a reason to enforce such stringent rules.

The Coggins Test

The Coggins Test (agar immunodiffusion) is a sensitive diagnostic test for Equine Infectious Anemia developed by Dr. Leroy Coggins in the 1970s.

Currently, the USDA does not have an eradication program due to the low rate of incidence, however many states require a negative Coggins test for interstate travel. In addition, most horse shows and events require a negative Coggins test. Most countries require a negative test result before allowing an imported horse into the country.

It is recommended to verify that all the horses at a breeding farm and or boarding facility have a negative Coggins test before using their services. A Coggins Test should be done on an annual basis. Tests every 6 months is recommended if there is increased traveling.

For More Information:

Equine Anemia Fact Sheet
New Control Strategies for Equine Infectious Anemia

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