Equine Infectious Anemia
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Equine Infectious Anemia

   

Equine Infectious Anemia 1

G.W. Meyerholz2

Equine infectious anemia (EIA) or swamp fever is a viral disease of horses that has been known to exist for more than 70 years. It is characterized by anemia, intermittent fever, depression, progressive weakness, loss of weight, and swelling of the legs, brisket, and lower abdomen. In the acute form, animals are extremely sick and may die. Horses that have the chronic form, or recover from the acute or subacute form to become chronic, usually have intermittent attacks ranging from one week to a month or more between attacks. Some horses die during these recurrent episodes. A latent or subclinical form of EIA may also develop in equines. These animals appear normal but are carriers of the virus in their blood. Carrier animals are potential sources of infection for susceptible healthy horses. Horses have been known to harbor the virus for more than 18 years.

Laws and Regulations

There are now laws and regulations for the control of equine infectious anemia (EIA) in Florida. The major provisions of these rules include the following:

  1. Test required for assembly and sale . --Horses moving to race tracks, rodeos, shows, fairs, boarding stables, or similar assembly points, including public or private sale, must be accompanied by a record of negative test for EIA conducted within the last 12 months.
  2. Test required for importation . --Equines imported into Florida must be accompanied by a certificate showing the animals were tested and negative to an approved test for EIA conducted at an approved laboratory within 6 months prior to entry.
  3. Identification of reactors . --Horses over 9 months of age that are positive to the official test in Florida shall be permanently identified by a lip tattoo or visible body brand by applying the letter "A" preceded by the numerals "58" and followed by a number assigned to indicate individual identification. Any animal under 9 months of age which reacts positively to an official test shall be quarantined and retested at 9 months of age.
  4. Quarantine . --Any horse found to be infected with EIA shall be quarantined until death on its home farm or such other premises as may be approved; provided however, the movement of infected animals may be authorized to approved facilities for research purposes or for slaughter to approved facilities. Horses not known to be infected on premises where infected animals are properly isolated are not considered to be in quarantine. Generally, quarantine has been interpreted to be a screened stall or 200 yards from any other horses. Foals born in quarantine facilities may be moved prior to reaching 9 months of age on evidence of negative test performed immediately prior to such movement.
  5. Official test . --The official test for the diagnosis of EIA is the agar gel immunodiffusion (AGID) blood test conducted by an approved laboratory. The horse inoculation test whereby blood is transferred from a suspect to a susceptible horse under supervision of regulatory officials is also considered an official test.
  6. Reporting . --The results of all tests for EIA must be reported to the Florida Department of Agriculture and Consumer Services. Any person having knowledge of the existence of EIA within the state must immediately make a written report to the State Veterinarian.
  7. Recommended procedures . --
A. Officials and veterinarians at race tracks, horse shows and rodeos should:

  1. See that sanitary and other protective measures prescribed are carried out.
  2. Insure that tattoo instruments and saliva collecting equipment are adequately sterilized prior to being used on any horse.
  3. Enforce rules preventing the use of hypodermic syringes and needles on horses by persons other than accredited veterinarians.
  4. Require provision for and operation of adequate isolation facilities.
B. Horse owners and practicing veterinarians should:

  1. Report immediately any suspect horses to the State Veterinarian.
  2. Use disposable hypodermic needles and syringes (one needle- one horse).
  3. Thoroughly sterilize all nondisposable needles, syringes, and other grooming equipment prior to reuse on any horse.
  4. Institute and carry out proper sanitary and preventive measures, including control of biting insects.
C. Organizations representing particular breeds of horses should recommend to individual farms and owners that the test for equine infectious anemia be administered to all animals and that the preventive measures as set forth in rules be instituted.

Transmission

The virus that causes equine infectious anemia is transmitted by biting insects such as horse flies, mosquitoes and biting lice. Contaminated hypodermic needles and surgical instruments can also spread the disease. Prolonged contact of a healthy horse with an infected animal usually results in infection of the exposed animal.

Diagnosis and Testing

The recent development of the agar gel immunodiffusion test (Coggins Test) has given a new dimension to the identification of infected animals and the possible control and eradication of EIA. Blood samples are collected and the blood serum is tested Test results indicate that the percentage of EIA carriers in Florida is much higher than previously recognized. Animals to be assembled or sold should be tested as well as any horses showing clinical signs.

Foals may be positive to the test for EIA up to 9 months of age if they receive material antibodies from the milk of their mother. These antibodies may cause a positive-positive test for a period up to 9 months of age even though the foal is not infected with the virus. Therefore, positive foals from reactor mothers should be isolated until 9 months of age and retested to define their exact status. Foals sometimes become infected through contact with their mothers. However, there is a good possibility of raising a foal free of the disease if it is removed and isolated from its mother as soon as practical.

Control Recommendations

Although research is in progress to develop new methods of control, there is no vaccine or approved treatment available for equine infectious anemia at this time. The following measures are recommended:

  1. Comply with laws and regulations for the control of EIA.
  2. Test all horses in the band or herd for EIA.
  3. Strictly isolate or "put down" infected animals to prevent exposure of other horses or foals. Disposal of infected horses to approved slaughter facilities or research institutions is acceptable. Elimination of infected animals will prevent spread of EIA to other animals.
  4. Bury deeply or burn carcasses of known infected animals.
  5. After elimination of positive animals, retest at intervals recommended by a veterinarian to establish a clean herd.
  6. In high risk areas or herds frequently exposed to other horses, test the herd at regular intervals as recommended by a veterinarian. Periodic testing is desirable until the disease is brought under reasonable control.
  7. Control biting flies, mosquitoes, and lice.
  8. Use only sterilized hypodermic needles and surgical instruments on each horse.
  9. Avoid the use of common equipment such as bits, stomach tubes, and grooming equipment between noninfected and infected horses or horses of unknown status.
  10. Maintain as much separation as possible (200 yards or more) from neighboring herds of unknown or infected status.
  11. Isolate and test all such animals suspected of having EIA.
  12. Isolate additions to the premises and retest in 60 to 90 days before comingling with other horses.

Footnotes

1. This document is VM-7, one of a series of the College of veterinarian Medicine, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Date revised: March 1998. Please visit the FAIRS Website at http://hammock.ifas.ufl.edu.

2. G.W. Meyerholz, D.V.M., extension veterinarian, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.

U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Larry Arrington, Dean.


Copyright Information

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