Control of EIA Virus Transmission

Once equine infectious anemia has been detected and confirmed in an index case through serologic tests, a series of procedures must be instituted with urgency to limit the spread of the infection to horses in close contact and limit the exposure to only that affected by blood-feeding insects. These procedures have proven effective in a variety of situations and are listed below.

It is important to note that all procedures must be strictly followed for control to be successful. These procedures are based on the knowledge that EIA is a blood-borne infection and that transmission by other means is negligible where humans are not involved.

  •  Identify every horse that has been in contact (defined as within 200 yards) with the index case(s) over the preceding 45 days (assuming the infection was recently acquired--if there is doubt, extend the retrospective surveillance beyond 45 days).
  • Without delay, quarantine all these contacts and premises. This must be implemented before results of confirmatory retests are available. As lab test results can be obtained generally in 24 hours, this action will prevent unwanted animal movement that would make effective traceback difficult.
  •  Immediately test all contacts and remove any positives; repeat traceback testing of all contacts of all positives (perform confirmatory tests to ensure accuracy).
  • Separate all contacts from other equids by 200 yards (or within vector-proof facilities) if possible until two negative tests are obtained (over at least 45 days beyond the last exposure date). If this is not possible, all equids within 200 yards of the contact are at risk and must be tested and retested as above (and each of their contacts must be followed if secondary spread occurs).
  •  Institute an extensive education program for veterinarians, trainers, owners, grooms, etc., about the extremely high potential for humans to transfer this blood-borne infection between horses. Insist on the adoption of standard precautions for control of EIA. (Standard precautions indicate a system of infection control that assumes that all blood and certain body fluids are treated as if known to be infectious.)
  • If possible, and especially if separation by 200 yards is not possible, separate contacts by as much distance as possible from other horses and institute measures to reduce vector pressures on horses, e.g., by stabling or by using fly repellants.
  • If new infections appear on any quarantined premises, restart the "at least 45 days" clock and require two negative tests

Strict adherence to these guidelines has led to the effective control of EIA virus transmission in multiple locations throughout the world.

About the Author

Charles Issel, DVM, PhD

Charles J. Issel, DVM, PhD, is the Wright Markey Chair of Equine Infectious Diseases at the Gluck Equine Research Center at the University of Kentucky. He has studied equine infectious anemia since 1974 while on the faculty at Louisiana State University (until 1990) and at UK. Issel bred Thoroughbreds in Louisiana prior to working at UK.

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