Equine infectious anemia: prospects for control.

Equine infectious anemia has been managed in most countries by the imposition of testing and quarantine regulations. In the United States, about 700,000 of the more than 7,000,000 horses are tested annually. As long as the status of greater than 90% of the horse population remains unknown and horses are transported and congregate in a relatively unrestricted manner, EIA will continue to exact its toll. Therefore, it is incumbent on the scientific community to continue to develop and refine practical and sensitive diagnostic tests for EIA which will be used in an expanding market, to reduce the number of untested horses and to increase the accuracy of test results. Under ideal conditions, EIA can spread rapidly in a localized population with potentially devastating results. Although strict adherence to sanitary regulations will minimize the likelihood of epizootics, the existence of a large reservoir of untested horses with occasional contact with uninfected test-negative horses will ensure the continued transmission of EIAV. The change of this transmission occurring as a result of human intervention can be eliminated but it is not possible to eliminate the threat posed by blood feeding insects. If these "chance encounters" between an untested EIAV infected horse and a test-negative horse occur under field conditions where horse flies are abundant and the proximate distance between the horses is minimal, transmission is efficient if the quantity of EIAV in the blood of the donor horse is high.(ABSTRACT TRUNCATED AT 250 WORDS)