History and introduction This paper will review the current serologic tests to Equine infectious anemia (EIA) has been recognized diagnose infections with EIAV, discuss limitations of as an important viral disease of members of the horse the procedures, and suggest improvements based on family since its “filterable virus” etiology was proven early in the twentieth century. Only since the 1970s EIAV and the horse have we been able to diagnose infection with equine infectious anemia virus (EIAV) accurately with the use The EIAV is a member of the lentivirus subfamily of serodiagnostic methods. Early attempts to define of retroviruses and shares morphologic, antigenic, and specific diagnostic tools for EIA failed in part because genetic characters with the other lentiviruses. 17 The of a lack of suitable in vivo laboratory animal models major core protein of EIAV is a product of the viral and in vitro techniques for virus propagation, as well gag gene, 45 has a molecular weight of 26,000 daltons as the tendency of EIAV to undergo “antigenic drift.” (p26), 37 represents about 40% of the virion mass, The recognition of the highly mutable typeor subtypeand has group and interspecies antigenic determispecific antigens of EIAV which stimulated neutraliznants. 12,30,31 The major core protein appears to be highing antibodies suggested that a widely applicable diagly conserved between EIAV isolates, 44 and the imnostic test for the disease would not be forthcoming. munodominant regions of the protein have been Complement fixation and precipitin tests were tried elucidated. 4 Antibodies to the major core protein are but held little promise as accurate and/or practical didetected in the AGID test because the p26 antigen agnostics. 21,43 Horse inoculation tests were standardpredominates in antigen preparations. Occasional reized for the diagnosis of EIA, but were expensive, actions to the pl5 protein of EIAV have been noted wasteful of equine resources and required facilities in in the AGID test. 25,47