Scientists Study
Recent study results suggest that horses can carry the virus for up to two years without being seropositive on a Coggins test, ELISA, or Western Blot blood test. | Photo: Erica Larson/The Horse
Why do horses that are seropositive (have a positive blood test) for equine infectious anemia virus (EIAV) pass the virus on to some nearby horses but not others?

Actually, they might be passing it on more than we think. Recent study results suggest that horses can carry the virus for up to two years without being seropositive on a Coggins test, ELISA, or Western Blot blood test.

This “silent” form of EIAV might sound terrifying, but researchers found silent cases (horses infected without seroconversion, or positive blood samples) only on farms where seropositive horses lived together with seronegative horses over a long period.

“I do not believe we would find the same situation if there were only seronegative horses,” said researcher Adriana Soutullo, PhD, of the Laboratory of Agricultural Diagnostics and Research in the Ministry of Production of the Santa Fe Province, and of the Immunology Laboratory at the Faculty of Biochemistry and Biological Sciences at Litoral National University, both in Argentina

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