The invention provides an equine infectious anemia (EIA) vaccine that provides immunity to mammals, especially equines, from infection with equine infectious anemia virus (EIAV) and which allows differentiation between vaccinated and non-vaccinated, but exposed, mammals or equines. Preferably said vaccine encompasses at least one mutation in an EIAV which produces a non-functional gene in the vaccine virus that is always expressed in disease-producing wild-type EIA viruses. Additionally, said EIA vaccine virus cannot cause clinical disease in mammals or spread or shed to other mammals including equines.