Diagnosis of Equine Infectious Anemia by Immunodiffusion Test

SUMMARY Equine infectious anemia (eia) antibody was detected by the immunodiffusion test in 111 experimental ponies after they were inoculated with known eia virus, whereas eia antibody was not found in 77 control ponies. In most of the ponies tested (65% of 57 ponies) antibody was produced by 3 weeks after eia virus inoculation and in the others antibody developed before the 45th postinoculation day. In the experiment to determine correlation between presence of antibody and infection with eia virus, blood from 84 serologically test-positive horses (from 5 states), representing acute, chronic, and inapparent eia, produced eia infection in 84 experimental ponies, as determined by clinical signs and production of eia antibody. Blood from 77 serologically test-negative horses did not infect ponies and eia antibody was not produced. Thus, the immunodiffusion test was accepted as being at least 95% accurate for the diagnosis of eia infection.