EN
The examinations comprised all the mares and stallions of the stud K in the period from January 1989 to February 1991. Mares aged 6—12 months to 12 years were divided into 13 groups (from A to M). Serological tests were performed three times (I, II, III) at intervals of 1 years. The percentage of mares with neutralizing antibodies against EAV was 53.3, 67.5 and 48.5 (consecutive years). The titers of the antibodies ranged from 4 to ≥ 512. In the course of examinations the titers were 64—128, 32—64 and 16—32. In 24 of 27 fresh cases of infections between the first and second examination the appearance of specific antibodies was observed at week 3 after covering by a stallion with antibodies against EAV. In the same period there was noticed also a significant per cent of infections in 6—12 old mares of the group A (50%) and L (27.7%) being in contact with the mares covered by an infected stallion. After elimination of that stallion from the stud the number of new infections decreased markedly and only two cases were found in that time (between the second and third examination). The findings indicate that the primary transmission of EAV in the stud K took place through the genital tract due to infection by the infected stallion, and the secondary — by the respiratory tract.