Serological Survey of Rhodococcus equi Infection in Horses in Hokkaido

Serological survey of Rhodococcus equi infection in horses in Hokkaido was performed using ELISA. Of 2,879 horse sera, 318 (11.0%) gave antibody-positive (OD greater than or equal to 0.3) reactions. The antibody-positive rate of female was significantly higher (p less than 0.01) than that of male, and no statistical difference between Anglo-Arab and thoroughbred was detected in the antibody-positive rate. The maximum antibody-positive rate (27.1%) was shown at 14 years of age. The antibody-positive rates on the 160 farms were found to vary widely from 0 to 78.9%. A significant difference (p less than 0.01) in the antibody-positive rate was detected among horse farms. It was elucidated that 100 (62.5%) out of 160 horse farms had an antibody-positive horse. These results indicate that R. equi was widespread on horse farms, and the level of environmental contamination with R. equi differed among horse farms.