Rhodococcus equi seroepidemiological studies were conducted. Sera used were collected from 290 apparently clinically normal mares and foals. The samples originated from 6 horse-breeding farms, located in the county of Bagé, Rio Grande do Sul, Brazil, which had different histories of Rhodococcus equi infections. To correlate the serological results with the presence of the agent in the intestine 123 fecal samples were collected. The synergistic hemolysis inhibition test was used. The test detects antibody against the "equi factor". Neutralizing antibodies against the equi factor were verified in 87.93% (255/290) of the animales tested. The geometric mean titer (GMT) of antibodies was higher in the foals when comparad with the mares. The serological results had a correlation with the isolation of R. equi in the feces. The rate of R. equi isolation and GMT titers was higher at the horse-breeding farm where clinical cases were registered. Further studies need to be done to establish the relation among the importance of serological titers and disease detection.
Horses; serology; synergistic hemolysis inhibition
