Detecting anti-Treponema hyodysenteriae antibodies in swine serum using immunofluorometry

An indirect fluorescent antibody test was adapted for measuring serum anti-Treponema hyodysenteriae antibodies with a fluorometer. The immunofluorescence was recorded as fluorescent signal units. Cultures of T. hyodysenteriae and Treponema innocens were used as antigen. There was a significant (P less than 0.01) correlation between the immunofluorescence recorded with the fluorometer and that evaluated visually with a microscope. The swine exposed orally to swine dysentery infective inoculum and subsequently hyperimmunized by the intravenous inoculation of live cultures of T. hyodysenteriae had the highest average fluorescent signal unit, which was 104.5. There was a significant (P less than 0.01) correlation between the level of anti-T. hyodysenteriae antibody and the interval length between the last day of diarrhea and the day of bleeding. However, in measuring fluorescent signal units in serum from swine infected with nonpathogenic large spirochetes, (T. innocens), there was also a significant (P less than 0.01) correlation between T. hyodysenteriae and T. innocens as antigen. The coefficient of variation of the average fluorescent signal unit for a highly positive serum and a highly negative serum between 16 runs of assays were 5.7% and 19% respectively; the coefficient of variation of the average fluorescent signal unit for duplicate samples on 358 serum samples tested was 5.8%.