Abstract
Swine were infected orally with pure cultures of Treponema hyodysenteriae, and the humoral antibody response was measured by a passive hemolysis test (passive hemagglutination test with the use of complement). Antibody to T. hyodysenteriae was detected as early as 1 week and later on at 4 months after exposure. However, peak serum titers were obtained after challenge at 4 weeks postinfection. The usefulness of the test as a potential diagnostic tool for antibody to T. hyodysenteriae is discussed.