Shedding of Treponema hyodysenteriae, transmission of disease, and agglutinin response to pigs convalescent from swine dysentery.

: Fecal shedding of Treponema hyodysenteriae, transmission of disease, and humoral antibody production against the large spirochete were evaluated in pigs convalescent from experimentally induced swine dysentery. Untreated pigs (n = 21) and 5 pigs that had been treated with virginiamycin were included in the study. Treponema organisms were culturally detected in the feces of 2 untreated pigs as long as 70 and 71 days, and in the feces of 1 treated pig as long as 83 days after the last clinical evidence of disease. Of 8 convalescent pigs that intermittently discharged T hyodysenteriae in their feces, 4 transmitted clinical disease to exposed susceptible pigs. One of the convalescent animals has been free of clinical signs of disease for 57 days before introduction of the susceptible pigs. Treated and untreated convalescent pigs developed similarly elevated agglutinin titers that were maintained as long as 150 days after infection. There was no apparent correlation between the frequency or duration of fecal shedding of the spirochetes and the magnitude of the agglutinin titers of the convalescent pigs.