Time Course of Shedding and Antibody Response in Naturally Infected Pigs During Grower-finisher Stage

A longitudinal trial was conducted to determine the course of shedding and antibody response in naturally infected grower-finisher pigs. Ten-week-old pigs ( = 45) were transferred from a farm with history of salmonellosis and housed at a research facility. Weekly fecal samples (weeks 1 to 11) as well as tissue samples at slaughter were cultured for Serum samples were tested for presence of antibody by enzyme-linked immunosorbent assay (ELISA). Data were analyzed using a multilevel mixed-effects logistic regression model. Over 10 wk, 91% and 9% of pigs shed ≤ 4 and > 5 times, respectively. The estimated median of shedding duration was 3 to 4 wk but some pigs shed for up to 8 wk. shedding increased 1 wk post-arrival but followed a decreasing pattern afterwards up to week 11 ( < 0.05). isolates ( = 29), which were recovered from 18 pigs at different occasions, were Typhimurium (28%), Livingstone (21%), Infantis (14%), Montevideo (7%), Benfica (3%), Amsterdam (3%), Senftenberg (17%), and I:Rough-O (7%). Of 11 pigs from which the first and last isolates were serotyped, 10 pigs were reinfected with a different serotype. At slaughter, was isolated from 7 pigs, of which 5 (71%) had not tested positive for at least 7 wk prior to slaughter. Antibody response peaked 4 wk after the peak of infection; shedding reduced as antibody response elevated ( < 0.05). These findings indicate that pigs may shed into the mid-point of the grower-finisher stage and may be reinfected with different serotypes.