Effect of induced molting on the recurrence of a previous Salmonella enteritidis infection

Previous work in the authors' laboratory had shown that hens infected with Salmonella enteritidis (SE) during the feed removal phase of an induced molt shed significantly more SE and more readily transmitted SE to uninfected hens in adjacent cages when compared with unmolted hens. A study was conducted to examine the effect of induced molting on the recurrence and horizontal transmission of a previous SE infection. Hens aged 59 and 69 wk in Trials 1 and 2, respectively, were infected with SE and then molted 21 days later. In Trial 1, more molted hens were SE-culture-positive on Days 38 (P < or = .005) and 45 (P < or = .005) postinfection, and these hens shed more SE on these days (P < or = .05 and P < or = .005, respectively) than unmolted hens. Horizontal transmission of SE to previously uninfected but contact-exposed hens in adjacent cages was also higher in the molted group than the unmolted group on Days 38 (P < or = .05) and 45 (P < or = .001). Molted, contact-exposed hens also shed significantly more SE than unmolted hens. In Trial 2, the molted infected hens shed progressively more SE than the unmolted hens but the differences were not significant. However, more molted contact-exposed hens became SE-positive at Day 31 (P < or = .05) and 38 (P < or = .005) and also shed more SE on these days (P < or = .05 and P < or = .01), respectively) than the unmolted hens. Serum and intestinal antibody titers to SE were also examined in Trial 2. Molting appeared to exert no effect on the serum SE titers, but antibody titers in the alimentary tract were lower in the molted hens than the unmolted hens on Days 45 (P < or = .005) and 52 (P < or = .05). In Trial 1, three of eight molted directly infected hens and two of eight molted contact-exposed hens produced any SE-contaminated eggs. In Trial 2, no SE-contaminated eggs were produced.