title: Development of challenge models to evaluate the efficacy of a vaccine to reduce carriage of Salmonella in peripheral lymph nodes of cattle.
abstract: Because challenge models to infect peripheral lymph nodes (PLNs) with Salmonella have not been reported, we performed a series of experiments to develop and refine challenge models to evaluate an intervention applied at the animal level and to provide initial estimates of efficacy of an intervention (i.e., a vaccine) to aid in the design of future studies. In each of four experiments, steers (control or vaccinated) were inoculated with Salmonella strains Montevideo or Newport, and in experiment IV, Salmonella Senftenberg was also used. Calves were euthanized 14 to 42 days postinoculation, and PLNs were collected. In the first experiment, calves were challenged with ∼10¹⁰ Salmonella cells, and few treatment differences were observed 14 days postchallenge. However, by day 21, Salmonella Newport was recovered from fewer vaccinated calves than control calves (P < 0.05). In experiment II, calves were challenged with ∼10⁷ Salmonella cells and, after two necropsies (14 and 28 days postchallenge), only one lymph node was Salmonella positive; therefore, the study was terminated. In experiment III, calves were again challenged with ∼10¹⁰ Salmonella cells, and no significant effect of vaccine was observed in calves challenged with Montevideo or Newport strains. A transdermal route of challenge was explored in experiment IV, using a 10-lancet, allergy testing instrument. Sixteen steers were challenged with either Salmonella Newport or Salmonella Montevideo (Salmonella Newport right legs; Salmonella Montevideo left legs), and all steers were challenged on the lower abdomen with Salmonella Senftenberg. Transdermal inoculation resulted in predictably Salmonella-positive PLNs, and a modest vaccine effect was detected. Because it is well tolerated by the calves and results in predictable and regionally specific Salmonella recovery from PLNs, the transdermal route of challenge may be preferred by researchers wishing to evaluate the impact of interventions designed to reduce the carriage of Salmonella in PLNs.
authors.affiliation: Food and Feed Safety Research Unit, Southern Plains Agricultural Research Center, Agricultural Research Service, U.S. Department of Agriculture, 2881 F&B Road, College Station, Texas 77845, USA. tom.edrington@ars.usda.gov
authors.forename: T S
authors.initials: TS
authors.lastname: Edrington
authors.forename: G H
authors.initials: GH
authors.lastname: Loneragan
authors.forename: J
authors.initials: J
authors.lastname: Hill
authors.forename: K J
authors.initials: KJ
authors.lastname: Genovese
authors.forename: D M
authors.initials: DM
authors.lastname: Brichta-Harhay
authors.forename: R L
authors.initials: RL
authors.lastname: Farrow
authors.forename: N A
authors.initials: NA
authors.lastname: Krueger
authors.forename: T R
authors.initials: TR
authors.lastname: Callaway
authors.forename: R C
authors.initials: RC
authors.lastname: Anderson
authors.forename: D J
authors.initials: DJ
authors.lastname: Nisbet
mesh_terms: D000818:Animals; D001428:Bacterial Vaccines / Q000008:administration & dosage*; D002353:Carrier State / Q000662:veterinary*; D002417:Cattle; D002418:Cattle Diseases / Q000276:immunology / Q000517:prevention & control*; D006801:Humans; D008198:Lymph Nodes / Q000382:microbiology*; D012475:Salmonella / Q000254:growth & development; D012480:Salmonella Infections / Q000517:prevention & control / Q000635:transmission; D012481:Salmonella Infections, Animal / Q000276:immunology / Q000517:prevention & control*; D014611:Vaccination; D015047:Zoonoses
chemical_list: D001428:Bacterial Vaccines