Evaluation of two commercially-available Salmonella vaccines on Salmonella in the peripheral lymph nodes of experimentally-infected cattle

Authors: Edrington, Thomas; Arthur, Terrance; LONERAGAN, GUY - Texas Tech University; Genovese, Kenneth - Ken; HANSON, DEVIN - Texas Tech University; Anderson, Robin; Nisbet, David

Submitted to: Therapeutic Advances in Vaccines and Immunotherapy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/17/2020
Publication Date: 10/5/2020
Citation: Edrington, T.S., Arthur, T.M., Loneragan, G.L., Genovese, K.J., Hanson, D.L., Anderson, R.C., Nisbet, D.J. 2020. Evaluation of two commercially-available Salmonella vaccines on Salmonella in the peripheral lymph nodes of experimentally-infected cattle. Therapeutic Advances in Vaccines and Immunotherapy. 8:1-7. https://doi.org/10.1177/2515135520957760.
DOI: https://doi.org/10.1177/2515135520957760

Interpretive Summary: Cattle may contain the bacteria Salmonella that can make people sick. Peripheral lymph nodes in these cattle may contain Salmonella that protects it from interventions in the slaughter plant. Two experiments were conducted in which two commercially available Salmonella vaccines were tested to see if they would reduce or eliminate Salmonella from the peripheral lymph nodes of cattle following experimental inoculation. The experiments demonstrated modest decreases in Salmonella prevalence and supports further research into this potential pre-harvest intervention strategy.

Technical Abstract: Bovine peripheral lymph nodes (PLN) may contain Salmonella, and unless contaminated nodes are removed during slaughter, they serve as a source of contamination for ground beef. Utilizing an experimental model of Salmonella inoculation of the PLN, two experiments were conducted to evaluate commercially available Salmonella vaccines: Salmonella Newport Bacterial Extract vaccine with SRP® Technology (Experiment I) and Endovac-Bovi® with Immune Plus® (Experiment II). Steers received their respective vaccine, per label directions, or a sham-injection of saline (controls). In the first experiment, approximately 4 months following the booster vaccination, 30 steers were inoculated with three serotypes of Salmonella intradermally: Newport, Montevideo, and Anatum administered to the right legs, left legs, and to the caudal thorax and abdomen, respectively. Cattle were inoculated every other day over the course of five days (three total inoculation events), and 6 and 12 days following the final Salmonella inoculation, 16 and 14 head in each treatment were euthanized, respectively. The right and left subiliac, popliteal, and pre-scapular lymph nodes were collected, weighed, and cultured for Salmonella. In Experiment II, 12 head of Holstein steers were utilized. Seven days following the booster and weekly thereafter for three weeks (4 total inoculation events), cattle were inoculated as above and euthanized 7 days following final inoculation. In Experiment I, no treatment differences were observed in Salmonella prevalence 6 days post-inoculation (necropsy 1). However, in the vaccinated cattle at the second necropsy, a reduction (P = 0.05) in Salmonella prevalence was observed in the sub-iliac and pre-scapular lymph nodes, as well as when all nodes were evaluated collectively (P = 0.04). In Experiment II, the vaccine reduced (P = 0.03) Salmonella prevalence in the right popliteal and tended (P = 0.09) to decrease prevalence in both popliteal lymph nodes. These data provide evidence of a partial vaccine effect on Salmonella within PLN and indicate that further research and development is warranted to improve efficacy.