Our objectives were to evaluate the clinical efficacy of oral and intranasal administration of a commercial modified-live Salmonella Dublin vaccine in dairy calves and to determine the serologic response associated with these extralabel routes of administration. We conducted a randomized field trial with calves from a New York dairy farm following an outbreak of Salmonella Dublin. A total of 399 Holstein calves were allocated by pen to 3 treatment groups: oral vaccination, intranasal vaccination, and an unvaccinated control group. Administration of the vaccine through oral and intranasal routes did not have a significant effect on pneumonia incidence risk or weight gain; however, calves vaccinated orally and intranasally had lower mortality risk as compared with control calves. Among calves tested using a Salmonella Dublin ELISA, vaccination did not induce an increase in antibody production relative to control calves, indicating that oral and intranasal administration will not hinder diagnosis based on this assay.
Keywords: Salmonella Dublin; dairy calf; field trial; vaccine.
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