SAFETY AND EFFICACY OF AN AVIRULENT LIVE SALMONELLA-CHOLERAESUIS VACCINE FOR PROTECTION OF CALVES AGAINST S-DUBLIN INFECTION

Objective-To evaluate the safety and efficacy of avirulent live Salmon ella choleraesuis strain 54 (SC54) as a vaccine to protect calves agai nst salmonellosis caused by S dublin. Animals-40 head of clinically no rmal 3 to 5-week-old male Holstein calves that were culture negative f or Salmonella sp. Procedure-Calves were randomly assigned to 4 test gr oups of 10 calves each. Group 1 received 8.5 x 10(7) colony-forming un its (CFU) of SC54 SC. Groups 2 and 3 received 1.13 x 10(9) CFU of SC54 , SC and intranasally, respectively. Group 4 received saline solution as a vaccine control. All carves were challenge exposed orally with 1. 74 x 10(9) CFU of virulent S dublin 14 days after vaccination. Clinica l signs and Salmonella shedding were monitored for 28 days after vacci nation. Calves were necropsied, and organs were cultured for Salmonell a sp 14 days after challenge exposure. Results-Calves of groups 2 and 3 had slightly high rectal temperature after vaccination. Salmonella d ublin challenge exposure resulted in mild clinical Signs of salmonello sis. All vaccinated groups had significantly (P < 0.05) lower rectal t emperature, fecal shedding of S dublin, and recovery of S dublin from organs after necropsy. SC54 was not recovered from fecal or blood samp les collected after vaccination or from injection site samples or orga ns collected at necropsy. Conclusions-SC54 given intranasally or SC to calves was safe and significantly (P < 0.05) reduced clinical signs a nd bacterial shedding after oral challenge exposure with S dublin. Cli nical Relevance-SC54 has potential as an effective vaccine to aid in p revention of salmonellosis caused by S dublin in calves.