A Corynebacterium pseudotuberculosis bacterin with muramyl dipeptide induces antibody titers, increases the time of onset, and decreases naturally occurring external abscesses in sheep and goats

Lambs from a university sheep flock and kids from a commercial goat dairy were injected with a bacterin containing Corynebacterium pseudotuberculosis (1 mg whole cells and 50 μg muramyl dipeptide in 10% light mineral oil) twice i.m. in the thigh, 1 month apart. All animals were then exposed to naturally infected adults under field conditions. Serum antibody titers to C. pseudotuberculosis, determined regularly up to 19 months in all animals vaccinated in 1990 and up to 7 months in all animals vaccinated in 1991, rose sharply after vaccination and remained higher (P<0.05) in vaccinated animals after that. Lambs and kids born in 1990 were watched for 28 months and 21 months, respectively, for development of naturally occurring external abscesses and lambs and kids born in 1991 were watched for 15 months and 8 months, respectively, until the project was ended. Vaccine efficacy was assessed by both the period of time for vaccinated animals to develop abscesses (i.e. time-to-infection) and the final number of vaccinated animals with abscesses. Abscesses occurred in 9/22 non-vaccinated lambs (time-to-infection 478±78 days) and in 4/21 (NS at P<0.05) vaccinated lambs (time-to-infection 665±42 days, NS at P<0.05). Lack of significance was due primarily to the low numbers of lambs with abscesses remaining in the trial after attrition losses. Abscesses occurred in 14/82 non-vaccinated kids (time-to-infection 483±35 days) and in 7/75 (NS at P<0.05) vaccinated kids (time-to-infection 595±20 days, P<0.05). Local injection site reactions (e.g. inflammation, abscess formation) or systemic reactions (e.g. lethargy) due to bacterin administration were not seen in any animal.