Efficacy of a flexible schedule for administration of a Leptospira borgpetersenii serovar Hardjo bacterin to beef calves.
OBJECTIVE
To determine whether a flexible vaccination regimen provides protection against challenge exposure with a virulent Leptospira borgpetersenii serovar Hardjo isolate.


METHODS
Fifty-five 4-week-old calves seronegative for antibodies against L borgpetersenii serovar Hardjo.


METHODS
Calves were assigned to 3 groups and administered 2 doses of adjuvant (control calves; n = 11), 1 dose of serovar Hardjo bacterin and 1 dose of adjuvant (22), or 2 doses of the serovar Hardjo bacterin (22); there was a 16-week interval between dose administrations. Three weeks after the second dose, all calves were challenge exposed by use of conjunctival instillation of a heterologous strain of L borgpetersenii serovar Hardjo for 3 consecutive days. Urine samples for leptospiral culture were collected for 5 weeks after challenge exposure; at that time, all calves were euthanized and kidney samples collected for leptospiral culture.


RESULTS
Antibody titers increased in both leptospiral-vaccinated groups of calves. A significant increase in antibody titers against L borgpetersenii serovar Hardjo was detected after administration of the second dose of L borgpetersenii serovar Hardjo bacterin and challenge exposure. In 10 of 11 adjuvant-treated control calves, serovar Hardjo was isolated from both urine and kidney samples. Leptospira borgpetersenii serovar Hardjo was not isolated from the urine or kidney samples obtained from any of the 21 remaining calves that received 1 dose of bacterin or the 20 remaining calves that received 2 doses of bacterin.


CONCLUSIONS
Protection in young calves was induced by vaccination with 1 or 2 doses of a serovar Hardjo bacterin.
Department of Veterinary Operations Cattle/Equine, Zoetis, 746 Veechdale Rd, Simpsonville, KY 40067.
Victor S
VS
Cortese
Guillermo F
GF
Gallo
Diane L
DL
Cleary
Jeffrey E
JE
Galvin
Randy D
RD
Leyh
D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D001428:Bacterial Vaccines / Q000008:administration & dosage* / Q000276:immunology; D002417:Cattle; D002418:Cattle Diseases / Q000276:immunology / Q000382:microbiology* / Q000517:prevention & control*; D004334:Drug Administration Schedule / Q000662:veterinary*; D005260:Female; D007668:Kidney / Q000382:microbiology; D007919:Leptospira / Q000276:immunology* / Q000302:isolation & purification; D007922:Leptospirosis / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary*; D014556:Urine / Q000382:microbiology; D014611:Vaccination / Q000662:veterinary*
D000907:Antibodies, Bacterial; D001428:Bacterial Vaccines