Objective—To evaluate the efficacy of vaccination with the Leptospira interrogans serovar hardjo type hardjoprajitno component of a pentavalent Leptospira bacterin against a virulent experimental challenge with Leptospira borgpetersenii serovar hardjo type hardjo-bovis strain 203 in cattle.
Animals—Fifty-five 6-month-old Holstein heifers.
Procedures—Heifers that were negative for persistent infection with bovine viral diarrhea virus determined via immunohistochemical testing and negative for Leptospira interrogans serovar pomona, Leptospira interrogans serovar hardjo, Leptospira interrogans serovar grippotyphosa, Leptospira interrogans serovar bratislava, Leptospira interrogans serovar canicola, and Leptospira interrogans serovar icterohaemorrhagiae determined via microscopic agglutination assay were enrolled in the study. Two heifers were separated and used for the challenge passage. The remaining heifers were vaccinated twice with a commercial pentavalent bacterin or a sham vaccine 21 days apart and subsequently challenged with L borgpetersenii serovar hardjo type hardjo-bovis strain 203. Urinary shedding, antibody titers, and clinical signs of leptospirosis infection were recorded for 8 weeks after challenge.
Results—Heifers that received the pentavalent bacterin did not shed the organism in urine after challenge and did not have renal colonization at necropsy. Heifers that were sham vaccinated shed the organism in urine and had renal colonization.
Conclusions and Clinical Relevance—Results provided evidence that a pentavalent Leptospira vaccine containing L interrogans serovar hardjo type hardjoprajitno can provide protection against challenge with L borgpetersenii serovar hardjo type hardjo-bovis strain 203. It is important to demonstrate cross-protection that is vaccine specific against disease-causing strains of organisms that are prevalent under field conditions.
Objective—To evaluate the efficacy of an inactivated bovine herpesvirus-1 (BHV-1) vaccine to protect against BHV-1 challenge-induced abortion and stillbirth.
Animals—35 beef heifers.
Procedures—Before breeding, heifers were vaccinated with a commercially available BHV-1 inactivated vaccine SC or IM. The estrous cycle was then synchronized, and heifers were artificially inseminated 30 to 60 days after vaccination. Heifers (n = 21) were challenge inoculated IV at approximately 180 days of gestation with virulent BHV-1. Fourteen control heifers were not vaccinated. Clinical signs of BHV-1 infection were monitored for 10 days following challenge; serologic status and occurrence of abortion or stillbirth were evaluated until time of calving.
Results—18 of 21 (85.7%) heifers that received vaccine were protected from abortion following challenge, whereas all 14 control heifers aborted.
Conclusions and Clinical Relevance—Results indicated that an inactivated BHV-1 vaccine can protect against abortion resulting from a substantial challenge infection, with efficacy similar to that of modified-live BHV-1 vaccines.
OBJECTIVE To evaluate cell-mediated and humoral immune responses of calves receiving 2 doses of a dual-adjuvanted vaccine containing inactivated bovine herpesvirus type 1 (BHV1) and bovine viral diarrhea virus types 1 (BVDV1) and 2 (BVDV2) before and after exposure to BHV1.
ANIMALS 24 Holstein steers negative for anti-BHV1 antibodies and proliferative cell-mediated immune responses against BHV1 and BVDV.
PROCEDURES Calves were randomly assigned to 3 groups. The vaccinated group (n = 10) received 2 doses of vaccine on days 0 and 21. Control (n = 10) and seeder (4) groups remained unvaccinated. Calves were commingled during the study except for the 3-day period (days 53 to 55) when seeders were inoculated with BHV1 (1.04 × 107 TCID50, IV) to serve as a source of virus for challenge (days 56 through 84). Rectal temperature and clinical illness scores were monitored, and blood and nasal specimens were obtained for determination of clinicopathologic and immunologic variables.
RESULTS After BHV1 challenge, mean rectal temperature and clinical illness scores were lower for vaccinates than controls. In vaccinates, antibody titers against BHV1 and BVDV2, but not BVDV1, increased after challenge as did extracellular and intracellular interferon-γ expression, indicating a T helper 1 memory response. Additional results of cell marker expression were variable, with no significant increase or decrease associated with treatment.
CONCLUSIONS AND CLINICAL RELEVANCE Calves administered 2 doses of a killed-virus vaccine developed cell-mediated and humoral immune responses to BHV1 and BVDV, which were protective against disease when those calves were subsequently exposed to BHV1.
Objective—To evaluate immunity induced by a multivalent vaccine containing a US Leptospira borgpetersenii serovar Hardjo type hardjo bovis (LHB) isolate in heifers challenged 12 months after vaccination.
Design—Prospective vaccine challenge study.
Animals—36 one-month old Holstein heifers.
Procedures—18 heifers were vaccinated at 4 and 8 weeks of age with an inactivated vaccine containing Leptospira fractions. Additionally, 18 heifers were vaccinated at the same age with the same vaccine without any Leptospira fractions. All heifers were challenged with a US-origin LHB 12 months following booster vaccination. Urine samples were collected weekly for 8 weeks after challenge, and serum was collected at −1, 28, and 56 days after challenge for serologic testing. At 8 weeks after challenge, all heifers were necropsied, and kidney and reproductive system samples were collected for bacteriologic culture.
Results—4 of 18 vaccinates had positive results of bacteriologic culture of urine samples, but only at 1 time point. All control heifers had positive results of bacteriologic culture of urine samples for at least 5 time points. Vaccinates had negative results of bacteriologic culture of kidney and reproductive system samples following necropsy, whereas all control heifers had positive results of bacteriologic culture of kidney samples and 5 of 18 had positive results of bacteriologic culture of reproductive system samples.
Conclusions and Clinical Relevance—The vaccine administered to calves at 1 month of age prevented leptospire colonization of kidney and reproductive system tissue and significantly reduced urine shedding following challenge 12 months after vaccination. This vaccine provides an opportunity to protect calves at an early age from becoming infected and ultimately from becoming an LHB reservoir.