Biosafety and antibody responses of adult bison bulls after vaccination with Brucella abortus strain RB51.

OBJECTIVE: To evaluate clearance, antibody responses, potential shedding, and histologic lesions in reproductive tissues of adult bison bulls after vaccination with Brucella abortus strain RB51. ANIMALS: 61 two- and 3-year-old bison bulls. PROCEDURE: 12 bison bulls were vaccinated s.c. with B abortus strain RB51, 3 were inoculated s.c. with 0.15 M NaCl, and antibody responses were evaluated. Various specimens were obtained to evaluate bacterial shedding. Four vaccinates and 1 control were necropsied 10, 20, and 30 weeks after vaccination. In a separate experiment, bison bulls were vaccinated s.c. with 0.15 M NaCl, or by hand or ballistically with strain RB51. Antibody responses were monitored 6 weeks after vaccination and during necropsy 13 weeks after vaccination. Tissue specimens obtained during necropsy from both studies were evaluated bacteriologically and histologically. RESULTS: Strain RB51 was recovered at various times from semen of 3 of 12 vaccinated bison bulls in experiment 1. During necropsy, strain RB51 was recovered 10 and 20, but not 30, weeks after vaccination. In experiment 2, strain RB51 was recovered from lymphoid tissues of hand- and ballistic-vaccinated bison bulls during necropsy. In both experiments, microscopic lesions in testes, epididymis, and seminal vesicles were minimal and did not differ between strain RB51-vaccinated and saline-inoculated bison bulls. CONCLUSIONS AND CLINICAL RELEVANCE: Strain RB51 does not induce relevant inflammatory lesions in reproductive tissues of adult bison bulls. Shedding of strain RB51 in semen may be transient in some bison bulls; however, the importance of this observation is unknown.     

Responses of cattle to two dosages of Brucella abortus strain RB51: serology, clearance and efficacy

A new brucellosis vaccine, Brucella abortus strain RB51 (SRB51), is currently recommended for use as a calfhood vaccine in the US at dosages between 1 x 10(10)and 3.4 x 10(10)colony-forming units (CFU). The purpose of the study reported here was to compare responses to minimal and maximal recommended SRB51 dosages. Eighteen heifer calves were vaccinated subcutaneously with 1.6 x 10(10)CFU of SRB51, 3.2 x 10(10)CFU of SRB51, or saline (n = 6 per treatment). The vaccine strain was recovered from the superficial cervical lymph node 14 weeks after vaccination in two of six animals that received 1.6 x 10(10)CFU SRB51, but not from any cattle vaccinated with 3.2 x 10(10)CFU SRB51. The higher SRB51 dosage stimulated greater antibody titres. Protection against abortion or infection following B. abortus strain 2308 (S2308) challenge was similar for both SRB51 dosages and greater than resistance of non-vaccinates. The vaccine strain was recovered from one heifer and her fetus at necropsy 1 week prior to estimated parturition. Data from this study suggests that SRB51 induces similar protective immunity across the recommended dosage range. The SRB51 vaccine may persist in some cattle into adulthood but the incidence and significance of this persistence remains unknown.     

Efficacy of calfhood vaccination with Brucella abortus strain RB51 in protecting bison against brucellosis

In the studies reported here, protection induced by calfhood vaccination of bison with 1.2-6.1 x 10(10)CFU of Brucella abortus strain RB51 (SRB51) against a virulent strain of B. abortus was evaluated. Non-vaccinated and SRB51-vaccinated bison were intraconjunctivally challenged during midgestation with 3 x 10(7)CFU of virulent B. abortus strain 2308 (S2308). Maternal and fetal tissues were obtained within 24hour after abortion or parturition. Incidence of abortion was greater (P<0.05) in non-vaccinated as compared to SRB51-vaccinated bison (62% and 15%, respectively), with abortions occurring between 5 and 8 weeks after experimental challenge. Calves from bison vaccinated with SRB51 had a reduced (P<0.05) prevalence of fetal infection with S2308 as compared to calves from non-vaccinated bison (19% and 62%, respectively). Although the ability to recover the 2308 challenge strain from maternal tissues did not differ (P>0.05) between nonvaccinates and vaccinates (100% and 78%, respectively), calfhood vaccination with SRB51 reduced (P<0.05) recovery of S2308 from uterine or mammary gland tissues. In bison which did not abort, S2308 was routinely recovered in low numbers from maternal lymphatic tissues; particularly the parotid, bronchial, supramammary, and mandibular lymph nodes. The RB51 vaccine strain was not recovered at any time from maternal or fetal samples obtained at necropsy. Histological lesions associated with Brucella-induced abortions were suppurative placentitis, fetal broncho-interstitial pneumonia, and fetal histiocytic splenitis. The results of our studies suggest that calfhood vaccination of bison with SRB51 is efficacious in protecting against intramammary, intrauterine, and fetal infection following exposure to a virulent strain of B. abortus during pregnancy. As brucellosis is transmitted horizontally through fluids associated with the birth or abortion of an infected fetus, or vertically to the calf through the ingestion of milk containing B. abortus, our data suggest that calfhood vaccination with SRB51 will be beneficial in preventing transmission of brucellosis in bison.     

Use of a monovalent leptospiral vaccine to prevent renal colonization and urinary shedding in cattle exposed to Leptospira borgpetersenii serovar hardjo.

OBJECTIVE: To determine whether a monovalent Leptospira borgpetersenii serovar hardjo (type hardjobovis) vaccine commercially available in Australia, New Zealand, Ireland, and the United Kingdom would protect cattle from renal colonization and urinary shedding when exposed to a US strain of Leptospira borgpetersenii serovar hardjo. ANIMALS: 24 Hereford heifers that lacked detectable antibodies against serovar hardjo. PROCEDURE: Heifers received 2 doses, 4 weeks apart, of the commercial hardjo vaccine (n = 8) or a monovalent US reference hardjo vaccine (8) or were not vaccinated (controls; 8). Heifers were challenged 16 weeks later by intraperitoneal inoculation or conjunctival instillation. Serum antibody titers were measured weekly, and urine samples were examined for leptospires. Heifers were euthanatized 11 to 14 weeks after challenge, and kidney tissue was examined for evidence of colonization. RESULTS: All 8 heifers vaccinated with the reference vaccine were found to be shedding leptospires in their urine and had evidence of renal colonization. All 4 control heifers challenged by conjunctival instillation and 2 of 4 control heifers challenged by intraperitoneal inoculation shed leptospires in their urine, and all 8 had evidence of renal colonization. In contrast, leptospires were not detected in the urine or tissues of any of the 8 heifers that received the commercial hardjo vaccine. Heifers that received the commercial hardjo vaccine had significantly higher antibody titers than did heifers that received the reference vaccine. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that cattle that received 2 doses of the commercial hardjo vaccine were protected against renal colonization and urinary shedding when challenged with L borgpetersenii serovar hardjo strain 203 four months after vaccination.     

The long term efficacy of a Hardjo-pomona vaccine in preventing leptospiruria in cattle exposed to natural challenge with Leptospira interrogans serovar hardjo

The long term efficacy of a commercially prepared bivalent vaccine against Leptospira interrogans serovar hardjo and L. interrogans serovar pomona was evaluated in a group of 82 dairy heifers exposed to natural challenge with L. interrogans serovar hardjo for up to 55 weeks after calfhood vaccination. Nineteen heifers were vaccinated twice with a one-month interval, at calfhood (9 to 10 months). A further 18 heifers received a similar calfhood vaccination regimen plus a third injection at adulthood (22 to 23 months), while 19 heifers were vaccinated twice at adulthood only and finally 22 heifers were used as unvaccinated controls. At 55 weeks after calfhood vaccination and prior to adulthood vaccination, only 2.7% of the vaccinated heifers were found to have leptospiruria compared with 58.5% of the unvaccinated heifers (p less than 0.0001). Microscopic agglutination (MA) titres at the same time in the unvaccinated heifers ranged from 32 to 4096 while those vaccinated at calfhood ranged from 32 to 64. Adult vaccination of infected animals did not significantly reduce leptospiruria . Prior to adulthood vaccination, 9 of 19 heifers had leptospiruria , in comparison to 4 of 15 after adulthood vaccination. At the same sampling periods 15 of 22 controls had leptospiruria in comparison to 4 of 9 subsequently tested.     

Parenteral vaccination of domestic pigs with Brucella abortus strain RB51

OBJECTIVE: To determine the immunogenicity and efficacy of Brucella abortus strain RB51 (SRB51) as a vaccine in domestic pigs. ANIMALS: Sixty-eight 6-week-old crossbred domestic pigs and twenty-four 4-month-old gilts. PROCEDURES: In experiment 1, pigs were vaccinated IM (n = 51) with 2 x 10(10) CFUs of SRB51 or sham inoculated (17). Periodic blood samples were obtained to perform blood cultures, serologic evaluations, and cell-mediated immunity assays. Necropsies were performed at selected times between weeks 1 and 23 after vaccination to determine vaccine clearance. In experiment 2, gilts were similarly vaccinated (n = 18) or sham inoculated (8) and similar samples were obtained after vaccination. Gilts were bred and challenged conjunctivally with 5.0 x 10(7) CFUs of virulent Brucella suis strain 3B. Necropsies were performed on gilts and on fetuses or neonates after abortion or parturition, respectively. Bacterial cultures and serologic evaluations were performed on samples obtained at necropsy to determine vaccine efficacy. RESULTS: Humoral and cell-mediated immune responses did not differ between vaccinates and controls. After vaccination, SRB51 was not isolated from blood cultures of either group and was isolated from lymphoid tissues of 3 pigs at 2 weeks (n = 2) and 4 weeks (1) after vaccination. No differences were found in isolation of B suis or in seroconversion between vaccinated and control gilts and between their neonates or aborted fetuses. CONCLUSIONS AND CLINICAL RElEVANCE: Parenteral vaccination with SRB51 does not induce humoral or cell-mediated immune responses. Vaccination with SRB51 did not protect gilts or their neonates and fetuses from virulent challenge with B suis.     

Prevention of persistent infection in calves by vaccination of dams with noncytopathic type-1 modified-live bovine viral diarrhea virus prior to breeding

OBJECTIVE: To determine the ability of a modified-live virus (MLV) bovine viral diarrhea virus (BVDV) type 1 (BVDV1) vaccine administered to heifers prior to breeding to stimulate protective immunity that would block transmission of virulent heterologous BVDV during gestation, thus preventing persistent infection of a fetus. ANIMAL: 40 crossbred Angus heifers that were 15 to 18 months old and seronegative for BVDV and 36 calves born to those heifers. PROCEDURE: Heifers were randomly assigned to control (n = 13) or vaccinated (27) groups. The control group was administered a multivalent vaccine where-in the BVDV component had been omitted. The vaccinated heifers were administered a single dose of vaccine (IM or SC) containing MLV BVDV1 (WRL strain). All vaccinated and control heifers were maintained in pastures and exposed to BVDV-negative bulls 21 days later. Thirty-five heifers were confirmed pregnant and were challenge exposed at 55 to 100 days of gestation by IV administration of virulent BVDV1 (7443 strain). RESULTS: All control heifers were viremic following challenge exposure, and calves born to control heifers were persistently infected with BVDV. Viremia was not detected in the vaccinated heifers, and 92% of calves born to vaccinated heifers were not persistently infected with BVDV. CONCLUSIONS AND CLINICAL RELEVANCE: These results document that vaccination with BVDV1 strain WRL protects fetuses from infection with heterologous virulent BVDV1.     

Protective effects against abortion and fetal infection following exposure to bovine viral diarrhea virus and bovine herpesvirus 1 during pregnancy in beef heifers that received two doses of a multivalent modified-live virus vaccine prior to breeding

Objective-To determine whether administration of 2 doses of a multivalent, modified-live virus vaccine prior to breeding of heifers would provide protection against abortion and fetal infection following exposure of pregnant heifers to cattle persistently infected (PI) with bovine viral diarrhea virus (BVDV) and cattle with acute bovine herpesvirus 1 (BHV1) infection. Design-Randomized controlled clinical trial. Animals-33 crossbred beef heifers, 3 steers, 6 bulls, and 25 calves. Procedures-20 of 22 vaccinated and 10 of 11 unvaccinated heifers became pregnant and were commingled with 3 steers PI with BVDV type 1a, 1b, or 2 for 56 days beginning 102 days after the second vaccination (administered 30 days after the first vaccination). Eighty days following removal of BVDV-PI steers, heifers were commingled with 3 bulls with acute BHV1 infection for 14 days. Results-After BVDV exposure, 1 fetus (not evaluated) was aborted by a vaccinated heifer; BVDV was detected in 0 of 19 calves from vaccinated heifers and in all 4 fetuses (aborted after BHV1 exposure) and 6 calves from unvaccinated heifers. Bovine herpesvirus 1 was not detected in any fetus or calf and associated fetal membranes in either treatment group. Vaccinated heifers had longer gestation periods and calves with greater birth weights, weaning weights, average daily gains, and market value at weaning, compared with those for calves born to unvaccinated heifers. Conclusions and Clinical Relevance-Prebreeding administration of a modified-live virus vaccine to heifers resulted in fewer abortions and BVDV-PI offspring and improved growth and increased market value of weaned calves.     

VACCINATION OF HEIFERS WITH A REDUCED DOSE OF BRUCELLA ABORTUS STRAIN 19 VACCINE BEFORE FIRST MATING

Ten Jersey heifers aged 14 to 23 months were vaccinated with 2.25 times 10⁸ cells of living Brucella abortus strain 19 vaccine. They and 10 similar non-vaccinated heifers were subsequently mated and when about 6 months pregnant were challenged by the conjunctival application of a virulent culture of B. abortus. The serological response to vaccination was much less than is usually seen following vaccination with the normal dose of strain 19, especially when the indirect haemolysis test was used. A persistent vaccinal reaction was observed in one heifer. Significant resistance to infection was demonstrated which was greater than that previously observed in calfhood vaccinates given the full dose but less than that shown by cows given the smaller dose in early pregnancy. The effectiveness of strain 19 vaccination appears to be related to the age of the animal at vaccination.     

Evaluation of cattle for experimental infection with and transmission of Brucella suis biovar 4

OBJECTIVE: To determine whether cattle can become persistently infected with Brucella suis biovar 4, whether the organism can be transmitted vertically or horizontally, and whether tests for bovine brucellosis are diagnostic. DESIGN: Observational study. ANIMALS: 24 pregnant cows and their calves and 6 bulls. PROCEDURE: Cows and bulls were housed separately in groups of 6 with each group consisting of 3 cattle experimentally infected with B suis biovar 4 and 3 na?ve animals. Cattle were observed for clinical signs daily; blood samples were collected weekly. Clotted blood from each sample was submitted for bacterial culture. Serum was tested with an indirect ELISA and the standard tube agglutination test (STAT), buffered plate agglutination test, brucellosis card test (BCT), and complemen't fixation test (CFT). Tissues collected at necropsy were submitted for bacterial culture and histologic examination. RESULTS: All 15 inoculated cattle seroconverted on 2 or more serologic tests, and bacteria were isolated from 4 inoculated cows at necropsy. There was no bacteriologic evidence of vertical or horizontal transmission, and none of the cattle developed clinical abnormalities or gross or histologic lesions. Results of the indirect ELISA were positive for all inoculated cattle. The other tests gave variable results; the CFT, STAT, and BCT yielded negative results for at least 1 of the 4 cattle from which the organism was isolated. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that cattle-to-cattle transmission of B suis biovar 4 is unlikely. Serologic tests for bovine brucellosis should be used cautiously when attempting to identify cattle with rangiferine brucellosis, as they do not discriminate between the 2 diseases and vary in their ability to detect exposed cattle.     

High- and low-challenge exposure doses used to compare intranasal and intramuscular administration of pseudorabies virus vaccine in passively immune pigs.

We compared 3 modified-live pseudorabies virus (PRV) vaccine strains, administered by the intranasal (IN) or IM routes to 4- to 6-week-old pigs, to determine the effect of high- and low-challenge doses in these vaccinated pigs. At the time of vaccination, all pigs had passively acquired antibodies to PRV. Four experiments were conducted. Four weeks after vaccination, pigs were challenge-exposed IN with virulent virus strain Iowa S62. In experiments 1 and 2, a high challenge exposure dose (10(5.3) TCID50) was used, whereas in experiments 3 and 4, a lower challenge exposure dose (10(2.8) TCID50) was used. This low dose was believed to better simulate field conditions. After challenge exposure, pigs were evaluated for clinical signs of disease, weight gain, serologic response, and viral shedding. When vaccinated pigs were challenge-exposed with a high dose of PRV, the duration of viral shedding was significantly (P less than 0.05) lower, and body weight gain was greater in vaccinated pigs, compared with nonvaccinated challenge-exposed pigs. Pigs vaccinated IN shed PRV for fewer days than pigs vaccinated IM, but this difference was not significant. When vaccinated pigs were challenge-exposed with a low dose, significantly (P less than 0.05) fewer pigs vaccinated IN (51%) shed PRV, compared with pigs vaccinated IM (77%), or nonvaccinated pigs (94%). Additionally, the duration of viral shedding was significantly (P less than 0.05) shorter in pigs vaccinated IN, compared with pigs vaccinated IM or nonvaccinated pigs. The high challenge exposure dose of PRV may have overwhelmed the local immune response and diminished the advantages of the IN route of vaccination.(ABSTRACT TRUNCATED AT 250 WORDS)     

An enzyme-linked immunosorbent assay for detection of Brucella abortus in cattle using monoclonal antibodies

One group of 24 cattle was vaccinated with the usual calfhood dose of B. abortus strain 19 and a further 27 cattle were similarly vaccinated but as adults. Twenty-four cattle (12 from each group) and a control group of 12 cattle were subsequently challenged with B. abortus strain 544. Two monoclonal antibodies (MA (A) and MA (B) ) conjugated to horseradish peroxidase were used independently in a competitive enzyme-linked immunosorbent assay (ELISA) to test the serums. After vaccination with B. abortus strain 19, the performance of the monoclonal antibodies was in general agreement with the CFT as fewer calfhood vaccinates were positive 12 weeks after vaccination to the ELISA with MA (A) and MA (B) than adult vaccinates. After challenge, MA (A) and MA (B) ELISA tests detected the infected cattle earlier than the CFT, but more positive reactions occurred in the cattle that proved uninfected at slaughter.     

Effect of various vaccination procedures on shedding, latency, and reactivation of attenuated and virulent pseudorabies virus in swine.

Various procedures of vaccination for pseudorabies were compared for their effects on shedding, latency, and reactivation of attenuated and virulent pseudorabies virus. The study included 6 groups: group 1 (10 swine neither vaccinated nor challenge-exposed), group 2 (20 swine not vaccinated, but challenge-exposed), and groups 3 through 6 (10 swine/group, all vaccinated and challenge-exposed). Swine were vaccinated with killed virus IM (group 3) or intranasally (group 4), or with live virus IM (group 5) or intranasally (group 6). The chronologic order of treatments was as follows: vaccination (week 0), challenge of immunity by oronasal exposure to virulent virus (week 4), biopsy of tonsillar tissue (week 12), treatment with dexamethasone in an attempt to reactivate latent virus (week 15), and necropsy (week 21). Vaccination IM with killed or live virus and vaccination intranasally with live virus mitigated clinical signs and markedly reduced the magnitude and duration of virus shedding after challenge exposure. Abatement of signs and shedding was most pronounced for swine that had been vaccinated intranasally with live virus. All swine, except 4 from group 2 and 1 from group 4, survived challenge exposure. Only vaccination intranasally with live virus was effective in reducing the magnitude and duration of virus shedding after virus reactivation. Vaccination intranasally with killed virus was without measurable effect on immunity. Of the 55 swine that survived challenge exposure, 54 were shown subsequently to have latent infections by use of dexamethasone-induced virus reactivation, and 53 were shown to have latent infections by use of polymerase chain reaction (PCR) with trigeminal ganglia specimens collected at necropsy. Fewer swine were identified by PCR as having latent infections when other tissues were examined; 20 were identified by testing specimens of olfactory bulbs, 4 by testing tonsil specimens collected at necropsy, and 4 by testing tonsillar biopsy specimens. Eighteen of the 20 specimens of olfactory bulbs and 3 of the 4 tonsil specimens collected at necropsy in which virus was detected by PCR were from swine without detectable virus-neutralizing antibody at the time of challenge exposure. One pig that had been vaccinated intranasally with live virus shed vaccine virus from the nose and virulent virus from the pharynx concurrently after dexamethasone treatment. Evaluation of both viral populations for unique strain characteristics failed to provide evidence of virus recombination.     

The effect of a high dose bovine herpes virus 1 marker vaccine in pregnant heifers: virological, bacteriological, immunological, and pathological findings

To determine a possible relationship between the compulsory vaccination against bovine herpesvirus 1 (BHV1) and cattle wasting disease, the effects of BHV1 vaccination on heifers were investigated. Twenty heifers in the third trimester of pregnancy were randomly allotted to a vaccine and a control group. The vaccine group was vaccinated twice with a 50-fold dose of BHV1 vaccine and the control group was inoculated with the diluent. The experiment was performed double blind. After vaccination, the cows were examined daily and condition scores were determined weekly. Blood, milk, and faeces samples were collected weekly for virological, bacteriological, and immunological investigation. The heifers were euthanized either 9 or 13 weeks after the first inoculation and pathological, virological, and bacteriological examination was performed. No differences were detected between the vaccine group and the control group. No concurrent infections were detected and there were no indications of immunosuppression after vaccination. No relationship between the BHV1 vaccination and wasting disease in cattle was detected.     

Fetal protection against continual exposure to bovine viral diarrhea virus following administration of a vaccine containing an inactivated bovine viral diarrhea virus fraction to cattle

OBJECTIVE: To evaluate the efficacy of a commercially available killed bovine viral diarrhea virus (BVDV) vaccine to protect against fetal infection in pregnant cattle continually exposed to cattle persistently infected with the BVDV. ANIMALS: 60 crossbred beef heifers and 4 cows persistently infected with BVDV. PROCEDURES: Beef heifers were allocated to 2 groups. One group was vaccinated twice (21-day interval between the initial and booster vaccinations) with a commercially available vaccine against BVDV, and the other group served as nonvaccinated control cattle. Estrus was induced, and the heifers were bred. Pregnancy was confirmed by transrectal palpation. Four cows persistently infected with BVDV were housed with 30 pregnant heifers (15 each from the vaccinated and nonvaccinated groups) from day 52 to 150 of gestation. Fetuses were then harvested by cesarean section and tested for evidence of BVDV infection. RESULTS: 1 control heifer aborted after introduction of the persistently infected cows. Bovine viral diarrhea virus was isolated from 14 of 14 fetuses obtained via cesarean section from control heifers but from only 4 of 15 fetuses obtained via cesarean section from vaccinated heifers; these proportions differed significantly. CONCLUSIONS AND CLINICAL RELEVANCE: A commercially available multivalent vaccine containing an inactivated BVDV fraction significantly reduced the risk of fetal infection with BVDV in heifers continually exposed to cattle persistently infected with BVDV. However, not all vaccinated cattle were protected, which emphasizes the need for biosecurity measures and elimination of cattle persistently infected with BVDV in addition to vaccination within a herd.     

Vaccination studies for the control of campylobacteriosis in Jamaican cattle

Following the first diagnosis of campylobacteriosis in Jamaican cattle a field study was undertaken to determine the pathogenicity of Campylobacter fetus subspecies venerealis Jam (Jamaican strain) and to evaluate the effectiveness of vaccination in controlling the disease. A total of 46 nonpregnant yearling heifers and four two-year-old bulls were used in two separate experiments. The results showed that C fetus subspecies venerealis Jam readily colonised the reproductive tract of susceptible heifers and persisted in some animals (68 per cent of unvaccinated and 33 per cent of vaccinated animals) for the duration of the experiment. Pregnancy was confirmed in 13 of 18 (72 per cent) culture-negative heifers but in only eight of 28 (29 per cent) of the heifers with two or more positive cultures. Vaccination appeared to be curative because 44 per cent of vaccinated heifers were cleared of infection whereas 85 per cent of unvaccinated, inoculated heifers remained infected for at least 17 weeks. Vaccination improved the fertility level of the infected heifers threefold. Infection was not established in vaccinated bulls used for breeding infected heifers.     

Effect of Vaccination with Brucella abortus Strain RB51 on Heifers and Pregnant Cattle

Thirteen cows, which had been vaccinated as calves with strain 19, were revaccinated twice or three times as adults with 1×10⁹ cfu of B. abortus strain RB51. Their serological responses following adult vaccination remained negative to conventional brucellosis surveillance tests. Vaccination with strain RB51 during the eighth month of pregnancy did not induce abortion, although strain RB51 was recovered from milk for up to 69 days after vaccination. In a parallel study, thirteen 8- to 10-month-old heifers were vaccinated as calves with 10⁹ cfu of strain RB51. The heifers remained seronegative to conventional brucellosis surveillance tests but antibody responses to RB51 could be demonstrated using an indirect ELISA. This study showed that multiple vaccination with strain RB51 did not induce seroconversion to brucellosis surveillance tests. In addition, this study suggests that 10⁹ cfu of strain RB51 is safe for use in pregnant cattle.     

Brucellosis induced by RB51 vaccine in a pregnant heifer

Brucellosis developed in a 14.5-month-old Gelbvieh heifer after the animal was vaccinated with the calfhood dose of strain RB51 Brucella abortus vaccine s.c. during the fourth month of its first pregnancy. The heifer experienced dystocia and was euthanatized during cesarean section because of a large uterine tear. The fetus was dead at delivery. Suppurative placentitis and fetal pneumonia were evident at necropsy. Brucella abortus strain RB51 was isolated from the placenta and the fetus' lung.     

Conjunctival and intramuscular vaccination of pigs with a live avirulent strain of Salmonella cholerae-suis

An avirulent mutant strain of Salmonella cholerae-suis was cloned for resistance to streptomycin and nalidixic acid. The mutant strain 33-13 also was used because of its avirulence and immunogenicity in mice. Weaned pigs were vaccinated with live strain 33-13; 5 pigs were vaccinated by conjunctivally administered 5.5 X 10(7) organisms (low dose), 5 were conjunctivally administered 5.5 X 10(9) organisms (high dose), and 5 pigs were administered 5.5 X 10(9) organisms (high dose) IM. Transient fever and transient fecal shedding of the vaccine strain developed in pigs vaccinated IM, but not in 2 groups of pigs vaccinated conjunctivally. After intratracheal administration of virulent strain 38-9, nonvaccinated control pigs (n = 9) developed persistent high fever, anorexia, bacteremia, diarrhea, and fecal shedding of strain 38-9, whereas vaccinated pigs remained afebrile and clinically normal. Nonvaccinated and uninfected sentinel pigs (n = 8) were kept in units of 2 pigs with each group of experimental pigs, and remained healthy throughout the experiment. Thirteen vaccinated and 7 nonvaccinated control pigs were killed 42 days after vaccination, and 2 vaccinated, 2 nonvaccinated, and 8 sentinel control pigs were killed 58 days after vaccination. Ten organs were evaluated by quantitative bacteriology on necropsy of all pigs for the presence of vaccine strain 33-13, and for virulent strain 38-9. Strain 33-13 was not found. Lung and liver, lesions were found in most of the nonvaccinated control pigs, with a high frequency of recovery of large numbers of strain 38-9 from the mesenteric lymph nodes, lungs, liver, and ileum.(ABSTRACT TRUNCATED AT 250 WORDS)