In vitro DNA synthesis in lymphocytes from turkeys vaccinated with LaSota, TC, and inactivated Newcastle disease vaccines.

In vitro cultures of peripheral blood lymphocytes from turkeys vaccinated and revaccinated with Newcastle disease (ND) vaccines were stimulated to transformation when exposed to the homologous and heterologous strains of ND virus. The mitogenesis was measured by the uptake of 3H-thymidine into newly synthesized DNA. There was considerable difference in DNA synthesis by lymphocytes drawn 0, 2, 5, and 10 days after vaccination and revaccination with the three vaccines. Stimulation of DNA synthesis, evident as early as the 2nd day, was highest in lymphocytes from turkeys vaccinated or revaccinated with TCND intramuscularly. Stimulation was least in lymphocytes from turkeys vaccinated and revaccinated with LaSota vaccine by aersol. Stimulation was intermediate from an inactivated vaccine given subcutaneously. DNA synthesis was greater with the homologous than with the heterologous strains of NDV. Synthesis was even greater when the same strain was used as a viral suspension in allantoic or cell-culture fluid than the commercial vaccine. The bovine paramyxovirus (PI3) resulted in a minimum DNA synthesis or completely inhibited it. A many-fold (order of magnitude) stimulatory effect was observed when PHA was used as an antigen. The stimulation of DNA synthesis did not parallel the HI antibody response.     

The Response of Ponies to Myxovirus influenzae A-equi 2 I. Serum and Antibody Titres Following Exposure

The antibody response in serum and nasal secretions of groups of ponies vaccinated or infected with Myxovirus influenzae A-equi 2 was examined. Following infection by aerosol with live virus, a weak antibody response was recorded in both serum and secretions. Antibody levels were undetectable in secretions at 31 days after infection.

After primary intramuscular vaccination with killed virus, using sodium alginate as an adjuvant, antibody was detected only in the serum. However, following revaccination, a pronounced antibody response was demonstrated in both serum and secretions. Antibody was still detectable in all four ponies when tested 135 days later.

Only a serum antibody response was detected in ponies after primary intramuscular vaccination with a commercial vaccine. Upon revaccination nasal antibody occurred in all ponies but this only persisted for about 30 days.

Neither serum nor nasal antibody response occurred following intranasal vaccination and revaccination with a killed virus vaccine.

     

Adequacy of commercial lentogenic vaccines against Canadian strains of viscerotropic Newcastle disease virus.

Three field strains of Newcastle Disease virus, designated S20, S21 and S23, isolated from chickens or turkeys in Ontario during the 1971-72 epizootic, were characterized as velogenic viscerotropic viruses. No significant antigenic differences were demonstrated among B1, LaSota and a field strain (S23) of velogenic vescerotropic virus by haemagglutination inhibition or protection tests. Primary water vaccination of chicks with commercial B1 and LaSota vaccines at five weeks of age and aerosol revaccination with the same strains four weeks later resulted in protection that lasted 16 weeks after revaccination against experimental challenge with strain S23. The differences in haemagglutination inhibition titres noted when the homologous or the heterologous viruses were used as haemagglutinating antigen were not statistically significant. The rates of decay of virus neutralizing and haemagglutination inhibition antibodies in vaccinated birds showed a divergence indicating the possible duality of antibodies measured in serum neutralization and haemagglutination inhibition tests.     

Comparison of Newcastle disease vaccines by serology using serum,tears and feather pulp samples

Seroconversion of 3 lentogenic commercial Newcastle disease (ND) vaccines and experimental V₄ vaccines was compared based on the haemagglutination inhibition (HI) test against ND. It was found that for primary vaccination all the vaccines produced similar response but for secondary vaccinations V₄ and LaSota were better than RDVF. Eighty-five samples each of serum, tears and feather pulp were collected from respective birds and antibody assessment was done against ND by HI test. The geometric mean HI titres (GMT) of serum samples were highest followed by tears and feather pulp samples before vaccination and 3 weeks after vaccination by oculonasal route and the difference was statistically significant (p<0.01). Three weeks after booster vaccination by oculonasal route, however, the GMT of serum samples were highest followed by feather pulp and tears samples. The ease of collection of feather pulp samples and their role in ND serology is discussed.     

Onset of immunity following in ovo delivery of avian metapneumovirus vaccines

Avian metapneumovirus (aMPV) is an important cause of disease in chickens and turkeys. As infection can occur early in life and spread of the virus throughout a flock is rapid, an early onset of immunity post-vaccination would be advantageous. We have studied the serological immune response and the onset of protective immunity of an aMPV vaccine delivered to chickens via the in ovo route compared to oculonasal delivery at day old. A 1000-fold lower dose delivered in ovo to chicken specific pathogen free (SPF) embryos, than vaccination at day old, provided a significantly higher antibody response. In the presence of maternally derived antibody (MDA), there was no significant difference in antibody response between the vaccination routes. However, the onset of immunity (OOI) for the vaccine delivered to MDA positive chicken embryos was 5 days post-hatch in comparison to 8 days post-hatch for the same dose of vaccine given at day old indicating that chicks would be protected against disease earlier in the field if vaccinated by the in ovo route. In further experiments the OOI for a turkey vaccine delivered to MDA positive turkey embryos was shown to be 8 days post-hatch.     

Results of vaccination of Asian elephants (Elephas maximus) with monovalent inactivated rabies vaccine

OBJECTIVE: To evaluate the humoral immune response of Asian elephants to a primary IM vaccination with either 1 or 2 doses of a commercially available inactivated rabies virus vaccine and evaluate the anamnestic response to a 1-dose booster vaccination. ANIMALS: 16 captive Asian elephants. PROCEDURES: Elephants with no known prior rabies vaccinations were assigned into 2 treatment groups of 8 elephants; 1 group received 1 dose of vaccine, and the other group received 2 doses of vaccine 9 days apart. All elephants received one or two 4-mL IM injections of a monovalent inactivated rabies virus vaccine. Blood was collected prior to vaccination (day 0) and on days 9, 35, 112, and 344. All elephants received 1 booster dose of vaccine on day 344, and a final blood sample was taken 40 days later (day 384). Serum was tested for rabies virus-neutralizing antibodies by use of the rapid fluorescent focus inhibition test. RESULTS: All elephants were seronegative prior to vaccination. There were significant differences in the rabies geometric mean titers between the 2 elephant groups at days 35, 112, and 202. Both groups had a strong anamnestic response 40 days after the booster given at day 344. CONCLUSIONS AND CLINICAL RELEVANCE: Results confirmed the ability of Asian elephants to develop a humoral immune response after vaccination with a commercially available monovalent inactivated rabies virus vaccine and the feasibility of instituting a rabies virus vaccination program for elephants that are in frequent contact with humans. A 2-dose series of rabies virus vaccine should provide an adequate antibody response in elephants, and annual boosters should maintain the antibody response in this species.     

Immune responses of Asian elephants (Elephas maximus) to commercial tetanus toxoid vaccine

Although captive elephants are commonly vaccinated annually against tetanus using commercially available tetanus toxoid vaccines marketed for use in horses and livestock, no data exists to prove that tetanus toxoid vaccination produces measurable antibody titers in elephants. An ELISA test was created to measure antibody responses to tetanus toxoid vaccinations in 22 Asian elephants ranging in age from 24 to 56 years (mean age 39 years) over a 7-month period. All animals had been previously vaccinated with tetanus toxoid vaccine, with the last booster administered 4 years before the start of the study. The great majority of elephants had titers prior to booster vaccination, and following revaccination all elephants demonstrated anamnestic increases in titers, indicating that this species does respond to tetanus vaccination. Surprisingly older animals mounted a significantly higher response to revaccination than did younger animals.     

THE SEROLOGICAL RESPONSE OF CHICKENS TO AUSTRALIAN LENTOGENIC STRAINS OF NEWCASTLE DISEASE VIRUS

SUMMARY: Australian lentogenic Newcastle disease viruses were evaluated as uninactivated vaccines in Australian chickens, the response being evaluated by the production of haemagglutination-inhibition (HI) antibodies. Two viruses, V4 and PM9, induced high levels of antibody and were readily transmissible between chickens by contact exposure. Three other viruses were poorly immunogenic and poorly transmissible. Chickens vaccinated intramuscularly with the V4 strain produced higher HI antibody titres than chickens vaccinated by the orotracheal, intranasal and intraocular routes. HI antibody titres in chickens vaccinated with the V4 strain reached peak levels 3 to 5 weeks after vaccination and waned considerably during the next 2 to 4 weeks. However, low levels of HI antibody persisted for at least 36 weeks after vaccination. Intramuscular vaccination with the V4 strain of one-day-old chicks lacking maternal antibody to Newcastle disease virus resulted in 42–70% mortality and the survivors developed very high titres of HI antibody. Similar chickens inoculated orotracheally showed signs of depression and developed high titres of HI antibody, but there were no mortalities. Chickens 1-, 2-, 3- and 4-weeks-old and lacking maternally derived HI antibody to Newcastle disease virus suffered no adverse reaction to intramuscular or orotracheal vaccination. The antibody response of the 1-week-old chickens was considerably poorer than that of the older chickens. Following orotracheal vaccination with the V4 strain, chickens with low levels of maternally derived antibody responded with low levels of HI antibody. On the other hand, in the progeny of hens hyperimmunised with the V4 strain the production of active antibody following orotracheal vaccination was delayed until the level of passive antibody had declined considerably. There was no response to intramuscular vaccination in congenitally hyperimmune chickens. The minimum HI antibody inducing dose of V4 vaccine, when measured 3 weeks after vaccination of 6-weeks-old chickens, was 10^5.6 50% egg infectious doses.     

Antibody response to strain combinations of Newcastle disease virus as measured by hemagglutination-inhibition

Differences in antibody response to three Newcastle disease virus (NDV) strains--B-1, LaSota, and Ulster--were investigated using the hemagglutination-inhibition (HI) micro-titer test in chickens hatched from ND-immune and unimmune flocks. When used singly as primary vaccines, the Ulster strain stimulated the lowest antibody response of the three in both immune and unimmune (susceptible) chickens. Subgroups of each of the primary-vaccinated groups were revaccinated with each of the three strains. Ulster-vaccinated chicks, revaccinated with Ulster, gave the poorest booster response. All other revaccination combinations gave a significant titer increase, though some were better than others. It is suggested that the Ulster strain as primary vaccine followed by booster does of B-1 or LaSota will induce a higher antibody response (i.e., immunity) in susceptible chicken populations with less risk of a post-vaccination reaction.     

Tracheal mucus transport rate and bacterial clearance in turkeys exposed by aerosol to La Sota strain of Newcastle disease virus

Tracheal mucus transport rate (TMTR) and quantitative clearance of aerosolized Escherichia coli from the trachea, lung, and air sac were measured in healthy unanesthetized turkeys and in turkeys exposed by aerosol to a La Sota vaccine strain of Newcastle disease virus (NDV). The TMTR of uninfected turkeys was 42.4 +/- 14.7 cm/min. The TMTR of NDV-infected turkeys was depressed on days 3 through 7 postexposure (PE); depression was significant (P less than or equal to 0.05) on day 7 PE. Tracheal E. coli clearance in NDV-infected turkeys was reduced on days 4 through 9 PE, significantly so on day 5 PE (P less than or equal to 0.01). Depression of TMTR and tracheal E. coli clearance were associated histologically with replacement of normal pseudostratified columnar epithelium by 3 to 8 layers of immature nonciliated cells. E. coli clearance by the lung and air sac of NDV-infected turkeys was depressed on days 5 through 9 PE.     

Vaccination of the brushtail possum (Trichosurus vulpecula) against Mycobacterium bovis infection with bacille Calmette-Guérin: the response to multiple doses.

In New Zealand, the brushtail possum (Trichosurus vulpecula) is the principal wildlife vector of bovine tuberculosis. Control of infected possum populations contributes to the control of tuberculosis in domestic livestock. Vaccination is potentially a complementary strategy to population control, but to be cost-effective, administration of the vaccine to possums would need to be from an appropriately designed automatic vaccinator. Possums themselves would activate the vaccinator so that it would deliver an aerosol spray of vaccine. There would be no direct way to prevent possums receiving multiple doses of vaccine. This study examined the effect on protective immunity of repeated vaccination. Captive possums were vaccinated with BCG strain pasteur 1173P2 either 12 times at weekly intervals, twice at 6-weekly intervals, or once. Vaccination was by a combination of intranasal aerosol and conjunctival instillation. Eight weeks after the last dose of vaccine, all possums were challenged intratracheally with Mycobacterium bovis strain 83/6235. Vaccination induced a significant immune response as measured by the lymphocyte proliferation assay (LPA). A significant level of protection, as measured by the response to challenge, developed in all the vaccinated possum groups, but protection was greatest in the group vaccinated 12 times. It was concluded that protection would be enhanced if vaccinations were repeated at short intervals (weekly), but no benefit or detriment resulted from revaccination after longer intervals (1-2 months).     

Vaccination of 1-day-old chicks with fowlpox virus by the aerosol, drinking water, or cutaneous routes

Administration of 10(4) mean cell-culture infectious dose (CCID50) per ml of a plaque-purified derivative of a commercial fowlpox virus (FPV) vaccine to 1-day-old chicks by aerosol or drinking water gave inconsistent serological responses and little evidence of protective immunity. In contrast, cutaneous vaccination with the same preparation protected against challenge with virulent FPV at 4 weeks of age. Administration of the vaccine at a concentration of 10(6) CCID50 per ml by the drinking-water route was as effective as conventional cutaneous vaccination in terms of the serological response in an enzyme-linked immuno-sorbent assay and in terms of protection against challenge. Drinking-water vaccination at 2 days of age was no more effective than vaccination on day 1, and oral dosing with the vaccine was less effective than incorporation of the vaccine in the drinking water. It was concluded that 1-day-old chicks may be vaccinated against fowlpox by the drinking-water route if the vaccine contains a sufficiently high concentration of virus.     

Immunisation of fancy chickens against Newcastle disease]

The German Regulation on Fowl plague which is in force since 1994 laid down that any chicken of all races and all hybrids must be vaccinated against Newcastle disease (ND) in a mode that an adequate immunity is achieved. Onset, duration, and resistance to challenge of immunity induced by vaccination is well documented in the scientific literature for hybrid chicken of the layer and meat types. These data prove also innocuity and efficacy of the registered vaccines. In contrast, only a few and incomplete data exist on the development of ND directed immunity in fancy chickens. The present study describes vaccinations of chickens of 14 different hobby breeds with live LaSota vaccine (conjunctival application of 10(6) embryo-infective dose50 per bird) and with an inactivated oil-emulsion vaccine (intramuscular application of 0.5 ml per bird) and subsequent intramuscular challenge infections using the highly virulent NDV strain Herts 33/66. Chickens of all 14 breeds tolerated the application of both vaccines. All fancy chickens reacted with the production of serum antibodies which were measured in the haemagglutination inhibition (HI) and virus neutralisation (VN) tests. According to the scientific literature, maximal antibody levels are reached in hybrid chickens between day 10 and 20 post vaccination. In contrast, in fancy chickens the antibody maxima are delayed to the seventh to eighth week post vaccination. All fancy chickens vaccinated either once with live LaSota virus or with live and inactivated vaccines resisted challenge with the highly virulent Herts 33/66 strain of NDV and did not develop any signs of disease. There are indications for gradual differences in susceptibility of different breeds of fancy chickens. The levels of non-specific neutralisation as measured in the virus neutralisation test differ between breed. Also, the viral content in tissues obtained from non-vaccinated but challenged birds differ markedly. It is concluded from the results of this study that fancy chickens can also successfully protected against Newcastle disease by using live and inactivated vaccines which are licensed for hybrid chickens. However, the optimal time for the detection of maximal antibody levels in fancy chickens is reached seven to eight weeks post vaccination.     

Consequence of Cryptosporidiosis on the immune response of vaccinated broiler chickens against Newcastle disease and/or avian influenza

The consequence of cryptosporidiosis on the immune response of vaccinated chickens against Newcastle disease and/or avian influenza was studied by using 240, 1 day old, male, white Hy-Line chicks and divided into 8 groups and subgroups. Each group or subgroup was consisting of 30 chicks (15?×?2 replicates). The first and second groups were kept as unvaccinated control, G1uninfected and G2 infected. G3, G4 and G5 contained 2 subgroups A&B (G3A, G3B, G4A, G4B, G5A and G5B). Chicks of subgroup A were vaccinated only while chicks of subgroup B were infected and vaccinated. These chicks were orally inoculated with 5?×?10⁵ oocysts of Cryptosporidium baileyi (C. baileyi) at 2 days of age. Chickens were vaccinated intraocular with live Newcastle disease (ND) vaccine (Hitchner on day 7th and LaSota on day 17th of chicken life) (G3) or vaccinated by subcutaneous route with Volvac®- H5N2- AI vaccine on day 10 of chicken life (G4). Last group (G5) was infected similarly and vaccinated with ND and AI vaccines with the same day, dose and route of vaccination for each one. Random blood samples were collected for 3 weeks post-vaccination for investigation of humoral immune response against Newcastle and/or avian influenza vaccines by the haemagglutination inhibition (HI) test. The results showed that H5N2 vaccine at day 10 of chicken life is effective in chickens indicated by the geometric mean of HI titer against AI virus. The findings of this study showed that the infection with Cryptosporidia in the broiler chicken has a depressive effect on the immune status of the birds vaccinated against ND and/or AI vaccination. Moreover, the obtained protection rates against challenge with virulent ND virus observed to be parallel to the results of HI- test. Also, by using 2 different antigens (one commercial and field prepared antigen) to avian influenza virus, lower Geometric mean (GM) HI titer were appeared in infected and vaccinated group than vaccinated group only. A study of the relative lymphoid organs weight such as bursa of Fabricius from the experimental chicks indicated that those organs were comparable between the groups infected-vaccinated and vaccinated only. Non significant variations in final live weight between uninfected control and infected groups were indicated. Also, H5N2-AI vaccination at 10 days old did not affect the final live weight. ND and/or AI Vaccination could not be a substitute to application of good hygienic measures and fecal examination of the birds especially for protozoal diseases such as cryptosporidiosis. It could be concluded that cryptosporidiosis could be one cause of ND and/or AI vaccination failure in poultry farms.     

Duration of serologic response to three viral antigens in cats

OBJECTIVE: To determine whether vaccinated cats either remained seropositive or responded serologically to revaccination against 3 key viral antigens after extended periods since their last vaccination. DESIGN: Serologic survey. ANIMALS: 272 healthy client-owned cats. PROCEDURE: Cats were > or = 2 years old and vaccinated for feline panleukopenia virus (FPV), feline calicivirus (FCV), and feline herpesvirus (FHV). On day 0, cats were revaccinated with a vaccine from the same line of vaccines as they had historically received. Antibody titers were measured in sera collected on day 0 (prevaccination titer) and 5 to 7 days later (postvaccination titer). Cats were considered to have responded serologically if they had a day-0 hemagglutination inhibition titer to FPV > or = 1:40, serum neutralization (SN) titer to FCV > or = 1:32, SN titer to FHV > or = 1:16, or > or = 4-fold increase in antibody titer after revaccination. RESULTS: The percentage of cats that had titers at or above the threshold values or responded to revaccination with a > or = 4-fold increase in titer was 96.7% for FPV, 97.8% for FCV, and 88.2% for FHV. CONCLUSIONS AND CLINICAL RELEVANCE: In most cats, vaccination induced a response that lasted up to and beyond 48 months for all 3 antigens. Although not equivalent to challenge-of-immunity studies as a demonstration of efficacy, results suggest that revaccination with the vaccine used in our study provides adequate protection even when given less frequently than the traditional 1-year interval. The study provides valuable information for clinicians to determine appropriate revaccination intervals.     

A field study of persistence of antibodies in California horses vaccinated against western, eastern, and Venezuelan equine encephalomyelitis.

As a result of the continuing threat of Venezuelan equine encephalomyelitis (VEE), a study was made to determine if revaccination against VEE (TC-83 vaccine) was feasible and if revaccination could be incorporated into other routine vaccination practices. Of the horses given annual vaccination with bivalent western equine encephalomyelitis (WEE) and eastern equine encephalomyelitis (EEE) vaccine, 57% retained detectable serum-neutralizing (SN) antiboyd titers for VEE 18 months after the initial VEE vaccination was given. Of horses with no record of WEE-EEE vacinnation, 100% retained detectable VEE SN antibody titers over the same period. The VEE geometric mean titer was 25 times greater for horses not previously vaccinated against WEE-EEE than for horses given annual WEE-EEE vaccination at the time of VEE vaccination. In horses vaccinated against VEE 18 months previously, the geometric mean titer increased from 4 to 70 at 48 days after the intitial WEE-EEE vaccination. This increase indicated that similar antigenic factors for VEE are possibly present in bivalent WEE-EEE vaccine. In horses previously vaccinated against WEE-EEE and VEE, the best SN antibody response to VEE revaccination occurred when VEE vaccine was given simultaneously with the bivalent WEE-EEE vaccine. Of 150 serum samples tested by both the SN and the hemagglutination-inhibiton tests, agreement between positive reactions at greater than or equal to 1:10 was 70% for VEE, 81% for EEE, and 87% for WEE.     

Duration of serologic response to five viral antigens in dogs

OBJECTIVE: To determine whether vaccinated dogs either remained seropositive or responded serologically to revaccination for 5 key viral antigens after extended periods since their last vaccination. DESIGN: Serologic survey. ANIMALS: 322 healthy client-owned dogs. PROCEDURE: Dogs were > or = 2 years old and vaccinated against canine distemper virus (CDV), canine adenovirus-1 (CAV-1), canine adenovirus-2 (CAV-2), canine parainfluenza virus (CPIV), and canine parvovirus (CPV). On day 0, dogs were revaccinated with a vaccine from the same vaccine line as they had historically received. Antibody titers were measured in sera collected at day 0 (prevaccination titer) and 5 to 7 days later (postvaccination titer). Dogs were considered to have responded serologically if they had a day-0 serum neutralization titer to CDV > or = 1:32; a serum neutralization titer to CAV-1, CAV-2, or CPIV > or = 1:16; a hemagglutination inhibition titer to CPV > or = 1:80; or a > or = 4-fold increase in antibody titer after revaccination. RESULTS: The percentage of dogs that had titers at or greater than the threshold values or responded to revaccination with a > or = 4-fold increase in titer was 98.1% for CDV, 98.4% for CAV-1, 99.0% for CAV-2, 100% for CPIV, and 98.1% for CPV. CONCLUSIONS AND CLINICAL RELEVANCE: In most dogs, vaccination induced a response that lasted up to and beyond 48 months for all 5 antigens. Although not equivalent to challenge-of-immunity studies as a demonstration of efficacy, results suggest that revaccination with the same vaccine provides adequate protection even when given less frequently than the traditional 1-year interval. The study provides valuable information for clinicians to help determine appropriate revaccination intervals.     

Comparison of the effect of live Newcastle disease vaccine Clone 30 in broilers administered at day 1 or at day 7 and the effect of H120 vaccination at 17 days of age: a field experiment

To analyse the results of a vaccination on the first day of age against Newcastle disease (ND) and on the 17th day of age against Infectious Bronchitis (IB) resp. with spray vaccines with Clone 30 and H120 vaccine. These vaccinations are compared in field circumstances with other vaccination methods. A serological examination and challenge test were used to be informed about the response and protection. From the present study the following conclusions can be drawn: Clear indications are obtained that following a spray vaccination against ND with Clone 30 vaccine of one-day-old broilers which possessed maternal antibodies, birds received a moderately good protection against ND, in spite of very low levels of HI antibodies. A spray vaccination against IB with H120 vaccine of broilers at 17 days of age gave some protection from two weeks after vaccination, however making a good conclusion about the protection is impossible and further investigation is required.     

1日龄火鸡新城疫免疫后外周血液的免疫学变化

应用ＮＤ来活苗与弱毒苗联合及单独弱毒苗对１日龄火鸡进行早期免疫，于第６０日进行ＮＤ强毒攻击。分别在第７、１４、２１、３５和日龄检测外周血液的免疫学变化。结果表明，１日龄火鸡疫苗接种后其外周血液中Ｔ细胞、Ｂ淋巴细胞和淋巴细胞数量、血清ＩｇＧ，ＩｇＭ，ＩｇＡ含量及ＨＩ抗体滴度均明显升高，可获得良好的免疫保护效应，其中活苗与死苗联合免疫组优于单独活苗免疫组。     

The effect of route and dosage of immunization on the serological response to a Pasteurella haemolytica and Haemophilus somnus vaccine in feedlot calves

The effect of route and dosage of administration on the serological response to a vaccine containing genetically attenuated leukotoxin of Pasteurella haemolytica combined with bacterial extracts of P. haemolytica and Haemophilus somnus (Somnu-Star Ph, Biostar Inc., Saskatoon, Saskatchewan) was evaluated in a controlled field trial in 301 feedlot calves. Vaccination of calves on arrival at the feedlot with Somnu-Star Ph significantly (p < 0.05) increased P. haemolytica and H. somnus serum antibody titers and reduced bovine respiratory disease (BRD) morbidity. A single subcutaneous vaccination with Somnu-Star Ph was as effective in stimulating a humoral antibody response and in reducing BRD morbidity as double vaccination by the intramuscular or the subcutaneous route. Furthermore, there were no swellings or adverse reactions observed with either subcutaneous or intramuscular administration of Somnu-Star Ph.

These results suggest that feedlot calves can be immunized subcutaneously once on arrival with Somnu-Star Ph. Double vaccination was of no added value in this trial, because the majority of BRD morbidity occurred prior to revaccination fourteen days postarrival. Additional larger-sized field trials are needed to monitor the duration of immunity following vaccination and to test the effect of route and dosage of vaccination on mortality.