Objective—To compare the efficacy of modified-live virus (MLV) vaccines containing either type 1 bovine viral diarrhea virus (BVDV) or types 1 and 2 BVDV in protecting heifers and their offspring against infection associated with heterologous noncytopathic type 2 BVDV challenge during gestation.
Design—Randomized controlled study.
Animals—160 heifers and their offspring.
Procedures—After inoculation with a placebo vaccine, 1 or 2 doses of an MLV vaccine containing type 1 BVDV, or 1 dose of an MLV vaccine containing both types 1 and 2 BVDV, heifers were bred naturally and challenge exposed with a type 2 BVDV field isolate between 62 and 104 days of gestation. Pregnancies were monitored; after parturition, virus isolation and immunohistochemical analyses of ear-notch specimens were used to determine whether calves were persistently infected. Blood samples were collected at intervals from heifers for serologic evaluation and virus isolation.
Results—Persistent infection was detected in 18 of 19 calves from heifers in the control group and in 6 of 18 calves and 7 of 19 calves from heifers that received 1 or 2 doses of the type 1 BVDV vaccine, respectively. None of the 18 calves from heifers that received the type 1–type 2 BVDV vaccine were persistently infected.
Conclusions and Clinical Relevance—Results suggest that the incidence of persistent BVDV infection among offspring from dams inoculated with 1 dose of the MLV vaccine containing types 1 and 2 BVDV was decreased, compared with 1 or 2 doses of the MLV vaccine containing only type 1 BVDV.
To assess the effect of serum total protein (STP) concentration on the early-life health and growth of dairy calves.
39,619 neonatal Holstein, Jersey, and crossbred calves from 15 dairy operations.
Calves arrived at a single calf-raising facility at approximately 2 days old. Each calf was weighed at facility arrival, and a blood sample was obtained the next day for determination of STP concentration by refractometry. All calves were managed in a standard manner, and health events were recorded for 120 days. A subset of 3,214 calves was weighed at 120 days old, and the average daily gain (ADG) was calculated. Linear mixed models were used to assess the effect of STP concentration on specific health events.
STP concentration was associated with the incidences of death, diarrhea, pneumonia, and whether a calf received IV fluid therapy. In general, the incidence of adverse health events decreased as STP concentration increased to 6.0 g/dL, plateaued at STP concentrations between 6.0 and 8.5 g/dL, and increased at STP concentrations > 8.5 g/dL. Although STP concentration was not associated with ADG, the ADG for Holsteins increased as STP concentration increased to 8.5 g/dL and then decreased at STP concentrations > 8.5 g/dL.
CONCLUSIONS AND CLINICAL RELEVANCE
Results suggested that, for neonatal dairy calves, an STP concentration between 6.0 and 8.5 g/dL was optimal for health and growth, and calves with an STP concentration < 5.0 or > 8.5 g/dL should be considered at high risk for adverse health events.
Objective—To determine the effect of maternally
derived antibodies on induction of protective immune
responses against bovine viral diarrhea virus (BVDV)
type II in young calves vaccinated with a modified-live
bovine viral diarrhea virus (BVDV) type I vaccine.
Design—Blinded controlled challenge study.
Animals—24 neonatal Holstein and Holstein-cross
calves that were deprived of maternal colostrum and
fed pooled colostrum that contained a high concentration
of (n = 6) or no (18) antibodies to BVDV.
Procedure—At 10 to 14 days of age, 6 seropositive
and 6 seronegative calves were given a combination
vaccine containing modified-live BVDV type I. All
calves were kept in isolation for 4.5 months. Six
calves of the remaining 12 untreated calves were vaccinated
with the same combination vaccine at approximately
4 months of age. Three weeks later, all calves
were challenged intranasally with a virulent BVDV
Results—Seronegative unvaccinated calves and
seropositive calves that were vaccinated at 2 weeks
of age developed severe disease, and 4 calves in each
of these groups required euthanasia. Seronegative
calves that were vaccinated at 2 weeks or 4 months
of age developed only mild or no clinical signs of disease.
Conclusions and Clinical Relevance—Results indicate
that a single dose of a modified-live BVDV type-I
vaccine given at 10 to 14 days of age can protect susceptible
young calves from virulent BVDV type II infection
for at least 4 months, but high concentrations of
BVDV-specific maternally derived antibodies can block
the induction of the response. (J Am Vet Med Assoc
Objective—To collect and partially characterize strains of bovine viral diarrhea viruses(BVDVs) isolated from persistently infected (PI) calves born to vaccinated dams, determine genetic diversity of the isolated viruses, and identify regional distribution of genetically similar virus subpopulations.
Sample Population—17 noncytopathic (NCP) BVDVs from PI calves from 11 herds of beef or dairy cattle.
Procedures—Viral RNA was extracted from infected cell cultures, and BVDV-specific PCR primers were used to amplify > 1,000 bases of the viral genome. Derived sequences were used for molecular phylogenetic analyses to determine the viral genotype and viral genogroup and to assess genetic similarity among BVDVs.
Results—Analysis of the 17 NCP strains of BVDV failed to detect a viral genotype or viral genogroup not already reported to exist in the United States. One virus was classified as genotype 1, genogroup 1b, and 16 viruses were classified as genotype 2, genogroup 2a. Genotype 2 strains were genetically diverse, and genetic similarities were not obvious among viruses from geographic regions larger than a small locale.
Conclusions and Clinical Relevance—Viruses isolated from herds where a genotype 1, genogroup 1a BVDV vaccine was administered prior to breeding were primarily genetically diverse genotype 2, genogroup 2a BVDVs. Vaccination with multiple BVDV genotypes may be needed to improve protection. Methods used in this study to obtain and analyze field strains are applicable to assessing efficacy of current BVDV vaccines. Candidates for future vaccines are viruses that appear able to elude the immune response of cattle vaccinated against BVDV with existing vaccines.
Objective—To evaluate the effects of a voluntary regional bovine viral diarrhea virus (BVDV) control project implemented in the Upper Peninsula of Michigan.
Sample—294 cattle producers and 11,917 cattle from the Upper Peninsula.
Procedures—Producer participation was assessed to determine the effectiveness of the project's promotional and educational campaigns. Participating herds were screened for cattle persistently infected (PI) with BVDV by real-time reverse transcriptase PCR assay on ear notch specimens from all newborn calves and cattle that did not calve (bulls and young stock) during the year of enrollment. Responses to a survey administered to producers 4 years after project initiation were evaluated to assess the project's effect on BVDV management practices implemented by producers.
Results—294 of 495 (59%) known cattle producers in the Upper Peninsula participated in the project, and 11,917 cattle from 232 herds were tested for BVDV, of which 22 (0.18%) cattle from 9 (3.9%) herds were identified as PI with BVDV and euthanized or slaughtered. Of 140 survey respondents, 85 (61%) indicated they would test all new herd additions for BVDV, 83 (59%) would quarantine new herd additions for 30 days before introducing them to the main herd, and 81 (58%) would use the fact that their herd was free of cattle PI with BVDV for marketing purposes.
Conclusions and Clinical Relevance—Results indicated that the project enhanced producer knowledge about BVDV and led to changes in producer behavior regarding BVDV management. Stakeholder engagement was as critical to project success as was increased BVDV knowledge.
Procedures—Weaned calves were or were not vaccinated against BVDV at feedlot arrival (trial 1) or 2 (trial 2) or 3 (trial 3) weeks before feedlot arrival. During trial 1, half of the calves were commingled with PI cattle throughout the feeding period. During trial 2, 63 calves were exposed to PI cattle before weaning and all calves were exposed to PI cattle throughout the feeding period. During trial 3, all study calves were exposed to PI cattle throughout the feeding period. Morbidity and mortality rates and average daily gain (ADG) data were analyzed.
Results—During trial 1, calves maintained with PI cattle had a higher morbidity rate regardless of BVDV vaccination than did calves not exposed to PI cattle; however, for calves maintained with PI cattle, the morbidity rate for those vaccinated against BVDV was less than that for those not vaccinated against BVDV. During trial 2, calves exposed to PI cattle before weaning or vaccinated against BVDV had lower morbidity and mortality rates and increased ADG, compared with those for calves not exposed to PI cattle before weaning or vaccinated against BVDV. During trial 3, health and performance did not vary between calves that were and were not vaccinated against BVDV.
Conclusions and Clinical Relevance—Exposure of cattle to BVDV naturally or through vaccination before or at feedlot arrival mitigated the negative effects of constant exposure to PI cattle.
Objective—To determine whether a flexible vaccination regimen provides protection against challenge exposure with a virulent Leptospira borgpetersenii serovar Hardjo isolate.
Animals—Fifty-five 4-week-old calves seronegative for antibodies against L borgpetersenii serovar Hardjo.
Procedures—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 and Clinical Relevance—Protection in young calves was induced by vaccination with 1 or 2 doses of a serovar Hardjo bacterin.
Objective—To assess the serologic response of calves to inactivated and modified-live (ML) Mannheimia haemolytica (MH) preparations given alone and concurrently with combination viral vaccines containing ML bovine herpesvirus type 1 (BHV-1).
Animals—642 calves seronegative for BHV-1.
Procedures—In experiment 1, 192 calves received 1 of 3 MH preparations alone or concurrently received 1 of 3 MH preparations and 1 of 4 combination viral vaccines. In experiment 2, 450 calves received 1 of 4 MH preparations alone or concurrently received 1 of 4 MH preparations and 1 of 5 combination viral vaccines. Pretreatment and posttreatment blood samples were processed to obtain serum, which was analyzed to detect concentrations of antibodies against MH leukotoxin and BHV-1.
Results—In experiment 1, antibody titers against MH leukotoxin in calves receiving MH and ML virus vaccine appeared decreased, albeit nonsignificantly, compared with titers for calves receiving MH preparations alone. In experiment 2, all groups (except for 1) concurrently receiving an MH preparation and viral vaccine had a significant decrease in antibodies against MH leukotoxin. In both experiments, there was a significant decrease in the number of calves responding to MH leukotoxin when ML viral vaccine was coadministered.
Conclusions and Clinical Relevance—Coadministration of ML BHV-1 and MH preparations interfered with the serologic response to MH leukotoxin in calves seronegative for BHV-1. Serologic response to MH leukotoxin may be substantially improved in seronegative calves when MH vaccination is delayed until after calves have received a dose of ML BHV-1 vaccine.