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  • Author or Editor: Steven Bolin x
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Abstract

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.

Full access
in American Journal of Veterinary Research

Abstract

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.

Full access
in American Journal of Veterinary Research

Abstract

Case Description—3 unrelated, densely populated, dynamic ferret populations with severe outbreaks of enteric coccidiosis were evaluated.

Clinical Findings—In each outbreak, morbidity rate was high, there were an appreciable number of deaths, and ferrets of all ages were affected. Affected individuals had acute onset of diarrhea, and feces often contained frank or digested blood. Other clinical signs included dehydration, weakness, lethargy, and weight loss. Fecal examinations of affected ferrets revealed sporadic and inconsistent shedding of coccidial oocysts. Necropsy findings included moderate to marked atrophic enteritis associated with numerous intraepithelial and fewer extracellular coccidial life stages. Sporulated oocysts isolated from feces were consistent with Eimeria furonis. A PCR assay was performed on formalin-fixed, paraffin-embedded sections of intestine for the gene encoding the small subunit of rRNA yielded products with sequences identical to those described for E furonis.

Treatment and Outcome—Supportive care and treatment with sulfadimethoxine over the course of these outbreaks was palliative, but long-term treatment was required and failed to completely eradicate infection as identified by the subsequent finding of oocysts in fecal samples.

Clinical Relevance—Enteric coccidiosis due to infection with E furonis has typically been reported to be subclinical rather than to cause severe gastrointestinal disease in ferrets. This report indicated that infection with E furonis may have contributed to severe enteric disease with high morbidity and mortality rates in 3 densely populated, dynamic groups of ferrets. Furthermore, long-term treatment with anti-coccidials may be required in outbreak situations, but may be ineffectual in completely eradicating infection.

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate the effects of a voluntary regional bovine viral diarrhea virus (BVDV) control project implemented in the Upper Peninsula of Michigan.

Design—Longitudinal study.

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.

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine whether an interferon (IFN)-γ response sufficient to categorize cattle as positive for tuberculosis can be detected in blood collected at commencement of exsanguination at slaughter.

Animals—15 Holstein cows.

Procedures—12 cows were experimentally sensitized by SC injection with inactivated Mycobacterium bovis in mineral oil, which induced an immune response that mimicked natural infection with M bovis. Three nonsensitized control cows were injected SC with mineral oil alone. By 5 weeks after injection, only the 12 sensitized cows had positive results for tuberculosis with whole blood IFN-γ assay. At that time, all 15 cows were sent to slaughter and samples of blood were collected from each cow immediately before stunning and at commencement of exsanguination (within 90 seconds after stunning). A whole blood IFN-γ assay was performed on the samples. Conditional probability and paired t tests were used to analyze changes in the categorical test interpretation and qualitative IFN-γ production, respectively.

Results—All 12 sensitized cows had positive results for tuberculosis in samples obtained immediately before stunning, and 9 retained positive results for samples obtained at commencement of exsanguination. There was a significant decrease in the mean background-corrected IFN-γ ELISA optical density values for samples obtained at commencement of exsanguination.

Conclusions and Clinical Relevance—IFN-γ response sufficient to classify cattle as positive for tuberculosis could be detected in blood collected at commencement of exsanguination. These findings support further development and use of the IFN-γ assay on blood samples collected at exsanguination as part of a bovine tuberculosis surveillance program.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the effects of constant exposure to cattle persistently infected (PI) with bovine viral diarrhea virus (BVDV) on health and performance of feedlot cattle.

Design—3 controlled trials.

Animals—Crossbred feedlot cattle (trial 1, n = 184; trial 2, 138; trial 3, 138).

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.

Full access
in Journal of the American Veterinary Medical Association

Abstract

CASE DESCRIPTION Within a 2-week period, 4 southern cassowaries (Casuarius casuarius) at an exhibit at a Virginia zoo died acutely subsequent to eastern equine encephalitis virus (EEEV) infection. This prompted a search for other EEEV outbreaks in cassowaries, which resulted in the identification of 2 additional cassowaries that died of EEEV infection at a conservation center in Florida.

CLINICAL FINDINGS Both juvenile and adult birds were affected. Three of the 6 birds died acutely with no premonitory signs. Clinical disease in the other 3 birds was characterized by lethargy and ataxia. Clinicopathologic findings typically included leukocytosis, hyperuricemia, abnormally high liver enzyme activities, and hyper–β globulinemia, which was indicative of acute inflammation.

TREATMENT AND OUTCOME The 3 birds with clinical disease died despite supportive treatment. Gross abnormalities commonly observed during necropsy included coelomitis and evidence of diarrhea. Frequently observed histologic abnormalities were encephalitis, vasculitis, hepatitis, nephritis, and splenitis. The diagnosis of EEEV infection was confirmed by detection of serum anti-EEEV antibodies or detection of viral RNA in brain tissue by use of a reverse-transcriptase PCR assay.

CLINICAL RELEVANCE Findings suggested that EEEV can cause high morbidity and mortality rates in southern cassowaries. Clinical disease might be reduced or prevented by vaccination, isolation of ill birds, and mosquito control strategies.

Full access
in Journal of the American Veterinary Medical Association

SUMMARY

Objective

To determine the duration for cross-neutralizing antibodies stimulated by administration of a single dose of a modified-live vaccine against bovine viral diarrhea virus (BVDV) to seronegative cattle.

Animals

23 Angus cows seronegative to BVDV.

Procedure

Cows were randomly assigned to control (unvaccinated) or test (vaccinated) groups. Eighteen BVDV-seronegative Angus cattle were vaccinated via IM injection with a modified-live BVDV (NADL strain) vaccine and commingled with 5 unvaccinated seronegative cows. Serum was obtained from the cows before vaccination, on the day of vaccination, and 1.5, 3, 6, 9, 12, and 18 months after vaccination. Serum neutralizing antibody tests were performed on samples obtained at each point after vaccination, using a panel of 12 strains of BVDV that, on the basis of reactivity with monoclonal antibodies, were identified as heterologous.

Results

Antibodies against all 12 strains of BVDV (which we tested) were detected by use of viral neutralization testing in samples obtained from vaccinated cattle 18 months after vaccination; however, concentration of antibody for some of the strains was low. Nonvaccinated cattle remained seronegative throughout the 18-month study period.

Clinical Implications

Analysis of these data indicated that modified-live BVDV vaccines could stimulate an antibody response in seronegative cows that was detectable for at least 18 months after vaccination. These antibodies were able to cross neutralize 12 antigenically diverse strains of BVDV. (Am J Vet Res 1998;59:848–850)

Free access
in American Journal of Veterinary Research

Summary

Cell lines from the repository of the American Type Culture Collection were examined for possible contamination with bovine viral diarrhea virus. During testing, hog cholera virus (HCV) was detected in the IB-RS-2 D10 porcine kidney cell line. This variant of HCV was avirulent for pigs and seldom induced detectable concentrations of antibody against reference viruses (HCV-Ames or bovine viral diarrhea virus-NY1) in serum of inoculated pigs. Additionally, this variant of HCV did not confer protection to pigs against virulent HCV. The contaminated cell line had been distributed to > 20 laboratories in the United States. The cell line was not used in field studies and has been destroyed.

Free access
in Journal of the American Veterinary Medical Association

SUMMARY

Tissues from cattle that died of experimentally induced mucosal disease (n = 3), naturally acquired mucosal disease (n = 6), or naturally acquired chronic bovine viral diarrhea (n = 4) were examined. Consistent findings were lymphocytic depletion of lymphoid tissues, degeneration of myenteric ganglion cells, and mild adrenalitis. Intracytoplasmic viral antigen was detected in myenteric ganglia and in endocrine glandular cells. Noncytopathic virus was isolated from all cattle, and cytopathic virus was isolated from 12 of 13 cattle.

Free access
in American Journal of Veterinary Research