Objective—To assess long-term effects and risk factors for the efficacy of hyperimmunization protocols against infectious bovine rhinotracheitis (IBR) during a longitudinal field study of dairy and dairy-beef mixed farms.
Animals—Approximately 7,700 cows from 72 farms.
Procedures—Farms were assigned to 3 treatment groups (hyperimmunization groups [HIGs] 1 and 2, which were hyperimmunized with glycoprotein E [gE]–deleted marker vaccines, and a nonintervention group [NIG]). Cattle in HIG 1 were initially vaccinated with an attenuated vaccine, whereas cattle in HIG 2 were initially vaccinated with an inactivated-virus vaccine. Cattle in both HIGs received booster inoculations with inactivated-virus vaccines at 6-month intervals. The risk for gE seroconversion was compared among experimental groups via a shared frailty model with a piecewise constant baseline risk to correct for seasonal and secular effects.
Results—Risk for gE seroconversion significantly decreased over time for the HIGs, compared with the NIG. Seasonal changes in the risk of gE seroconversion were detected, with a higher risk during winter periods, compared with grazing periods. No significant difference was detected between HIGs 1 and 2. The only significant risk factor was the number of buildings for cattle on a farm; the higher the number of buildings, the lower the risk for gE seroconversion. Prevalence of IBR decreased over time in both HIGs but remained constant or increased in the NIG.
Conclusions and Clinical Relevance—Hyperimmunization via repeated administration of attenuated and inactivated-virus gE-deleted marker vaccines as well as inactivated-virus vaccines may provide a method for control of IBR.
Objective—To evaluate disease progression in sheep experimentally inoculated with Anaplasma phagocytophilum and determine the Anaplasma spp seroprevalence in sheep in free-ranging flocks in the Sierra Nevada foothills and Oregon Coast Range.
Animals—10 mature ewes seronegative for Anaplasma spp and 251 sheep from 8 flocks.
Procedures—10 ewes received 1 of 3 treatments: A phagocytophilum Webster strain (n = 4), A phagocytophilum MRK strain (4), or human promyelocytic leukemia cells (control treatment ). Sheep were monitored for signs of clinical disease, and blood samples were obtained for serologic and PCR assay evaluation intermittently for 48 days. From a subsample of sheep from each of 8 free-ranging flocks, blood samples were obtained to determine Anaplasma spp seroprevalence.
Results—Sheep inoculated with A phagocytophilum developed subclinical or mild disease, whereas sheep inoculated with the control treatment did not develop any signs of disease. Only 2 ewes seroconverted; both had received the MRK strain. Anaplasma-specific DNA was detected in blood samples from 1 sheep in the Webster strain–inoculated group and 3 sheep in the MRK strain–inoculated group. Sheep seropositive for Anaplasma spp were detected in 5 of 8 flocks, and flocks in the Sierra Nevada foothills had higher within-flock seroprevalence (22%) than did flocks in the Oregon Coast Range (6.4%).
Conclusions and Clinical Relevance—Infection with A phagocytophilum in mature sheep generally resulted in subclinical disease. Higher Anaplasma spp seroprevalence in sheep in the Sierra Nevada foothills corresponded to the geographic distribution of anaplasmosis reported for dogs, horses, and humans.
Objective—To elucidate the species and biovariants of Pasteurellaceae isolated from clinically normal bighorn sheep (Ovis canadensis) or bighorn sheep with evidence of respiratory disease.
Sample—675 Pasteurellaceae isolates from 290 free-ranging bighorn sheep in Idaho, Oregon and Wyoming.
Procedures—Nasal and oropharyngeal swab specimens were inoculated onto selective and nonselective blood agar media. Representatives of each colony type were classified via a biovariant scheme. The association of respective β-hemolytic isolates with respiratory disease was evaluated via χ2 analyses.
Results—Bacterial isolates belonged to 4 species: Histophilus somni, Mannheimia haemolytica, Pasteurella multocida, and Bibersteinia (Pasteurella) trehalosi. Within the latter 3 species, 112 subspecies, biotypes, and biovariants were identified. Bibersteinia trehalosi 2 and B trehalosi 2B constituted 345 of 675 (51%) isolates. Most (597/618 [97%]) isolates from adult sheep were from clinically normal animals, whereas most (47/57 [82%]) isolates from lambs were from animals with evidence of respiratory disease. Twenty-two Pasteurellaceae biovariants were isolated from sheep with respiratory disease; 17 of these biovariants were also isolated from clinically normal sheep. The ability of isolates to cause β-hemolysis on blood agar was associated with respiratory disease in adult bighorn sheep (OR, 2.59; 95% confidence interval, 1.10 to 6.07).
Conclusions and Clinical Relevance—Bighorn lambs appeared more susceptible to respiratory disease caused by Pasteurellaceae than did adult sheep. β-Hemolytic Pasteurellaceae isolates were more likely to be associated with respiratory disease than were non–β-hemolytic isolates in adult sheep. Identification of Pasteurellaceae with the greatest pathogenic potential will require studies to estimate the risk of disease from specific biovariants.
Objective—To develop and evaluate a rapid and accurate assay involving PCR amplification and electrospray ionization mass spectrometry of nucleic acid extracts from whole blood samples for the detection of Dirofilaria immitis infection in dogs.
Sample—Whole blood nucleic acid extracts from 29 dogs experimentally infected with D immitis (and in which circulating D immitis antigen was detected) and 10 uninfected dogs.
Procedures—16 of the 29 whole blood samples from infected dogs were examined at the time of collection for circulating microfilaria. Nucleic acids were extracted from all whole blood specimens and underwent PCR amplification with 12 PCR primer pairs designed to detect a wide range of pathogens (including the Wolbachia endosymbiont of D immitis) and electrospray ionization mass spectrometry.
Results—On the basis of assay results, heartworm infection was detected in 13 of 13 antigen-positive dogs of unknown microfilaria status, 11 of 11 antigen-positive dogs with circulating microfilaria, 0 of 3 antigen-positive dogs tested at 3 months after larval infection, 0 of 2 antigen-positive dogs with occult infections, and 0 of 10 uninfected dogs.
Conclusions and Clinical Relevance—With the assay under investigation, it was possible to identify D immitis infection in dogs with circulating microfilaria via detection of the obligate Wolbachia endosymbiont of D immitis. It was not possible to identify dogs with occult infections, which suggested that circulating microfilaria must be present to detect infection with this assay, although further studies would be required to verify that finding.
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.
Objective—To assess the transmission of bovine viral diarrhea virus (BVDV) from experimentally infected white-tailed deer fawns to colostrum-deprived calves by use of a BVDV strain isolated from hunter-harvested white-tailed deer.
Animals—5 white-tailed deer (Odocoileus virginianus) fawns and 6 colostrum-deprived calves.
Procedures—Fawns were inoculated intranasally with a noncytopathic BVDV-1a isolate (2 mL containing 106.7 TCID50/mL), and 2 days after inoculation, animals were commingled until the end of the study. Blood and serum samples were obtained on days −6, 0, 7, 14, and 21 after inoculation for reverse transcriptase PCR assay, virus neutralization, and BVDV-specific antibody ELISA. Nasal, oral, and rectal swab specimens were collected on days 0, 3, 7, 14, 17, and 21 for reverse transcriptase PCR testing. By 21 days after inoculation, all animals were euthanized and necropsied and tissues were collected for histologic evaluation, immunohistochemical analysis, and virus isolation.
Results—All fawns became infected and shed the virus for up to 18 days as determined on the basis of reverse transcriptase PCR testing and virus isolation results. Evidence of BVDV infection as a result of cohabitation with acutely infected fawns was detected in 4 of the 6 calves by means of reverse transcriptase PCR testing and virus isolation.
Conclusions and Clinical Relevance—On the basis of these findings, BVDV transmission from acutely infected fawns to colostrum-deprived calves appeared possible.
Objective—To evaluate cross protection provided by administration of contagious ecthyma vaccines against strains of orf virus in goats.
Animals—126 Boer-Spanish crossbred goats (3 to 20 days old).
Procedures—85 goats were vaccinated with a goat-derived contagious ecthyma vaccine. Of these, 41 were challenge exposed with the virus strain for the contagious ecthyma vaccine, 40 were challenge exposed with a more virulent field strain of orf virus, and 4 were lost to predation or died. Another 41 goats were vaccinated with a vaccine produced from a more virulent field strain of orf virus; of these, 18 were challenge exposed with the virus strain of the goat-derived contagious ecthyma vaccine, 18 were challenge exposed with the more virulent field strain of orf virus, and 5 were lost to predation or died.
Results—Vaccination with the goat-derived contagious ecthyma vaccine did not significantly reduce the number of goats with lesions or lesion severity caused by challenge exposure with the more virulent field strain of orf virus. Vaccination with the vaccine produced from the more virulent field strain of orf virus significantly reduced the number of goats with lesions attributable to challenge exposure with the virus strain of the goat-derived contagious ecthyma vaccine, but it failed to significantly reduce lesion severity.
Conclusions and Clinical Relevance—Vaccination did not result in cross protection for the 2 strains of orf virus. This may have been attributable to antigenic differences and may be a factor in outbreaks of contagious ecthyma in vaccinated goats.
Objective—To characterize the impact of Mannheimia haemolytica infection on feed intake and weight gain in feedlot heifers and to evaluate the clinical efficacy of isoflupredone acetate administered in combination with oxytetracycline.
Animals—96 weanling heifers in a research feedlot facility.
Procedures—Bronchopneumonia was induced by intrabronchial infusion of M haemolytica. Control heifers underwent a sham procedure. Infected heifers were treated with oxytetracycline alone or in combination with isoflupredone acetate (OXY-ISO) or with nothing. Clinical variables were recorded daily for 7 days following disease induction, and feedlot performance indices were measured over a 12-week period.
Results—Infection caused a reduction in dry-matter intake and average daily gain (ADG) in heifers that received no treatment. Oxytetracycline treatment alone did not prevent reductions in feed intake and ADG during the first week after infection was induced, whereas OXY-ISO treatment did prevent these reductions. Treatment with OXY-ISO also resulted in faster clinical improvement. No significant differences were evident between the oxytetracycline and OXY-ISO groups with respect to dry-matter intake or ADG throughout the study period.
Conclusions and Clinical Relevance—Isoflupredone acetate appeared to be a useful clinical adjunct to treatment with oxytetracycline in cattle with acute M haemolytica bronchopneumonia.
Objective—To investigate the effect of opsonization of Rhodococcus equi with R equi-specific antibodies in plasma on bacterial viability and phagocyte activation in a cell culture model of infection.
Sample—Neutrophils and monocyte-derived macrophages from 6 healthy 1-week-old foals and 1 adult horse.
Procedures—Foal and adult horse phagocytes were incubated with either opsonized or nonopsonized bacteria. Opsonization was achieved by use of plasma containing high or low concentrations of R equi-specific antibodies. Phagocyte oxidative burst activity was measured by use of flow cytometry, and macrophage tumor necrosis factor (TNF)-α production was measured via an ELISA. Extracellular and intracellular bacterial viability was measured with a novel R equi-luciferase construct that used a luminometer.
Results—Opsonized bacteria increased oxidative burst activity in adult horse phagocytes, and neutrophil activity was dependent on the concentration of specific antibody. Secretion of TNF-α was higher in macrophages infected with opsonized bacteria. Opsonization had no significant effect on bacterial viability in macrophages; however, extracellular bacterial viability was decreased in broth containing plasma with R equi-specific antibodies, compared with viability in broth alone.
Conclusions and Clinical Relevance—The use of plasma enriched with specific antibodies for the opsonization of R equi increased the activation of phagocytes and decreased bacterial viability in the extracellular space. Although opsonized R equi increased TNF-α secretion and oxidative burst in macrophages, additional factors may be necessary for effective intracellular bacterial killing. These data have suggested a possible role of plasma antibody in protection of foals from R equi pneumonia.
Objective—To determine the Helicobacter spp present in the oral cavity of dogs and the relationship of those organisms with gastric Helicobacter spp to better define the potential for dog-human and dog-dog transmission.
Sample—Saliva and dental plaque from 28 dogs and gastric biopsy specimens from a subset of 8 dogs.
Procedures—PCR-based screening for Helicobacter spp was conducted on samples obtained from the oral cavity of 28 dogs. Comparative analysis was conducted on Helicobacteraceae 16S rDNA clone libraries from the oral cavity and stomach of a subset of 8 dogs (5 vomiting and 3 healthy) that had positive PCR results for Helicobacter spp.
Results—Helicobacteraceae DNA was identified in the oral cavity of 24 of 28 dogs. Analysis of cloned 16S rDNA amplicons from 8 dogs revealed that Wolinella spp was the most common (8/8 dogs) and abundant (52/57 [91%] clones) member of the Helicobacteraceae family in the oral cavity. Only 2 of 8 dogs harbored Helicobacter spp in the oral cavity, and 1 of those was coinfected with Helicobacter heilmannii and Helicobacter felis in samples obtained from the stomach and saliva. Evaluation of oral cavity DNA with Wolinella-specific PCR primers yielded positive results for 16 of 20 other dogs (24/28 samples were positive for Wolinella spp).
Conclusions and Clinical Relevance—Wolinella spp rather than Helicobacter spp were the predominant Helicobacteraceae in the oral cavity of dogs. The oral cavity of dogs was apparently not a zoonotically important reservoir of Helicobacter spp that were non–Helicobacter pylori organisms.