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- Author or Editor: Charles W. Purdy x
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Abstract
Objective
To determine the effectiveness of Pasteurella multocida biovar A, serovar 3 (Pm A:3) killed by exposure to UV light and incorporated with a polyacrylate bead carrier as a vaccine.
Animals
18 weanling male Spanish goats.
Procedure
Prospective, randomized controlled study with 3 treatment groups: positive-control (PC), negative-control (NC), and principal Pm A:3 bacterin (PA) groups. Six PC goats each received live Pm A:3 and polyacrylate beads twice, 22 days apart, by transthoracic injection into the left lung. Six NC goats each received only PA beads twice, 22 days apart, by transthoracic injection. Six principal goats each received Pm A:3 vaccine SC twice, 22 days apart. Fourteen days after the second vaccination, all goats were challenge exposed with live Pm A:3 by transthoracic injection into the right lung, and 4 days later they were euthanatized and necropsied.
Results
Mean volume of consolidated lung tissue at the challenge site was 1.75 cm3 for the PC group, 15.18 cm3 for the NC group, and 3.9 cm3 for the PA vaccine group. The NC group had a significantly (P ≤ 0.002) larger mean volume of consolidated lung tissue than did the PC and PA groups after challenge exposure.
Conclusions
The PA bacterin and the PC groups developed protective immunity against live Pm A:3 challenge exposure. An SC administered, UV light-killed, Pm A:3 bacterin induced protective immunity similar to that induced by virulent live Pm A:3 injected into the target organ, the lung. (Am J Vet Res 1997;58:841–847)
Abstract
Objective—To determine effects of vaccination prior to transit and prophylactic administration of florfenicol at time of arrival at a feedyard on health of cattle and colonization of the nasopharynx by Mannheimia haemolytica (MH).
Animals—121 steers from Tennessee and 84 steers from New Mexico.
Procedure—Half of the steers were vaccinated before transport to a feedyard. Steers from Tennessee were vaccinated with MH bacterin-toxoid, and steers from New Mexico were vaccinated intranasally with modified-live leukotoxin-deficient MH. Half of the vaccinates and nonvaccinates were randomly selected to receive florfenicol on arrival at the feedyard. Steers were observed daily for respiratory tract disease (RTD).
Results—Administration of florfenicol at time of arrival reduced the incidence of RTD, delayed the interval before onset of RTD, and reduced the incidence of MH colonization of the nasopharynx for at least 4 days, but vaccination did not have any effect. Vaccination elicited an increase in serum antibody titers to MH. Administration of florfenicol at time of arrival reduced the development of serum antibody titers in intranasally vaccinated steers and both groups of nonvaccinated steers, but intranasal vaccination did not affect colonization by wild-type MH.
Conclusions and Clinical Relevance—Administration of florfenicol at time of arrival decreased the incidence of MH organisms in the nasopharynx and delayed the onset of RTD. Prophylactic use of suitable antibiotics is likely to reduce the incidence of acute RTD in calves for several days after arrival at feedyards, which is the period when they are most susceptible to infectious organisms. (Am J Vet Res 2002;63:251–256)
Abstract
Objective—To determine whether increased conglutinin titers are evident in stressed calves that do not develop respiratory tract disease in feedlots,compared with respiratory tract disease, and to determine the increase in immunoconglutinin titers.
Animals—101 mixed-breed beef calves.
Procedure—Calves were processed at 4 farms of origin and allowed to remain with their dams for another 100 days. Calves from each farm were brought to a centrally located order-buyer barn. In a feedlot, 101 calves were assigned to pens and observed daily for clinical signs of acute respiratory tract disease. When sick calves were detected, they were treated with antibiotics and isolated in a pen for 4 days. Conglutinin and immunoconglutinin titers were determined for all calves.
Results—During the 28-day study, 73 calves developed respiratory tract disease, whereas 28 calves remained healthy. Mean conglutinin titers differed significantly among calves from the 4 farms. Significant differences were not detected in conglutinin titers among calves on the basis of sex, morbidity, or vaccination status against Mannheimia haemolytica at each farm, the order-buyer barn, or the feedlot on days 8, 15, and 28 after arrival. Immunoconglutinin titers in calves differed significantly among farms and morbidity status.
Conclusions and Clinical Relevance—Mean conglutinin titers in calves do not appear to be associated with the incidence of acute respiratory tract disease; however, increased immunoconglutinin titers appear to be associated with recovery of stressed calves from respiratory tract disease during the first 15 days after arrival in a feedlot. (Am J Vet Res 2000;61:1403–1409)
Abstract
Objective—To determine the effect of tilmicosin treatment on number of Pasteurella haemolytica (PH) organisms in nasal secretion specimens of calves with respiratory tract disease.
Animals—206 British mixed-breed beef calves, 2 to 5 months old.
Procedure—In 2 separate studies of outbreaks, calves (study 1, n = 101; study 2, n = 105) that developed respiratory tract disease after transport to a feedlot were treated with tilmicosin. Nasal secretion specimens were examined for PH organisms to determine the status of colonization.
Results—In both studies, PH serotypes A1 and A6 were isolated. In study 1, tilmicosin treatment eliminated or markedly reduced the number of PH organisms in calves on days 1, 4, and 5 after treatment. In study 2, tilmicosin treatment eliminated PH organisms in calves on days 1, 2, 5, and 6 after treatment.
Conclusions and Clinical Relevance—Overall, tilmicosin treatment increased the number of culture-positive calves that became culture-negative and decreased the number of culture-negative calves that became culture-positive for up to 6 days after treatment. Tilmicosin treatment decreased the number of PH organisms in nasal secretion specimens, which indicated that fewer PH organisms were available to infect the lungs or to infect other calves. By reducing colonization, prophylactic use of tilmicosin before transport or at the time of arrival at a feedlot is likely to reduce the incidence of acute respiratory tract disease in calves for the initial several days after arrival, which is the period when they are most susceptible to infectious organisms. ( Am J Vet Res 2000;61: 525–529)
Abstract
Objective
To determine the rate and mode of infectious spread of Pasteurella haemolytica among calves maintained under typical conditions during collection, transport, and the first month of feeding.
Animals
101 two- to five-month-old Angus-crossbred calves.
Procedure
Samples obtained from cattle prior to and after they were transported to a feedlot were used for isolation and characterization of P haemolytica. Samples were also obtained from additional calves, some of which were sick, and these calves were then commingled with the transported calves for 3 days. A strain of P haemolytica that contains a rare deletion of the 4.2-kilobase streptomycin- and sulfonamide-resistance plasmid was inoculated into both palatine tonsils of 12 calves. Nasal secretions were aspirated from the ventral nasal meatus. Tonsillar wash specimens were procured. Pasteurella haemolytica organisms were quantitatively cultured and identified on the basis of colony morphology and response to specific antisera. Plasmids were isolated by an alkaline lysis procedure and identified by agarose gel electrophoresis.
Results
A single plasmid profile was observed from P haemolytica isolated from samples obtained prior to shipment. Commingled calves were shedding P haemolytica containing each known plasmid profile. After shipment, samples contained P haemolytica isolates with each known plasmid profile. The plasmid profile of the unique P haemolytica isolate was recovered from all 12 inoculated calves and 10 other calves. Some calves simultaneously shed P haemolytica isolates with differing plasmid profiles.
Conclusions and Clinical Relevance
Pasteurella haemolytica serotype 1 was horizontally transmitted among calves within days of commingling, which continued after calves were transported to a feedlot. (Am J Vet Res 1998;59:401–405)
Abstract
Objectives
To follow incidence of Pasteurella haemolytica (PH) in the upper respiratory tract of healthy calves at the farm and through the marketing process, and to determine the effect of vaccination on PH colonization of the upper respiratory tract and on the incidence of respiratory tract disease (RTD).
Animals
2- to 5-month-old calves (n = 104) from 4 farms.
Procedure
Calves were vaccinated with a killed PH serotype-1 product. Nasal secretion and tonsil wash specimens were cultured for PH, and serum antibody was measured by indirect hemagglutination. Calves with RTD were treated with tilmicosin phosphate.
Results
At the feedyard, 73 calves had RTD. The incidence of RTD was significantly related to the farm of origin, and was inversely related to the PH serum titer at the farm, but was not influenced by vaccination. Isolations of PH serotype 1 however, were reduced by vaccination. The major serotypes of PH encountered were 1 and 6.
Conclusion
Vaccination can reduce the frequency of colonization of the uoper respiratory tract by PH. (Am J Vet Res 1936;57:1317-1320)
Abstract
Objective—To determine the impact of feedyards on endotoxin concentration, fecal coliform count, and other water quality measurements during winter and summer in feedyard playas (shallow lakes).
Sample Population—Water samples obtained from 7 feedyard playas and 3 nonfeedyard control playas.
Procedure—Surface water samples were collected from each playa and at various depths from 3 feedyard playas. Endotoxin concentrations, 22 water quality variables, and fecal coliform counts were determined in samples collected in summer and winter from various combinations of playas.
Results—Cattle numbers per feedyard ranged from 40,000 to 175,000 head/y. Mean endotoxin concentrations were significantly lower in control playas than in feedyard playas in winter and summer. Endotoxin concentration appeared to be homogenous at various water depths. Values for 20 of 22 water quality variables were higher in the feedyard playas than in control playas in winter and summer. In winter only, mean total fecal coliform concentration in feedyard playas was significantly greater than in control playas.
Conclusions and Clinical Relevance—Results indicated that feedyards have the potential to impact water quality in playas, and cattle should not be allowed access to them. Feedyard playa water should not be used under high pressure to settle dust in pens with cattle or to cool cattle, because aerosols containing pathogens and high concentrations of endotoxin are a health hazard for humans and cattle. (Am J Vet Res 2001;62:1402–1407)
Abstract
Objective—To determine the clinical, clinicopathologic, and histologic effects of aerosolized feedyard dust that contains natural endotoxins on adult sheep.
Animals—Eighteen 3-year-old Saint Croix sheep.
Procedure—A prospective randomized controlled study was conducted. There were 2 treatment groups (dust-endotoxin group, n = 9; control group, 9). Aerosolized feedyard dust was provided continuously during a 4-hour period for each application (once in week 1, 3 times in week 2, and 7 times in week 3) to sheep in a semiairtight tent. All sheep were euthanatized and necropsied 8 hours after the treatment group received the last dust treatment. Variables measured before and after each dust treatment were rectal temperature, total WBC count, and concentrations of fibrinogen and haptoglobin.
Results—Mean amount of dust administered during each treatment was 451 g/4 h. Filter collection indicated 51 mg of dust/m3 and 7,423 ng of endotoxin. Mean rectal temperature at 8 hours (40.4 C) and mean WBC counts 12 and 24 hours after dust treatment were significantly higher for the treated group than the means of the respective variables for the control group. Similar responses were observed with repeated dust-endotoxin treatments; however, with each subsequent treatment, there was a diminished response. Sheep in the treatment group had generalized alveolar septal thickening and hypercellularity.
Conclusion and Clinical Relevance—Feedyard dust induced a temporary febrile response and leukocytosis in sheep in the treatment group. Exposure to dust that contains endotoxins may be a stressor preceding acute infectious respiratory tract disease of marketed sheep. (Am J Vet Res 2002;63:28–35)
Abstract
Objective—To determine the bacterial, fungal, and endotoxin concentrations in aerosolized ambient air during the winter and summer in feedyards located in the Southern High Plains, identify aerosolized microbial pathogens, and determine the size of microbial and dust components.
Sample Population—Aerosol samples were obtained from 7 feedyards.
Procedure—Aerosol samples were collected upwind, on-site, and downwind from each feedyard at a point 1 m above the ground by use of biological 2- and 6- stage cascade impactors.
Results—Significantly more microbes were cultured from on-site and downwind samples than upwind samples. There were significantly more microbes during the summer than during the winter. However, mean endotoxin concentration was significantly higher during the winter (8.37 ng/m3) than the summer (2.63 ng/m3). Among 7 feedyards, mean ± SE number of mesophilic bacteria (1,441 ± 195 colony-forming units [CFUs]/m3) was significantly higher than mean number of anaerobic bacteria (751 ± 133 CFUs/m3) or thermophilic bacteria (54 ± 10 CFUs/m3) in feedyard air. Feedyard aerosol samples contained more mesophilic fungi (78 ± 7 CFUs/m3) than thermophilic fungi (2 ± 0.2 CFUs/m3). Eighteen genera of bacteria were identified by use of an automated identification system.
Conclusions and Clinical Relevance—It appeared that gram-negative enteric pathogens offered little risk to remote calves or humans via ambient aerosols and that gram-positive pathogens of the Bacillus, Corynebacterium, and Staphylococcus spp can be spread by aerosols in and around feedyards. It was common to detect concentrations of endotoxin in the ambient air of 7 feedyards. ( Am J Vet Res 2004; 65:45–52)
Abstract
Objective—To identify cytocidal viruses and Pasteurella spp that could be isolated from cattle involved in 2 natural outbreaks of shipping fever.
Design—105 and 120 castrated male 4- to 8-monthold feedlot cattle involved in 1997 and 1998 outbreaks, respectively.
Animals—Nasal swab specimens and blood samples were collected, and cattle were vaccinated on arrival at an order-buyer barn from 4 local auction houses. Four days later, they were transported to a feedlot, and additional nasal swab specimens and blood samples were collected. Nasal swab specimens were submitted for virus isolation and bacterial culture; blood samples were submitted for measurement of respiratory bovine coronavirus (RBCV) hemagglutinin inhibition titers.
Results—93 of 105 cattle and 106 of 120 cattle developed signs of respiratory tract disease during 1997 and 1998, respectively, and RBCV was isolated from 81 and 89 sick cattle, respectively, while at the orderbuyer's barn or the day after arrival at the feedlot. During the 1997 outbreak, bovine herpesvirus 1 was isolated from 2 cattle at the order-buyer's barn and from 5 cattle 7 and 14 days after arrival at the feedlot, and parainfluenza virus 3 was isolated from 4 cattle 14 days after arrival at the feedlot. During the 1998 outbreak, bovine herpesvirus 1 was isolated from 2 cattle at the order-buyer's barn and on arrival at the feedlot and from 5 cattle 7 and 14 days after arrival at the feedlot, and parainfluenza virus 3 was isolated from 1 animal the day of, and from 18 cattle 7 and 14 days after, arrival at the feedlot. Pasteurella spp was cultured from 4 and 6 cattle at the order-buyer's barn and from 92 and 72 cattle on arrival at the feedlot during the 1997 and 1998 outbreaks, respectively.
Conclusion and Clinical Relevance—Results suggest that RBCV may play a causative role in outbreaks of shipping fever in cattle. More than 80% of the sick cattle shed RBCV at the beginning of 2 outbreaks when the Pasteurella spp infection rate was low. (J Am Vet Med Assoc 2000;216:1599–1604)
