Search

Objective—To compareSalmonellaisolates cultured from feedyard and nonfeedyard (control) playas (ie, temporary shallow lakes) of the Southern High Plains.Sample Population—Water and muck (sediment) samples were obtained from 7 feedyard playas and 3 nonfeedyard playas in the winter and summer.Procedure—Each water and muck sample was enriched with sulfur-brilliant-green broth and incubated in a shaker at 37°C for 24 hours. A sample (100 mL) of the incubated bacterial-enriched broth was then mixed with 100 mL of fresh sulfur-brilliant-green enrichment broth and incubated in a shaker at 37°C for 24 hours. After the second incubation, a swab sample was streaked on differential media. SuspectSalmonellaisolates were further identified by use of biochemical tests, and Salmonella isolates were confirmed and serovar determinations made.Results—Salmonellaisolates were not recovered from the 3 control playas. SevenSalmonellaenterica serovars were isolated from 5 of 7 feedyard playas in the summer, and 13 S enterica serovars were isolated from 7 of 7 feedyard playas in the winter. In the summer, 296 isolates were cultured, and 47 wereSalmonellaorganisms. In the winter, 288 isolates were cultured, and 171 wereSalmonellaorganisms.Conclusions and Clinical Relevance—Results indicated that feedyard playas are frequently contaminated with manySalmonellaserovars. These pathogens should be considered whenever feedyard managers contemplate the use of water from these playas. Water from feedyard playas should not be used to cool cattle in the summer or for dust abatement. (Am J Vet Res2004;65:40–44)

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)

Objective—To investigate the effects of sterile fine dust aerosol inhalation on antibody responses and lung tissue changes induced by Mucor ramosissimus or Trichoderma viride spores following intratracheal inoculation in goats. Animals—36 weanling Boer-Spanish goats. Procedures—6 goats were allocated to each of 2 M ramosissimus–inoculated groups, 2 T viride–inoculated groups, and 2 control (tent or pen) groups. One of each pair of sporetreated groups and the tent control group were exposed 7 times to sterilized fine feedyard dust (mean ± SD particle diameter, < 7.72 ± 0.69 μm) for 4 hours in a specially constructed tent. Goats in the 4 fungal treatment groups were inoculated intratracheally 5 times with a fungal spore preparation (30 mL), whereas tent control goats were intratracheally inoculated with physiologic saline (0.9% NaCl) solution (30 mL). Pen control goats were not inoculated or exposed to dust. Goats received an IV challenge with equine RBCs to assess antibody responses to foreign antigens. Postmortem examinations were performed at study completion (day 68) to evaluate lung tissue lesions. Results—5 of 7 deaths occurred between days 18 and 45 and were attributed to fine dust exposures prior to fungal treatments. Fine dust inhalation induced similar lung lesions and precipitating antibodies among spore-treated goats. Following spore inoculations, dust-exposed goats had significantly more spores per gram of consolidated lung tissue than did their nonexposed counterparts. Conclusions and Clinical Relevance—Fine dust inhalation appeared to decrease the ability of goats to successfully clear fungal spores from the lungs following intratracheal inoculation.

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)

Objective—To determine effects of repeated aerosol exposures to fly ash dust on respiratory tracts of tent-confined goats. Animals—12 weanling Boer-Spanish crossbred goats. Procedure—Goats were randomly assigned to 2 groups: fly ash treatment group (principal goats, n = 6) or control group (control goats, 6). Aerosolized fly ash dust was provided during a 4-hour period for each of 6 applications given over 3 months and one 2-hour application prior to necropsy. Fly ash particle diameters ranged from 0.1 to 130 µm and averaged 17.8 µm, with 1.5% of fly ash particles in the 0.1- to 5-µm-diameter range. A mean ± SD of 748 ± 152 g/treatment was delivered inside a tent containing principal goats; control goats were placed inside a similar tent for 4-hour treatments without dust. Following treatment, rectal temperatures were taken at 0, 4, 6, 8, 24, and 72 hours; Hcts were recorded at 0, 24, and 72 hours. Results—Rectal temperatures were significantly increased at 4, 6, and 8 hours and decreased at 72 hours, compared with 0 hours. Mean ± SEM Hct values were significantly increased for principal goats (37.47 ± 0.39%), compared with control goats (36.17 ± 0.42%). A significant increase in the mean area of gross atelectatic lung lesions (1,410 mm2) was found in principal goats (n = 6), compared with control goats (440 mm2; 5). Conclusions and Clinical Relevance—An increase in atelectatic lung lesions was observed in principal goats, compared with control goats; however, overall, fly ash dust effects were nontoxic. ( Am J Vet Res 2005;66:991–995)

Objective—To compare the virulence of spores of 7 fungi by tracheal inoculation of goats following exposure of goats to an aerosol of sterilized feedyard dust. Animals—54 weanling Boer-Spanish goats. Procedure—A prospective randomized controlled study was conducted. There were 7 fungal treatment groups, a tent control group, and a pen control group (n = 6 goats/group). Goats in the 7 treatment and tent control groups were exposed to autoclaved aerosolized feedyard dust for 4 hours in a specially constructed tent. Goats in the 7 treatment groups were then inoculated intratracheally with 30 mL of a fungal spore preparation, whereas tent control goats were intratracheally inoculated with 30 mL of physiologic saline (0.9% NaCl) solution. These treatments were repeated each week for 6 weeks. Results—Severity of pathologic changes differed significantly among the 7 fungal treatment groups as determined on the basis of gross atelectatic and consolidated lung lesions and histologic lesions of the lungs. Descending order for severity of lesions was Mucor ramosissimus, Trichoderma viride, Chaetomium globosum, Stachybotrys chartarum, Aspergillus fumigatus, Penicillium chrysogenum, and Monotospora lanuginosa. Trichoderma viride spores were the most invasive and were isolated from the bronchial lymph nodes and thoracic fluid of all 6 goats administered this organism. Spores were observedhistologically in lung tissues harvested 72 hours after inoculation from all treatment groups. Conclusions and Clinical Relevance—4 of 7 fungal spore types induced significantly larger lung lesions, compared with those induced by the other 3 spore types or those evident in control goats. (Am J Vet Res 2005;66:615–622)

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)

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)

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.18 weanling male Spanish goats.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.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 (Por = 0.002) larger mean volume of consolidated lung tissue than did the PC and PA groups after challenge exposure.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.

To determine the effectiveness of Pasteurella haemolytica biovar A, serovar 1 (Ph A1) killed by UV light and incorporated with an oil adjuvant or carriers.40 weaning male Spanish goats.Goats were randomly allotted to 1 of 6 treatment groups: 4 Ph A1 bacterins (agar beads, polyacrylate beads [PA], phosphate-buffered saline solution, Freund's incomplete adjuvant), live Ph A1 with polyacrylate beads (LiPhPA), and polyacrylate beads (UnVac). Each of 4 Ph A1 vaccines was administered SC twice, 21 days apart, to 1 of 4 groups; another group received only PA beads SC, and the last group received live Ph A1 with PA beads by transthoracic injection into the left lung. 14 days after the second vaccination, all goats were challenge exposed with live Ph A1 by transthoracic injection into the right lung, and 4 days later, all goats were euthanatized and necropsied.Mean volume of consolidated right lung tissue was 1.02 cm3 for the LiPhPA group, 168.1 cm3 for the UnVac group, 2.3 cm3 for the Freund's incomplete adjuvant bacterin group, 5.53 cm3 for the PA bacterin group, 9.01 cm3 for the agar beads bacterin group, and 7.51 cm3 for the phosphate-buffered saline solution bacterin group. Mean volume of consolidated lung tissue was significantly different between the UnVac group and the other 5 groups.The LiPhPA group and 4 bacterin groups developed protective immunity against live Ph A1 challenge exposure.An s.c. administered, UV light-killed Ph A1 bacterin induced protective immunity equal to that induced by virulent live Ph A1 injected into the target organ, the lung.

The effectiveness of Pasteurella haemolytica biovar A, serovar 1 (Ph1) subunit vaccines was tested in goats, using challenge exposure by transthoracic injection. Twenty-two weanling male Spanish goats were randomly allotted to 4 groups. Six goats were given 2 transthoracic injections into the lung 18 days apart with live Ph1 impregnated in agar beads (positive controls). Six goats were not given injections (negative controls). Five goats were given 2 transthoracic injections into the lung 18 days apart with 4.6 mg of cytotoxin in agar beads. The remaining 5 goats were given 2 IM injections, 18 days apart, into the thigh with 4.6 mg of cytotoxin emulsified in incomplete Freund's adjuvant. Twenty-four days after the second injection, all goats were challenge-exposed to live Ph1 by transthoracic injection into the lung, and 4 days later, all goats were euthanatized and necropsied. Serum neutralizing anticytotoxin titer was measured throughout the experiment. Mean volume of consolidated lung tissue was 0.38 cm3 for the positive control group, 32 cm3 for the negative control group; 19 cm3 for the cytotoxin-lung group; and 88 cm3 for the cytotoxin-adjuvant-IM group. Only the positive control group was protected from Ph1 challenge exposure. The Ph1 cytotoxin subunit vaccine alone appeared to be ineffective, and the anticytotoxin titer was not correlated with protection. In a separate trial, 32 weanling male Spanish goats were randomly allotted to 5 groups. Each was given 2 transthoracic injections into the lung 22 days apart. Six goats were given Ph1 cytotoxin impregnated into agar beads; 6 were given Ph1 lipopolysaccharide impregnated in agar beads; 6 were given Ph1 capsule impregnated in agar beads. Six goats were given agar beads only (negative controls), and 6 were given live Ph1 impregnated into agar beads (positive controls). Twenty days after the second injection, all goats were challenge-exposed to live Ph1 by transthoracic injection into the lung, and 4 days later, all goats were euthanatized and necropsied. Mean volume of consolidated lung tissue was 0.14 cm3 for the positive control group, 7.59 cm3 for the negative control group, 11.21 cm3 for the cytotoxin group, 10.19 cm3 for the lipopolysaccharide group, and 1.6 cm3 for the capsule group. Again, only injection of live Ph1 (positive controls) induced solid protection; however, the capsule subunit vaccine induced partial protection against challenge exposure in this trial. Lipopolysaccharide and cytotoxin subunit vaccines were ineffective in protecting goats against challenge exposure with live Ph1.

A method of inducing Pasteurella haemolytica serotype 1 (Ph1) lung infection in goats, using low numbers of bacteria and without impairing host immunity, was developed. Two trials were conducted. Results of trial 1, using 10 principals (Ph1 agar beads) and 6 controls (agar beads alone), indicated that Ph1 organisms imbedded in agar beads could survive host lung defenses for 32 days. Results of trial 2 indicated that lung immunity in the inoculated goats (principals) was high and they were more protected than controls against a transthoracic challenge of Ph1 (1.18 x 10(7) colony-forming units) injected into a lung of each goat on posttreatment day 35. When comparing challenge-exposed principals with controls, the controls developed rectal temperatures above normal for a longer time, duration of anorexia was longer, and signs of depression were seen. The controls developed large areas of consolidated lung tissue, more Ph1 isolates were recovered from nasal turbinates and lung tissue, and higher Ph1 concentrations were found in the lungs. The serum Ph1 indirect hemagglutination antibody titers in the principals of both trials increased, compared with titers in controls. Principal goats in trial 2 had higher Ph1 indirect hemagglutination antibody titers after injection of Ph1-impregnated agar beads and less severe lung lesions after challenge exposure than did controls. The small pneumonic consolidated lesions in the principals, compared with extensive lesions in controls after Ph1 challenge exposure, indicated a high degree of immunity after exposure to Ph1 organisms imbedded in agar beads.