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Objective

To monitor the prevailing viral respiratory tract infections in cattle after transportation to feedlots.

Animals

100 cattle with signs of respiratory tract disease on arrival at 2 feedlots.

Procedures

Nasal swab samples were obtained from each animal and were used for inoculation of defined cell culture systems that detected bovine viruses known to cause respiratory tract infections, as well as viruses previously not recognized as respiratory pathogens for cattle.

Results

Bovine respiratory coronaviruses were isolated from 38 of the 100 cattle, including 6 of 50 cattle from California, 22 of 31 cattle from Oklahoma, 6 of 11 cattle from Texas, and 4 of 8 cattle of unknown origin. Parainfluenza 3 viruses also were isolated from 4 California cattle, but other bovine viruses were not detected.

Clinical Implications

The high rate of coronavirus isolations from feedlot cattle with signs of respiratory tract disease implied wide distribution and high susceptibility among cattle to this infection, which had not been detected by use of viral isolation systems in previous etiologic evaluations of feedlot cattle affected with bovine respiratory disease complex. (J Am Vet Med Assoc 1996; 208:1452-1455)

Free access
in Journal of the American Veterinary Medical Association

SUMMARY

A sublethal dose of ethylene glycol was administered orally to 3 groups of dogs; dogs of a control group were given distilled water instead. Renal cortical biopsy samples were obtained from dogs of experimental and control groups at various times after treatment. Tissue was examined by use of light microscopy and transmission electron microscopy. In dogs of the control group, the light and electron microscopic appearances of tissue were within normal limits at all sample collection hours. In dogs of the experimental groups, renal corpuscular structure remained within normal limits by use of light and electron microscopy throughout the study, though morphologic change was seen in other structures of the cortex. Light microscopic lesions first appeared at 12 hours, and were similar to those reported in the literature. Ultrastructural lesions were first observed in the 5-hour samples, and similar to the light microscopic lesions, were most common in the proximal convoluted tubules (pct). Initial pct cellular changes included vacuolization of cells and distention of the parabasal extracellular spaces; pct cellular lesions seen in later-hour samples included formation of apical buds and cellular rupture. Internalization or sloughing of the pct brush border was not observed. Distal convoluted tubules (dct) were frequently dilated and/or packed with cellular debris. A few dct cells had degenerative or necrotic changes. In pct and dct, abnormal cells were frequently flanked by normal or nearly normal cells. During later hours, a few cells with types of changes first observed in early hours continued to be observed, implying ongoing response of cells to the toxin.

Free access
in American Journal of Veterinary Research

SUMMARY

A series of experiments was performed in vitro and in vivo to determine the influence of FK-565, a heptanoyl tripeptide, on lymphocyte and macrophage function in swine. Compared with values for control cultures, mitogen-stimulated lymphocyte blastogenesis and interleukin-2 production were unaffected in cells preincubated with 0.1, 1.0, and 10.0 μg of FK-565/ml. Natural killer cell activity was increased by preincubation with 1.0 μg of FK-565/ml; however, this increase was not statistically significant. In vitro treatment of porcine alveolar macrophages with FK-565 did not enhance cytolytic activity or bactericidal activity. In in vivo experiments, FK-565 given orally to pigs at concentrations of 6 or 60 μg·kg-1·d-1 for 5 days did not affect lymphocyte blastogenesis, interleukin-2 production, or alveolar macrophage bactericidal activity. A trend toward increased natural killer cell activity was evident in pigs treated with FK-565. In contrast, pigs treated with 6 μg·kg-1·d-1 had significantly (P < 0.01) decreased alveolar macrophage cytolytic activity. These data indicate that at the dosages tested, FK-565 is not a suitable immunomodulator for enhancement of nonspecific immunity in swine.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine the usefulness of physiologic, behavioral, and pathological changes as objective indicators of early respiratory disease in calves with Mannheimia haemolytica pneumonia.

Animals—14 crossbred beef steers.

Procedures—Disease was experimentally induced in healthy calves through endoscopic pulmonary inoculation of M haemolytica. Calves were necropsied on days 1, 2, 3, 5, 7, and 9 after inoculation. Physical examination variables (rectal temperature, heart rate, and respiration characteristics), clinical illness score, and degree of activity were assessed 3 times daily beginning 4 days prior to inoculation and continuing throughout the study. Twice before inoculation and on days 1, 2, 3, 5, 7, and 9, arterial blood gas measurements, serum biochemical analyses, and CBCs were performed. Pedometers and accelerometers were used to monitor cattle behavior and activity throughout the trial.

Results—All calves became clinically ill after inoculation and had gross and histopathologic signs of bronchopneumonia. No variable was a reliable indicator of disease progression as judged by percentage of pulmonary involvement. However, activity as measured by total steps taken in a 24-hour period was lower after versus before disease induction.

Conclusions and Clinical Relevance—This single-pathogen challenge model successfully yielded clinical signs and pathological effects consistent with naturally acquired respiratory disease. Routine laboratory variables and subjective measures were not reliable indicators of lung involvement or the progression of pneumonia. However, activity, objectively measured with pedometers and accelerometers, appeared to be a promising indicator for early recognition of bovine respiratory disease.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate scintigraphy, radiography, and histomorphometric analysis for assessing incorporation of intercalary bone grafts and to compare incorporation of cortical autografts and allografts by the recipient.

Animals—12 skeletally mature sheep.

Procedures—A 5-cm tibial defect was filled with a cortical allograft (n = 6) or autograft (6) and stabilized with an interlocking nail. Radiography, scintigraphy, and fluorochrome bone labeling were performed every 3 months for 24 months. Radiographic evaluation included grading of the host and graft union and assessment of implants and grafts. Technetium-99m-hydroxymethylene diphosphonate radionuclide uptake was measured. Sheep were euthanatized 24 months after surgery, and bone formation was evaluated via histomorphometric analysis of fluorochrome labeling.

Results—Complete union was detected on radiographs by 21 months in all sheep but developed earlier in sheep that received an autograft versus in those that received an allograft. Radionuclide uptake peaked at 3 months and returned to presurgical values at 12 months. Histomorphometric analysis revealed fluorochrome labeling corresponding to each time point, with most bone formation at 9 through 15 months. Scintigraphy findings did not correlate well with fluorochrome labeling of newly formed bone.

Conclusions and Clinical Relevance—Although bone production around cortical bone grafts was detected by use of scintigraphy, this method did not provide accurate assessment of graft incorporation in sheep. Furthermore, bone produced by activated periosteum could not be distinguished scintgraphically from bone that replaced the graft. Intercalary autografts healed more rapidly and had greater incorporation into the host bone, compared with findings for allografts.

Full access
in American Journal of Veterinary Research

Objective

To describe 3 laparoscopic approaches for, and the normal laparoscopic anatomy of, the abdomen in adult llamas and to evaluate the effects of laparoscopy in those llamas.

Design

Prospective clinical trial.

Animals

Six adult castrated male llamas.

Procedure

After induction of general anesthesia, 3 surgical approaches to the abdomen were performed: left paralumbar, ventral midline, and right paralumbar. The abdomen was systematically examined, and anatomic features described. After recovery from anesthesia, all llamas were examined daily for 10 days and CBC was repeated 24, 72, and 120 hours after laparoscopy.

Results

Laparoscopy was successfully performed in all llamas by use of the ventral midline and right paralumbar approaches. The laparoscope was inadvertently placed into the left retroperitoneal space in 1 of the 6 llamas when the left paralumbar approach was used. Also, hemorrhage into the abdomen limited the view from the left side in another llama. Various approaches allowed viewing of the first and third forestomach compartments, liver, spleen, kidneys, small intestine, ileum, proximal loop of the ascending colon, spiral colon, and urinary bladder. Postoperative findings included subcutaneous emphysema and edema. Mean WBC count peaked 24 hours after surgery (mean, 23,500 cells/μl). Generally, neutrophil count increased and lymphocyte count decreased during the 120 hours after surgery.

Clinical Implications

Laparoscopy may be used for differentiation of medical and surgical lesions in the abdomen of llamas. The site for laparoscopy should be chosen on the basis of the most likely site of the suspected lesion.

Free access
in Journal of the American Veterinary Medical Association

SUMMARY

Milk antimicrobial residues are a serious concern for the dairy industry. Residues of the tetracycline family of antimicrobials have been reported in market milk by investigators, using radioimmunoassay and microbial receptor technology (hereafter referred to as the Charm II test). In response to these reports, an investigation was conducted to determine the potential of 3 extra-label routes of oxytetracycline (otc) administration to cause milk residues above the Food and Drug Administration safe value of 30 parts per billion (ppb). Lactating Holstein cows were administered otc once by use of 1 of 3 routes: iv at 16.5 mg/kg of body weight (n = 6); im at 11 mg/kg (n = 6); and intrauterine (iu) at 2 g in 500 ml of saline solution/cow (n = 6). Duplicate milk samples were collected at the milking prior to drug administration and for the next 13 milkings at 12-hour intervals. Concentrations of otc in milk samples were analyzed by use of the Charm II test for tetracyclines (lmit of otc detection, approx 5 ppb) and were compared with concentrations determined by use of a high-performance lquid chromatography (hplc) method (lower lmit of otc quantitation, approx 2 ppb).

The potential for milk otc residues above the Food and Drug Administration safe value of 30 ppb after treatment was considerably greater for the iv and im routes, compared with the iu route. Mean peak otc concentrations in milk at the first milking after treatment for the hplc and Charm II tests were approximately 3,700 to 4,200 ppb for the iv route, 2,200 to 2,600 ppb for the im route, and 186 to 192 ppb for the iu route, respectively.

Pharmacokinetic analysis, based on milk otc concentrations, indicated that the area under the curve (auc) and milk maximal concentration (Cmax) differed significantly (P < 0.001) among routes of administration. The auc was similar for iv and im administrations; values for both were greater than the auc for iu administration. The Cmax was greatest for iv, intermediate for im, and least for iu administration. There were significant (P ≤ 0.01) differences in auc between assay methods (Charm II vs hplc) for the iv route. Concentrations of otc in milk determined by the Charm II test were often greater than those determined by hplc.

Administration of otc to lactating cows via these routes is extra-label drug use. Failure to withhold the product from early milkings of cows administered otc by the iv or im route should be considered a potential cause of otc residues in market milk. Milk from nearly all cows contained otc (< 30 ppb), the Food and Drug Administration safe level, by 120 hours after otc administration. Use of appropriate withholding times and antibiotic residue testing is indicated to avoid otc residues.

Free access
in American Journal of Veterinary Research

Abstract

Objective

A microbial receptor assay method (MRAM; Charm II test) for β-lactam antibiotics and a liquid chromatography (LC) method with a detection limit of 2 to 5 ppb were evaluated for detection of ampicillin or amoxicillin residues in milk samples from individuell cows.

Design

The MRAM was compared to the LC in 2 respects. Measured concentrations of drugs were compared, as well as the classification of samples relative to the FDA tolerance value of 10 ppb.

Animals

A total of 6 clinically normal lactating Holstein cows were used per drug.

Procedure

Ampicillin trihydrate or amoxicillin trihydrate was administered at an extra-label dosage of 22 mg/kg of body weight, IM, once to each of 6 cows/drug. Milk samples were collected at milkings prior to and for 156 hours after drug administration. Drug concentrations in milk samples from individual cows were determined by use of the MRAM and LC tests. Additionally, the classification of milk samples relative to the presence or absence of residues above the FDA tolerance value was determined. Pharmacokinetic analysis was performed on derived milk drug concentrations.

Results

Concentration of ampicillin in milk samples from all cows was < 10 ppb by the MRAM and LC methods by the fourth milking (48 hours) after treatment with ampicillin. Values were < 10 ppb by both methods for all cows treated with amoxicillin by the sixth milking (72 hours) after treatment. For individual milk samples, significant differences were found between test methods in the proportion of positive (failing) tests; the MRAM had a higher proportion of presumptive positives.

Conclusions

Even at an extra-label dosage of 22 mg/kg, IM, milk residues > 10 ppb (the FDA tolerance value) were not detected beyond the label milk withholding times for ampicillin (48 hours) and amoxicillin (96 hours). When used for testing milk of individual cows by the control point procedure, the MRAM had a tendency to give presumptive positive test results for milk samples containing < 10 ppb ampicillin or amoxicillin as determined by LC. (Am J Vet Res 1996;57:73-78)

Free access
in American Journal of Veterinary Research

Summary

Clinical trials have shown that currently available commercial vaccines against porcine pleuropneumonia provide inconsistent, serotype-specific protection from the disease. Recovery from naturally acquired infection, however, provides solid, serotype cross-protective immunity. We examined various serum responses of pigs receiving 1 of 4 commercial vaccines or a cell extract, and compared the serologic responses of these pigs after challenge exposure with virulent Actinobacillus pleuropneumoniae serotype 1. Evaluation of serum included complement-mediated killing, opsonizing capacity, IgG titers to whole organisms, and cytotoxin neutralization titers. Pigs that received the cell extract had fewer clinical signs of pleuropneumonia than pigs in other vaccinated groups, and also were significantly (P< 0.05) better protected from development of lung lesions and death. Such vaccinates were the only pigs that developed significant (P< 0.05) serum antibody titers (ie, protective immune response) to whole-cell antigens and to cytotoxin.

Free access
in American Journal of Veterinary Research