Objective: To determine whether the concentration of airborne virulent Rhodococcus equi varied by location (stall vs paddock) and month on horse farms. Sample: Air samples from stalls and paddocks used to house mares and foals on 30 horse breeding farms in central Kentucky. Procedures: Air samples from 1 stall and 1 paddock were obtained monthly from each farm from January through June 2009. Concentrations of airborne virulent R equi were determined via a modified colony immunoblot assay. Random-effects logistic regression was used to determine the association of the presence of airborne virulent R equi with location from which air samples were obtained and month during which samples were collected. Results: Of 180 air samples, virulent R equi was identified in 49 (27%) and 13 (7%) obtained from stalls and paddocks, respectively. The OR of detecting virulent R equi in air samples from stalls versus paddocks was 5.2 (95% confidence interval, 2.1 to 13.1). Of 60 air samples, virulent R equi was identified in 25 (42%), 18 (30%), and 6 (10%) obtained from stalls during January and February, March and April, and May and June, respectively. The OR of detecting virulent R equi from stall air samples collected during May and June versus January and February was 0.22 (95% confidence interval, 0.08 to 0.63). Conclusions and Clinical Relevance: Foals were more likely to be exposed to airborne virulent R equi when housed in stalls versus paddocks and earlier (January and February) versus later (May and June) during the foaling season.

Objective: To determine the effects of oral prednisone administration with or without ultralow-dose acetylsalicylic acid on coagulation parameters in healthy dogs and to assess intraindividual variation in thromboelastography results. Animals: 14 healthy research dogs and 10 healthy client-owned dogs. Procedures: In a randomized controlled trial, research dogs underwent thromboelastography twice (3 days apart), and intraindividual variation in test results was calculated. Dogs were given prednisone (2 mg/kg/d, PO) plus acetylsalicylic acid (0.5 mg/kg/d, PO) or prednisone (2 mg/kg/d, PO) plus a placebo for 14 days, after which thromboelastography and other tests were repeated. Differences from preadministration (baseline) test results between and within groups were compared. In a separate trial, client-owned dogs also underwent thromboelastography twice 2 days apart to assess intraindividual variation in untreated dogs. Results: Intraindividual variation in thromboelastography results for research dogs was ≤ 10% for maximum amplitude (MA) and α angle. In the research dogs, MA and fibrinogen values significantly increased from baseline, whereas percentage lysis 30 minutes after attainment of the MA as well as antithrombin activity significantly decreased within each group. In the dogs that received prednisone plus a placebo, percentage lysis 60 minutes after attainment of the MA was significantly lower than at baseline. For all parameters for research dogs, there was no difference between groups for change from baseline. Intraindividual variation in findings for client-owned dogs was similar to the variation for research dogs. Conclusions and Clinical Relevance: Prednisone administration resulted in hypercoagulability in healthy dogs as indicated by an increase in MA and plasma fibrinogen concentration and a decrease in antithrombin activity. Concurrent ultralow-dose acetylsalicylic acid use had no effect on measured thromboelastography values. The high intraindividual variation in some thromboelastography parameters may preclude routine use of this technique in clinical practice.

Objective: To determine the pharmacokinetics of methylprednisolone (MP) and the relationship between MP and hydrocortisone (HYD) concentrations in plasma and urine after intra-articular (IA) administration of 100 or 200 mg of MP acetate (MPA) to horses. Animals: Five 3-year-old Thoroughbred mares. Procedures: Horses exercised on a treadmill 3 times/wk during the study. Horses received 100 mg of MPA IA, then 8 weeks later received 200 mg of MPA IA. Plasma and urine samples were obtained at various times for 8 weeks after horses received each dose of MPA; concentrations of MP and HYD were determined. Pharmacokinetic-pharmacodynamic estimates for noncompartmental and compartmental parameters were determined. Results: Maximum concentration of MP in plasma was similar for each MPA dose; concentrations remained greater than the lower limit of quantitation for 18 and 7 days after IA administration of 200 and 100 mg of MPA, respectively. Maximum concentration and area under the observed concentration-time curve for MP in urine were significantly higher (approximately 10-and 17-fold, respectively) after administration of 200 versus 100 mg of MPA. Hydrocortisone concentration was below quantifiable limits for ≥ 48 hours in plasma and urine of all horses after administration of each MPA dose. Conclusions and Clinical Relevance: Pharmacokinetics of MP may differ among IA MPA dosing protocols, and MP may be detected in plasma and urine for a longer time than previously reported. This information may aid veterinarians treating sport horses. Further research is warranted to determine whether plasma HYD concentration can aid identification of horses that received exogenous glucocorticoids.

Objective: To measure the effect of induced myopia on field trial performance in dogs. Animals: 7 Labrador Retrievers and 1 Chesapeake Bay Retriever trained in field trial competition. Procedures: Dogs were commanded to retrieve targets at 137.2 m (150 yards). Each dog participated in 3 trials while their eyes were fitted with 0- (plano), +1.50-, or +3.00-diopter (D) contact lenses, applied in random order. Retrieval times were measured objectively, and dog performances were evaluated subjectively by masked judges. Results: Retrieval times were significantly faster with plano lenses than with +1.50- or +3.00-D lenses, but there were no significant differences in times between +1.50- and +3.00-D lenses. Masked judges assigned the best performance scores to dogs with plano lenses and the lowest scores to dogs fitted with +3.00-D lenses. Conclusions and Clinical Relevance: Even mild myopic defocusing had a significant negative impact on both the subjective and objective assessments of dogs' performances. Dogs with demanding visual tasks or signs of visual deterioration should be evaluated retinoscopically to determine the refractive state because they may have ametropia.

Objective: To describe the anatomic features of dentition and surrounding structures of the head in rabbits assessed by use of a newly developed micro-computed tomography (CT) device. Sample: Cadavers of 7 clinically normal adult Dendermonde White domestic rabbits raised for human consumption. Procedures: The rabbits were slaughtered in a slaughterhouse, flayed, and decapitated; the rabbit heads were frozen for micro-CT examination. Transverse images were obtained from the nares to the occipital condyles with a custom-designed micro-CT scanner built at the Ghent University Centre for X-ray Tomography. Scan settings were chosen to highlight bony structures on the basis of the designers' experience. The micro-CT images were reviewed, and all recognizable anatomic features were labeled. Afterward, micro-CT images were used to create 3-D reconstructions by use of a custom-developed reconstruction package and 3-D rendering with dedicated software. Results: Microstructures of the bones and teeth were clearly visible on micro-CT images. Conversely, soft tissue contrast was relatively poor on these images. Conclusions and Clinical Relevance: Micro-CT appeared to be a promising technique for appropriate diagnosis of dental disease in rabbits. Further research is needed to determine the clinical applications of micro-CT imaging.

Objective: To determine whether high-frequency diagnostic ultrasonography is useful for assessment of skin thickness in Shar-Peis. Animals: 10 healthy Shar-Peis and 10 healthy Beagles used as controls. Procedures: Ultrasonographic examination of the skin was performed on 4 cutaneous sites by use of a 13-MHz linear-array transducer, and the mean of 3 measurements was calculated. Ultrasonography results were compared with histologic findings of skin specimens stained with H&E, Alcian blue at a pH of 2.5, and Masson trichrome stains, with histometric measurements of skin thickness made by use of a microscope, and with measurements of skin thickness made by use of a plicometer. Ultrasonograpy results were also compared via age and sex of selected animals. Results: A clear correlation was detected between ultrasonography results and results of histologic and histometric analysis in both groups. In Shar-Peis, no correlation was found between ultrasonography results and age and sex, whereas in Beagles, a weak positive correlation was found only between skin thickness in dorsal cervical and frontal (on the rostral margins of the supraorbital processes) regions and age. A positive overall correlation was found in Shar-Peis between measurements made via ultrasonography and plicometery. Conclusions and Clinical Relevance: Ultrasonography was a useful tool to assess skin thickness, and in Shar-Peis, it might be considered a valid alternative to invasive methods such as histologic examination to objectively estimate the severity of hereditary cutaneous hyaluronosis.

Objective: To determine reference ranges for serum cobalamin (Cbl), urine methylmalonic acid (uMMA), and plasma total homocysteine (tHcys) concentrations and to compare values for healthy control dogs with values for Border Collies (BCs), a breed in which hereditary cobalamin deficiency has been identified. Animals: 113 BCs, 35 healthy control dogs fed a typical diet, and 12 healthy dogs fed a bone and raw food diet exclusively. Procedures: Urine and blood samples were obtained from each dog and Cbl, uMMA, and tHcys concentrations were determined. Results: Reference ranges for Cbl (261 to 1,001 ng/L), uMMA (0 to 4.2 mmol/mol of creatinine), and tHcys (4.3 to 18.4 μmol/L) concentrations were determined. Four BCs had a Cbl concentration lower than the assay detection limit (150 ng/L); median uMMA and tHcys concentrations in these dogs were 4,064 mmol/mol of creatinine and 51.5 μmol/L, respectively. Clinical abnormalities included stunted growth, lethargy, anemia, and proteinuria. Abnormalities improved after administration of cobalamin. Of the 109 healthy BCs with Cbl and tHcys concentrations within reference ranges, 41 (37.6%) had a high uMMA concentration (range, 5 to 360 mmol/mol). Results for dogs fed raw food were similar to those for control dogs. Conclusions and Clinical Relevance: Hereditary cobalamin deficiency is a rare disease with various clinical signs. The finding of methylmalonic aciduria in healthy eucobalaminemic BCs and BCs with clinical signs of Cbl deficiency was surprising and indicated these dogs may have defects in intracellular processing of Cbl or intestinal Cbl malabsorption, respectively. Studies investigating Cbl absorption and metabolic pathways are warranted.

Objective: To investigate the effects of gonadectomy on collagen homeostasis in cranial cruciate ligaments of male rabbits. Animals: 30 sexually immature (16-week-old) male New Zealand White rabbits. Procedures: Rabbits were randomly assigned to 5 groups of 6 rabbits each: sexually intact, placebo (control group); castrated, placebo; castrated, testosterone; castrated, dihydrotestosterone; and castrated, 17β-estradiol (E2). Control rabbits underwent a sham operation, and all other rabbits underwent gonadectomy. At the time of gonadectomy, the placebo and sex hormones were administered via slow-release pellets implanted subcutaneously as assigned. After 21 days of hormone supplementation, measurements were obtained of serum testosterone and E2 concentrations, ligament collagen characteristics, and androgen receptor, estrogen receoptor α, and matrix metalloproteinase expression. Results: Following gonadectomy and hormone supplementation, the treatment groups differed in serum testosterone and E2 concentrations to various degrees. Collagen concentrations were lower and fiber diameters higher in the absence of sex hormones, in association with the degrees of estrogen receptor a and androgen receptor expression. Although differences were detected among the groups in matrix metalloproteinase expression, these differences were not significant. Conclusions and Clinical Relevance: Sex hormones appeared to play a role in cranial cruciate ligament homeostasis in male rabbits. Physiologic changes triggered by the lack of sex hormones following gonadectomy in sexually immature rabbits may potentially predispose those rabbits to orthopedic injuries.

Objective: To determine pharmacokinetics after IV and oral administration of a single dose of tramadol hydrochloride to Hispaniolan Amazon parrots (Amazona ventralis). Animals: 9 healthy adult Hispaniolan Amazon parrots (3 males, 5 females, and 1 of unknown sex). Procedures: Tramadol (5 mg/kg, IV) was administered to the parrots. Blood samples were collected from −5 to 720 minutes after administration. After a 3-week washout period, tramadol (10 and 30 mg/kg) was orally administered to parrots. Blood samples were collected from −5 to 1,440 minutes after administration. Three formulations of oral suspension (crushed tablets in a commercially available suspension agent, crushed tablets in sterile water, and chemical-grade powder in sterile water) were evaluated. Plasma concentrations of tramadol and its major metabolites were measured via high-performance liquid chromatography. Results: Mean plasma tramadol concentrations were > 100 ng/mL for approximately 2 to 4 hours after IV administration of tramadol. Plasma concentrations after oral administration of tramadol at a dose of 10 mg/kg were < 40 ng/mL for the entire time period, but oral administration at a dose of 30 mg/kg resulted in mean plasma concentrations > 100 ng/mL for approximately 6 hours after administration. Oral administration of the suspension consisting of the chemical-grade powder resulted in higher plasma tramadol concentrations than concentrations obtained after oral administration of the other 2 formulations; however, concentrations differed significantly only at 120 and 240 minutes after administration. Conclusions and Clinical Relevance: Oral administration of tramadol at a dose of 30 mg/kg resulted in plasma concentrations (> 100 ng/mL) that have been associated with analgesia in Hispaniolan Amazon parrots.

Objective: To determine the prevalence and types of tooth resorption in dogs with oral tumors and to compare findings with those for control dogs. Animals: 101 dogs with oral tumors and 128 control dogs that did not have oral tumors and for which dental radiographs were available. Procedures: Exclusion criteria for dogs included systemic disease, long-term administration of anti-inflammatory drugs, traumatic occlusion, severe semigeneralized or generalized periodontitis, and endodontic disease. For each dog with an oral tumor, histologic sections of biopsy specimens of tumors were examined. Dental radiographic images of dogs were examined, and the presence and type of tooth resorption were determined for each tooth. Statistical analyses were performed to compare data regarding prevalence of tooth resorption. Results: Teeth at tumor sites in dogs with nonodontogenic tumors were significantly more frequently affected with external inflammatory resorption, compared with teeth at tumor sites in dogs with odontogenic tumors. Teeth at sites distant from tumors in dogs with oral tumors were 3.2 times as likely to have external surface resorption (OR, 3.2; 95% confidence interval, 1.3 to 7.9) and 83.4 times as likely to have external inflammatory resorption (OR, 83.4; 95% confidence interval, 9.7 to 719.6) as teeth in control dogs. Conclusions and Clinical Relevance: Resorption of teeth at tumor sites and at sites distant from tumors was common in dogs with oral tumors. Results of the present study will contribute to an understanding of the complex effects of oral tumors on local and distant hard tissues.