Search Results

Abstract

Objective—To determine the value of serial measurements of peritoneal fluid lactate concentration (PFL) for detecting strangulating intestinal lesions (SLs) in referred horses with signs of colic.

Design—Retrospective cohort study.

Animals—94 horses with signs of colic.

Procedures—Medical records of horses evaluated between September 2006 and February 2010 because of signs of colic were reviewed. All included horses had ≥ 2 peritoneal fluid samples collected, including one at admission and another within 1 to 6 hours after admission. Of the 94 horses, 26 were assigned to the SL group on the basis of findings at surgery or necropsy and 68 were assigned to the nonstrangulating intestinal lesion group because their signs of colic resolved with medical management. Peritoneal fluid lactate concentration was measured by use of a handheld lactate monitor. Data were analyzed by use of univariable and multivariable logistic regression analysis.

Results—PFL at admission > 4 mmol/L, an increase in PFL over time, and especially an increase in PFL over time in horses with a PFL < 4 mmol/L at admission (OR, 62; sensitivity, 95%; specificity, 77%) were significant predictors of horses with an SL.

Conclusions and Clinical Relevance—Serially determined PFL was a strong predictor for differentiating horses with SLs from horses with nonstrangulating intestinal lesions. Given the high OR, sensitivity, and specificity of these tests, serially determined PFL may have potential as a screening test for identifying horses with SLs. Further evaluation of the clinical value of PFL for predicting SLs in a prospective, multicenter study is warranted.

Abstract

OBJECTIVE To evaluate the effect of volume of IV regional limb perfusion (IVRLP) on amikacin concentrations in synovial and interstitial fluid of horses.

ANIMALS 8 healthy adult horses.

PROCEDURES Each forelimb was randomly assigned to receive IVRLP with 4 mL of amikacin sulfate solution (250 mg/mL) plus 56 mL (total volume, 60 mL) or 6 mL (total volume, 10 mL) of lactated Ringer solution. Horses were anesthetized, and baseline synovial and interstitial fluid samples were collected. A tourniquet was placed, and the assigned treatment was administered via the lateral palmar digital vein. Venous blood pressure in the distal portion of the limb was recorded. Additional synovial fluid samples were collected 30 minutes (just before tourniquet removal) and 24 hours after IVRLP began; additional interstitial fluid samples were collected 6 and 24 hours after IVRLP began.

RESULTS 30 minutes after IVRLP began, mean amikacin concentration in synovial fluid was significantly greater for the large-volume (459 μg/mL) versus small-volume (70 μg/mL) treatment. Six hours after IVRLP, mean concentration in interstitial fluid was greater for the large-volume (723 μg/mL) versus small-volume (21 μg/mL) treatment. Peak venous blood pressure after large-volume IVRLP was significantly higher than after small-volume IVRLP, with no difference between treatments in time required for pressure to return to baseline.

CONCLUSIONS AND CLINICAL RELEVANCE Study findings suggested that large-volume IVRLP would deliver more amikacin to metacarpophalangeal joints of horses than would small-volume IVRLP, without a clinically relevant effect on local venous blood pressure, potentially increasing treatment efficacy.

Abstract

Abstract

Objective—To ascertain the frequency of ultrasonographic identification of liver at sites recommended for blind percutaneous liver biopsy in middle-aged horses and to determine whether the liver is obscured by other organs or too thin for safe sample collection at recommended locations.

Design—Prospective case series.

Animals—36 healthy middle-aged (between 6 and 18 years old) Quarter Horses or Quarter Horse crosses.

Procedures—Blood samples were collected from each horse and submitted for evaluation of liver function. Horses with any indication of liver dysfunction on serum biochemical analysis were excluded. The region just below a line drawn between the dorsal aspect of the tuber coxae and the point of the elbow joint in the right 11th, 12th, 13th, and 14th intercostal spaces (ICSs) was imaged by ultrasonography for the presence of liver. In each ICS, liver thickness and whether there was partial obstruction in viewing the liver caused by other abdominal or thoracic organs were recorded.

Results—39% (14/36) of horses had liver imaged on ultrasonographic examination in all of the 11th to 14th ICSs. None of the 36 horses had liver of adequate thickness (ie, liver thickness ≥ 3.5 cm) for biopsy in all of the imaged ICSs. For 22 horses in which the liver was not visible on ultrasonographic examination of an ICS, lung was imaged instead in 12 (55%) horses, intestine in 8 (36%), and both intestine and lung in 2 (9%).

Conclusions and Clinical Relevance—On the basis of the results of this study, the practice of blind percutaneous liver biopsy in horses is not recommended because of the risk of serious complications.

Abstract

Objective—To describe frequency, types, and clinical outcomes of extrapulmonary disorders (EPDs) in foals in which Rhodococcus equi infection was diagnosed, and to identify factors determined at the time of admission that differentiated foals that developed EPDs from foals with R equi infection identified only in the lungs.

Design—Retrospective case series.

Animals—150 foals aged 3 weeks to 6 months with a diagnosis of R equi infection.

Procedures—Medical records were reviewed for information on date of admission, signalment, history, clinical signs, diagnostic testing, treatment, duration of hospitalization, invoice, and outcome. For each EPD identified, further information was collected on the identification, location, treatment, and outcome of the lesion.

Results—Of 150 foals with R equi infections, 111 (74%) had at least 1 of 39 EPDs. Survival was significantly higher among foals without EPDs (32/39 [82%]) than among foals with EPDs (48/111 [43%]), but many EPDs were only recognized after death. Risk factors significantly associated with EPDs included referral status, duration of clinical signs prior to admission, leukocytosis, and neutrophilia. Foals with EPDs also had a higher heart rate and BUN concentration than foals without.

Conclusions and Clinical Relevance—Practitioners should recognize that extrapulmonary manifestations of R equi occur with high prevalence affecting diverse organ systems, that multiple systems are generally affected when EPDs occur, and that suspicion of R equi infection should prompt evaluation and monitoring of extrapulmonary sites. Improved recognition of the presence of these disorders will help practitioners to better advise their clients in the treatment and outcome of foals with R equi infections.

Abstract

Objective—To evaluate sensitivity and specificity of a multiplex polymerase chain reaction (PCR) assay for simultaneous detection of Rhodococcus equi and differentiation of strains that contain the virulence-associated gene (vapA) from strains that do not.

Sample Population—187 isolates of R equi from equine and nonequine tissue and environmental specimens and 27 isolates of bacterial species genetically or morphologically similar to R equi.

Procedure—The multiplex PCR assay included 3 gene targets: a universal 311-bp bacterial 16S ribosomal RNA amplicon (positive internal control), a 959-bp R equi-specific target in the cholesterol oxidase gene ( choE ), and a 564-bp amplicon of the vapA gene. Duplicate multiplex PCR assays for these targets and confirmatory singleplex PCR assays for vapA and choE were performed for each R equiisolate. An additional PCR assay was used to examine isolates for the vapB gene.

Results—Results of duplicate multiplex and singleplex PCR assays were correlated in all instances, revealing high specificity and reliability (reproducibility) of the vapA multiplex assay. Of the pulmonary isolates from horses with suspected R equi pneumonia, 97.4% (76/78) yielded positive results for vapA. Seven of 50 (14%) human isolates of R equi yielded positive results for vapA. Six human R equi isolates and 1 porcine isolate yielded positive results for vapB. No isolates with vapA and vapB genes were detected.

Conclusions and Clinical Relevance—The multiplex PCR assay is a sensitive and specific method for simultaneous confirmation of species identity and detection of the vapA gene. The assay appeared to be a useful tool for microbiologic and epidemiologic diagnosis and research. (Am J Vet Res 2005;66:1380–1385)

Abstract

Objective—To evaluate the effect of an indwelling nasogastric tube on gastric emptying of liquids in horses.

Animals—9 healthy adult horses.

Procedure—A randomized block crossover design was used. For treatment group horses, a nasogastric tube was placed and 18 hours later, acetaminophen was administered; the nasogastric tube remained in place until the experiment was complete. For control group horses, a nasogastric tube was passed into the stomach, acetaminophen was administered, and the nasogastric tube was removed immediately. Serial blood samples were collected 15 minutes before and after administration of acetaminophen. Serum concentration of acetaminophen was determined by use of fluorescence polarization immunoassay. The variables, time to maximum acetaminophen concentration (T_max) and the appearance constant for acetaminophen (K_app), were determined. The values for K_app and T_max in horses with and without prolonged nasogastric tube placement were compared.

Results—No significant difference was found in K_app between horses with and without prolonged nasogastric tube placement; the median difference in Kapp was 0.01 min^–1 (range, –0.48 to 0.80 min^–1). No significant difference was found in T_max between horses with and without prolonged nasogastric tube placement; the median difference in T_max was 5 minutes (range, –30 to 50 minutes). Reanalysis of data following the removal of possible outlier values from 1 horse resulted in a significant difference in T_max between horses with and without prolonged nasogastric tube placement.

Conclusions and Clinical Relevance—Although no clinically important impact of 18 hours of nasogastric intubation was found on gastric emptying in healthy horses, considerable variability in K_app and T_max was found among horses. (Am J Vet Res 2005;66:642–645)

Abstract

Objective—To determine the effect of azithromycin chemoprophylaxis on the cumulative incidence of pneumonia caused by Rhodococcus equi, age at onset of pneumonia, and minimum inhibitory concentration (MIC) of azithromycin for R equi isolates cultured from fecal and clinical samples.

Design—Controlled, randomized clinical trial.

Animals—338 foals born and raised at 10 equine breeding farms; each farm had a history of endemic R equi infections.

Procedures—Group 1 foals were control foals, and group 2 foals were treated with azithromycin (10 mg/kg [4.5 mg/lb], PO, q 48 h) during the first 2 weeks after birth. Foals were monitored for development of pneumonia attributable to R equi infection and for adverse effects of azithromycin. Isolates of R equi were tested for susceptibility to azithromycin.

Results—The proportion of R equi–affected foals was significantly higher for control foals (20.8%) than for azithromycin-treated foals (5.3%). Adverse effects of azithromycin treatment were not detected, and there were no significant differences between groups for the MICs of azithromycin for R equi isolates cultured from fecal or clinical samples.

Conclusions and Clinical Relevance—Azithromycin chemoprophylaxis effectively reduced the cumulative incidence of pneumonia attributable to R equi among foals at breeding farms with endemic R equi infections. There was no evidence of resistance to azithromycin. Nonetheless, caution must be used because it is possible that resistance could develop with widespread use of azithromycin as a preventative treatment. Further investigation is needed before azithromycin chemoprophylaxis can be recommended for control of R equi infections.

Abstract

Objective—To determine sex, breed, and age distributions in a population of horses with cervical vertebral compressive myelopathy (CVCM), compared with contemporaneous control horses.

Design—Retrospective case-control study.

Animals—811 horses with CVCM and 805 control horses.

Procedures—The Veterinary Medical Database was searched to identify horses with CVCM and contemporaneous control horses registered between July 1974 and August 2007. Admission date, admitting institution, sex, breed, age at the time of registration in the database, weight, and discharge status (alive, died, or euthanized) were recorded for each case and control horse.

Results—On the basis of results of multivariable logistic regression analysis, geldings and sexually intact males had a significantly higher likelihood of having CVCM than females (odds ratio [OR], 2.0 [95% confidence interval, 1.5 to 2.6]; and OR, 2.4 [95% confidence interval, 1.8 to 3.2], respectively). Thoroughbreds, Tennessee Walking Horses, and Warm-bloods were overrepresented in the CVCM group, compared with Quarter Horses. Horses that ranged from < 6 months to < 7 years of age had significantly higher odds of having CVCM, compared with horses ≥ 10 years of age.

Conclusions and Clinical Relevance—Sex, breed, and age predilections were detected in horses with CVCM. Improved understanding of these factors will aid clinical recognition of the disease in groups that may have a high prevalence of CVCM or were previously not recognized to be commonly affected. The results may also stimulate future investigations to further delineate etiopathogenesis, such as breed-related genetic causality.

Abstract

Objective—To quantify and compare geochemical factors in surface soils from horse-breeding farms with horses with pneumonia caused by Rhodococcus equi (affected farms) and horse-breeding farms with no history of pneumonia caused by R equi (unaffected farms).

Sample Population—Soil from 24 R equi-affected farms and 21 unaffected farms.

Procedure—Equine veterinary practitioners throughout Texas submitted surface soil samples from areas most frequented by foals, on R equi affected and unaffected horse-breeding farms in their practice. Soil samples were assayed for the following factors: pH, salinity, nitrate, phosphorus, potassium, calcium, magnesium, sodium, sulfur, zinc, iron, manganese, and copper. Median values for all factors were recorded, and differences between affected and unaffected farms were compared.

Results—Significant differences in soil factors were not detected between affected and unaffected farms; hence, there was no association between those factors and R equi disease status of the farms.

Conclusion and Clinical Relevance—The surface soil factors monitored in this study were not significant risk factors for pneumonia caused by R equi. As such, it is not possible to determine whether foals on a given farm are at increased risk of developing disease caused by R equi on the basis of these factors. Data do not support altering surface soil for factors examined, such as alkalinization by applying lime, as viable control strategies for R equi. (Am J Vet Res 2002;63:95–98)