Association of leukergy (in vitro leukocyte aggregation) with systemic inflammation in dogs and cats (2017-2022).

BACKGROUND: Leukergy is the phenomenon of aggregation of leukocytes on a peripheral blood film, and in humans, it is used as an indicator of systemic inflammation and infection. OBJECTIVES: To assess the association of leukergy on blood film examination with biochemical and clinical evidence of systemic inflammation, infection, neoplasia, or specific organ system disease. METHODS: A case-control study using retrospective analysis (2017-2022) identified all canine and feline patients that had been presented to an academic referral center with a finding of leukergy on peripheral blood film and an equal number of species-matched controls. RESULTS: A total of 127 cases (canine n = 44, feline n = 83) were identified, as well as 127 controls. Feline samples were 7.6× more likely to exhibit leukergy (0.019%) than canine (0.0025%). A positive association was noted between leukergy and higher globulin concentrations in dogs (marginal difference 0.5 mg/dL, P = .016) and cats (marginal difference 0.67 mg/dL, P = <.001). Cats with leukergy had higher WBC counts and were less likely to be diagnosed with cardiac or urinary tract disease than controls. Dogs with leukergy had lower WBC counts and were more likely to be febrile but were less likely to have urinary tract disease than controls. No association was found with neutrophil toxic change or band forms, systemic antimicrobial therapy, or signalment. CONCLUSIONS: We conclude that there is a positive association between increased globulin concentrations and leukergy and inconsistent associations between leukergy and other markers of inflammation or infection. Leukergy is rare overall but markedly more common in cats than dogs.

Spindle-cell thymoma colliding with a bronchogenic cyst in a Yorkshire terrier.

An 8-year-old male Yorkshire terrier was presented to the Tufts Veterinary Hospital for evaluation of increased respiratory effort. A mediastinal mass composed of a spindle-cell thymoma within a bronchogenic cyst was diagnosed with computed tomography thoracic imaging, ultrasound-guided fine-needle aspirate biopsy, and histopathologic evaluation after surgical removal. Histologic evaluation showed a multilocular cyst structure as well as a mass characterized by spindle to polygonal thymic epithelial cells. The cyst was characterized by a lining of ciliated pseudostratified respiratory epithelium. To the authors' knowledge, this is the first report of a spindle-cell thymoma being associated with a mediastinal bronchogenic cyst in a dog.

Equine Granulocytic Anaplasmosis.

Equine granulocytic anaplasmosis is a clinically significant and common disease of equids that has a broader prevalence than was once thought. The most common clinical signs include high fever and edema, with mild to mderate thrombocytopenia and lymphopenia typically noted on complete blood count. Subclinical cases are reported and many are self-limiting. Rare clinical presentations include neurologic disease, vasculitis, dysphagia, rhabdomyolysis, or bicavitary effusion. Most cases resolve rapidly with appropriate antimicrobial intervention.

Modification of empirical antimicrobial regimens in large animal medicine.

BACKGROUND: Empirical antimicrobial regimens can be modified following new diagnostic information or when empirical treatment fails. Little is known about the frequency or clinical context in which these modifications occur. We characterised these modifications in a large animal hospital to identify when antimicrobial use could be optimised. METHODS: Chart reviews were performed for all inpatients and outpatients administered antimicrobials at a large animal veterinary referral and teaching hospital in 2017-2018 (n=1163 visits) to determine when and why empirical regimens were modified. Multinomial logistic regression was performed to identify factors associated with reasons for modification. RESULTS: Empirical antimicrobial regimens were modified in 17.3 per cent of visits. The main reasons were parenteral-oral conversions in horses and failure of disease prevention or treatment in ruminants. Empirical therapy for disease prevention was more likely to be modified because of complications in ruminants and in animals on the emergency/critical care service. Empirical therapy for disease treatment was more often modified for reasons other than de-escalation in ruminants and in animals with longer lengths of stay. CONCLUSIONS: Empirical antimicrobial regimens were modified infrequently and mostly for purposes of parenteral-oral conversion in horses and lack of response in ruminants. De-escalation of antimicrobials administered for disease treatment, when guided by diagnostics, is a major tenet of judicious antimicrobial use. However, more research is needed to determine when and how antimicrobial regimens administered for disease prevention should be modified.

Equine Inflammatory Markers in the Twenty-First Century: A Focus on Serum Amyloid A.

Serum amyloid A (SAA) is a marker of inflammation and infection in the horse that can be assessed in the field, with rapid and marked changes seen following initiation of an inflammatory stimulus. This quality of SAA also makes its clinical use challenging, because even small inflammatory conditions can cause large changes in SAA levels. Review of the current literature provides guidelines for responses of SAA to various conditions, which can be applied to specific clinical cases. The practitioner is encouraged to use SAA in conjunction with physical examination and other diagnostic modalities to guide treatment and monitor case progression.

Antimicrobial prescribing patterns of clinicians and clinical services at a large animal veterinary teaching hospital.

OBJECTIVE: To characterize antimicrobial prescribing patterns of clinicians and clinical services at a large animal veterinary teaching hospital and identify factors associated with antimicrobial prescribing. ANIMALS: All large animals (ie, equids, bovids, sheep, goats, camelids, swine, and cervids) evaluated at the New Bolton Center hospital at the University of Pennsylvania from 2013 through 2018. PROCEDURES: In a cross-sectional study design, data on antimicrobial use by clinicians and clinical services were collected from administrative and billing records. Multivariable regression modeling was performed to identify factors associated with antimicrobial prescribing patterns. RESULTS: Antimicrobials and critically important antimicrobials of the highest priority were dispensed in 42.1% (9,853/23,428) and 24.0% (2,360/9,853) of visits, respectively, and these proportions differed significantly among clinicians. Per visit, the median (interquartile [25th to 75th percentile] range) number of animal-defined daily doses dispensed was 3.6 (0.8 to 11.1) and the mean (SD) number of antimicrobial classes dispensed was 2.0 (1.3). Patient species, age, affected body system, and duration of hospitalization as well as submission of specimens for bacterial culture were significantly associated with prescribing patterns. CONCLUSIONS AND CLINICAL RELEVANCE: The frequency and quantity of antimicrobials prescribed differed significantly among clinicians within and across services, even for animals with clinical signs affecting the same body system. Patient- and visit-level factors explained some but not all of the heterogeneity in prescribing patterns, suggesting that other clinician-specific factors drove such practices. More research is needed to better understand antimicrobial prescribing patterns of clinicians, particularly in situations for which no antimicrobial use guidelines have been established.

Characterization of antimicrobial prescription frequency and diversity in a large animal veterinary medical teaching hospital.

Antimicrobials are commonly used in veterinary medicine for therapeutic and prophylactic purposes, but little is known about the frequency with which they are prescribed or the quantity administered, especially in large animals. Furthermore, there are no standardized metrics for characterizing antimicrobial use, which can lead to confusion when comparing antimicrobial use among different units (institution, clinical service, clinician). Because there is no gold standard metric, the most comprehensive characterization of antimicrobial use will be achieved using a variety of metrics. The goal of this study was to characterize antimicrobial use from 2013 to 2018 at a tertiary care teaching hospital for large animals using different metrics, including novel ones. We found that at least one antimicrobial was prescribed in 42% of visits and that antimicrobials were prescribed at a rate of 919 animal-defined daily doses (ADDs) per 1000 animal days. A median of 3.6 ADDs and a mean of 2 different classes of antimicrobial were prescribed per patient, and penicillin was the most commonly used antimicrobial. The prescription diversity, a metric accounting for richness and evenness (similarity of frequencies) of different types of antimicrobials, was 0.82, with 1.0 representing maximal richness and diversity. Antimicrobial use differed significantly by species and by organ system affected for all metrics, though in general antimicrobials were prescribed most frequently and with the largest amounts in animals presenting with integumentary or respiratory signs. Many of our findings were consistent with those of other studies examining antimicrobial use in the species represented in our patient population, but more research is needed to determine how to best characterize antimicrobial use and assess appropriateness of prescribing.

Effect of long-term oral administration of a low dosage of clenbuterol on body fat percentage in working and nonworking adult horses.

OBJECTIVE: To determine the anabolic and lipolytic effects of a low dosage of clenbuterol administered orally in working and nonworking equids. ANIMALS: 8 nonworking horses and 47 polo ponies in active training. PROCEDURES: Each polo pony continued training and received either clenbuterol (0.8 µg/kg) or an equal volume of corn syrup (placebo) orally twice daily for 21 days, and then was evaluated for another 21-day period. Nonworking horses received clenbuterol or placebo at the same dosage for 21 days in a crossover trial (2 treatments/horse). For working and nonworking horses, percentage body fat (PBF) was estimated before treatment and then 2 and 3 times/wk, respectively. Body weight was measured at intervals. RESULTS: Full data sets were not available for 8 working horses. For working horses, a significant treatment effect of clenbuterol was detected by day 3 and continued through the last day of treatment; at day 21, the mean change in PBF from baseline following clenbuterol or placebo treatment was -0.80% (representing a 12% decrease in PBF) and -0.32%, respectively. By day 32 through 42 (without treatment), PBF change did not differ between groups. When treated with clenbuterol, the nonworking horses had a similar mean change in PBF from baseline from day 6 onward, which peaked at -0.75% on day 18 (an 8% decrease in PBF). Time and treatment had no significant effect on body weight in either experiment. CONCLUSIONS AND CLINICAL RELEVANCE: Among the study equids, long-term low-dose clenbuterol administration resulted in significant decreases in body fat with no loss in body weight.

Clinical and diagnostic features of inflammatory airway disease subtypes in horses examined because of poor performance: 98 cases (2004-2010).

OBJECTIVE: To determine whether there are important differences relating to seasonality of signs or clinical features between subtypes of inflammatory airway disease (IAD) in horses caused by neutrophilic and eosinophilic-mastocytic inflammation having dissimilar etiopathologic pathways. DESIGN: Retrospective case series. ANIMALS: 98 horses. PROCEDURES: Data were compiled from medical records of horses examined because of poor performance from 2004 through 2010. Horses underwent a standardized high-speed treadmill test, lameness evaluation, cardiac evaluation, and postexercise bronchoalveolar lavage (BAL). By means of standard BAL cytologic criteria, horses were divided into 4 groups: eosinophilic-mastocytic inflammation, neutrophilia only, mixed inflammation, or no inflammation (control). Associations between IAD subtype and clinical parameters were investigated. RESULTS: Data for 98 horses were obtained, including age, career, season of admission, and results of hematologic evaluation, high-speed treadmill arterial blood gas analysis, upper airway endoscopy, cardiologic evaluation, and BAL. Cytologic evidence of IAD was found in 81% (79/98) of the horses, and 30% (30/98) had erythrocytes present in the BAL fluid after exercise. Horses in the eosinophilic-mastocytic inflammation and mixed-inflammation groups were significantly more likely to be Thoroughbred than Standardbred and have larger amounts of mucus in their BAL fluid. No significant differences were found in season of evaluation, results of exercising blood gas analyses, or comorbidities. CONCLUSIONS AND CLINICAL RELEVANCE: No association between season and cytologic profile of BAL fluid and no major effects of IAD subtype on pulmonary gas exchange during exercise were seen in this population of horses.

Detection of two equine trisomies using SNP-CGH.

Chromosomal aberrations in the horse are known to cause congenital abnormalities, embryonic loss, and infertility. While diagnosed mainly by karyotyping and FISH in the horse, the use of SNP array comparative genome hybridization (SNP-CGH) is becoming increasingly common in human diagnostics. Normalized probe intensities and allelic ratios are used to detect changes in copy number genome-wide. Two horses with suspected chromosomal abnormalities and six horses with FISH-confirmed aberrant karyotypes were chosen for genotyping on the Equine SNP50 array. Karyotyping of the first horse indicated mosaicism for an additional small, acrocentric chromosome, although the identity of the chromosome was unclear. The second case displayed a similar phenotype to human disease caused by a gene deletion and so was chosen for SNP-CGH due to the ability to detect changes at higher resolutions than those achieved with conventional karyotyping. The results of SNP-CGH analysis for the six horses with known chromosomal aberrations agreed completely with previous karyotype and FISH analysis. The first undiagnosed case showed a pattern of altered allelic ratios without a noticeable shift in overall intensity for chromosome 27, consistent with a mosaic trisomy. The second case displayed a more drastic change in both values for chromosome 30, consistent with a complete trisomy. These results indicate that SNP-CGH is a viable method for detection of chromosomal aneuploidies in the horse.

Flow rates of large animal fluid delivery systems used for high-volume crystalloid resuscitation.

OBJECTIVES: Large animal species in states of shock can require particularly high flow rates for volume resuscitation and the ability to deliver adequate volumes rapidly may be a rate-limiting step. The objective of this study was to determine the maximum flow rates of common combinations of IV catheter, extension set, and fluid administration sets. SETTINGS: University veterinary teaching hospital. DESIGN: In vitro experimental study. INTERVENTIONS: Maximum flow rates were measured using combinations of 4 IV catheters (3 14-Ga and a single 10-Ga), 2 IV catheter extension sets (small bore and large bore), and 2 types of fluid administration sets (standard 2-lead large animal coiled IV set and nonpressurized 4-lead arthroscopic irrigation set). The catheter, extension sets, and administration sets were arranged in 16 configurations, and flow rates measured in triplicate using tap water flowing into an open receptacle. MEASUREMENTS AND MAIN RESULTS: Flow rates ranged from 7.4 L/h with an over-the-wire 14-Ga catheter, small-bore extension, and coil set, to 51.2 L/h using a 10-Ga catheter, no extension, and arthroscopic irrigation set. There was an increase of 1.3-8.9% in flow rates between the large- versus small-bore extension sets. Crystalloid delivery in vivo to an adult horse was 21% slower (9.1 L/h versus 11.5 L/h) than the corresponding in vitro measurement. CONCLUSIONS: Extremely high flow rates can be achieved in vitro using large-bore catheters and delivery systems, although the clinical necessity for rates >50 L/h has not been determined. The use of large-bore extension sets resulted in only a minimal increase in flow rate.

Effect of prolonged administration of clenbuterol on airway reactivity and sweating in horses with inflammatory airway disease.

OBJECTIVE: To determine whether prolonged administration of clenbuterol results in tachyphylaxis, specifically regarding its bronchoprotective properties and effect on sweating in horses. ANIMALS: 8 Thoroughbreds with inflammatory airway disease. PROCEDURES: In a crossover design, horses received clenbuterol (0.8 µg/kg, p.o., q 12 h) or placebo for 21 days, with a washout period of ≥ 30 days between the 2 treatments. Airway reactivity was evaluated by use of flowmetric plethysmography and histamine broncho-provocation before (day 0; baseline) and every 7 days after the start of treatment. Sweat function was evaluated via response to epinephrine administered ID before and every 10 days after the start of treatment. RESULTS: The concentration of histamine required to increase total airway obstruction by 35% (PC35) was significantly reduced during treatment with clenbuterol (mean change, 11.5 mg/mL), compared with during administration of the placebo (mean change, -1.56 mg/mL), with a peak effect at 14 days. Tachyphylaxis was evident by day 21, with 7 of 8 horses having a PC35 below the baseline value (mean change, -0.48 mg/mL), which returned to baseline values during the washout period. No effect of clenbuterol was seen in sweat response to epinephrine administration. CONCLUSIONS AND CLINICAL RELEVANCE: Clenbuterol initially reduced airway sensitivity to inhaled histamine, but tachyphylaxis that resulted in increased airway reactivity was evident by day 21. Although no effects on sweating were detected, the technique may not have been sensitive enough to identify subtle changes. Prolonged administration of clenbuterol likely results in a clinically important reduction in its bronchodilatory effects.

Multinodular pulmonary fibrosis in five horses.

CASE DESCRIPTION: 5 horses were evaluated because of decreased appetite, weight loss, fever, cough, tachypnea, and respiratory distress. CLINICAL FINDINGS: Tachycardia, tachypnea, increased respiratory effort, lethargy, fever, poor body condition, and nasal discharge were detected in various combinations on initial physical examination. Evaluation of the lower portion of the respiratory tract via radiography and ultrasonography revealed a severe nodular interstitial pattern. Histologic examination of lung tissue revealed interstitial expansion of alveolar parenchyma with collagen, intraluminal accumulation of neutrophils and macrophages within the alveoli, and occasional intranuclear inclusion bodies within alveolar macrophages. Equine herpesvirus type 5 was detected in samples of lung tissue, bronchoalveolar lavage fluid, or both via polymerase chain reaction assay in all cases. A diagnosis of equine multinodular pulmonary fibrosis (EMPF) was established. TREATMENT AND OUTCOME: Horses were provided supportive treatment and were administered a variety of medications including corticosteroids and acyclovir. Two horses survived and returned to their previous level of activity. Three horses were euthanized because of either deterioration of clinical condition (n=2) or failure to improve within 4 weeks of initiation of treatment (1). CLINICAL RELEVANCE: EMPF should be considered as a differential diagnosis for adult horses with interstitial pneumonia and should be suspected on the basis of characteristic radiographic, ultrasonographic, and histopathologic findings. Equine herpesvirus type 5 is found in association with EMPF; although the exact pathogenic role this virus plays in EMPF is unknown, equine herpesvirus type 5 may be an etiologic agent or cofactor in the development of EMPF.

Eastern equine encephalitis in 9 South American camelids.

BACKGROUND: Eastern equine encephalitis (EEE) virus is a mosquito-borne togavirus (alphavirus) that causes severe (often fatal) encephalitis in many mammalian species, but it has not been reported previously in South American camelids. HYPOTHESIS: South American camelids can become naturally infected with EEE virus and show encephalitic signs similar to those observed in other affected species. ANIMALS: Nine cases (8 alpacas and 1 llama, aged 3.5 weeks to 12 years) were identified; 4 of 9 were 510 weeks old. All cases were from the East Coast of the United States and presented in late summer and fall. METHODS: A retrospective study was performed to include confirmed cases of EEE in camelids in North America before 2006. RESULTS: Eight of nine (89%) camelids died or were euthanized in extremis, with the mean time to death of 2 days. Clinical signs were consistent with encephalitis and included fever, lethargy, ataxia, seizures, recumbency, torticollis, opisthotonus, and vestibular signs. No consistent hematologic abnormalities were identified, and cerebrospinal fluid contained an increased protein concentration in the single camelid analyzed. No successful therapy was identified. EEE was confirmed by alphavirus detection by using immunohistochemistry (IHC) and polymerase chain reaction (PCR) in the central nervous system (CNS) and by serology. Findings included polioencephalitis with lymphocytic perivascular cuffing; neutrophil infiltration; gliosis; neuron satellitosis; necrosis; and edema, with intracytoplasmic alphavirus within neurons and glial cells. No virus was detected in extraneural tissues. CONCLUSIONS AND CLINICAL IMPORTANCE: In endemic areas, EEE should be considered a differential diagnosis for young and adult camelids with CNS disease. Brain histopathology with indirect IHC or PCR is diagnostic.

Evidence-based gastrointestinal medicine in horses: it's not about your gut instincts.

The use of an evidence-based approach allows veterinary clinicians to assess questions that are clinically relevant to the diagnosis and treatment of equine gastrointestinal tract disease. This approach involves formulating a clinical question, searching the literature, and answering the question with the best available evidence, with the results summarized as a clinical "bottom line." This article is organized to reinforce the principle that the cornerstone of evidence-based medicine is the clinical question. Specific questions are further categorized as to topic, with epidemiologic risk factors, diagnostic process, clinical examination, differential diagnosis, diagnostic tests, treatment, harm, prognosis, and prevention as general themes. The topics covered in this article are by no means exhaustive but give an example of how the veterinary literature can be used to answer clinically important questions in an evidence-based manner.

Acute recumbency associated with Anaplasma phagocytophilum infection in a horse.

An 11-year-old Hanoverian-cross gelding was evaluated because of acute onset of ataxia, recumbency, and fever. At the stable, this and other horses had recently been infested with ticks. Results of analysis of a sample of CSF were within reference limits, but hematologic abnormalities included lymphopenia, thrombocytopenia, mild anemia, and intracytoplasmic inclusion bodies in neutrophils that were consistent with Anaplasma phagocytophilum (previously Ehrlichia equi). Results of serum biochemical analyses were characteristic of infection and included high, unconjugated bilirubin concentration. Other common causes of recumbency in horses, such as equine protozoal myeloencephalitis, infection with eastern or western equine encephalitis viruses and equine herpesvirus-1, West Nile viral encephalitis, trauma, and metabolic disease, were ruled out. The horse responded quickly to i.v. administration of oxytetracycline and recovered fully within 6 days.