Utility of serum amyloid A in monitoring clinical response to antimicrobial treatment in horses with bacterial pneumonia.

BACKGROUND: Serum amyloid A (SAA) is a major acute phase protein in horses which could be a useful tool for assessing clinical response to treatment of bacterial pneumonia in adult horses. OBJECTIVES: To monitor SAA concentration in response to treatment and identify associations among SAA concentration, WBC and neutrophil counts, and fibrinogen in bacterial pneumonia in adult horses. ANIMALS: Eighteen adult horses with bacterial pneumonia. METHODS: Prospective clinical study. Horses hospitalized with bacterial pneumonia were enrolled and SAA concentration and vital signs were assessed daily. SAA concentration was measured by a handheld meter. CBC and plasma fibrinogen were assessed on days 0, 1, and 2, then every 3 days until discharge. Data were not normally distributed and therefore were log transformed. Log-transformed data were analyzed and comparisons were performed on LSMeans by the 2-sided Student's t-test at the 5% level of significance. RESULTS: Geometric mean SAA concentration on day 0 was 537 µg/mL (SE 383 µg/mL). Geometric mean SAA concentration decreased significantly over time (P = .0001), peaking at day 2 (geomean 1038 µg/mL, SE 261.7 µg/mL) and decreasing until discharge. Plasma concentration of fibrinogen (P = .06), neutrophil count (P = .48), and WBC count (P = .07) did not change significantly over time. CONCLUSIONS AND CLINICAL IMPORTANCE: SAA concentration decreased significantly over the course of treatment and correlated with clinical improvement of pneumonia whereas fibrinogen, neutrophil, and WBC counts did not.

Variations in haematological and biochemical parameters in healthy ponies.

BACKGROUND: Breed specific reference ranges for selected blood parameters are recommended for proper interpretation of blood tests, but there are only few reports dealing with ponies. The purpose of this study was to investigate if blood parameters differ among ponies' classes and to check if general normal values for equine species are applicable to ponies. RESULTS: All, except total protein concentration, biochemical parameter significantly (p < 0.05) differed among ponies' classes. The most pronounced difference was noted in blood lactate concentrations, higher (p < 0.001) in the smallest ponies (class A). In all groups of ponies muscle enzymes (aspartate aminotransferase and creatine kinase) and urea were high when compared to normal values for equine species, but triglycerides and creatinine were low. Blood lactate concentration was high in comparison with normal values for horses only in class A ponies'. CONCLUSIONS: In healthy ponies, blood lactate concentration significantly differs between height classes. Normal values for equine species should not be directly applied to interpret the lactate, triglycerides, aspartate aminotransferase and creatine kinase values in ponies.

An unusual case of giant cell tumor of soft parts in an American Warmblood horse.

Fine needle aspiration and tissue biopsy samples were taken from a subcutaneous mass in the cranial stifle region of a 10-yr-old horse. Key cytologic features included numerous mildly to moderately pleomorphic histiocytic cells admixed with mononuclear inflammatory cells, occasional fibroblasts, multinucleated cells, and hemosiderin-laden macrophages. Based on these features, cytologic differentials included granulomatous inflammation with reactive fibroplasia, histiocytic sarcoma, giant cell tumor of soft parts (GCTSPs), and giant cell tumor of bone. The tissue biopsy supported a diagnosis of superficial GCTSPs. This neoplasm is of controversial origin but generally considered to be a soft tissue sarcoma and classified in the World Health Organization classification of tumors under fibrous histiocytic tumors as a giant cell tumor of soft tissue with low risk of malignancy. When found in the subcutis, this neoplasm rarely metastasizes in the horse and has a low rate of local reoccurrence. In this case, there was no local recurrence of the tumor after 6 mo, after which the horse was lost to follow-up.

In vitro susceptibility of Borrelia burgdorferi isolates to three antibiotics commonly used for treating equine Lyme disease.

BACKGROUND: Lyme disease in humans is predominantly treated with tetracycline, macrolides or beta lactam antibiotics that have low minimum inhibitory concentrations (MIC) against Borrelia burgdorferi. Horses with Lyme disease may require long-term treatment making frequent intravenous or intramuscular treatment difficult and when administered orally those drugs may have either a high incidence of side effects or have poor bioavailability. The aim of the present study was to determine the in vitro susceptibility of three B. burgdorferi isolates to three antibiotics of different classes that are commonly used in practice for treating Borrelia infections in horses. RESULTS: Broth microdilution assays were used to determine minimum inhibitory concentration of three antibiotics (ceftiofur sodium, minocycline and metronidazole), for three Borrelia burgdorferi isolates. Barbour-Stoner-Kelly (BSK K + R) medium with a final inoculum of 106 Borrelia cells/mL and incubation periods of 72 h were used in the determination of MICs. Observed MICs indicated that all isolates had similar susceptibility to each drug but susceptibility to the tested antimicrobial agents varied; ceftiofur sodium (MIC = 0.08 µg/ml), minocycline hydrochloride (MIC = 0.8 µg/ml) and metronidazole (MIC = 50 µg/ml). CONCLUSIONS: The MIC against B. burgorferi varied among the three antibiotics with ceftiofur having the lowest MIC and metronidazole the highest MIC. The MIC values observed for ceftiofur in the study fall within the range of reported serum and tissue concentrations for the drug metabolite following ceftiofur sodium administration as crystalline-free acid. Minocycline and metronidazole treatments, as currently used in equine practice, could fall short of attaining MIC concentrations for B. burgdorferi.

Multiple etiologies of equine recurrent uveitis--A natural model for human autoimmune uveitis: A brief review.

Equine recurrent uveitis (ERU) has various etiologies, with Leptospira infection and genetic predisposition being the leading risk factors. Regardless of etiology, expression of ocular proteins associated with maintenance of the blood-ocular barrier is impaired in ERU. The recurring-remitting cycle of ERU repeatedly disrupts the blood-ocular barrier, allowing the previously immune-privileged ocular environment to become the site of a progressive local autoimmune pathology that ultimately results in tissue destruction and vision loss. The immune-mediated process involves humoral and cellular mechanisms. Intraocular antibodies either produced in the eye or that leak through the blood-ocular barrier, are often present at higher levels than in serum and react with antigens in ocular tissue of horses with ERU. Ocular infiltration of auto-aggressive lymphocytes occurs with each uveitis episode and is the most crucial contributor to inflammation and eye damage. Recurring uveitis episodes may be initiated when epitopes of an ocular antigen become visible to the immune system (intramolecular spreading) or another autoantigen (intermolecular spreading), resulting in a new inflammatory reaction.

Effects of the insulin sensitizing drug, pioglitazone, and lipopolysaccharide administration on markers of systemic inflammation and clinical parameters in horses.

Equine metabolic syndrome (EMS) is a condition of obese horses characterized by insulin resistance, systemic inflammation, and an increased risk of laminitis. The pathogenesis of EMS is thought, in part, to be due to inflammatory proteins produced by adipose tissue. Reducing inflammation may decrease the incidence of laminitis in horses with EMS. Pioglitazone hydrochloride, a thiazolidinedione, has efficacy to reduce obesity associated inflammation in humans. Eight normal, adult, horses were administered 1mg/kg pioglitazone for 14 days, and eight horses served as controls. Physical examination and hematologic variables, transcript abundance of pro-inflammatory cytokines in skeletal muscle and adipose tissue, and circulating concentrations of the acute phase protein, serum amyloid A and pro-inflammatory cytokine, TNF-α were assessed prior to, and following, an LPS infusion (35 ng/kg). The objective was to determine if pre-treatment with pioglitazone would mitigate the development of inflammation and associated clinical markers of inflammation following LPS administration. Lipopolysaccharide administration induced systemic inflammation, as assessed by clinical and hematological aberrations, increased TNF-α, SAA and adipose tissue IL-6 mRNA abundance, however no mitigating effects of pioglitazone were detected. A longer treatment period or higher dose might be indicated for future experiments.

Effects of acute hyperinsulinemia on inflammatory proteins in horses.

Laminitis is a painful, inflammatory disease of the equine hoof that often results in euthanasia. Elevated plasma insulin concentrations are a predictive factor for laminitis, and in previously healthy horses and ponies, laminitis was induced by infusion of insulin. Thus, we chose to determine if an infusion of insulin would increase plasma concentrations of inflammatory cytokines and cytokine mRNA abundance in subcutaneous adipose tissue, skeletal muscle, and white blood cells. Ten mature Thoroughbred mares received an insulin infusion that elevated plasma insulin concentrations for 6h or an equivalent volume of isotonic saline in a switchback design. Insulin infusion altered plasma concentrations of both TNF (P=0.037) and IL-6 (P=0.044), but did not result in consistent changes to either skeletal muscle or adipose tissue cytokine mRNA. Insulin may be involved in the production of inflammatory cytokines, and this could be a mechanism for insulin increasing the risk of laminitis.

Quantitative pertechnetate thyroid scintigraphy and the ultrasonographic appearance of the thyroid gland in clinically normal horses.

We characterized the scintigraphic and sonographic appearance of the thyroid gland in clinically normal horses to establish the value of these modalities for assessment of the thyroid gland in this species. Horses were divided into two age groups. One group consisted of eight horses between 3 and 10 years of age and the other of seven horses between 11 and 20 years of age. Total T4 concentrations were within the laboratory reference interval in all horses. Thyroid to salivary (T/S) ratio, percent dose uptake of pertechnetate (Na99mTcO4) and thyroid lobe volume were calculated. The echogenicity of thyroid lobes and presence of nodules was documented. The two groups were compared using appropriate parametric and nonparametric statistics. Mean total T4 concentration was lower in older horses. Sixty minute mean +/- standard deviation (SD) T/S ratios for old vs. young horses were 5.8 +/- 3.0 and 5.3 +/- 2.2, respectively. Sixty-minute median and interquartile ranges for percent dose uptake of pertechnetate for old vs. young horses were 3.64% (1.5-3.98%) and 2.55% (2.33-2.90%), respectively. Mean +/- SD thyroid lobe volume for old vs. young horses were 18.93 +/- 5.16 cm 3 and 13.55 +/- 3.56 cm3, respectively. Differences between groups were not significant. Most thyroid lobes were hyper or isoechoic to the sternocephalicus muscle. Prevalence of thyroid nodules did not differ between groups. Further study is needed to determine if thyroidal percent dose uptake is significantly different in horses with thyroid dysfunction and if it is clinically useful.

Measurement of ascorbic acid concentration and glutathione peroxidase activity in biological samples collected from horses with recurrent airway obstruction.

OBJECTIVE: To measure the ascorbic acid (AA) concentration in bronchoalveolar lavage fluid (BALF) and cellular glutathione peroxidase (cGPx) activity in RBCs and WBCs from peripherally obtained blood and in cells from BALF to determine whether differences existed between the 2 major redox systems in recurrent airway obstruction (RAO)-affected and -nonaffected (control) horses and between systemic and local pulmonary responses in the glutathione redox system. ANIMALS: 16 adult horses in pairs: 8 healthy (control) and 8 RAO-affected horses. PROCEDURES: Physical examination data and biological samples were collected from horses before (remission), during, and after (recovery) environmental challenge with dusty straw and hay. At each stage, BALF cell AA concentration and RBC, WBC, and BALF cell cGPx activity were measured. RESULTS: Compared with control horses, RAO-affected horses had significantly higher cGPx activity in RBCs at all points and in WBCs during remission and challenge. The BALF cell cGPx activity was higher in RAO-affected horses during recovery than during remission The BALF cell AA concentration did not differ significantly in control horses at any point, but total and free AA concentrations were significantly lower in RAO-affected horses during the challenge period than during remission and recovery periods. CONCLUSIONS AND CLINICAL RELEVANCE: High cGPx activity suggested this redox system was upregulated during exposure to dusty straw and hay to combat oxidative stress, as AA was depleted in RAO-affected horses. The relative delay and lack of comparative increase in cGPx activity within the local environment (represented by BALF cells), compared with that in RBCs and WBCs, might contribute to disease in RAO-affected horses.

Imaging diagnosis--Dorsal mediastinal T-cell lymphoma in an alpaca.

A 14-year-old male alpaca had refractory pleural effusion. The cause of the effusion was not apparent either radiographically or sonographically, or following a pleural fluid cytologic examination. Using computed tomographic (CT) examination, a dorsal paravertebral mass was identified and similar masses were found in the cranial mediastinum, retroperitoneal space, and adjacent to the hepatic entry of the portal vein. The histopathologic diagnosis was multicentric T-cell lymphoma. CT examination may prove to be a valuable imaging modality in the localization and staging of neoplasia in new world camelids.

De novo fatty acid synthesis and NADPH generation in equine adipose and liver tissue.

The lipogenic capacities of equine liver and adipose tissue explants were investigated in vitro. Preference for glucose or acetate as the primary carbon source for de novo fatty acid synthesis was determined using (14)C labeled substrates. Additional aims included determining the relative contribution of NADPH generating pathways to reducing equivalent generation and comparing the lipogenic activity of two adipose depots, mesenteric and subcutaneous harvested from the crest region of the neck. Mesenteric adipose tissue had greater lipogenic activity than subcutaneous adipose tissue, and liver tissue showed minimal (14)C incorporation into fatty acids, indicating a low hepatic lipogenic capacity. Acetate was found to be the primary carbon source for fatty acid synthesis due to both the appearance of the (14)C label in the lipid fraction and the low activity of ATP-citrate lyase. Finally, the pentose phosphate and isocitrate dehydrogenase enzymes contributed to NADPH production in equine adipose tissue.

Comparison of serum iohexol clearance and plasma creatinine clearance in clinically normal horses.

Objective-To determine whether a limited sampling time method based on serum iohexol clearance (Cl(iohexol)) would yield estimates of glomerular filtration rate (GFR) in clinically normal horses similar to those for plasma creatinine clearance (Cl(creatinine)). Animals-10 clinically normal adult horses. Procedures-A bolus of iohexol (150 mg/kg) was administered IV, and serum samples were obtained 5, 20, 40, 60, 120, 240, and 360 minutes after injection. Urinary clearance of exogenous creatinine was measured during three 20-minute periods. The GFR determined by use of serum Cl(iohexol) and plasma Cl(creatinine) was compared with limits of agreement plots. Results-Values obtained for plasma Cl(creatinine) ranged from 1.68 to 2.69 mL/min/kg (mean, 2.11 mL/min/kg). Mean serum Cl(iohexol) was 2.38 mL/min/kg (range, 1.95 to 3.33 mL/min/kg). Limits of agreement plots indicated good agreement between the methods. Conclusions and Clinical Relevance-Use of serum Cl(iohexol) yielded estimates of GFR in clinically normal adult horses similar to those for plasma Cl(creatinine). This study was the first step in the evaluation of the use of serum Cl(iohexol) for estimating GFR in adult horses.

Blood proteins and inflammation in the horse.

Activation of the host response to infection, the "acute-phase response," is a highly organized physiologic reaction that includes changes in concentrations of plasma acute-phase proteins (APPs). The APPs are increasingly being used as markers for prognosis and monitoring response to therapy along with general determinants of equine health. Use of APPs in veterinary medicine is becoming more widespread as more commercial diagnostic kits are being validated. This article reviews the salient features of APPs and examines their current application and potential utility in equine inflammatory disorders.

Immunodeficiency disorders in horses.

Immunodeficiencies are characterized as primary (genetic) or secondary (acquired). Primary immunodeficiencies are relatively uncommon; however, clinically, they present a significant challenge to the practitioner, especially if the underlying disorder goes unrecognized. Secondary immunodeficiencies may present at any age, but failure of passive transfer in neonatal foals is most commonly encountered. This article provides a general overview of clinical signs and diagnosis of primary and secondary immunodeficiencies currently recognized in horses.

Diagnostic equine serology.

This article is presented with two main goals: (1) to provide equine clinicians with a resource for identifying types of serum tests available and (2) to outline briefly the necessary sample type, assay principle, and relative strengths and weakness of the various methods. Specific etiologies are presented and grouped by clinical diagnosis categories, along with brief comments concerning each disorder and its relevant diagnostic assays. This organization provides an abstracted list of infectious disorders commonly considered for the various clinical presentations and a summary of available serologic tests for narrowing the differential diagnosis list. The reader is also provided with a list of specific laboratories that perform the diagnostic assay for the mentioned disorders.

Mycoplasma haemolamae infection in a 4-day-old cria: support for in utero transmission by use of a polymerase chain reaction assay.

Blood smear examination in a 4-day-old alpaca revealed massive erythrocyte parasitism by Mycoplasma haemolamae. Blood collected from both the nonparasitemic dam and the cria were positive for M. haemolamae by polymerase chain reaction (PCR) analysis. These findings suggest in utero transmission of M. haemolamae in camelids, even when the dam is not parasitemic.

Effects of feeding large amounts of grain on colonic contents and feces in horses.

OBJECTIVE: To assess changes in systemic hydration, concentrations of plasma electrolytes, hydration and physical properties of colonic contents and feces, and gastrointestinal transit in horses with access to large amounts of grain. ANIMALS: 6 horses with right dorsal colon (RDC) fistulas. PROCEDURE: In a crossover design, horses were alternately fed 1 of 3 diets: orchard grass hay ad libitum after being adapted to this diet for at least 5 days, orchard grass hay ad libitum and 4.55 kg of grain offered every 12 hours after being adapted to orchard grass hay ad libitum for at least 5 days, or orchard grass hay ad libitum and 4.55 kg of grain offered every 12 hours after being adapted to this diet for at least 5 days. Physical examinations were performed and samples of blood, colonic contents, and feces were collected every 6 hours during a 48-hour observation period. RESULTS: Grain ingestion had several effects, including changes in the concentrations of electrolytes in plasma; RDC contents became more homogenous, dehydrated, foamy, and less dense; RDC contents flowed spontaneously when the cannula was opened; RDC contents expanded when heated in an oven; and feces became fetid and less formed. Horses did not have any clinical signs of colic, endotoxemia, or laminitis. CONCLUSIONS AND CLINICAL RELEVANCE: Changes observed in the colonic contents and feces may be explained by the large amounts of hydrolyzable carbohydrates provided by grain. Access to large amounts of grain may increase the risk of tympany and displacement of the large intestine.

Effects of enteral and intravenous fluid therapy, magnesium sulfate, and sodium sulfate on colonic contents and feces in horses.

OBJECTIVE: To assess changes in systemic hydration, concentrations of electrolytes in plasma, hydration of colonic contents and feces, and gastrointestinal transit in horses treated with IV fluid therapy or enteral administration of magnesium sulfate (MgSO4), sodium sulfate (NaSO4), water, or a balanced electrolyte solution. ANIMALS: 7 horses with fistulas in the right dorsal colon (RDC). PROCEDURE: In a crossover design, horses alternately received 1 of 6 treatments: no treatment (control); IV fluid therapy with lactated Ringer's solution; or enteral administration of MgSO4, Na2SO4, water, or a balanced electrolyte solution via nasogastric intubation. Physical examinations were performed and samples of blood, RDC contents, and feces were collected every 6 hours during the 48 hour-observation period. Horses were muzzled for the initial 24 hours but had access to water ad libitum. Horses had access to hay, salt, and water ad libitum for the last 24 hours. RESULTS: Enteral administration of a balanced electrolyte solution and Na2SO4 were the best treatments for promoting hydration of RDC contents, followed by water. Sodium sulfate was the best treatment for promoting fecal hydration, followed by MgSO4 and the balanced electrolyte solution. Sodium sulfate caused hypocalcemia and hypernatremia, and water caused hyponatremia. CONCLUSIONS AND CLINICAL RELEVANCE: Enteral administration of a balanced electrolyte solution promoted hydration of RDC contents and may be useful in horses with large colon impactions. Enteral administration of either Na2SO4 or water may promote hydration of RDC contents but can cause severe electrolyte imbalances.