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Abstract

Objectives

To identify Sarcocystis neurona-specific DNA sequences in the nuclear small subunit ribosomal RNA (nss-rRNA) gene that could be used to distinguish S neurona from other closely related protozoal parasites, and to evaluate a polymerase chain reaction (PCR) test, using broad based primers and a unique species-specific probe on CSF for detection of S neurona in equids.

Procedures

Sequencing of the nuclear small subunit ribosomal RNA gene from a new S neurona isolate (UCD 1) was performed. The sequence was compared with that of other closely related Sarcocystidae parasites. From this sequence, conserved DNA sequence primers were selected and an oligonucleotide probe was designed to hybridize with a unique region of the S neurona gene. For clinical evaluation, horses were considered test positive for S neurona infection on the basis of immunohistochemical detection of the parasites in the CNS.

Results

Sensitivity of this PCR and probe-based detection system was approximately 1 to 5 merozoites. Cerebrospinal fluid from 2 of 5 horses with histologic lesions consistent with equine protozoal myeloencephalitis were PCR- and probe-positive in a blind test of this procedure, and all uninfected horses were test negative.

Conclusion and Clinical Relevance

This PCR- based system is a useful method of confirming S neurona in CSF and has the advantage of facilitating detection of other apicomplexan protozoans that may be infective for horses. The usefulness of this test is limited by the presence of parasites free in the CSF of clinically affected horses. (Am J Vet Res 1996;57:975–981)

Free access
in American Journal of Veterinary Research

Summary

Pituitary pars intermedia dysfunction is a slowly progressive disorder that afflicts most breeds of horses. Because it shares features with human Cushing disease, it has been referred to as equine Cushing disease. A variety of tests of pituitary-adrenocortical function were performed on horses with evidence of pituitary pars intermedia dysfunction, and results were compared with those in healthy control horses. Diurnal variations in plasma cortisol concentration were not statistically different between control horses and those with pituitary pars intermedia dysfunction. An ACTH stimulation (1 U of natural ACTH gel/kg of body weight, IM) test or a combined dexamethasone suppression test (10 mg, IM) and ACTH stimulation (100 mg of synthetic ACTH, IV) test also failed to distinguish horses with pituitary pars intermedia dysfunction from control horses. A significant (P < 0.001) dose-related suppression of cortisol concentration in response to increasing doses (5, 10, 20, and 40 μg/kg) of dexamethasone was observed in control horses but not in those with pituitary pars intermedia dysfunction. On the basis of plasma cortisol concentration, the dexamethasone suppression test, using 40 μg/kg, whether initiated at 5 PM with sample collection at 15 (8 AM) and 19 (12 PM) hours after dexamethasone administration, or initiated at 12 AM with sample collection at 8 (8 AM), 12 (12 PM), 16 (4 PM), 20 (8 PM), and 24 (12 AM) hours after dexamethasone administration, reliably distinguished between control horses and those with pituitary pars intermedia dysfunction. Several horses did not have clinical evidence of pituitary pars intermedia dysfunction, but did have abnormal dexamethasone suppression test results. In these horses, adenomatous hypertrophy and hyperplasia of the pars intermedia of the pituitary gland was confirmed at necropsy.

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To test the hypothesis that application of a rope restraint device would result in behavioral, electroencephalographic, and humoral changes consistent with sleep and analgesia in neonatal foals.

Animals—8 healthy neonatal foals.

Procedures—Following acclimatization to experimental conditions, each foal underwent a series of assessments before and during or at the end of a period of restraint via application of a restraint device (soft linen rope). Assessments included measurements of heart and respiratory rates, rectal temperature, and circulating β-endorphin and steroid hormone concentrations and evaluations of mentation and body position (behavior), electroencephalographic patterns, and pain tolerance.

Results—All foals were lively with apparently normal behavior prior to restraint. During application of the restraint device, foals assumed lateral recumbency with relaxed, somnolent behavior. Heart and respiratory rates and rectal temperature uniformly decreased as a result of the procedure. Electroencephalographic recordings (completed for 3 foals only) revealed patterns consistent with slow wave sleep. Plasma ACTH, dehydroepiandrosterone sulfate, and androstenedione concentrations significantly increased during restraint, compared with prerestraint values. The foals' tolerance to noxious stimuli significantly increased during restraint; however, this was independent of the concentration of circulating β-endorphin.

Conclusions and Clinical Relevance—In neonatal foals, the evaluated form of restraint resulted in a decrease in heart and respiratory rates and rectal temperature. Squeeze-induced somnolence may resemble the effects of compression of the fetus in the birth canal and lead to inhibition of voluntary activity. Use of this technique to safely restrain neonatal foals during minor procedures warrants further evaluation.

Full access
in American Journal of Veterinary Research

Wildfires are a serious and expanding threat in western North America, and wildfire encroachment on human populations leads to widespread evacuation and emergency housing operations for residents and their companion animals and livestock. Veterinarians are frequently part of wildfire response efforts and are called upon to assist in rescue, evacuation, and emergency housing operations as well as to provide medical care for evacuated animals. Although veterinarians are likely familiar with the principles of transporting and housing terrestrial animals, emergency response for aquatic companion animals presents unique logistic challenges. Veterinarians familiar with aquatic animal evacuation, housing, and care prior to a wildfire response can extend the scope of disaster recovery. This report offers general guidance for rescuing, evacuating, housing, and caring for aquatic animals in the wake of a wildfire.

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To describe epidemiological, clinical, and pathological features of neuroaxonal dystrophy in Quarter Horses (QHs) on a single farm.

Design—Prospective case series.

Animals—148 horses.

Procedures—Neurologic, pathological, and toxicological evaluations were completed in selected neurologically affected horses over a 2-year period. Descriptive statistical analysis was performed.

Results—87 QHs and 1 QH-crossbred horse were affected. Most (50/88 [56.8%]) affected horses were 1 to 2 years old (median age, 2 years [range, 2 months to 34 years]). Neurologic deficits included obtundation (53/88 [60%] horses), decreased to absent menace response (33/88 [37.5%]), proprioceptive positioning deficits, wide-based stance, ataxia, and dysmetria (88/88 [100%]). Most (78/88 [88.6%]) horses had mild ataxia, but some (10/88 [11.4%]) had moderate to severe ataxia. Low serum concentrations of vitamin E (≤ 2 mg/L) were detected in 3 index case horses and 16 of 17 randomly selected horses (13/14 affected and 3/3 unaffected) during study year 1. Dietary vitamin E supplementation did not improve neurologic deficits in affected horses; vitamin E administration in pregnant mares appeared to decrease but not prevent disease development among offspring born the following year. Lesions detected at necropsy included bilaterally symmetric neuroaxonal degeneration with axonal spheroids in the nucleus gracilis, nucleus cuneatus medialis, nucleus cuneatus lateralis, and nucleus thoracicus (5/5 horses).

Conclusions and Clinical Relevance—Neuroaxonal dystrophy should be considered in evaluation of young horses with ataxia and proprioceptive positioning deficits. Vitamin E deficiency may contribute to disease severity.

Full access
in Journal of the American Veterinary Medical Association