Beatrice T. Sponseller

Equine Multiple Acyl‐CoA Dehydrogenase Deficiency (MADD) Associated with Seasonal Pasture Myopathy in the Midwestern United States

BACKGROUND Seasonal pasture myopathy (SPM) is a highly fatal form of nonexertional rhabdomyolysis that occurs in pastured horses in the United States during autumn or spring. In Europe, a similar condition, atypical myopathy (AM), is common. Recently, a defect of lipid metabolism, multiple acyl-CoA dehydrogenase deficiency (MADD), has been identified in horses with AM. OBJECTIVE To determine if SPM in the United States is caused by MADD. ANIMALS Six horses diagnosed with SPM based on history, clinical signs, and serum creatine kinase activity, or postmortem findings. METHODS Retrospective descriptive study. Submissions to the Neuromuscular Diagnostic Laboratory at the University of Minnesota were reviewed between April 2009 and January 2010 to identify cases of SPM. Inclusion criteria were pastured, presenting with acute nonexertional rhabdomyolysis, and serum, urine, or muscle samples available for analysis. Horses were evaluated for MADD by urine organic acids, serum acylcarnitines, muscle carnitine, or histopathology. RESULTS Six horses had clinical signs and, where performed (4/6 horses), postmortem findings consistent with SPM. Affected muscle (4/4) showed degeneration with intramyofiber lipid accumulation, decreased free carnitine concentration, and increased carnitine esters. Serum acylcarnitine profiles (3/3) showed increases in short- and medium-chain acylcarnitines and urinary organic acid profiles (3/3) revealed increased ethylmalonic and methylsuccinic acid levels, and glycine conjugates, consistent with equine MADD. CONCLUSIONS AND CLINICAL IMPORTANCE Similar to AM, the biochemical defect causing SPM is MADD, which causes defective muscular lipid metabolism and excessive myofiber lipid content. Diagnosis can be made by assessing serum acylcarnitine and urine organic acid profiles.

Idiopathic Arterial Medial Calcification of the Thoracic Arteries in an Adult Horse

A 6-year-old, gelded, Paint horse displayed clinical signs of muscle wasting and limb stiffness for a 6-month period. The horses clinical signs abated with corticosteroid therapy, but returned upon cessation of treatment. Upon necropsy, severe lesions of aortic thickening and aortic valve rigidity were observed. Histologically, the tunica media of the aorta, coronary arteries, and pulmonary arteries were expanded by foci of elastin fiber calcification and extracellular matrix with lacunae formation. The vascular lesions are comparative to what has been described as medial arterial calcification, seen in humans suffering from chronic renal failure or diabetes mellitus. No exposure to vitamin D-containing plants or feedstuff could be documented at the time of onset or during the period of clinical signs. The current case describes dramatic lesions of arterial medial calcification of the aorta, coronary, and pulmonary arteries of undetermined cause.

Isolation of Corynebacterium pseudotuberculosis Biovar equi from a Horse in Central Iowa

Corynebacterium pseudotuberculosis biovar equi is the causative agent of “pigeon fever,” or “dryland distemper” in horses. The agent is typically identified in the Western United States but has recently been identified in Canada; it has not previously been documented as cause of infection in horses in Iowa. This report describes the clinical findings of two horses in Iowa that presented with pectoral abscessation, confirmed in one to be C. pseudotuberculosis biovar equi.

Measured and calculated variables of global oxygenation in healthy neonatal foals

OBJECTIVE To assess multiple central venous and arterial blood variables that alone or in conjunction with one another reflect global oxygenation status in healthy neonatal foals. ANIMALS 11 healthy neonatal foals. PROCEDURES Central venous and arterial blood samples were collected from healthy neonatal foals at 12, 24, 36, 48, 72, and 96 hours after birth. Variables measured from central venous and arterial blood samples included oxygen saturation of hemoglobin, partial pressure of oxygen, lactate concentration, partial pressure of carbon dioxide, and pH. Calculated variables included venous-to-arterial carbon dioxide gap, estimated oxygen extraction ratio, ratio of partial pressure of oxygen in arterial blood to the fraction of inspired oxygen, bicarbonate concentration, base excess, and blood oxygen content. RESULTS Significant differences between arterial and central venous blood obtained from neonatal foals were detected for several variables, particularly partial pressure of oxygen, oxygen saturation of hemoglobin, and oxygen content. In addition, the partial pressure of carbon dioxide in central venous blood samples was significantly higher than the value for corresponding arterial blood samples. Several temporal differences were detected for other variables. CONCLUSIONS AND CLINICAL RELEVANCE Results of this study provided information about several variables that reflect global oxygenation in healthy neonatal foals. Values for these variables in healthy foals can allow for comparison with values for critically ill foals in future studies. Comparison of these variables between healthy and ill foals may aid in treatment decisions and prognosis of clinical outcome for critically ill foals.

Macrophage effector responses of horses are influenced by expression of CD154

Reactive intermediates contribute to innate immunity by providing phagocytes with a mechanism of defense against bacteria, viruses and parasites. To better characterize the role of CD154 in the production of reactive intermediates, we cloned and expressed recombinant equine CD154 (reqCD154) in Chinese Hamster Ovary (CHO). In co-culture experiments, CHO cells ectopically expressing reqCD154 elicited superoxide production in monocyte-derived macrophages (MDM). Collectively, our results indicate that regulation of CD154 expression plays a role in innate host defenses.