Sarcocystis fayeri-Induced Granulomatous and Eosinophilic Myositis in 2 Related Horses.

This report describes 2 genetically related paint mares, case Nos. 1 and 2, presented to the Oklahoma State University Boren Veterinary Medical Teaching Hospital for chronic weight loss and abnormal gait, respectively. Notable findings in both cases included marked persistent eosinophilia and multiple intramuscular lateral thoracic masses. Histologic examination of masses revealed eosinophilic, centrally necrotic granulomas and marked eosinophilic myositis. Granulomas in case No. 1 also contained intralesional Sarcocystis sp material, and adjacent muscle fibers contained intact protozoal cysts. Case No. 1 developed severe refractory muscle pain and recurrent esophageal dysphagia. At necropsy, disseminated, grossly visible granulomas were present throughout all examined striated muscles. Nested polymerase chain reaction of the 18S rRNA gene revealed >99% homology with Sarcocystis fayeri. Sarcocystis spp are apicomplexan protozoa that infect striated muscle of many omnivorous species, typically without inciting clinical disease. Sarcocystosis should be considered a rare cause of granulomatous eosinophilic myositis and choke in horses.

Lathyrus hirsutus (Caley Pea) intoxication in a herd of horses.

BACKGROUND: Caley Pea (Lathyrus hirsutus) is potentially toxic to horses, but large case series are not reported. OBJECTIVES: To describe the clinical signs of horses intoxicated with Lathyrus hirsutus and speculate on the neuroanatomical lesion localization and pathogenesis based upon the observed clinical signs. ANIMALS: Twenty-two of 25 horses ranging in age from 6 to 34 months were affected. Five affected horses were presented to the OSUCHVS for evaluation and treatment after having been attended at the ranch by a local veterinarian (ALA). An additional horse that had been euthanized was also presented for necropsy. METHODS: A case series is presented. Diagnostic evaluation included: physical examination, complete blood count, serum biochemistry, CSF analysis, EMG, ERG, upper airway endoscopy, muscle biopsy, and serum vitamin E analysis. The grain ration consumed by the affected horses was analyzed for ionophores and cultured for fungi: the hay was examined for toxic plants. RESULTS: Bermuda grass hay consumed by the horses contained large quantities of mature Lathyrus hirsutus. Acute clinical signs conform to earlier descriptions of Lathyrus hirsutus intoxication in cattle. Residual neurologic signs were characterized by incoordination in the rhythmicity of multiple gaits. Evidence of mild neurogenic muscle atrophy was recognized in 1 of 5 horses biopsied. CONCLUSIONS AND CLINICAL IMPORTANCE: Caley Pea intoxication may occur within days of seed pod consumption. The neurologic signs are unique and suggest involvement of the upper motor neuron system and regions of the spinal cord influencing voluntary motor movement. Drought conditions during plant growth may increase the risk of toxicosis.

Evaluation of efficacy of mineral oil, charcoal, and smectite in a rat model of equine cantharidin toxicosis.

BACKGROUND: The efficacy of orally administered therapeutics for the treatment of cantharidin intoxication has not been evaluated in controlled studies. OBJECTIVE: To develop a model of acute cantharidin intoxication in laboratory rats and to evaluate in this model the relative efficacy of 3 gastrointestinal therapies used to treat equine cantharidin toxicosis. ANIMALS: Sixty-four male Sprague-Dawley rats. METHODS: A blinded, randomized, controlled study was performed on rats surgically implanted with telemetry transmitters for evaluating heart rate, locomotor activity, and body temperature. Orogastric administration of cantharidin was performed within 15 seconds before administration of mineral oil, activated charcoal, or smectite. Negative control groups received therapeutic agents alone. Urine was collected for cantharidin analysis. Rats were sacrificed 24 hours after intoxication, and tissues were collected for histopathologic evaluation. Data analysis included ANOVA procedures and contingency tables. RESULTS: Six of 8 cantharidin-intoxicated rats treated with mineral oil died; bradycardia and hypothermia developed in the animals of this group 0-8 hours after intoxication. Rats treated with mineral oil had higher urine cantharidin concentrations than rats receiving cantharidin alone or with smectite (P = .04). The most severe hypothermia (30.6°C ± 1.0) developed in rats administered mineral oil at 4-8 hours after intoxication, whereas those treated with charcoal (35.2°C ± 0.8) had mean body temperatures higher than all other treatment groups (P = .03). Survival times in the charcoal (P = .16) and smectite (P = .12) treatment groups were not statistically different from negative controls. CONCLUSIONS AND CLINICAL IMPORTANCE: Mineral oil is often used in the treatment of equine cantharidin toxicosis. Our findings suggest that mineral oil increases cantharidin absorption, worsening morbidity and fatality in rats.

Cardiotoxicity, inflammation, and immune response after rattlesnake envenomation in the horse.

BACKGROUND: Cardiac abnormalities are reported in rattlesnake-bitten horses. The prevalence and cause are unknown. OBJECTIVES: To detect cardiac damage in rattlesnake-bitten horses by measuring cardiac troponin I (cTnI) and evaluating ECG recordings for presence of arrhythmias, and explore causes of this cardiac damage by measuring venom excretion, anti-venom antibodies, and tumor necrosis factor alpha (TNFα). ANIMALS: A total of 20 adult horses with a clinical diagnosis of rattlesnake bite and 6 healthy adult horses. METHODS: In a prospective clinical study, bite site swabs, blood samples, and urine samples were collected at various time points from 20 horses with a clinical diagnosis of snake bite. Continuous ECG recordings were obtained on the 20 affected horses and 6 normal control horses using 24-hour holter monitors. Plasma samples were assayed for cTnI, serum samples were assayed for TNFα and anti-venom antibodies, and bite site swabs and urine were assayed for venom. RESULTS: Forty percent of rattlesnake-bitten horses (8/20) experienced myocardial damage (increased cTnI). Seventy percent (14/20) experienced a cardiac arrhythmia. There was a positive correlation between cTnI and TNFα (P < .02). Horses with cTnI ≥ 2 ng/mL were more likely to have antibody titers >5,000 (P < .05). No correlations were found between venom concentration and cTnI, anti-venom antibody titers, TNFα, or presence of arrhythmias. CONCLUSIONS AND CLINICAL IMPORTANCE: Cardiac abnormalities in this population of horses indicate that cardiac damage after rattlesnake bite is common. Rattlesnake-bitten horses should be monitored for signs of cardiac damage and dysfunction. Long-term follow-up should be encouraged to detect delayed cardiac dysfunction.

Neuroendocrine and non-neuroendocrine markers of inflammation associated with performance in endurance horses.

REASONS FOR PERFORMING STUDY: The inflammatory and neuroendocrine response to endurance exercise and relationship of these parameters to performance is not well documented in horses. HYPOTHESES OR OBJECTIVES: Evidence of systemic inflammation is associated with poor performance in horses competing in endurance events. METHODS: Blood was collected prior to and at the finish or elimination point from horses competing in both the 80 and 160 km American Endurance Ride National Championship competitions in 2006. Immunoreactive alpha-melanocyte stimulating hormone (α-MSH) and tumour necrosis factor-alpha (TNF-α) were quantified utilising radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA) techniques, respectively. The concentration of total thiobarbituric acid reactive substances (TBARS) was measured fluorometrically. RESULTS: Thirty horses were included in the study. Endurance exercise was associated with a significant increase in TBARS in the 80 km group but not the 160 km group. TNF-α and α-MSH did not significantly change as a result of exercise in either distance group. Precompetition TBARS was significantly higher in horses that failed to finish the 80 km race, as well as when distances were combined. In addition, precompetition α-MSH was significantly lower in nonfinishers in the 160 km group. Furthermore, competition speed was positively correlated with precompetition α-MSH in the 80 km and negatively correlated with precompetition TNF-α when distances were combined. CONCLUSIONS: Our results suggest that basal oxidative stress markers, circulating cytokines and anti-inflammatory neuroendocrine hormones appear to correlate with endurance performance in horses. POTENTIAL RELEVANCE: Basal oxidative stress markers, circulating cytokines and anti-inflammatory neuroendocrine hormones may be predictive of athletic performance in endurance horses. Future studies evaluating the effect of training on these markers in endurance horses are warranted.

Retrospective multicentre study of methicillin-resistant Staphylococcus aureus infections in 115 horses.

REASONS FOR PERFORMING STUDY: Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging veterinary and zoonotic pathogen, associated with increasing reports of disease in horses. OBJECTIVES: To provide an overview of the characteristics of clinical MRSA infections in horses. METHODS: A retrospective case study was performed on 115 horses admitted to 6 participating veterinary teaching hospitals in Canada and the United States between 2000 and 2006, and diagnosed with clinical MRSA infection. Descriptive statistics, univariate and multivariable analyses for community- (CA) vs. hospital-associated (HA) MRSA infections, and survival vs. nonsurvival at discharge were performed. RESULTS: The age range of MRSA-infected horses was zero (born in hospital) to 31 years. HA (58/114, 50.9%) and CA infections (56/114, 49.1%) were equally common. Infection of surgical incisions was most frequently reported (44/115, 38.0%). Overall 93/111 (83.8%) cases survived to discharge. Previous hospitalisation and treatment with gentamicin were associated significantly with CA-MRSA, whereas infected incision sites were associated significantly with HA-MRSA. Factors significantly associated with nonsurvival included i.v. catheterisation, CA-MRSA infection and dissemination of infection to other body sites. CONCLUSIONS: Equine MRSA infections have a broad range of clinical presentations, appear to be primarily opportunistic and the overall prognosis for survival to discharge is good. POTENTIAL RELEVANCE: These results should help direct future research with regard to investigation of risk factors for equine MRSA infection in community and hospital populations.

Cytokine dysregulation in aged horses and horses with pituitary pars intermedia dysfunction.

BACKGROUND: Equine pituitary pars intermedia dysfunction (PPID) is the result of a loss of dopaminergic inhibition of the pars intermedia secondary to neurodegeneration of periventricular hypothalamic neurons. The pathologic events contributing to development of neurodegeneration or clinical signs in equids with PPID are unknown. Chronic inflammation may contribute to initiation or progression of PPID. HYPOTHESIS: Horses with PPID have a distinct systemic cytokine profile compared with that of normal adult or aged horses. The cytokine profile of healthy aged horses differs from that of adult horses. ANIMALS: Aged horses with PPID, healthy aged-matched controls, and adult controls (n = 14 per group). METHODS: Total leukocyte cytokine expression was determined by quantitative polymerase chain reaction (PCR), and tumor necrosis factor (TNF)-alpha plasma concentration was determined by enzyme-linked immunosorbent assay (ELISA). Peripheral blood mononuclear cell (PBMC) TNF-alpha response after endotoxin (lipopolysaccharide [LPS]) treatment was assessed by ELISA. RESULTS: Aged healthy horses had increased expression of interleukin (IL)-6, IL-8, and interferon-gamma as well as PBMC TNF-alpha release after LPS stimulation compared with healthy adult horses. In contrast, aged horses with PPID had increased IL-8 expression, but expression of other cytokines was similar to that of healthy adult horses, not age-matched controls. CONCLUSIONS AND CLINICAL IMPORTANCE: Aged horses show evidence of a proinflammatory state that may contribute to development of age-associated diseases. Horses with PPID have increased expression of IL-8, which may influence the ability of horses with PPID to respond to bacterial pathogens. The general decrease in proinflammatory cytokine expression observed in horses with PPID may be the outcome of high plasma concentrations of anti-inflammatory hormones.

Pulmonary aspergillosis and ischemic distal limb necrosis associated with enteric salmonellosis in a foal.

A 5-month-old mixed-breed filly presented with diarrhea due to Salmonella typhimurium infection and subsequently developed pneumonia in addition to ischemic necrosis of distal limbs. Pulmonary lesions were characterized by numerous discrete, disseminated pyogranulomas with intralesional fungal hyphae. The morphologic characteristics of fungal hyphae were consistent with Aspergillus spp., and large numbers of A fumigatus were isolated from lung tissue via fungal culture. Lesions in all 4 limbs were similar in distribution, duration, and severity and were characterized by coagulation necrosis accompanied by occasional thrombi in small vessels without evidence of thrombosis of larger limb arteries. Thus, limb lesions are consistent with symmetrical peripheral gangrene, a potential complication of sepsis.

Severe pulmonary disease due to multisystemic eosinophilic epitheliotropic disease in a horse.

Multisystemic eosinophilic epitheliotropic disease was diagnosed histologically in a 17-year-old Quarter Horse intact mare that was presented with a chronic history of respiratory distress. At necropsy, the lungs were poorly collapsed and the pulmonary parenchyma contained innumerable, discrete, spherical nodules in a miliary pattern. A few similar nodules were scattered in the liver and the renal lymph nodes. Histologically, these nodules consisted of fibrosing eosinophilic granulomas. Based on histologic findings and the absence of an etiologic agent, a diagnosis of multisystemic eosinophilic epitheliotropic disease was made.

Endurance exercise is associated with increased plasma cardiac troponin I in horses.

REASON FOR PERFORMING STUDY: Information is lacking regarding the influence of long distance exercise on the systemic concentration of cardiac troponin I (cTnI) in horses. OBJECTIVES: To determine if the concentration of cTnI in horses competing in 80 and 160 km endurance races increases with exercise duration and if cTnI concentrations can be correlated with performance data. METHODS: Blood samples for the measurement of cTnI and 3 min electrocardiogram recordings were obtained from horses prior to, during and after completion of 80 and 160 km endurance races at 3 ride sites during the 2004 and 2005 American Endurance Ride Conference competition seasons. RESULTS: Full data sets were obtained from 100 of the 118 horses. Endurance exercise was associated with a significant increase in cTnI over baseline in both distance groups. Failure to finish competition (poor performance) was also associated with an increased cTnI concentration over baseline at the time of elimination when data from both distances were combined. Other than one horse that developed paroxysmal atrial fibrillation, no arrhythmias were noted on the 3 minute ECG recordings that were obtained after endurance exercise in either distance group. CONCLUSIONS: Systemic concentrations of cTnI increase in endurance horses competing in both 80 and 160 km distances. Although final cTnI concentrations were significantly increased over their baseline values in horses that failed to finish competition, the degree of increase was not greater than the increase over baseline seen in the horses that successfully completed competition. The clinical significance of increased cTnI in exercising horses could not be ascertained from the results of this study. POTENTIAL RELEVANCE: These data indicate that cardiac stress may occur in horses associated with endurance exercise. Future studies utilising echocardiograpy to assess cardiac function in horses with increased cTnI are warranted.

Changes in selected physiological and laboratory measurements in elite horses competing in a 160 km endurance ride.

REASON FOR PERFORMING STUDY: Limited information exists about the physiological changes and clinical problems that occur in elite horses competing in high-speed 160 km endurance races. OBJECTIVES: To provide initial data describing changes in physiological and laboratory measurements in horses competing in a high-speed, 160 km endurance race under temperate conditions and to compare data between horses that successfully completed the race and those that failed to finish. METHODS: Body mass (BM) was measured, blood samples were collected, and veterinary examinations performed on horses before, during, and at the finish of a CEI*** 160 km endurance race. RESULTS: Of 36 horses participating in the study, 22 (61%) completed the race. Twelve horses were eliminated for lameness and 2 for persistent heart rate elevation. Mean speed of finishers was 15.2 km/h. Mean +/- s.d. BM loss of finishers at the end of the race (5.7 +/- 2.6%) was not different (P = 0.58) from BM loss of nonfinishers at elimination (6.7 +/- 34%). Similarly, there were no significant differences in heart rate or veterinary assessment of hydration at the race end for finishers as compared to the elimination point for nonfinishers. PCV increased while sodium, chloride and potassium concentrations decreased with exercise but differences between finishers and nonfinishers were not detected. In contrast, both total and ionised calcium concentrations decreased in successful horses but remained unchanged in nonfinishers. CONCLUSIONS: Elite endurance horses are more likely to be eliminated from competition for lameness than metabolic problems; however, it remains unclear whether these conditions are entirely distinct. The magnitude of the decrease in sodium concentration in both finishers and nonfinishers was greater than in previous reports of 160 km rides. POTENTIAL RELEVANCE: These data should be of use for both organisers and participants in elite 160 km endurance races. The tendency toward hyponatraemia as well as the difference in calcium concentrations between finishers and nonfinishers warrant further study.

Effect of repeated oral administration of hypertonic electrolyte solution on equine gastric mucosa.

REASONS FOR PERFORMING STUDY: Electrolyte supplementation is common in horses during endurance competitions, but the effect on the gastric mucosa is unknown. HYPOTHESIS: Repeated oral administration of hypertonic electrolyte solution is associated with exacerbation of gastric ulcers in mature horses. METHODS: The study design was a randomised, blinded, crossover trial. Fourteen horses were divided randomly into equal groups and administered either 60 ml water (placebo) or 56.7 g commercial electrolyte supplement mixed with 60 ml water by dose syringe orally once an hour for 8 h. The minimum concentration of individual constituent electrolytes/28.35 g dry commercial product used was: sodium (5528 mg); chloride (11,886 mg); potassium (3657 mg); calcium (754 mg); and magnesium (153 mg). Gastric lesions were scored prior to and after oral treatments, and analysis of variance procedures were then performed. RESULTS: Administration of hypertonic electrolytes resulted in a significant increase in mean ulcer number (P = 0.0174) and severity (P = 0.0006) scores in the nonglandular stomach. Mean ulcer number score was 3.6 and mean ulcer severity score 2.7 after hypertonic electrolyte treatment. CONCLUSIONS: Oral hypertonic electrolyte administration to horses in this model was associated with exacerbation of gastric ulcers. POTENTIAL RELEVANCE: Our findings suggest that one schedule of electrolyte supplementation used commonly in endurance horses may be harmful to the gastric mucosa.

Anti-inflammatory and immune support in endotoxemia and septicemia.

Endotoxemia and septicemia are encountered frequently in equine veterinary practice. The deleterious effects of endotoxin are related to the severity of the response of the host's inflammatory system. Consequently, it is imperative that appropriate steps be taken to identify animals at risk of developing endotoxemia or septicemia, and to initiate treatments that will reduce the inflammatory response. This article discusses the anti-inflammatory and immune support of horses and foals with endotoxemia and septicemia.

Neurologic dysfunction associated with hypernatremia and dietary indiscretion in Vietnamese pot bellied pigs.

Neurologic disease associated with hypernatremia in 2 young Vietnamese potbellied pigs is discussed. Both pigs had recent dietary changes likely associated with excessive salt intake. Case 1 was changed from a commercial mini pig ration to a commercial cat food diet containing up to 1.5% salt 3-4 days before the onset of clinical signs. Case 2 was being maintained on a commercial mini pig ration, however the owner often fed the pig potato chips as treats since its purchase 3 weeks previously. There was no history of water deprivation in either pig. Clinical signs in case 1 included facial-motor seizures, sialorrhea, generalized seizures, tenesmus, disorientation, circling, head pressing, and blindness. Case 2 was disoriented, ataxic, underweight, and appeared blind. Both pigs fully recovered with medical therapy. The rationale for fluid and ancillary therapy are discussed in light of the pathophysiology of salt toxicosis in commercial swine.

Assessment of the nervous system.

This article describes the examination of the neurologic and ophthalmic systems in ruminants. Neuroanatomy with respect to lesion localization is reviewed. Pertinent age and species differences are addressed. The practical aspects of assessing the neurologic system are stressed, and the reader is directed to other sources of information for assistance in determining the differential diagnosis and therapy of neurologic disease.

Ancillary tests for assessment of the nervous system.

This article addresses the minimum data base needed to assist the clinician's diagnostic approach to neurologic diseases. The collection, storage, and processing of cerebrospinal fluid samples are discussed. Additional diagnostic tests are described under selected specific etiologies.

Contrast-enhanced computed tomography and myelography in six horses with cervical stenotic myelopathy.

The cervical spines of 6 horses with cervical stenotic myelopathy (CSM) were examined using myelography and contrast-enhanced computed tomography (CECT). Histopathology of the spinal cord of these horses identified 10 neurologically significant compressive lesions. Myelography and CECT were both able to demonstrate all 10 spinal cord compressive lesions, but myelography falsely identified 2 sites and CECT falsely identified 1 site as compressive lesions of the spinal cord which were not supported by histopathology. Additional qualitative information was obtained by CECT regarding the source, severity and location of spinal cord compression. Computed tomography identified stenosis of the vertebral canal with circumferential loss of contrast agent and documented lateral compressive lesions of the spinal cord due to malformed articular facets. Compression of the peripheral nerve roots by malformed articular facets encroaching on the intervertebral foramen was easily identified by CECT in the axial plane. No compressive lesions were identified in 3 unaffected horses by either method. Minimum sagittal diameter (MSD) values obtained from CECT images were strongly correlated with necropsy measurements, validating CECT as an accurate method of obtaining MSD values. The MSD values in the CSM-affected horses were significantly narrowed (P less than 0.05) from C3C6 regardless of the site of spinal cord compression, when compared with the unaffected controls. This finding supports previous reports suggesting that generalised stenosis of the vertebral canal is an important feature in the pathogenesis of cervical stenotic myelopathy.