Equine intervertebral disc disease with dorsal protrusion and spinal cord compression: A computed tomography, myelography, MRI, and histopathologic case study.

A 3-year-old American Saddlebred gelding presented for progressive tetraparesis, ataxia, and cervical hyperaesthesia. Radiographic myelography identified spinal cord compression at C6-7 in neutral, extended, and flexed positions and at C4-5 in the flexed position. CT myelography and postmortem MRI identified severe vertebral canal stenosis/compression at C6-7. MRI further identified severe intervertebral disc herniation at C6-7 with intramedullary changes. Disc protrusion was confirmed macroscopically at postmortem. Lesions consistent with compressive myelopathy were confirmed microscopically at C6-7. This is the first report of equine disc protrusion and myelocompression confirmed by multiple advanced imaging modalities and postmortem examination.

The Equine Neonatal Central Nervous System: Development and Diseases.

Neonatal encephalopathy is the most common neurologic condition affecting newborn foals and shares similarities with perinatal asphyxia syndrome of human infants. In many cases of neonatal encephalopathy there is no obvious episode of acute or chronic hypoxia and other mechanisms likely play a role in the pathogenesis. Increased concentrations of neuroactive progestagens are found in affected foals; whether these molecules are protective, as has been suggested, or play a role in the pathogenesis is unknown. Neurologic diseases other than neonatal encephalopathy affect foals occasionally and should be considered when evaluating sick foals with clinical signs of neurologic dysfunction.

Equine protozoal myeloencephalitis.

Equine protozoal myeloencephalitis (EPM) can be caused by either of 2 related protozoan parasites, Sarcocystis neurona and Neospora hughesi, although S. neurona is the most frequent etiologic pathogen. Horses are commonly infected, but clinical disease occurs infrequently; the factors influencing disease occurrence are not well understood. Risk factors for the development of EPM include the presence of opossums and prior stressful health-related events. Attempts to reproduce EPM experimentally have reliably induced antibody responses in challenged horses but have not consistently produced acute neurologic disease. Diagnosis and options for treatment of EPM have improved over the past decade.

Association of the neutrophil-lymphocyte ratio with outcome in sick hospitalized neonatal foals.

BACKGROUND: The neutrophil-lymphocyte ratio (NLR) in human medicine is an objective biomarker that reflects prognosis. The NLR as an independent biomarker to help predict nonsurvival in hospitalized neonatal foals has not been thoroughly interrogated. OBJECTIVES/HYPOTHESIS: Retrospectively evaluate if the NLR at admission is associated with nonsurvival in sick hospitalized foals <4 days old. We hypothesized that a lower NLR will be associated with nonsurvival. ANIMALS: One thousand one hundred ninety-six client-owned foals <4 days old of any breed and sex: 993 hospitalized foals and 203 healthy foals. METHODS: Retrospective multicenter study. Medical records of foals presenting to 3 equine referral hospitals were reviewed. Foals were included if they had complete CBCs, sepsis scores, and outcome data. The NLR was calculated by dividing the absolute neutrophil count by the absolute lymphocyte count. Data were analyzed by nonparametric methods and univariate analysis. RESULTS: Of the 993 sick hospitalized foals, 686 were sick nonseptic and 307 were septic. The median NLR was lower in sick hospitalized foals (median [95% confidence interval], 3.55 [0.5-13.9]) compared with healthy foals (6.61 [3.06-18.1]). Septic foals had the lowest NLR (2.00 [0.20-9.71]). The NLR was lower in nonsurviving (1.97 [1.67-2.45]) compared with surviving foals (4.10 [3.76-4.33]). Nonsurviving septic foals had the lowest NLR (1.47 [1.70-3.01]). Foals with a NLR of <3.06 or <1.6 at admission had odds ratio of 3.21 (2.24-4.29) and 4.03 (2.86-5.67) for nonsurvival, respectively. CONCLUSIONS AND CLINICAL IMPORTANCE: A NLR < 3.06 at admission in sick hospitalized foals is readily available and clinically useful variable to provide prognostic information.

Evaluation of the diagnostic value of transcranial electrical stimulation (TES) to assess neuronal functional integrity in horses.

Medical imaging allows for the visualization of spinal cord compression sites; however, it is impossible to assess the impact of visible stenotic sites on neuronal functioning, which is crucial information to formulate a correct prognosis and install targeted therapy. It is hypothesized that with the transcranial electrical stimulation (TES) technique, neurological impairment can be reliably diagnosed. Objective: To evaluate the ability of the TES technique to assess neuronal functional integrity in ataxic horses by recording TES-induced muscular evoked potentials (MEPs) in three different muscles and to structurally involve multiple ancillary diagnostic techniques, such as clinical neurological examination, plain radiography (RX) with ratio assessment, contrast myelography, and post-mortem gross and histopathological examination. Methods: Nine ataxic horses, showing combined fore and hindlimb ataxia (grades 2-4), were involved, together with 12 healthy horses. TES-induced MEPs were recorded bilaterally at the level of the trapezius (TR), the extensor carpi radialis (ECR), and tibialis cranialis (TC) muscles. Two Board-certified radiologists evaluated intra- and inter-sagittal diameter ratios on RX, reductions of dorsal contrast columns, and dural diameters (range skull-T1). Post-mortem gross pathological and segmental histopathological examination was also performed by a Board-certified pathologist. Results: TES-MEP latencies were significantly prolonged in both ECR and TC in all ataxic horses as opposed to the healthy horses. The TR showed a mixed pattern of normal and prolonged latency times. TES-MEP amplitudes were the least discriminative between healthy and ataxic horses. Youden's cutoff latencies for ataxic horses were 24.6 ms for the ECR and 45.5 ms for the TC (sensitivity and specificity of 100%). For healthy horses, maximum latency values were 22 and 37 ms, respectively. RX revealed spinal cord compression in 8 out of 9 involved ataxic horses with positive predictive values of 0-100%. All ataxic horses showed multi-segmental Wallerian degeneration. All pathological changes recorded in the white matter of the spinal cord were widely dispersed across all cervical segments, whereas gray matter damage was more localized at the specific segmental level. Conclusion: TES-MEP latencies are highly sensitive to detect impairment of spinal cord motor functions for mild-to-severe ataxia (grades 2-4).

The Second Case of Non-Mosaic Trisomy of Chromosome 26 with Homologous Fusion 26q;26q in the Horse.

We present cytogenetic and genotyping analysis of a Thoroughbred foal with congenital neurologic disorders and its phenotypically normal dam. We show that the foal has non-mosaic trisomy for chromosome 26 (ECA26) but normal 2n = 64 diploid number because two copies of ECA26 form a metacentric derivative chromosome der(26q;26q). The dam has normal 64,XX karyotype indicating that der(26q;26q) in the foal originates from errors in parental meiosis or post-fertilization events. Genotyping ECA26 microsatellites in the foal and its dam suggests that trisomy ECA26 is likely of maternal origin and that der(26q;26q) resulted from Robertsonian fusion. We demonstrate that conventional and molecular cytogenetic approaches can accurately identify aneuploidy with a derivative chromosome but determining the mechanism and parental origin of the rearrangement requires genotyping with chromosome-specific polymorphic markers. Most curiously, this is the second case of trisomy ECA26 with der(26q;26q) in the horse, whereas all other equine autosomal trisomies are 'traditional' with three separate chromosomes. We discuss possible ECA26 instability as a contributing factor for the aberration and likely ECA26-specific genetic effects on the clinical phenotype. Finally, because ECA26 shares evolutionary homology with human chromosome 21, which trisomy causes Down syndrome, cytogenetic, molecular, and phenotypic similarities between trisomies ECA26 and HSA21 are discussed.

Serum and cerebrospinal fluid phosphorylated neurofilament heavy protein concentrations in equine neurodegenerative diseases.

BACKGROUND: Currently, there is little information regarding the concentrations of phosphorylated neurofilament heavy protein (pNfH) in the serum and cerebrospinal fluid (CSF) of horses with neurodegenerative diseases. Specifically, pNfH concentrations have not yet been evaluated in horses with equine neuroaxonal dystrophy/equine degenerative myeloencephalopathy (eNAD/EDM). OBJECTIVES: To determine pNfH concentrations using a commercial enzyme-linked immunosorbent assay (ELISA) in serum and CSF from control horses and horses with eNAD/EDM, cervical vertebral compressive myelopathy (CVCM) and Shivers. STUDY DESIGN: Case-control study using biobanked samples from diseased horses and prospective or biobanked samples from control horses. METHODS: The pNfH ELISA was performed on samples from horses diagnosed with eNAD/EDM (n = 64), CVCM (n = 26) and Shivers (n = 9) and 51 neurologically normal control horses. RESULTS: Median and 95% confidence interval (CI) serum pNfH concentrations in control, CVCM, and eNAD/EDM horses were 0.08 ng/mL (0.07-0.15), 0.07 ng/mL (0.07-0.15) and 0.07 ng/mL (0.07-1.13), respectively. Serum pNfH concentrations were below the limit of detection (<0.07 ng/mL) for all Shivers horses. CSF pNfH concentrations in control, CVCM-, eNAD/EDM- and Shivers-affected horses were 1.26 ng/mL (1.06-1.5), 3.07 ng/mL (1.15-29.9), 1.78 ng/mL (1.5-2.28) and 1.39 ng/mL (0.74-3.89), respectively. CSF pNfH concentrations were significantly higher in CVCM (P = .001) and eNAD/EDM (P  = .01) affected horses compared to control horses. Serum pNfH concentrations >1 ng/mL were significantly associated with eNAD/EDM (P = .01) with only 12% sensitivity but 99% specificity. CSF pNfH concentrations >3 ng/mL were significantly associated with CVCM (P = .0002), with 50% sensitivity and 86% specificity. MAIN LIMITATIONS: A limited number of control horses tested were <1 year of age. CONCLUSIONS: Serum pNfH concentrations are specifically increased (>1 ng/mL) in some horses with eNAD/EDM. Increased CSF pNfH concentrations (>3 ng/mL) can be observed with eNAD/EDM or CVCM.

Horses affected by EPM have increased sCD14 compared to healthy horses.

Equine protozoal myeloencephalitis (EPM) is a debilitating neurologic disease affecting horses across the Americas. Gaps in understanding the inflammatory immune response in EPM-affected horses create difficulties with diagnosis and treatment, subsequently negatively impacting the prognosis of affected horses. The purpose of the current study was to evaluate circulating levels of the inflammatory immune marker soluble CD14 (sCD14), in horses with EPM (n = 7) and determine if they differed from healthy neurologically normal horses (n = 6). Paired sera and cerebrospinal fluid (CSF) samples were analyzed for sCD14. Inclusion criteria for EPM horses consisted of the presence of neurologic signs consistent with EPM, Sarcocystis neurona surface antigens 2, 4/3 (SnSAG 2, 4/3) ELISA serum: CSF antibody ratio ≤ 100, and a postmortem diagnosis of EPM. Control horses were neurologically normal, healthy horses with SnSAG 2, 4/3 ELISA serum: CSF antibody ratios of > 100. Serum anti-Sarcocystis neurona antibodies indicate that healthy control horses were exposed to S. neurona but resistant to developing clinical EPM. EPM cases had significantly greater concentrations of sCD14 in CSF samples compared to control horses and increased serum sCD14 concentrations. A positive correlation between sCD14 serum and CSF concentrations was observed in EPM-affected horses but not healthy horses. Soluble CD14 is an inflammatory marker, and the study results suggest it is elevated in EPM patients. When performed in conjunction with clinical evaluation and standard antibody testing, there may be potential for sCD14 to be utilized as a correlate for EPM.

Multicenter case-control study of signalment, diagnostic features, and outcome associated with cervical vertebral malformation-malarticulation in horses.

OBJECTIVE: To compare signalment of horses with cervical vertebral malformation-malarticulation (CVM) with that of control horses and to describe results of clinical examination, diagnostic imaging and necropsy findings, and reported outcome in horses with CVM. DESIGN: Retrospective case-control study. ANIMALS: 270 horses with CVM and 608 control horses admitted to 6 veterinary hospitals from 1992 through 2007. PROCEDURES: Medical records of participating hospitals were reviewed to identify horses with CVM (ie, case horses) and contemporaneous control (non-CVM-affected) horses that were admitted for treatment. Signalment was compared between case horses and control horses. Results of clinical examination, laboratory and diagnostic imaging findings, necropsy results, and outcome were assessed for horses with CVM. RESULTS: Case horses were younger (median age, 2 years) than were control horses (median age, 7 years). Thoroughbreds, warmbloods, and Tennessee Walking Horses were overrepresented in the CVM group. Gait asymmetry and cervical hyperesthesia were frequently detected in horses with CVM. Vertebral canal stenosis and articular process osteophytosis were commonly observed at necropsy; agreement between the results of radiographic or myelographic analysis and detection of lesions at necropsy was 65% to 71% and 67% to 78%, respectively. Of 263 horses with CVM for which outcome was recorded, 1 died and 172 (65.4%) were euthanatized. CONCLUSIONS AND CLINICAL RELEVANCE: Odds of a diagnosis of CVM were greater in young horses and horses of specific breeds. Detection of gait asymmetry and cervical hyperesthesia were frequently reported in association with CVM. Accurate diagnosis of lesions associated with CVM by use of radiography and myelography can be challenging.

Searching for the Big Pictures.

My goal in searching for the big pictures is to discover novel ways of organizing information in psychology that will have both theoretical and practical significance. The first section lists my reasons for writing each of five articles. The second section discusses an additional five articles that integrate advancements in artificial intelligence and cognitive psychology. The following two sections elaborate on my collaboration with ontologists to use formal ontologies to organize psychological knowledge, including the National Institute of Mental Health Research Domain Criteria, for formulating a biological basis for mental illness. I next discuss strategies for writing integrative articles. The following section describes the helpfulness of the integrations for making psychology relevant to a general audience. I conclude with recommendations for creating breadth in doctoral training.

Comparative H-gal-GP and H11 specific antibody binding in equine cyathostomins.

The biological-based vaccine (Barbervax®) generates effective antibodies against the biologically essential H-gal-GP and H11 protein complex of the ruminant parasite Haemonchus contortus to target and kill the parasites after taking a blood meal. A comparative analysis of several parasite genera was performed to determine if a similar protein complex or one that is recognized by H-gal-GP and H11 specific antibodies was present. If so, it suggests the vaccine could be effective for other nematode parasites. Ancylostoma caninum, H. contortus, equine cyathostomins, bovine Bunostomum phlebotomum, Dracunculus lutrae, Parascaris sp., Ixodes scapularis, Amblyomma americanum, Dirofilaria immitis and Brugia malayi were evaluated for specific antibody binding using hyperimmunized antibodies against H-gal-GP and H11 native proteins. Of the parasites evaluated, specific and reproducible staining was observed in H. contortus and adult and encysted cyathostomins only. To further evaluate the similar reactivities between cyathostomins and H. contortus, cross-reactivity of equine serum with antibodies to cyathostomins on a H. contortus adult histology cross-section was observed using immunofluorescence. These findings pave the way for future studies on the safety and efficacy of H-gal-GP and H11 protein complex as a potential control for cyathostomins.

Extramuscular Recording of Spontaneous EMG Activity and Transcranial Electrical Elicited Motor Potentials in Horses: Characteristics of Different Subcutaneous and Surface Electrode Types and Practical Guidelines.

INTRODUCTION: Adhesive surface electrodes are worthwhile to explore in detail as alternative to subcutaneous needle electrodes to assess myogenic evoked potentials (MEP) in human and horses. Extramuscular characteristics of both electrode types and different brands are compared in simultaneous recordings by also considering electrode impedances and background noise under not mechanically secured (not taped) and taped conditions. METHODS: In five ataxic and one non-ataxic horses, transcranial electrical MEPs, myographic activity, and noise were simultaneously recorded from subcutaneous needle (three brands) together with pre-gelled surface electrodes (five brands) on four extremities. In three horses, the impedances of four adjacent-placed surface-electrode pairs of different brands were measured and compared. The similarity between needle and surface EMGs was assessed by cross-correlation functions, pairwise comparison of motor latency times (MLT), and amplitudes. The influence of electrode noise and impedance on the signal quality was assessed by a failure rate (FR) function. Geometric means and impedance ranges under not taped and taped conditions were derived for each brand. RESULTS: High coherencies between EMGs of needle-surface pairs degraded to 0.7 at moderate and disappeared at strong noise. MLTs showed sub-millisecond simultaneous differences while sequential variations were several milliseconds. Subcutaneous MEP amplitudes were somewhat lower than epidermal. The impedances of subcutaneous needle electrodes were below 900 Ω and FR = 0. For four brands, the FR for surface electrodes was between 0 and 80% and declined to below 25% after taping. A remaining brand (27G DSN2260 Medtronic) revealed impedances over 100 kΩ and FR = 100% under not taped and taped conditions. CONCLUSION: Subcutaneous needle and surface electrodes yield highly coherent EMGs and TES-MEP signals. When taped and allowing sufficient settling time, adhesive surface-electrode signals may approach the signal quality of subcutaneous needle electrodes but still depend on unpredictable conditions of the skin. The study provides a new valuable practical guidance for selection of extramuscular EMG electrodes. This study on horses shares common principles for the choice of adhesive surface or sc needle electrodes in human applications such as in intraoperative neurophysiological monitoring of motor functions of the brain and spinal cord.

Factors predictive of abnormal results for computed tomography of the head in horses affected by neurologic disorders: 57 cases (2001-2007).

OBJECTIVE: To determine neurologic indications associated with abnormal results for computed tomography (CT) imaging of the head of horses affected by neurologic disorders. DESIGN: Retrospective case series. ANIMALS: 57 horses. PROCEDURES: Signalment, history, clinical abnormalities, and clinicopathologic findings were obtained from medical records of horses examined because of neurologic disorders, and precontrast and postcontrast CT images of the head were reviewed. Data were analyzed by use of univariate and multivariate logistic regression. RESULTS: For a horse with abnormal mentation, odds of having abnormal results for CT imaging of the head was 30 times (95% confidence interval [CI], 2.36 to 374.63) the odds for a similar horse without abnormal mentation. For a horse with cranial nerve deficits, odds of having abnormal results for CT imaging of the head was 11 times (95% CI, 1.00 to 127.96) the odds for a similar horse without cranial nerve deficits. For a horse with seizure-like activity, odds of having abnormal results for CT imaging of the head was 0.05 times (95% CI, 0 to 0.90) the odds for a similar horse without seizures. CONCLUSIONS AND CLINICAL RELEVANCE: These results suggested that alterations in consciousness and cranial nerve deficits were strong predictors of abnormal CT findings for the head of affected horses. Thus, CT can be a useful complementary diagnostic test in horses with these neurologic deficits. In contrast, alternative diagnostic tests (eg, electroencephalography and magnetic resonance imaging) should be considered in horses with seizure-like activity that do not have head trauma or cranial nerve deficits.

Use of kinetic gait analysis for detection, quantification, and differentiation of hind limb lameness and spinal ataxia in horses.

OBJECTIVE: To evaluate use of kinetic gait analysis for detection, quantification, and differentiation of hind limb lameness and spinal ataxia in horses. DESIGN: Prospective clinical study. ANIMALS: 36 horses. Procedures-Kinetic gait analysis with a force plate was performed for 12 clinically normal horses, 12 horses with hind limb lameness, and 12 horses with spinal ataxia. Kinetic variables were compared among groups, correlated to subjective grading, and used to build predictive models to assess the accuracy of discrimination. RESULTS: Subsets of kinetic variables were characteristically altered in ataxic and lame gaits. Ataxic horses had significantly increased lateral force peak and variation in vertical force peaks in both hind limbs. Lame horses had significantly decreased vertical force peak and increased variation in vertical force peaks only in the lame hind limb. These variables were used to differentiate between spinal ataxia and hind limb lameness with excellent accuracy. There were significant correlations between a subset of kinetic variables and subjective lameness and neurologic grades. CONCLUSIONS AND CLINICAL RELEVANCE: Kinetic gait variables, specifically lateral force peak and the variation in vertical force, can be used to support the differential diagnosis between spinal ataxia and hind limb lameness in horses. Kinetic gait analysis may also be applied for quantification of equine hind limb gait abnormalities as well as confirming lack of lameness and ataxia in soundness examinations.

Accelerating protons to therapeutic energies with ultraintense, ultraclean, and ultrashort laser pulses.

Proton acceleration by high-intensity laser pulses from ultrathin foils for hadron therapy is discussed. With the improvement of the laser intensity contrast ratio to 10(-1) achieved on the Hercules laser at the University of Michigan, it became possible to attain laser-solid interactions at intensities up to 10(22) W/cm2 that allows an efficient regime of laser-driven ion acceleration from submicron foils. Particle-in-cell (PIC) computer simulations of proton acceleration in the directed Coulomb explosion regime from ultrathin double-layer (heavy ions/light ions) foils of different thicknesses were performed under the anticipated experimental conditions for the Hercules laser with pulse energies from 3 to 15 J, pulse duration of 30 fs at full width half maximum (FWHM), focused to a spot size of 0.8 microm (FWHM). In this regime heavy ions expand predominantly in the direction of laser pulse propagation enhancing the longitudinal charge separation electric field that accelerates light ions. The dependence of the maximum proton energy on the foil thickness has been found and the laser pulse characteristics have been matched with the thickness of the target to ensure the most efficient acceleration. Moreover, the proton spectrum demonstrates a peaked structure at high energies, which is required for radiation therapy. Two-dimensional PIC simulations show that a 150-500 TW laser pulse is able to accelerate protons up to 100-220 MeV energies.

Outbreak of neurologic disease caused by equine herpesvirus-1 at a university equestrian center.

BACKGROUND: Equine herpesvirus type 1 (EHV-1) infection causes neurologic disease in horses. However, risk factors for the disease and long-term prognosis are poorly characterized. HYPOTHESIS: There are identifiable risk factors for equine herpes-1 myeloencephalopathy. ANIMALS: The entire population of 135 horses housed within the equestrian facility. METHODS: A descriptive study investigated the clinical, serologic, virologic, and management aspects of an outbreak of EHV-1 myeloencephalopathy. RESULTS: Out of 135 horses at the facility, 117 displayed signs of EHV-1 infection. Forty-six horses developed neurologic deficits characterized by symmetrical hind limb ataxia and weakness. Twelve horses that developed neurologic deficits became recumbent and did not survive. The development of severe neurologic deficits during the outbreak was associated with the presence of residual deficits at the 6-month examination. Within 1 year of the outbreak onset, all horses that survived had returned to an exercise level comparable to that experienced before the outbreak. Factors associated with the development of neurologic disease included age of > 5 years, location in the south or arena stall areas, and highest rectal temperature on day 3 or later of the febrile period. CONCLUSIONS AND CLINICAL IMPORTANCE: Being > 5 years of age, having had a rectal temperature of > 103.5 degrees F, and highest rectal temperature occurring on or after the 3rd day of the febrile period were the factors most predictive of the development of neurologic disease and death. Data obtained during this outbreak substantiate previous findings relating to clinical aspects and diagnosis of EHV-1 myeloencephalopathy. The prophylactic and therapeutic use of acyclovir during this outbreak is described.

Pharmacokinetics of voriconazole following intravenous and oral administration and body fluid concentrations of voriconazole following repeated oral administration in horses.

OBJECTIVE: To determine the pharmacokinetics of voriconazole following IV and PO administration and assess the distribution of voriconazole into body fluids following repeated PO administration in horses. ANIMALS: 6 clinically normal adult horses. PROCEDURES: All horses received voriconazole (10 mg/kg) IV and PO (2-week interval between treatments). Plasma voriconazole concentrations were determined prior to and at intervals following administration. Subsequently, voriconazole was administered PO (3 mg/kg) twice daily for 10 days to all horses; plasma, synovial fluid, CSF, urine, and preocular tear film concentrations of voriconazole were then assessed. RESULTS: Mean +/- SD volume of distribution at steady state was 1,604.9 +/- 406.4 mL/kg. Systemic bioavailability of voriconazole following PO administration was 95 +/- 19%; the highest plasma concentration of 6.1 +/- 1.4 microg/mL was attained at 0.6 to 2.3 hours. Mean peak plasma concentration was 2.57 microg/mL, and mean trough plasma concentration was 1.32 microg/mL. Mean plasma, CSF, synovial fluid, urine, and preocular tear film concentrations of voriconazole after long-term PO administration were 5.163 +/- 1.594 microg/mL, 2.508 +/- 1.616 microg/mL, 3.073 +/- 2.093 microg/mL, 4.422 +/- 0.8095 microg/mL, and 3.376 +/- 1.297 microg/mL, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that voriconazole distributed quickly and widely in the body; following a single IV dose, initial plasma concentrations were high with a steady and early decrease in plasma concentration. Absorption of voriconazole after PO administration was excellent, compared with absorption after IV administration. Voriconazole appears to be another option for the treatment of fungal infections in horses.

A multicenter case-control study of risk factors for equine protozoal myeloencephalitis.

OBJECTIVE: To identify risk factors for equine protozoal myeloencephalitis (EPM) among horses examined at 11 equine referral hospitals. DESIGN: Case-control study. ANIMALS: 183 horses with EPM, 297 horses with neurologic disease other than EPM (neurologic controls), and 168 horses with non-neurologic diseases (non-neurologic controls) examined at 11 equine referral hospitals in the United States. PROCEDURES: A study data form was completed for all horses. Data were compared between the case group and each of the control groups by means of bivariate and multivariate polytomous logistic regression. RESULTS: Relative to neurologic control horses, case horses were more likely to be > or = 2 years old and to have a history of cats residing on the premises. Relative to non-neurologic control horses, case horses were more likely to be used for racing or Western performance. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that cats may play a role in the natural epidemiology of EPM, that the disease is less common among horses < 2 years of age relative to other neurologic diseases, and that horses used for particular types of competition may have an increased risk of developing EPM.

Small sarcocysts can be a feature of experimental infections with Sarcocystis neurona merozoites.

Several reports indicate the presence of small tissue cysts associated with Sarcocystis neurona infections. Several failed attempts to develop tissue cysts in potential intermediate host using in vitro derived parasites originally isolated from horses with equine protozoal myeloencephalitis suggest that the experimental methods to achieve bradyzoites with those isolates was not possible. Those prior studies reported the lack of detectable sarcocysts based on histology and in vivo feeding trials. A recent report of successful production and detection of small sarcocysts triggered us to review archived tissues from earlier experimental infection studies. The retrospective review sought to determine if small sized sarcocysts were not detected due to their relatively smaller size and infrequency as compared to larger sized sarcocysts produced with other isolates in these experimental inoculation trials. Tissues from two prior in vivo inoculation studies, involving in vitro-produced parasites inoculated into laboratory-reared cats and raccoons, were re-examined by immunohistochemistry staining to more easily detect the tissue cysts. In the experimental cat study no small tissue cysts were seen, consistent with the original publication results. However, in the experimental raccoon study, one raccoon inoculated with an EPM-derived isolate, SN-UCD1, had small sarcocysts not reported in the original publication. This retrospective study suggests that much closer scrutiny of tissues, including the use of immunohistochemistry on tissue sections is required to detect the smaller S. neurona sarcocysts associated with the experimental inoculations of the isolates originally derived from horses with EPM.