Incorporation of Equine Learning Theory into the Undergraduate Curriculum.

Working as an equine veterinarian carries a high risk of occupational injury, with the behavior of the horse frequently reported as a cause for these injuries. Risk of injury is one reason cited by undergraduate veterinary students that would prevent them from entering large animal practice, and newly graduated veterinarians have been shown to be at increased risk of sustaining an occupational injury compared with more experienced colleagues. A cohort of pre-final-year undergraduate veterinary students were given a 45-minute lecture on learning theory and its application in equine practice, completing a questionnaire before (pre) and after (immediately [post] and several weeks [delayed post]) to investigate whether receiving a single lecture alters undergraduate veterinary students' perception of dealing with difficult horses in equine practice. The undergraduate veterinary students' attitudes to the behavior scenarios altered from the pre-questionnaire to the post- and delayed post-questionnaires. They were less likely to choose more traditional methods of restraining or controlling the horse (such as a twitch) and more likely to choose an option based on learning theory after the lecture. They also reported that if they had to deal with one of these scenarios in practice following the lecture, they would feel more confident, more likely to succeed in completing the intervention, and less likely to be injured. This study suggests that an educational intervention can help change the attitudes and confidence of undergraduate students when working with difficult horses.

Examination of Horses with Cardiac Disease.

Despite advances, increased convenience, and availability of echocardiography and other diagnostic techniques in equine cardiology, a comprehensive history and clinical examination still forms the essential first step in any cardiac evaluation. This article summarizes the approach to the cardiac examination at rest, highlighting key areas for the clinician to assess, and stressing the importance of context for assessing the significance of any abnormalities detected. Ancillary techniques, such as blood pressure measurement and the laboratory assessment of cardiac disease in the horse, are also introduced.

Proteomic Profiling of Cranial (Superior) Cervical Ganglia Reveals Beta-Amyloid and Ubiquitin Proteasome System Perturbations in an Equine Multiple System Neuropathy.

Equine grass sickness (EGS) is an acute, predominantly fatal, multiple system neuropathy of grazing horses with reported incidence rates of ∼2%. An apparently identical disease occurs in multiple species, including but not limited to cats, dogs, and rabbits. Although the precise etiology remains unclear, ultrastructural findings have suggested that the primary lesion lies in the glycoprotein biosynthetic pathway of specific neuronal populations. The goal of this study was therefore to identify the molecular processes underpinning neurodegeneration in EGS. Here, we use a bottom-up approach beginning with the application of modern proteomic tools to the analysis of cranial (superior) cervical ganglion (CCG, a consistently affected tissue) from EGS-affected patients and appropriate control cases postmortem. In what appears to be the proteomic application of modern proteomic tools to equine neuronal tissues and/or to an inherent neurodegenerative disease of large animals (not a model of human disease), we identified 2,311 proteins in CCG extracts, with 320 proteins increased and 186 decreased by greater than 20% relative to controls. Further examination of selected proteomic candidates by quantitative fluorescent Western blotting (QFWB) and subcellular expression profiling by immunohistochemistry highlighted a previously unreported dysregulation in proteins commonly associated with protein misfolding/aggregation responses seen in a myriad of human neurodegenerative conditions, including but not limited to amyloid precursor protein (APP), microtubule associated protein (Tau), and multiple components of the ubiquitin proteasome system (UPS). Differentially expressed proteins eligible for in silico pathway analysis clustered predominantly into the following biofunctions: (1) diseases and disorders, including; neurological disease and skeletal and muscular disorders and (2) molecular and cellular functions, including cellular assembly and organization, cell-to-cell signaling and interaction (including epinephrine, dopamine, and adrenergic signaling and receptor function), and small molecule biochemistry. Interestingly, while the biofunctions identified in this study may represent pathways underpinning EGS-induced neurodegeneration, this is also the first demonstration of potential molecular conservation (including previously unreported dysregulation of the UPS and APP) spanning the degenerative cascades from an apparently unrelated condition of large animals, to small animal models with altered neuronal vulnerability, and human neurological conditions. Importantly, this study highlights the feasibility and benefits of applying modern proteomic techniques to veterinary investigations of neurodegenerative processes in diseases of large animals.

Equine grass sickness is associated with major abnormalities in the ultrastructure of skeletal neuromuscular junctions.

BACKGROUND: Equine grass sickness (EGS) is a frequently fatal multisystem neuropathy of equids. The aetiology is unknown; proposed causes include toxicoinfection with Clostridium botulinum and a mycotoxicosis. The effect of EGS on the organisation and structural integrity of the skeletal neuromuscular junction (NMJ), the target of botulinum neurotoxins (BoNTs), is unknown. OBJECTIVES: To compare the organisation and structural integrity of skeletal NMJs from EGS horses, control horses and one horse with a presumptive diagnosis of botulism. STUDY DESIGN: Blinded, retrospective case control. METHODS: NMJs in samples of diaphragm or intercostal muscle from six EGS horses, three control horses and one equine botulism case were compared using electron microscopy, morphometry and confocal light microscopy. RESULTS: A significantly higher percentage of EGS NMJs had abnormal morphology (EGS 72.2%, 95% CI 55.6-84.4; Controls 6.9%, 1.7-23.8; OR 35.1, 8.47-244.8; p < 0.001). EGS NMJs had a significantly lower mean volume fraction occupied by synaptic vesicles (SVs) (EGS 18.7%, 12.6-28.0; Controls 36.3%, 20.8-63.4; p = 0.024). EGS NMJs had evidence of accelerated SV exocytosis and SV depletion, accumulation of neurofilament-like material in terminal boutons and/or bouton degeneration. NMJs from the botulism horse had dense packing of SVs towards the presynaptic membrane active zone, consistent with BoNT intoxication, but had absence of the abnormalities identified in EGS NMJs. MAIN LIMITATIONS: Group sizes were limited by difficulties obtaining suitably processed samples. Ages of control and EGS horses differed. Botulism was diagnosed based on clinical and post mortem findings. CONCLUSIONS: EGS is associated with major changes in skeletal NMJ ultrastructure that are inconsistent with the effects of BoNTs. SV depletion may reflect increased exocytosis coupled with reduced repopulation of SVs via anterograde axonal transport and endocytosis, consistent with the action of an excitatory presynaptic toxin and/or neurotransmitter reuptake inhibitor. Skeletal NMJs represent a previously unrecognised target for the toxin that causes EGS.

The effect of season, management and endocrinopathies on vitamin D status in horses.

BACKGROUND: Vitamin D deficiency is common in humans and is increasingly linked to the pathogenesis of a multitude of diseases including obesity and metabolic syndrome. The biology of vitamin D in horses is poorly described; the relative contribution of the diet and skin synthesis to circulating concentrations is unclear and associations with the endocrine disease have not been explored. OBJECTIVES: To determine the relationship between management, season and endocrine disease and vitamin D status in horses. STUDY DESIGN: Cross-sectional cohort study. METHODS: Plasma concentrations of 25-hydroxyvitamin D2 (25(OH)D2 ) and D3 (25(OH)D3 ) were measured by liquid chromatography-tandem mass spectrometry in 34 healthy unsupplemented grazing ponies and 22 stabled Thoroughbreds receiving supplementary vitamin D3 in feed. A nested group of 18 grazing ponies were sampled on long and short days (>12 and <12 h of light/day) to determine the effect of sunlight exposure. In addition, the relationships between age, sex, adiposity, serum insulin, adrenocorticotropic hormone and vitamin D status were assessed in a mixed group of 107 horses using a linear regression model. RESULTS: All animals had a measurable level of 25(OH)D2 (median 10.7 nmol/L) whilst 25(OH)D3 was only detected in Thoroughbreds receiving D3 supplementation. Thoroughbreds had lower concentrations of 25(OH)D2 than ponies (7.4 vs. 12.6 nmol/L, p < 0.01). In grazing ponies, 25(OH)D2 concentrations were significantly higher on long days compared to short days (14.4 vs. 8.7 nmol/L, p < 0.01), whilst 25(OH)D3 was undetectable. Measures of increased adiposity, but not basal insulin, were associated with higher 25(OH)D2 concentrations, conversely to humans. Increasing ACTH was associated with lower 25(OH)D2 (p < 0.01). MAIN LIMITATIONS: Vitamin D2 concentrations were not measured in grass or forage. CONCLUSIONS: In horses 25(OH)D2 is the predominant vitamin D metabolite, and there is an apparent lack of endogenous vitamin D3 production. The relationship between vitamin D and endocrine disorders in horses does not reflect that of other species and warrants further investigation.

Real-time three-dimensional echocardiography for left atrial volume assessment in Thoroughbred racehorses: Observer variability and comparison with two-dimensional echocardiography.

BACKGROUND: Left atrial size predicts cardiac morbidity and mortality in humans and dogs. Real-time three-dimensional echocardiography (3DE) may be reliable for assessing left atrial volume (LAV) in horses. OBJECTIVES: To determine intra- and interobserver variability estimates of 3DE-LAV and compare it to that of 2DE-LAV estimates. STUDY DESIGN: Method comparison. METHODS: 3DE datasets were obtained from 40 horses, then graded for quality, creating a final study population of 22 horses. The 3DE and 2DE maximum LAV (LAVmax ) and minimum LAV (LAVmin ) were measured, and left atrial emptying volume (LA EV) and left atrial ejection fraction (LA EF) were calculated, from the same 3D dataset on four occasions using (a) a semi-automatic surface recognition algorithm and (b) a modified Simpson's method of discs. 3DE LAV measurements were repeated by a second observer. RESULTS: For 3DE, median LAVmax was 596cm3 for observer one, and 852 cm3 for observer two, LAVmin was 373 cm3 for observer one and 533 cm3 for observer two. Low intraobserver measurement variation was observed for LAVmax and LAVmin , with horse-level intraclass correlation coefficients (ICChorse ) for both observers between 76% and 85% (horse added as random effect). The interobserver ICC was 58% for LAVmax and 50% for LAVmin on averaged measurements (with observer added as random effect), indicating consistent differences between observers. While intraobserver variation was similar for 2DE LAVmax measurements, it was greater for LAVmin (ICChorse  = 67%). The intermethod ICC for 3DE vs 2DE was low at 14% for LAVmax and ~0% for LAVmin , indicating less-consistent differences with method. MAIN LIMITATIONS: Small study population, low observer number, use of different imaging modalities (fundamental frequency and octave harmonics). CONCLUSIONS: 3DE assessment of LAV was reliable, suggesting suitability for longitudinal evaluation of clinical cases. Clinicians should be aware of differences in LAV measurements between observers. More defined measurement guidelines may improve repeatability.

Coactivation of pre- and postsynaptic signaling mechanisms determines cell-specific spike-timing-dependent plasticity.

Synapses may undergo long-term increases or decreases in synaptic strength dependent on critical differences in the timing between pre-and postsynaptic activity. Such spike-timing-dependent plasticity (STDP) follows rules that govern how patterns of neural activity induce changes in synaptic strength. Synaptic plasticity in the dorsal cochlear nucleus (DCN) follows Hebbian and anti-Hebbian patterns in a cell-specific manner. Here we show that these opposing responses to synaptic activity result from differential expression of two signaling pathways. Ca2+/calmodulin-dependent protein kinase II (CaMKII) signaling underlies Hebbian postsynaptic LTP in principal cells. By contrast, in interneurons, a temporally precise anti-Hebbian synaptic spike-timing rule results from the combined effects of postsynaptic CaMKII-dependent LTP and endocannabinoid-dependent presynaptic LTD. Cell specificity in the circuit arises from selective targeting of presynaptic CB1 receptors in different axonal terminals. Hence, pre- and postsynaptic sites of expression determine both the sign and timing requirements of long-term plasticity in interneurons.

Equine grass sickness (a multiple systems neuropathy) is associated with alterations in the gastrointestinal mycobiome.

BACKGROUND: Equine grass sickness (EGS) is a multiple systems neuropathy of grazing horses of unknown aetiology. An apparently identical disease occurs in cats, dogs, rabbits, hares, sheep, alpacas and llamas. Many of the risk factors for EGS are consistent with it being a pasture mycotoxicosis. To identify potential causal fungi, the gastrointestinal mycobiota of EGS horses were evaluated using targeted amplicon sequencing, and compared with those of two control groups. Samples were collected post mortem from up to 5 sites in the gastrointestinal tracts of EGS horses (EGS group; 150 samples from 54 horses) and from control horses that were not grazing EGS pastures and that had been euthanased for reasons other than neurologic and gastrointestinal diseases (CTRL group; 67 samples from 31 horses). Faecal samples were also collected from healthy control horses that were co-grazing pastures with EGS horses at disease onset (CoG group; 48 samples from 48 horses). RESULTS: Mycobiota at all 5 gastrointestinal sites comprised large numbers of fungi exhibiting diverse taxonomy, growth morphology, trophic mode and ecological guild. FUNGuild analysis parsed most phylotypes as ingested environmental microfungi, agaricoids and yeasts, with only 1% as gastrointestinal adapted animal endosymbionts. Mycobiota richness varied throughout the gastrointestinal tract and was greater in EGS horses. There were significant inter-group and inter-site differences in mycobiota structure. A large number of phylotypes were differentially abundant among groups. Key phylotypes (n = 56) associated with EGS were identified that had high abundance and high prevalence in EGS samples, significantly increased abundance in EGS samples, and were important determinants of the inter-group differences in mycobiota structure. Many key phylotypes were extremophiles and/or were predicted to produce cytotoxic and/or neurotoxic extrolites. CONCLUSIONS: This is the first reported molecular characterisation of the gastrointestinal mycobiota of grazing horses. Key phylotypes associated with EGS were identified. Further work is required to determine whether neurotoxic extrolites from key phylotypes contribute to EGS aetiology or whether the association of key phylotypes and EGS is a consequence of disease or is non-causal.

Pathological bradyarrhythmia in horses.

Pathological bradyarrhythmia is rare in horses but should be especially considered when presented with a horse that has signs consistent with episodic weakness or collapse. This paper reviews the literature describing our current knowledge of, and possible mechanisms causing, clinically significant bradyarrhythmia in horses.

Inducing weight loss in native ponies: is straw a viable alternative to hay?

BACKGROUND: Obesity is a growing problem in UK equine population. Achieving weight loss in obese horses and ponies at risk of laminitis is an important but often challenging objective. METHODS: We hypothesised that supplementing poor winter pasture with a mix of barley straw and hay (50:50) rather than hay alone (group B) would lead to weight loss in grazing equids over winter. For this purpose, a group of 40 horses were fed either the straw mix (group A) or hay alone (group B) over winter. RESULTS: Over the study period, all animals in group A (n=25) lost weight with a mean weight change of -27±17 kg, while in group B (n=15) only 3 out of 15 lost weight (20 per cent), and overall, group B gained weight (+6±18 kg). CONCLUSIONS: This study suggests that straw is a cost-effective and low-energy roughage, which may be a useful alternative to hay alone when trying to induce weight loss in grazing equids over winter. There were no episodes of colic or laminitis during the study period in either group.

What is the point: will screening mammography save my life?

BACKGROUND: We analyzed the claim "mammography saves lives" by calculating the life-saving absolute benefit of screening mammography in reducing breast cancer mortality in women ages 40 to 65. METHODS: To calculate the absolute benefit, we first estimated the screen-free absolute death risk from breast cancer by adjusting the Surveillance, Epidemiology and End Results Program 15-year cumulative breast cancer mortality to account for the separate effects of screening mammography and improved therapy. We calculated the absolute risk reduction (reduction in absolute death risk), the number needed to screen assuming repeated screening, and the survival percentages without and with screening. We varied the relative risk reduction from 10%-30% based on the randomized trials of screening mammography. We developed additional variations of the absolute risk reduction for a screening intervention, including the average benefit of a single screen, as well as the life-saving proportion among patients with earlier cancer detection. RESULTS: Because the screen-free absolute death risk is approximately 1% overall but rises with age, the relative risk reduction from repeated screening mammography is about 100 times the absolute risk reduction between the starting ages of 50 and 60. Assuming a base case 20% relative risk reduction, repeated screening starting at age 50 saves about 1.8 (overall range, 0.9-2.7) lives over 15 years for every 1000 women screened. The number needed to screen repeatedly is 1000/1.8, or 570. The survival percentage is 99.12% without and 99.29% with screening. The average benefit of a single screening mammogram is 0.034%, or 2970 women must be screened once to save one life. Mammography saves 4.3% of screen-detectable cancer patients' lives starting at age 50. This means 23 cancers must be found starting at age 50, or 27 cancers at age 40 and 21 cancers at age 65, to save one life. CONCLUSION: The life-saving absolute benefit of screening mammography increases with age as the absolute death risk increases. The number of events needed to save one life varies depending on the prospective screening subset or reference class. Less than 5% of women with screen-detectable cancers have their lives saved.

Evaluation of equine laminar vein function: harvesting, dissection and the use of functional methods to distinguish between veins and arteries.

INTRODUCTION: Pharmacological evaluation of the unique equine laminar microvasculature is crucial to understanding its role in health and in diseases such as laminitis. However, separating the distinctive characteristics of arterial versus venous components of this complex vascular network has previously proved to be extremely difficult. Encased in a hard hoof capsule, isolation of individual blood vessels presents a considerable challenge. Exacerbating this difficulty, the laminar venous network is adapted to sustain high intravascular pressures and consequently has thickened walls, making the normally straightforward visual distinction between arteries and veins problematic. Here we describe a novel harvesting and dissection method coupled with a functional analysis procedure that facilitates distinction of arteries and veins. METHODS: Laminar tissue was recovered from the hoof of euthanized, clinically normal horses by dissection at the coronary band and stored in cold Krebs-Henseleit physiological salt solution prior to further dissection in the laboratory to remove 2 mm segments of vessels 100-500 microm in diameter. Active length tension measurements were made to evaluate optimal conditions for experimentation, and based on the differences in contractility and appearance, an experimental protocol was set up to allow a) initial distinction between arteries and veins and b) in vitro pharmacological evaluation. RESULTS: Active length tension studies clearly revealed the presence of two populations of vessels distinguished by either a large or a lower maximal contraction that subsequent histological evaluation confirmed to be arteries and veins respectively. Functional distinction using relative contractility to 60 mM potassium salt solution then demonstrated equine laminar veins to have increased sensitivity to the agonist endothelin 1 (ET-1) compared to arteries. DISCUSSION: In vitro evaluation of laminar vessels is possible despite anatomical obstacles. Furthermore, a clear distinction can be made between laminar veins and arteries using functional characteristics providing vessels of a similar size range are selected. Utilising these novel procedures, investigators can unambiguously analyse the pharmacological characteristics of equine laminar veins and arteries to decipher the physiological mechanisms responsible for the control of laminar blood flow.

How does age affect baseline screening mammography performance measures? A decision model.

BACKGROUND: In order to promote consumer-oriented informed medical decision-making regarding screening mammography, we created a decision model to predict the age dependence of the cancer detection rate, the recall rate and the secondary performance measures (positive predictive values, total intervention rate, and positive biopsy fraction) for a baseline mammogram. METHODS: We constructed a decision tree to model the possible outcomes of a baseline screening mammogram in women ages 35 to 65. We compared the single baseline screening mammogram decision with the no screening alternative. We used the Surveillance Epidemiology and End Results national cancer database as the primary input to estimate cancer prevalence. For other probabilities, the model used population-based estimates for screening mammography accuracy and diagnostic mammography outcomes specific to baseline exams. We varied radiologist performance for screening accuracy. RESULTS: The cancer detection rate increases from 1.9/1000 at age 40 to 7.2/1000 at age 50 to 15.1/1000 at age 60. The recall rate remains relatively stable at 142-157/1000, which varies from 73-236/1000 at age 50 depending on radiologist performance. The positive predictive value of a screening mammogram increases from 1.3% at age 40 to 9.8% at age 60, while the positive predictive value of a diagnostic mammogram varies from 2.9% at age 40 to 19.2% at age 60. The model predicts the total intervention rate = 0.013*AGE2 - 0.67*AGE + 40, or 34/1000 at age 40 to 47/1000 at age 60. Therefore, the positive biopsy (intervention) fraction varies from 6% at age 40 to 32% at age 60. CONCLUSION: Breast cancer prevalence, the cancer detection rate, and all secondary screening mammography performance measures increase substantially with age.