MSK

Question 1

Atypical myopathy in the South-East of England: Clinicopathological data and outcome in hospitalized horses

Answer 1

• 56% mortality: lower than previous European reports (74–97%) but comparable to a UK study (61%- hospitalised cases only
•High admission serum CK activities and increasing CK levels during hospitalisation were associated with poorer outcomes.
•Nonsurvivors had significantly higher blood lactate concentrations and lower body temperatures on admission.
•Use of sedation correlated with nonsurvival, potentially reflecting greater disease severity or poor prognosis due to pain or complications.

Metabolic Abnormalities:
•Hyperglycaemia, hyperlactataemia, and hypertriglyceridaemia
•Blood glucose and lactate concentrations were positively correlated, suggesting altered glucose metabolism.
•Admission triglyceride concentrations were not predictive of outcomes, but increasing levels during hospitalisation were associated with nonsurvival.

•Sedation, particularly with alpha-2 agonists, was more common in nonsurvivors, potentially due to complications like esophageal obstruction or pain.
•Despite their use, vitamins and antioxidants did not show a clear association with better outcomes, likely due to uniform treatment protocols across cases.
•Oral carnitine was administered in all cases, but its low bioavailability limits its potential efficacy.

Question 2

Development of an equine muscle condition score

Answer 2

Developed a descriptive muscle condition score in healthy TB (n=25)
•Ultrasonographic measurement of all muscles had a coefficient of variation under 5%.
•All muscle sizes were significantly correlated to each other except for m. brachiocephalicus, which was not correlated to m. semitendinosus and m. multifidus.
•All muscles were significantly larger in trained horses than in untrained horses except for m. brachiocephalicus and m. splenius.
•After testing, minor adjustments were made to optimise usability of the score

Not particularly useful for anything else, no clinical correlation

Question 3

The influence of equine hoof conformation on the initiation and progression of laminitis

Answer 3

•Recursive damage modeling, previously used for human cartilage degeneration, was adapted for equine LJ tissues.
•While mechanical causation of laminitis was emphasized, the model lacked validation against other complex factors contributing to laminitis.

•LJ degeneration initiated in the inner layer near the P3 attachment in both hoof models, progressing outward.
•In the toe-in conformation, injury distribution was more severe and asymmetric compared to the normal model.
•Degeneration in toe-in models initiated earlier during simulation cycles, confirming the heightened risk associated with abnormal conformations.
•Degeneration predominantly occurred at midstance and breakover phases of the gait cycle, correlating with high stress loads in these stages.
•Capsular rotation of P3 was evident in both hoof conformations, attributed to LJ degeneration and the resultant load distribution.

•Symmetric distal P3 displacement in the normal model contrasted with the asymmetric lateral sinking seen in the toe-in model, mirroring clinical findings of laminitis-linked hoof abnormalities.
•Clinical reports of medial sinking in toe-out laminitic hooves provided additional context to findings.

Question 4

Rib fractures in adult horses as a cause of poor performance; diagnosis, treatment and outcome in 73 horses

Answer 4

• Clinical examination, including palpation, had limited utility, identifying the fracture site in only 38% of cases.
• Ultrasonography was highly effective, confirming fractures in 98% of cases
• Nuclear scintigraphy was sensitive (100%) in identifying fractures when clinical signs were inconclusive
• Radiography had limited success -laterodorsal-lateroventral oblique (skyline) view
• Poor performance 56% of cases- subtle or low-grade lameness in many cases
• Horses with caudal rib fractures displayed discomfort when ridden, while cranial rib fractures were linked to forelimb lameness and altered gait (e.g., abduction during protraction).

• The 18th rib was the most commonly affected site, potentially due to its anatomical and biomechanical susceptibility.
• T1 rib fractures were uniquely associated with forelimb lameness and pain during shoulder extension.
• Conservative management was effective in most cases, involving rest and gradual return to exercise.
• Surgical intervention was reserved for cases with ongoing clinical signs, fracture instability, or rib displacement affecting adjacent structures.
• Surgical methods included partial rib resection and, less commonly, internal fixation with a locking compression plate.

Outcomes:
• 51% of horses returned to their previous level of athletic performance after treatment.
• Only 5% of horses did not recover due to rib-fracture-related complications, suggesting a favorable prognosis for most cases.

Question 5

Evaluation of cervical radiographs in Dutch Warmblood horses using a novel radiographic grading system

Answer 5

cAPJs grading: periarticular modelling, asymmetry, radiolucencies, increased opacity, and fragmentation.
•Higher grades (Grade 3–4) were more common in horses with clinical complaints.
•Significant associations were found for cAPJs at C2-3, C5-6, C6-7, and C7-T1 with clinical signs.
•No significant association was observed for the midcervical region (C3-4 and C4-5).
•Cranial joints primarily exhibit ventral enlargement, while caudal joints show both dorsal and ventral enlargements.

Anatomical Observations:
• Variations in the ventral lamina of C6 and spinous processes of C7 and T1 were described. These variations had no significant clinical relevance in this study, aligning with other research.
•Asymmetric enlargements and radiolucencies were detectable but lacked precision compared to advanced imaging like CT.

Significance of Occiput Changes:
• Radiographic changes at the occiput were associated with clinical signs, suggesting clinical importance.
• Proper evaluation methods were stressed to avoid over-interpretation due to superimposition by auricular cartilage.

• No significant association between intra- and intervertebral ratios or minimum intercentral joint space measurements and clinical complaints.
• These findings were consistent with previous studies.

Question 6

Type 2 polysaccharide storage myopathy in Quarter Horses is a novel glycogen storage disease causing exertional rhabdomyolysis

Answer 6

• PSSM2 in Quarter Horses (QH) is characterized as a glycogen storage disease with muscle glycogen concentrations 1.6 times higher than controls.
• Histopathological features included small numbers of fibers with abnormal polysaccharide inclusions (both amylase-resistant and amylase-sensitive) along the periphery of muscle fascicles.

PSSM2 differs from PSSM1 in terms of the quantity and properties of polysaccharide inclusions:
•PSSM1: Higher glycogen concentrations and more extensive amylase-resistant inclusions.
•PSSM2: Smaller inclusions with variability in amylase resistance.
•The filamentous structure in PSSM2 was less extensive than in PSSM1, potentially explaining the increased sensitivity of PSSM2 polysaccharides to amylase digestion.

Potential Genetic and Molecular Basis:
• No significant association was found between PSSM2-QH and mutations in 12 candidate genes known for glycogen storage diseases.
• PSSM2 may result from unknown genetic mutations or a combination of variants affecting glycogen synthesis, metabolism, or post-translational modifications.
• Pedigree analysis highlighted familial clustering, particularly among performance types like barrel racing and working cow horses.

Response to Management:
• Horses managed with a low-starch, fat-supplemented diet and regular exercise showed a reduction in clinical signs and improved performance.
• Owners emphasized the importance of consistent daily exercise in managing rhabdomyolysis.

Histopathological and Ultrastructural Insights:
• Polysaccharide inclusions in PSSM2 resemble polyglucosan but with distinct structural properties compared to PSSM1.
• Ultrastructural studies revealed amorphous material with a frosted-glass appearance, suggesting abnormal glycogen metabolism but requiring further confirmation.

Question 7

Clinical effects of a combination of phenylbutazone and omeprazole on chronic lameness in Mongolian horses

Answer 7

• Both phenylbutazone (PBZ- 4.4mg/ka po q24h for 15d) and the combination of PBZ and omeprazole (OME) significantly reduced lameness scores in Mongolian horses.
• No therapeutic advantage was observed in combining OME with PBZ for alleviating chronic lameness compared to PBZ alone.
• The combination of PBZ and OME reduced the occurrence of equine glandular gastric disease (EGGD) compared to PBZ alone.

Gastric Health Observations:
•PBZ treatment alone increased EGGD severity and lowered gastric fluid pH
• The addition of OME significantly increased gastric fluid pH and reduced EGGD severity
• No significant impact was found on equine squamous gastric disease (ESGD) scores among the treatment groups.

Biochemical and Physiological Effects:
• PBZ treatment reduced serum total protein and albumin concentrations, likely reflecting gastrointestinal protein loss due to ulceration or systemic inflammation.
• The addition of OME mitigated these reductions, supporting its role in protecting against PBZ-induced gastric damage.
• PBZ treatment affected oxidative stress markers, reducing myeloperoxidase (MPO) and catalase (CAT) levels, while increasing superoxide dismutase (SOD) activity. The combination with OME partially attenuated these changes.
• PBZ alone increased serum gastrin 17 (GT-17) and pepsinogen-1 (PG1) concentrations, indicating enhanced gastric mucosal injury. Co-administration of OME reduced GT-17 and PG1 levels, reflecting its role in mitigating gastric acid secretion and mucosal damage.

Question 8

Detection of hypoglycin A and MCPA-carnitine in equine serum and muscle tissue: Optimisation and validation of a LC-MS–based method without derivatisation

Answer 8

• Developed and validated a novel LC-MS method for detecting hypoglycin A (HGA) and MCPA-carnitine in equine serum and muscle without requiring derivatisation.
• Achieved lower limits of quantitation compared to previous methods while reducing analysis time and costs.
•Previous methods reported low recoveries (~20%) for both analytes; this new method achieved 97%-100% recoveries in serum.
• Simultaneous detection of HGA and MCPA-carnitine in a single run, unlike earlier methods requiring separate techniques.
• Reliable quantitation with no selectivity issues observed during validation.

Findings on HGA and MCPA-Carnitine Distribution:
• HGA and MCPA-carnitine were detectable in serum and muscle of AM-affected horses but not in control horses with other neuromuscular conditions.
• MCPA-carnitine was undetectable in liver tissue of affected horses, suggesting low hepatic metabolism of HGA in equines.

Implications for Toxin Metabolism:
• Highlights species-specific differences in the metabolism of HGA.
• In horses, HGA intoxication manifests primarily as myopathy, whereas in humans and rats, hepatopathy is more prominent.
• Suggests that glycine-N-acylase enzymes in the liver and kidneys may be less active in equines compared to other species.

Validation and Method Performance:
• Precision, accuracy, and reproducibility met stringent validation criteria.
• Stability tests confirmed the method’s robustness for both serum and muscle samples across different storage conditions.

Question 9

Dynamic three-dimensional computed tomographic imaging facilitates evaluation of the equine cervical articular process joint in motion

Answer 9

Dynamic 2D and 3D CT imaging is confirmed to be feasible for assessing equine cervical articular process joints (APJs) based on cadaver models.
High-quality images were achieved, enabling detailed visualization of the APJ dynamics during flexion and extension.
Superior imaging quality was achieved in dynamic 3D CT compared to 2D CT for both flexion and extension movements.

Translational displacement of APJ surfaces was significantly greater during flexion than extension, suggesting flexion imposes more movement stress on APJs.
Specific regions (e.g., cranial margin of C5 and caudal margin of C4) demonstrated potential high-pressure points during full flexion and extension, which could contribute to pathologies like osteoarthritis or osteochondrosis.

CT with a detector coverage of 16 cm and a rotation speed of 0.32 seconds provides highquality images

Question 10

Absence of myofibrillar myopathy in Quarter Horses with a histopathological diagnosis of type 2 polysaccharide storage myopathy

Answer 10

• Despite rigorous desmin staining, no Quarter Horses exhibited characteristic features of MFM, suggesting it is rare or nonexistent in this breed.

Genetic Testing Limitations:
•The commercial genetic tests based on P variants (P2, P3a, P3b, P4) were not predictive of PSSM2 or MFM in QH.
•P variants were prevalent in both control and PSSM2-affected horses, undermining their diagnostic validity.
•Odds ratios and predictive metrics (e.g., sensitivity, specificity) for these genetic variants were not statistically significant.
•More than 57% of healthy QH carried at least one P variant, which would falsely indicate susceptibility if the commercial tests were used diagnostically.
•The widespread presence of these variants among healthy horses suggests they are benign and not linked to muscle pathology.

Comparison with Other Breeds:
• MFM in Warmbloods and Arabians involves distinct clinical signs (e.g., exercise intolerance) and histopathological features (desmin aggregation).
• In QH, PSSM2 is primarily characterized by exertional rhabdomyolysis, highlighting different etiologies and presentations across breeds.
•True diagnosis of PSSM2 should rely on a combination of clinical history, serum creatine kinase activity, and muscle histopathology rather than these genetic tests

Question 11

Sidewinder gait in horses

Answer 11

Neurologic Findings:
• leaning toward the affected side with contralateral pelvic limb abduction.
• Compressive Myelopathy: Caused by trauma, instability, or intervertebral disc disease.
• EPM: Confirmed in two cases and presumed in others; characterized by spinal cord or brainstem lesions.
• Ischemic Injury: Rare vascular events such as thrombosis, affecting motor and sensory tracts.
• Gliosis and Perivascular Cuffing: Suggestive of potential viral or inflammatory etiologies.

Musculoskeletal Findings:
• Advanced coxofemoral osteoarthritis.
• Multiple pelvic fractures.
• Severe myonecrosis of pelvic limb muscles (rare).
• Horses with musculoskeletal causes leaned contralateral to the most affected limb due to pain or mechanical limitations.

•Electromyography (EMG) was effective in distinguishing neurologic from non-neurologic causes and in localizing spinal cord lesions.
•Cerebrospinal fluid (CSF) centesis near the lesion site increased diagnostic yield but was not feasible in all cases.

• Supportive treatments included NSAIDs, antiprotozoals (e.g., ponazuril for EPM), and antioxidants, with minimal success in resolving the gait abnormality.
• Overall prognosis for recovery of function and quality of life is poor, with a high case fatality rate (79%).
• Remaining live horses showed persistent gait abnormalities despite treatment, precluding return to physical activity

Question 12

Computed tomography and myelography of the equine cervical spine: 180 cases (2013-2018)

Answer 12

• Lesions were identified in 98% of cases, with the most common findings being osteoarthritis (OA) of the articular process joints (APJs), vertebral canal stenosis, and spinal cord compression.
• The most frequently affected regions were the caudal cervical spine, particularly C5–C6 and C6–C7.
• Multiplanar reformatting improved the detection of lesions, particularly medial APJ abnormalities and dorsolateral spinal canal stenosis, which are challenging to visualize on standard radiography.

• Findings support the critical importance of imaging the caudal cervical spine, as most lesions were located caudal to C5.
• CT imaging enhances preoperative planning by allowing detailed visualization of pathology, potentially guiding surgical interventions such as arthroscopy or spinal decompression.
• Warmblood breeds and male horses (stallions and geldings) were overrepresented in the study population
• Horses older than four years were more likely to have OA and static stenosis at C5–C7, possibly due to cumulative microtrauma or aging-related degenerative changes.

Procedure-Related Complications:
• Adverse events were observed in 7% of cases, which is lower than the 34% reported for radiographic myelography.
• Shorter anesthesia times (mean of 52 minutes with myelography) may have contributed to the reduced complication rate.
• Most complications were related to post-anesthetic recovery and included ataxia progression, seizures, and mild colic, with one fatality due to pre-existing severe spinal cord compression.

Question 13

Plasma concentration of serum amyloid A and lipopolysaccharide binding protein in horses with laminitis resulted from hindgut acidosis

Answer 13

This was a pretty poor study.

• Horses fed a high-concentrate diet (30:70 forage-to-concentrate ratio) exhibited significant increases in plasma lipopolysaccharide-binding protein (LBP) and serum amyloid A (SAA), as well as a higher Obel laminitis score.
• Plasma LBP concentrations increased significantly within the first 10 days, preceding significant changes in SAA levels and laminitis severity scores.
• LBP showed earlier and more consistent elevation compared to SAA, suggesting its greater sensitivity for detecting early inflammatory responses to hindgut acidosis.
• SAA levels increased more prominently between days 10 and 20, correlating with the progression of laminitis and inflammation in the lamellae.
• Horses on the high-concentrate diet had a significant reduction in cecal pH (from 6.3 to 5.81 by day 10), facilitating bacterial lysis and LPS release.
• Elevated VFA concentrations further supported the occurrence of hindgut fermentation disruptions, contributing to acidosis and subsequent laminitis.

Question 14

Pseudohyperkalemia in horses with rhabdomyolysis reported by an enzymatic chemistry analyzer

Answer 14

•The VetScan VS2 analyzer reported falsely elevated serum potassium concentrations in horses with rhabdomyolysis due to its enzymatic methodology.
• Ion-specific analyzers (Cobas, i-STAT, Catalyst) provided more accurate potassium readings, correlating less with creatine kinase (CK) activity.

Mechanism of Pseudohyperkalemia:
• The VetScan VS2 utilizes a lactate dehydrogenase (LDH)-coupled enzymatic method, which overestimates potassium when CK and LDH levels are high. Elevated CK and LDH levels in rhabdomyolysis increase the conversion of pyruvate to lactate, artificially elevating potassium measurements.

Correlation with Muscle Damage Markers:
• A strong positive correlation was observed between potassium levels and CK activity on the VetScan VS2 but not on ion-specific analyzers. This suggests that muscle damage markers interfere with the VetScan VS2 readings.

Question 15

Influence of specific management practices on blood selenium, vitamin E, and beta‐carotene concentrations in horses and risk of nutritional deficiency

Answer 15

• Suboptimal selenium concentrations were identified in 16.7% of horses, while 35.5% showed inadequate alpha-tocopherol levels.

Role of Selenium Supplementation:
• Selenium intake below the recommended 1 mg/day significantly increased the risk of deficiency, especially in horses relying on selenium salt blocks alone.
• Horses supplemented with selenomethionine and sodium selenite had significantly better selenium status
• Selenium-containing salt blocks were inadequate as a sole source of supplementation

Alpha-Tocopherol and Pasture Access:
• Horses with pasture access exceeding six hours daily had higher plasma alpha-tocopherol levels, reinforcing the importance of fresh forage.
• Restricted pasture access (<6 hours/day) combined with inadequate vitamin E supplementation (<500 IU/day) markedly increased deficiency risk.
• Despite supplementation, some horses exhibited deficiencies, potentially due to issues with supplement bioavailability, quality, or ingestion.
• No significant difference in alpha-tocopherol levels was observed between horses supplemented with natural (d-alpha-tocopherol) or synthetic (dl-alpha-tocopherol) forms, despite known bioavailability differences.
• Inconsistent supplement labeling and varying bioavailability likely contributed to suboptimal results even in apparently adequately supplemented horses.

• Plasma beta-carotene levels correlated strongly with pasture access, emphasizing the importance of fresh forage as its primary source.
• Horses with restricted pasture access had significantly lower beta-carotene levels, which could impact immune and reproductive health.

Question 16

Commercial genetic testing for type 2 polysaccharide storage myopathy and myofibrillar myopathy does not correspond to a histopathological diagnosis

Answer 16

• Commercial genetic tests (P2, P3, and P4 variants) for PSSM2 and MFM do not reliably predict these conditions.
• No significant association was found between the tested genetic variants and histopathological diagnoses. The sensitivity of the tests was low (<33%), with no significant odds ratios or predictive values for any variant.
• Healthy control horses were as likely as affected horses to possess P variants, undermining the tests’ diagnostic utility.

•The P2, P3, and P4 variants have been present in equine populations since before modern breed formation.
•PSSM2 and MFM diagnoses rely on specific histopathological features, such as polysaccharide aggregates (PSSM2) and desmin-positive aggregates (MFM).

•The study highlights the likelihood of polygenic or environmental contributions to these conditions rather than single-gene causation.
•Genetic predisposition, if present, likely involves other untested loci or interactions.

Question 17

Prevalence of clinical signs and factors impacting expression of myosin heavy chain myopathy in Quarter Horse-related breeds with the MYH1E321G mutation

Answer 17

My/My Horses (Homozygous for MYH1E321G Mutation):
• 80% developed muscle atrophy, and 30% showed moderate-to-severe stiffness.
• Rapid muscle atrophy occurred in 75% of affected horses, often leading to incomplete recovery.
• The likelihood of developing atrophy and stiffness was significantly higher than in N/N or My/N horses.

My/N Horses (Heterozygous for MYH1E321G Mutation):
• 17% developed muscle atrophy, with rapid onset in most cases (59%).
• Atrophy often resolved, with 71% achieving recovery.
• Muscle stiffness was less common compared to homozygotes.

N/N Horses (No Mutation):
• Muscle atrophy occurred in 11%, typically developing slowly over months, unrelated to MYH1E321G-associated disease.

Triggering Factors:
• Potential inciting factors included vaccinations and infections, though these were apparent in only: 25% of My/My horses. 46% of My/N horses.
• Vaccines (e.g., influenza, herpes virus) were associated with clinical signs in some My/N horses but did not trigger disease in My/My horses.
• Respiratory or gastrointestinal disease was reported prior to clinical signs in 25% of My/My and 21% of My/N horses.

Performance Outcomes:
• My/N horses achieved high levels of performance, including national and world championships, similar to N/N horses.
• Only 40% of My/My horses met performance expectations, partly due to disease severity and incomplete recovery.

Clinical Implications:
• Homozygosity for MYH1E321G is a significant risk factor for severe clinical signs of MYHM, often leading to permanent deficits.
• Rapid muscle atrophy in heterozygous horses warrants high clinical suspicion for MYHM.
• Screening for MYH1E321G can inform breeding and management decisions, particularly in performance-oriented disciplines.

Management Recommendations:
• Owners of MYH1E321G-positive horses should space vaccinations over 3–6 weeks and monitor closely for signs of muscle atrophy or stiffness.
• Early intervention with corticosteroids is advised for affected horses to mitigate muscle damage.

Question 18

Common and atypical presentations of Anaplasma phagocytophilum infection in equids with emphasis on neurologic and muscle disease

Answer 18

•presented commonly as fever, lethargy, anorexia, and limb edema, with neurologic (41%) and muscle diseases (18%) being significant atypical presentations.
Neurologic Disease:
•Symmetrical proprioceptive ataxia was the most frequent sign, often involving both thoracic and pelvic limbs.
•Severe cases occasionally resulted in recumbency.
•Less common signs included obtundation, multiple cranial nerve deficits, and brainstem involvement.

Muscle Disease:
•Quarter Horses with MYHM allele (hetero) displayed rapid-onset rhabdomyolysis, marked by muscle swelling, pain, and increased serum CK and AST activities.
•IMM (immune-mediated myositis) was identified in two cases via muscle biopsy, with treatment involving corticosteroids and supportive care.
•Horses recovered muscle mass over weeks to months post-treatment, though severe initial atrophy was noted.

Additional Presentations:
•Rare cases of cardiomyopathy (ventricular tachycardia), cavitary effusions (pleural or peritoneal), and DIC were observed, emphasizing the potential severity of EGA complications.

Seasonal and Demographic Patterns:
• Cases peaked in winter and spring, correlating with tick activity.
• A male predisposition was noted (77% of cases), similar to trends in human granulocytic anaplasmosis.
• Horses under 4 years of age rarely exhibited clinical disease, potentially due to milder infections in younger animals.

Diagnostic Insights:
•qPCR testing of buffy coat samples provided sensitive and specific detection of A. phagocytophilum DNA.
•Muscle biopsy revealed immune-mediated processes in some horses with muscle disease, supporting a dual role of infection and immune dysfunction.

Treatment and Outcomes:
•Tetracyclines were highly effective, with clinical signs resolving within 24–96 hours of treatment initiation.
•Corticosteroids were crucial for managing IMM and associated muscle damage, contributing to the rapid recovery.
•All horses survived and showed no recurrence or long-term sequelae during follow-up.

Question 19

A single bout of high-intensity exercise modulates the expression of vitamin D receptor and vitamin D-metabolising enzymes in horse skeletal muscle

Answer 19

• A single high-intensity exercise session significantly increased Pax7 and VDR protein expression within 30 minutes post-exercise.
• Serum 25(OH)D2 levels and CYP27B1 expression decreased over 1–3 weeks post-exercise, suggesting reduced vitamin D metabolism following acute exercise.
• No significant change in CYP24A1 expression was observed, indicating limited alteration in vitamin D degradation pathways.

Muscle Response to High-Intensity Exercise:
• The upregulation of Pax7, a marker of SMSC activation, reflects enhanced satellite cell activity for muscle repair following exercise-induced microtrauma.
• Increased VDR expression in skeletal muscle post-exercise suggests its involvement in the regenerative process and repair mechanisms.
• The co-localization of Pax7 and VDR proteins indicates a functional interaction between the vitamin D system and muscle stem cell activity during repair.

• The findings support a role for vitamin D in muscle repair and regeneration after exercise-induced injury in horses.
• Declines in vitamin D metabolites after high-intensity exercise highlight the potential need for vitamin D supplementation to support recovery in athletic horses.

Question 20

Primary phenotypic features associated with caudal neck pathology in Warmblood horses

Answer 20

Warmblood horses with caudal neck pathology exhibit distinct clinical features compared to controls, including:
•Thoracic limb lameness.
•Neck stiffness or pain.
•Neurological signs such as ataxia and proprioceptive deficits.
•Features like focal muscle atrophy, patchy sweating, hypoesthesia, and hyperesthesia were unique to affected horses.

Differentiating Features:
•Root signature postures, focal cervical hypoesthesia or hyperesthesia, and hopping-type lameness were not observed in controls.
•EMG provided additional diagnostic value, confirming neurologic involvement in cases with spinal cord or nerve root compression.
•Moderate to severe EMG abnormalities aligned with thoracic limb lameness and stumbling, supporting neurologic origins.

•Showjumping horses were more prone to neck pathology compared to dressage horses, potentially due to biomechanical stress during jumps.

Question 21

Candidate gene expression and coding sequence variants in Warmblood horses with myofibrillar myopathy

Answer 21

•426 variants were identified in candidate genes, including 26 missense variants classified as having “moderate” predicted effects.
•Variants, including two commercially offered for MFM genetic testing, did not correlate with the MFM phenotype.
•Variants in FLNC and MYOT, marketed as diagnostic markers, showed no significant difference in allele frequencies between MFM-affected and control WB.
•High genetic variation among breeds was noted, emphasizing the need for breed-specific validation of purported disease-causing variants.
• Muscle fiber composition, cross-sectional area, and specific isometric force generation did not differ significantly between MFM and control WB. Study was underpowered for this.
•Commercial tests based on FLNC and MYOT variants lack scientific validation for diagnosing MFM in horses.These tests showed low predictive value, as allele frequencies were similar across affected and control horses.

Question 22

Digital lamellar inflammatory signaling in an experimental model of equine preferential weight bearing

Answer 22

•Inflammatory signaling pathways, including IL-6, COX-2, and STAT3, were significantly activated in lamellar tissues of the supporting limb (SL) in horses subjected to unilateral weight bearing.
•The findings suggest a shared pathophysiological mechanism among the three major types of laminitis: supporting limb laminitis (SLL), sepsis-related laminitis (SRL), and hyperinsulinemia-associated laminitis.

Inflammatory Pathways in Laminitis:
• Activation of pro-inflammatory cytokines (e.g., IL-6) and increased COX-2 expression were prominent in SL tissues compared to controls.
•Elevated phosphorylated STAT3 levels indicate the involvement of JAK/STAT signaling in SLL pathogenesis
• Prolonged mechanical stretch of lamellar tissues due to unilateral weight bearing contributes to the activation of inflammatory pathways.
•Local ischemia and impaired lamellar perfusion exacerbate sterile inflammation, further activating damage-associated molecular pattern (DAMP)-mediated signaling.

• structural changes such as secondary epidermal lamellar flattening were noted.
• Altered lamellar perfusion was evident in the SL, supporting the hypothesis of ischemia contributing to the development of SLL.
• In contrast to SRL, SLL lacks leukocyte infiltration, indicating a “non-classical” inflammatory response driven by mechanical and metabolic stress rather than infection or systemic inflammation.

•JAK/STAT inhibitors and IL-17A pathway blockers, already in use for human inflammatory diseases, could have therapeutic potential for managing or preventing laminitis in horses.

Question 23

Muscle fibre transition and transcriptional changes of horse skeletal muscles during traditional Mongolian endurance training

Answer 23

•Endurance training induced a shift from fast-twitch (glycolytic) to slow-twitch (oxidative) muscle fibres, marked by a 5.86% increase in slow fibres.
•Increased succinate dehydrogenase (SDH) activity (oxidative marker) and decreased phosphofructokinase (PFK) activity (glycolytic marker) indicate a metabolic adaptation favoring aerobic energy production.

Gene Expression Changes:
•Transcriptomic analysis revealed downregulation of 64% of differentially expressed genes (DEGs) and upregulation of 36%.
•Fast fibre-associated genes (Actn3, Casq1, Myl1, Myom2, Tnni2) were significantly downregulated, further supporting the fast-to-slow fibre transition.
•Pathways linked to glycolysis and gluconeogenesis were enriched with downregulated genes, reflecting reduced carbohydrate metabolism.

•Endurance training decreased protein synthesis markers (e.g., reduced AKT and mTOR protein levels) while promoting protein degradation via upregulation of FOXO-related pathways and autophagy markers (e.g., BNIP3, LC3A, LC3B).
•Muscle-specific microRNAs (myomiRs), such as miR-499 and miR-208b, were upregulated, facilitating the fast-to-slow fibre shift by inhibiting fast fibre transcriptional repressors.
•Long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) showed significant changes, potentially modulating transcriptional networks during muscle adaptation.
•Differential alternative splicing (DAS) events were prominent in titin (Ttn), particularly within the PEVK domain, associated with sarcomere elasticity and extensibility.
•Exon retention in Ttn could predispose muscles to atrophy under fasting-induced stress, balancing the training benefits with potential risks.

•The combination of intermittent fasting and endurance training promoted reliance on fat oxidation, reducing dependence on carbohydrate metabolism.
•This metabolic adaptation enhances endurance capacity but may also increase the risk of muscle atrophy due to protein mobilization during energy deficits.

Question 24

Radiological prevalence of osteoarthritis of the cervical region in 104 performing Warmblood jumpers

Answer 24

•OA was most prevalent in the caudal cervical articular process joints (APJs), particularly C6-C7 (67.3% affected) and C5-C6 (39.5% affected).
•The prevalence of OA increased progressively from C3-C4 to C6-C7.
•Moderate-to-severe OA at C6-C7 was identified in 25% of horses, indicating a common site of significant pathology.

•Substantial agreement was observed between two academic radiologists (Kappa = 0.61), but only fair agreement with the third radiologist (Kappa = 0.37-0.38).
•Despite these challenges, the simple three-grade system (absent, mild, moderate/severe) was deemed practical for clinical use.

•Horses with higher peak performance levels had significantly higher OA grades at C6-C7 (P = .01).
•No significant association was found between OA grades and age, age when horses started jumping, neck pain, or reduced neck mobility.
•The lack of correlation with age may be explained by the relatively narrow age range (76% aged 8-13 years) and the study’s focus on actively performing horses.

•The high prevalence of cervical OA in jumpers likely reflects the biomechanical demands of their discipline, such as repetitive flexion and extension during take-offs and landings.
•Core strength and fitness in these horses might mask clinical signs, emphasizing the need for radiographic assessment, especially during prepurchase evaluations.

•Prevalence of OA at C6-C7 in this study (67.3%) is higher than previously reported in both clinical and nonclinical populations.
•Unlike symptomatic populations, no link was found here between cervical OA and clinical signs, supporting the hypothesis that these radiographic changes may often be subclinical in high-performance athletes.

Question 25

Intralesional application of medical grade honey improves healing of surgically treated lacerations in horses

Answer 25

•The intralesional application of medical-grade honey (MGH) improved healing outcomes in sutured equine lacerations. NON BLINDED, CLINICAL CONTROLLED, FLAWED
•MGH-treated wounds had higher rates of complete healing, reduced infection signs, and increased practitioner satisfaction compared to controls.
•Wounds treated with MGH had significantly fewer infection signs, likely due to its antimicrobial properties, including activity against multidrug-resistant bacteria.
•MGH is effective against common equine pathogens and multidrug-resistant organisms (e.g., Staphylococcus aureus, Pseudomonas aeruginosa).

The antimicrobial mechanisms include:
•Osmotic effect from high sugar concentration.
•Low pH.
•Hydrogen peroxide production via glucose oxidase.
•MGH also promotes healing by reducing inflammation and providing nutrients for tissue repair.

• Unlike antibiotics, which target specific bacterial processes and contribute to resistance development, honey’s multifactorial mechanisms reduce this risk.

Question 26

Osteochondral fragmentation of the cervical articular process joints: prevalence in horses undergoing CT for investigation of cervical dysfunction

Answer 26

•Osteochondral fragmentation (OF) was identified in 24% of horses with cervical dysfunction undergoing CT imaging.
•Fragments were identified across all cervical articular process joints (APJs), with varied clinical significance.

OF may arise from multiple pathologies, including:
•Osteochondrosis-like processes without ischaemic chondronecrosis, differentiating it from classical osteochondritis dissecans (OCD).
•Synovial osteochondromatosis (rare), involving intra-articular osteochondral masses from synovial tissue.
•Trauma, though no consistent history or typical radiological features (e.g., callus or sclerosis) supported this in the study population.

Location and Characteristics:
•Most fragments were located in synovial outpouchings ventromedial or dorsolateral to the joint space, often appearing as loose bodies.
• OF was considered the primary cause of clinical signs in 6 cases, a partial cause in 3, and incidental in 4 due to other significant pathologies.
•Spinal cord compression by OF was rare, occurring in only one case, despite the proximity of medial fragments to the spinal cord.
•OF often co-occurred with other cervical pathologies, including arthropathy and cervical vertebral dysplasia, complicating assessment of its standalone impact.

• Radiography identified fragments in only a few cases, underscoring the superiority of CT for detailed assessment.
•The clinical significance of OF requires further investigation through postmortem and histological studies.

•Post-anesthetic complications occurred in 7.4% of cases, with seizure activity linked to myelography contrast medium in some horses.Improved recovery protocols (e.g., head elevation) reduced the risk of contrast-related complications.

Question 27

A cross-sectional survey of the diagnosis and treatment of distal limb cellulitis in horses by veterinary surgeons in the United Kingdom

Answer 27

•Distal limb cellulitis is a common condition, with 83.5% of survey respondents treating more than five cases annually.
•Nearly half of respondents noted seasonality, with higher case numbers during colder and wetter months (October to February), potentially linked to skin breakages from conditions like pastern dermatitis.
•Diagnosis was primarily based on clinical signs, such as edema, pain on palpation, and lameness.
•There is diagnostic overlap and confusion between cellulitis and lymphangitis, stemming from the lack of clear, well-defined criteria in equine literature.
•Ultrasonography was rarely used at the initial examination but employed when cases did not respond to treatment.

Treatment Approaches:
•The majority of respondents used a combination of NSAIDs (95.5%) and antimicrobials (95.5%), with phenylbutazone and trimethoprim-sulphonamide (TMPS) being the most common choices.
•Cold hosing and light exercise were frequently recommended for managing inflammation and improving lymphatic drainage.
•Corticosteroids were prescribed by 41% of respondents, primarily dexamethasone administered intravenously.
•Treatment duration typically ranged from 5 to 10 days.
• Despite uncertainties about the infectious etiology of cellulitis, most respondents prescribed antimicrobials, even when believing the condition to be non-infectious.
•Culture and sensitivity testing were underutilized, with only 5.6% of respondents performing wound swabs at the initial presentation.
•A reliance on TMPS, combined with increasing reports of resistance among staphylococcal and streptococcal isolates, highlights a potential risk for antimicrobial resistance.

:•The general prognosis for distal limb cellulitis was favorable, with most cases resolving within 5–10 days with treatment.

Question 28

Prognosis for survival to discharge and racing performance in Thoroughbred foals treated for single joint septic arthritis

Answer 28

•The study found a higher survival rate (93%) compared to prior reports (56.6%–84.1%), attributed to the exclusion of foals with comorbidities or multiple affected joints.

Key Prognostic Indicator:
•The final synovial cell count (SNCC) was a critical predictor of survival: Higher final SNCC was associated with decreased survival likelihood.

• Advanced treatments (e.g., arthroscopy, arthrotomy) did not significantly improve survival rates but should not exclude cases from athletic potential.
•No significant difference was found between cases and maternal sibling controls regarding starting in a race.
•Total winnings were significantly lower for cases compared to controls, potentially due to factors not explored in the study.

Infectious Agents:
•Gram-positive bacteria, especially Streptococcus spp., were the most common isolates, consistent with prior studies.
•The predominance of Gram-positive bacteria may reflect regional trends or increased antimicrobial resistance among equine pathogens.

Question 29

Factors associated with survival and racing performance of 114 Thoroughbred foals with septic arthritis compared with maternal siblings

Answer 29

•78% of foals diagnosed with septic arthritis survived to discharge, consistent with previous reports.

The survival rate was influenced by:
•Age: Foals under 26 days old had significantly lower survival odds.
•Concurrent disease: Foals with comorbid conditions like osteomyelitis were six times less likely to survive.

•Gram-positive bacteria (Streptococcus spp. most commonly) were the predominant isolates, consistent with geographic trends.
•Negative culture results did not correlate with survival, suggesting aggressive treatment, including lavage and antibiotics, mitigated bacterial influence on outcomes.

•Among surviving foals, 67% started at least one race, comparable to their maternal siblings (74%).
There was no significant difference in:
•Racing starts, wins, or prize earnings between cases and controls.
•Median age of first race (3 years for both groups), consistent with Australian racing trends.
•The lack of performance differences suggests that prompt and effective management minimized long-term articular damage.

•Previous studies reported poorer racing outcomes in foals with septic arthritis, possibly due to smaller sample sizes and higher proportions of foals with multiple joint involvement.
•This study’s stringent case definition and the inclusion of single-joint cases contributed to more favorable findings.

Question 30

Hoof kinetic patterns differ between sound and laminitic horses

Answer 30

•Horses with laminitis exhibited a significant shift in load distribution from the toe region to the middle hoof region compared to sound horses.
•Laminitic horses displayed reduced relative vertical force and vertical impulse in the toe region, with corresponding increases in the middle hoof region.
•The toe region of laminitic horses bore peak loading during the break-over phase, unlike sound horses, where peak loading occurred during mid-stance.
• Contrary to common belief, laminitic horses did not show increased relative vertical force or vertical impulse in the heel region compared to sound horses.
•Peak loading remained focused on the middle hoof region, emphasizing the need to rethink therapeutic approaches targeting the heel region alone.

Mechanics of Laminitic Gait:
• A heel-first contact was observed in 89% of laminitic horses, compared to variable initial contacts in sound horses (flat-foot, heel-first, or lateral wall-first).
• The prolonged time to peak vertical force in the toe region and peak loading during break-over reflect attempts to relieve pain in the toe region by redistributing load to less sensitive areas.

•Supportive therapy for laminitic horses should focus on the middle and caudal hoof regions, including frog and heel support, to reduce peak pressure and distribute load more evenly.
•Adjusting shoeing strategies to ease break-over could minimize strain on the damaged lamellae in the toe region and improve overall comfort.