Training failure among yearling horses

T2 mapping of cartilage in the equine distal interphalangeal joint with corresponding histology using 0.27 T and 3.0 T magnetic resonance imaging

BACKGROUND

Low-field magnetic resonance imaging (MRI) is widely available to equine veterinarians yet is insensitive at detecting cartilage damage in the distal interphalangeal joint (DIPJ). T2 mapping is a quantitative imaging technique that can detect cartilage damage before morphological change is apparent.

OBJECTIVES

Validation of a T2 mapping sequence on a low-field MR system. Correlation of the mean T2 relaxation time in sections of cartilage with varying levels of pathology using low- and high-field MRI.

STUDY DESIGN

Cross-sectional study.

METHODS

Eight phantoms with known (nominal) T2 values underwent low-field (0.27 T) MRI and 38 ex vivo DIPJs were imaged. A further 9 ex vivo DIPJs were imaged on both the low- and high-field MR systems. Immediately after imaging, the DIPJs were disarticulated and samples collected for histology. Histological sections were graded using the Osteoarthritis Research Society International (OARSI) scoring system. Fiji ImageJ software with the MRIAnalysisPak plugin was used to calculate T2 maps and draw the regions of interest (ROIs).

RESULTS

There was close agreement between the nominal and the measured T2 values in the phantom study. Spearman's rank correlation demonstrated significant positive correlation between low- and high-field T2 measurements, rho 0.644 (p < 0.001). The intrarater agreement for T2 measurements was excellent, intraclass correlation coefficient (ICC) = 0.99 (95% confidence interval [CI] = 0.99-1.00), the inter-rater agreement was excellent, ICC = 0.88 (95% CI = 0.82-0.92) and there was good intrarater agreement for OARSI scores (к = 0.76).

MAIN LIMITATIONS

Only a small number of histological samples were analysed. Both articular cartilage surfaces were measured within the ROI. There were no OARSI grade 0 control samples.

CONCLUSIONS

A T2 mapping sequence on a low-field 0.27 T MR system was validated. There was a positive correlation between low- and high-field T2 measurements. The findings suggest a higher mean T2 relaxation time in pathological cartilage tissue examined in this study compared to normal equine cartilage tissue.

Implication of Cellular Senescence in Osteoarthritis: A Study on Equine Synovial Fluid Mesenchymal Stromal Cells

Osteoarthritis (OA) is described as a chronic degenerative disease characterized by the loss of articular cartilage. Senescence is a natural cellular response to stressors. Beneficial in certain conditions, the accumulation of senescent cells has been implicated in the pathophysiology of many diseases associated with aging. Recently, it has been demonstrated that mesenchymal stem/stromal cells isolated from OA patients contain many senescent cells that inhibit cartilage regeneration. However, the link between cellular senescence in MSCs and OA progression is still debated. In this study, we aim to characterize and compare synovial fluid MSCs (sf-MSCs), isolated from OA joints, with healthy sf-MSCs, investigating the senescence hallmarks and how this state could affect cartilage repair. Sf-MSCs were isolated from tibiotarsal joints of healthy and diseased horses with an established diagnosis of OA with an age ranging from 8 to 14 years. Cells were cultured in vitro and characterized for cell proliferation assay, cell cycle analysis, ROS detection assay, ultrastructure analysis, and the expression of senescent markers. To evaluate the influence of senescence on chondrogenic differentiation, OA sf-MSCs were stimulated in vitro for up to 21 days with chondrogenic factors, and the expression of chondrogenic markers was compared with healthy sf-MSCs. Our findings demonstrated the presence of senescent sf-MSCs in OA joints with impaired chondrogenic differentiation abilities, which could have a potential influence on OA progression.

Frequency of Detection and Prevalence Factors Associated with Common Respiratory Pathogens in Equids with Acute Onset of Fever and/or Respiratory Signs (2008–2021)

A voluntary biosurveillance program was established in 2008 in order to determine the shedding frequency and prevalence factors for common respiratory pathogens associated with acute onset of fever and/or respiratory signs in equids from the USA. Over a period of 13 years, a total of 10,296 equids were enrolled in the program and nasal secretions were analyzed for the qPCR detection of equine influenza virus (EIV), equine herpesvirus-1 (EHV-1), EHV-4, equine rhinitis A and B virus (ERVs), and Streptococcus equi subspecies equi (S. equi). Single infections with respiratory pathogens were detected in 21.1% of the submissions with EIV (6.8%) and EHV-4 (6.6%) as the two most prevalent viruses, followed by S. equi (4.7%), ERVs (2.3%), and EHV-1 (0.7%). Multiple pathogens were detected in 274 horses (2.7%) and no respiratory pathogens in 7836 horses (76.2%). Specific prevalence factors were determined for each of the six respiratory pathogen groups; most differences were associated with age, breed, and use of the horses, while the clinical signs were fairly consistent between viral and bacterial respiratory infections. Monitoring the frequency of detection of common respiratory pathogens is important in order to gain a better understanding of their epidemiology and to implement management practices aimed at controlling disease spread.

The clinical and histopathologic effects of potentiated chlorhexidine in the upper respiratory tract of horses

OBJECTIVE

To describe the bactericidal and fungicidal properties of a 0.0005% chlorhexidine (CHD) solution potentiated with EDTA-Tris buffers (CHD-EDTA-Tris) and evaluate the safety of 0.0005% CHD-EDTA-Tris in the upper respiratory tract (URT) of normal horses.

STUDY DESIGN

Clinical, prospective study.

ANIMALS

Eight healthy, skeletally mature horses.

METHODS

In vitro-serial dilutions of CHD-EDTA-Tris and EDTA-Tris alone were evaluated for bactericidal and fungicidal activity against Aspergillus fumigatus, Escherichia coli, Staphylococcus aureus, Streptococcus equi subspecies ssp. equi, Streptococcus equi ssp. zooepidemicus, and Pseudomonas aeruginosa. In vivo-eight healthy horses were topically treated twice with 30 ml of 0.0005% CHD-EDTA-Tris. Mucosal samples from each location were evaluated for the presence of inflammation or pathologic lesions.

RESULTS

Solutions containing CHD were superior in fungal and bacterial killing to those without. In vitro-a 0.005% CHD-EDTA-Tris was 100% effective against all bacterial and fungal species evaluated, while a 0.0005% CHD-EDTA-Tris was less efficacious against A. fumigatus and S. equi ssp. equi. In vivo-a 0.0005% CHD-EDTA-Tris did not cause any clinical, gross, or histologic abnormalities when topically applied to the equine URT.

CONCLUSIONS

A 0.0005% CHD-EDTA-Tris was highly effective for killing of common bacterial and fungal isolates in the equine upper respiratory tract. Short-term topical treatment of the equine URT with dilute CHD did not cause gross or histological inflammation in the tissue.

CLINICAL SIGNIFICANCE

A 0.0005% CHD solution with EDTA-Tris should be considered for treatment of clinically relevant inflammatory or infectious conditions or in the URT of the horse.

Infrared Thermography Applied to Monitoring Musculoskeletal Adaptation to Training in Thoroughbred Race Horses

Infrared thermography has been used to help in diagnosing lameness. It is hypothesized that, if used in a routine basis, it could help in understanding musculoskeletal modifications during race training. This study aimed to evaluate thermal variation in the musculoskeletal regions of young Thoroughbred (TB) horses during their initial months of race training. Thermographic examinations were performed once every 2 weeks on 16 (10 male, 6 female) two-year-old TB racehorses, from arrival to the racetrack in June 2016, until January 2017, for a total of 16 evaluations. Thermographic imaging was performed using the appropriate protocol. Temperature (°C) was measured at the dorsal and palmar/plantar aspects of specific regions of interest (fetlock, metacarpal, metatarsal, carpal, tarsal, thoracolumbar, sacroiliac spine, and both hips). Initially, we found a thermal balance and all regions demonstrated a positive correlation with one another. However, a significant difference was noted between the left and right sides as training progressed. Four horses were withdrawn from the study after 50% of evaluations because of metacarpal conditions associated with training. Thermographic examination revealed changes before the clinical manifestation of these conditions. In conclusion, this study demonstrated that infrared thermography is an image technique that can facilitate understanding of musculoskeletal system modifications to race training and should be further investigated as a predictive tool to anticipate the occurrence of lesions.

Risk factors for duration of equine rhinitis A virus respiratory disease

BACKGROUND

Infectious respiratory disease is common in young horses and can impact athletic performance and long-term health. Significant variation in the duration of clinical disease has been observed, even in the absence of secondary complications. The determination of factors associated with disease chronicity may facilitate clinical decision-making and the development of improved biosecurity protocols.

OBJECTIVE

To investigate contact network characteristics, and demographic variables associated with time to clinical recovery from Equine Rhinitis A virus respiratory disease.

STUDY DESIGN

Prospective cohort study.

METHODS

Yearling Standardbred racehorses (n = 58) housed in a multi-barn training facility in Southern Ontario were included. Horses were monitored daily for clinical signs of acute respiratory disease over a 41-day period in Autumn 2017. Contact patterns between horses, including older racehorses, were determined through use of proximity loggers attached to halters during the initial 7-day of the study. Associations between duration of disease, demographic factors (birth month, gait, sex and yearling sale), serologic titres and network metrics (degree, betweenness and Eigenvector centrality) were investigated using a Cox proportional hazard model.

RESULTS

Yearling attack rate for infectious respiratory disease was 87.9% (n = 51). Median time to recovery was 6 days (IQR = 1-32) and 17 horses were censored due to early withdrawal or failure to recover during the study period. In those yearlings born February-May, birth month was significant in the Cox proportional hazard model (Hazard Ratio 0.7, 95% CI 0.49-1, P = 0.05).

MAIN LIMITATION

Probability of censoring was not independent of outcome which necessitated use of sensitivity analysis.

CONCLUSIONS

These findings suggest late born foals are less likely to recover quickly from infectious respiratory disease.

Equine Rhinitis A Virus Infection at a Standardbred Training Facility: Incidence, Clinical Signs, and Risk Factors for Clinical Disease

Respiratory disease is a common morbidity of young racehorses. Infections can lead to compromised welfare, and economic loss. Identification of risk factors for infection through clinical signs monitoring and collection of demographic, serologic, and contact network data can aid in the development of prevention and control strategies. The study objectives were to: (1) describe the transmission and clinical course of infectious respiratory disease in standardbred racehorses in a multi-barn training facility and, (2) identify demographic, serological, and contact network risk factors associated with Equine Rhinitis A virus (ERAV) respiratory disease. The study population included standardbred racehorses (age 1-5 years: n = 96) housed at a multi-barn training facility in southern Ontario. Clinical signs were monitored daily over a 41-day period in fall 2017. Descriptive statistics, including incidence rate, prevalence and incidence risk were calculated for the observed period. Associations between demographic, serologic, and contact pattern variables, and clinical disease status were investigated using multivariable logistic regression. Respiratory disease cases were characterized by mucopurulent discharge (100%), intermittent cough (37.7%), and ocular discharge (62.3%). Fever (>38.5°C) and inappetence were rarely reported (15.2 and 3.8%). Seroconversion to ERAV among cases was 75%. Total, and yearling-specific incidence risks were 52.5 and 87.9%. The cumulative incidence was 0.027 new cases/horse day. A negative association (OR = 0.011) between increasing age and respiratory disease was significant (p = < 0.001) in the final regression model. Yearling horses were at increased risk of infectious respiratory disease as demonstrated by the high yearling-specific incidence risk, and the negative association between age and infection. Disease control strategies, such as vaccination programs and isolation of new horses arriving from auction, should be targeted at young animals entering training facilities.

Relationship between serum biomarkers of cartilage and bone metabolism and joint injury in young Thoroughbred racehorses in training

OBJECTIVE

To compare serum concentrations of biomarkers of cartilage and bone metabolism between racehorses with a carpal or metacarpophalangeal or metatarsophalangeal (ie, fetlock) joint injury and matched uninjured control horses, determine changes in biomarker concentrations following joint injury, and establish the biomarkers' diagnostic test performance.

ANIMALS

50 Thoroughbred racehorses with a carpal or fetlock joint injury and 50 matched uninjured horses (control horses).

PROCEDURES

Serum concentrations of 2 cartilage synthesis biomarkers (carboxy-terminal propeptide of type II collagen [CPII] and chondroitin sulfate epitope 846 [CS846]), 2 cartilage degradation biomarkers (neoepitope generated by collagenase cleavage of type II collagen [C2C] and cross-linked carboxy-terminal telopeptide fragments of type II collagen [CTX-II]), and serum activity of a bone formation marker (bone-specific alkaline phosphatase [BAP]) were measured around the time of injury diagnosis and monthly thereafter for as long as possible.

RESULTS

Injured horses as a group and horses specifically with fetlock joint injuries had significantly lower serum CPII concentrations and significantly higher serum BAP activities than matched control horses. Concentrations of CTX-II were decreased between 2 and 4 months following joint injury. Measurement of CPII concentration at baseline could distinguish between injured horses and control horses with a sensitivity of 82% and specificity of 50%.

CONCLUSIONS AND CLINICAL RELEVANCE

Although significant differences in specific biomarker concentrations between horses with carpal and fetlock joint injuries and matched control horses were identified, there was no convincing evidence of the suitability of these biomarkers as diagnostic or prognostic tools in a clinical setting.

The foot-surface interaction and its impact on musculoskeletal adaptation and injury risk in the horse

The equine limb has evolved for efficient locomotion and high-speed performance, with adaptations of bone, tendon and muscle. However, the system lacks the ability seen in some species to dynamically adapt to different circumstances. The mechanical interaction of the limb and the ground is influenced by internal and external factors including fore-hind mass distribution, lead limb, moving on a curve, shoeing and surface properties. It is unclear which of the components of limb loading have the largest effect on injury and performance but peak load, impact and vibration all play a role. Factors related to the foot-ground interface that limit performance are poorly understood. Peak performance varies vastly between disciplines but at high speeds such as racing and polo, force and grip are key limits to performance.

Short- and long-term racing performance of Standardbred pacers and trotters after early surgical intervention for tarsal osteochondrosis

REASONS FOR PERFORMING STUDY

Osteochondrosis (OC) is commonly diagnosed in young Standardbred racehorses but its effect on performance when surgically treated at a young age is still incompletely understood. This is especially true for Standardbred pacers, which are underrepresented in the existing literature.

OBJECTIVE

To characterise the short- (2-year-old) and long-term (through 5-year-old) racing performance in Standardbred pacers and trotters after early surgical intervention (<17 months of age) for tarsal OC.

STUDY DESIGN

Retrospective clinical study.

METHODS

The study population consisted of related, age-matched Standardbred racehorses (n = 278; 151 pacers, 127 trotters) with (n = 133) or without (n = 145) one or more tarsal OC lesions. All OC-affected horses were treated surgically prior to being sold as yearlings. Data obtained from publicly available race records for each horse included starts, wins, finishes in the top 3 (win, place or show), earnings and fastest time. Comparisons between OC-affected and unaffected horses were made for the entire population and within gaits. A smaller related population (n = 94) had these performance measures evaluated for their 2-5-year-old racing seasons.

RESULTS

Osteochondrosis status was associated with few performance measures. Trotters were at higher risk for lesions of the medial malleolus but lower risk for lesions of the distal intermediate ridge of the tibia than were pacers. Horses with bilateral OC lesions and lateral trochlear ridge (LTR) lesions started fewer races at 2 years of age than those with unilateral lesions or without LTR lesions.

CONCLUSIONS

Osteochondrosis seemed to have minimal effect on racing performance in this cohort, although horses with bilateral and LTR lesions started fewer races at 2 years. There was evidence for different distribution of OC lesions among pacers and trotters, which should be explored further. Standardbreds undergoing early removal of tarsal OC lesions can be expected to perform equivalently to their unaffected counterparts.

Fatal musculoskeletal injuries of Quarter Horse racehorses: 314 cases (1990-2007)

OBJECTIVE

To determine major causes of death and the anatomic location of musculoskeletal injuries in Quarter Horse racehorses in California.

DESIGN

Retrospective case series.

ANIMALS

314 Quarter Horse racehorses with musculoskeletal injuries that were necropsied through the California Horse Racing Board Postmortem Program from 1990 to 2007.

PROCEDURES

Postmortem pathology reports were retrospectively reviewed. Musculoskeletal injuries were categorized by anatomic region and described. The number of Quarter Horse starts and starters for the same period of time were obtained from a commercial database for determination of fatal injury incidence.

RESULTS

Musculoskeletal injuries accounted for 314 of the 443 (71 %) Quarter Horse racehorses that died during the 18-year study period. Fatal musculoskeletal injuries occurred at a rate of 2.0 deaths/1,000 race starts and 18.6 deaths/1,000 horses that started a race. Musculoskeletal injuries occurred predominantly during racing (84%) and in the forelimbs (81%). The most common fatal musculoskeletal injuries were metacarpophalangeal and metatarsophalangeal joint (fetlock) support injuries (40%) and carpal (24%), vertebral (10%), and scapular (8%) fractures. Proximal interphalangeal (pastern) joint luxations resulted in death of 3% of horses. Fracture configurations of some bones were consistent with those of Thoroughbred racehorses. Evidence of preexisting stress remodeling of bone was reported for some fractures.

CONCLUSIONS AND CLINICAL RELEVANCE

Knowledge of common locations and types of fatal musculoskeletal injuries in racing Quarter Horses may enhance practitioners' ability to detect mild injuries early, rest horses, and help prevent catastrophic injuries.

Effects of various presale radiographic findings for yearling Thoroughbreds on 2-year-old racing performance

OBJECTIVE

To determine the effects of various presale radiographic findings for Thoroughbreds sold at a yearling sale on 2-year-old racing performance of those horses.

ANIMALS

397 Thoroughbreds.

DESIGN

Cohort study.

PROCEDURES

Thoroughbreds offered for sale at a Thoroughbred sales facility in Kentucky were selected via a randomization procedure. Effects of various presale radiographic findings on the following measures of 2-year-old racing performance were determined: having started a race and having placed (ie, finished in first, second, or third place) in a race at least once, total amount of money earned, and amount of money earned per start.

RESULTS

Of the 397 horses, 192 (48%) started in at least 1 race during the 2-year-old racing year. The odds of failure to start a race as a 2-year-old were 1.78 times as great for horses with forelimb proximal sesamoid bone osteophytes or enthesophytes as for horses without this finding (95% confidence interval, 1.01 to 3.16). The odds of failure to start a race as a 2-year-old were 2.02 times as great for horses with hind limb proximal phalanx osteochondral fragments as for horses without this finding (95% confidence interval, 0.95 to 4.31), although this result was not significant. Radiographic findings did not have an effect on total amount of money earned, amount of money earned per start, or whether horses placed in a race.

CONCLUSIONS AND CLINICAL RELEVANCE

Presale radiographic detection of forelimb proximal sesamoid bone osteophytes or enthesophytes or hind limb proximal phalanx osteochondral fragments in yearlings were associated with failure to start a race during the 2-year-old racing year in study horses.

Effects of yearling sale purchase price, exercise history, lameness, and athletic performance on purchase price of Thoroughbreds at 2-year-old in-training sales

OBJECTIVE

To determine the effects of yearling sale purchase price, exercise history, lameness, and athletic performance (speed) on purchase price of 2-year-old in-training Thoroughbreds and to compare the distance exercised within 60 days prior to 2-year-old in-training sales between horses with high yearling sale purchase prices versus those with low yearling sale purchase prices and between horses with lameness during training and those without lameness during training.

DESIGN

Prospective study.

ANIMALS

51 Thoroughbreds.

PROCEDURES

Thoroughbreds purchased at a yearling sale were trained prior to resale at 2-year-old in-training sales. Amount of exercise and lameness status during training and speed of horses at 2-year-old in-training sales were determined. Data were analyzed via the Wilcoxon rank sum test and ANOVA.

RESULTS

Median purchase price of horses at 2-year-old in-training sales was $37,000. The 2-year-old in-training sale purchase price was associated with yearling sale purchase price and distance galloped within 60 days prior to and speed recorded at 2-year-old in-training sales.

CONCLUSIONS AND CLINICAL RELEVANCE

Horses with high yearling sale purchase prices typically had high 2-year-old in-training sale purchase prices, had low distances galloped within 60 days prior to 2-year-old in-training sales, and were classified as fast at 2-year-old in-training sales. Lameness alone was not associated with 2-year-old in-training sales purchase price. However, lameness was associated with a low distance galloped before 2-year-old in-training sales, particularly for horses with a high yearling sale purchase price; this finding suggested that yearling sale purchase price can affect training management decisions for horses with lameness.

Changes in MMP-2 and -9 activity and MMP-8 reactivity after amphotericin B induced synovitis and treatment with bufexamac

The objective here was to evaluate the acute effects of induced arthritis on synovial fluid (SF) levels of matrix metalloproteinases (MMP) -2, -8 and -9 in horses. To evaluate MMP-2 and -9 activities and the effect of non-steroidal anti-inflammatory drug (NSAID) bufexamac during remission from acute arthritis. Aseptic arthritis was induced in 24 Standardbred horses using 20 mg of amphotericin B as a single intra-articular (IA) injection in the right intercarpal joint. After 1 week and 2 weeks, horses were treated intra-articularly with 10, 20, or 40 mg of bufexamac suspension or with sterile saline solution as control. SF was sampled prior to induction and at weekly intervals for 5 weeks. Fluids were evaluated for MMP-2 and MMP-9 activity by gelatin zymography or for MMP-8 immunoreactivity by Western Blotting. IA injection of amphotericin B consistently resulted in significant increase in the immunoreactivity of MMP-8 and activity of both the latent and the active forms of MMP-2 and -9, among which the active form of MMP-2 increased the most. MMP-9 levels declined to pre-induction levels within 2 weeks, whereas levels of MMP-2 remained still high after 5 weeks. Treatment with bufexamac did not significantly affect levels of gelatinolytic MMP. Results suggest that after acute arthritis of horses, elevated MMP activity is present in the joint, for several weeks, to a degree that could promote cartilage degradation, and treatment with the NSAID bufexamac is not likely to affect that. Furthermore, analysing levels of MMP-9 activity and especially levels of active forms of MMP-2 activity may be valuable to predict the time of occurrence of arthritis in horses.

Effects of the omega-3 fatty acid, α-linolenic acid, on lipopolysaccharide-challenged synovial explants from horses

OBJECTIVE

To determine the effects of pretreatment with alpha-linolenic acid, an omega-3 polyunsaturated fatty acid, on equine synovial explants challenged with lipopolysaccharide (LPS).

ANIMALS

8 mature mixed-breed horses (4 mares and 4 geldings).

PROCEDURE

Synovial explants were assigned to receive 1 of 7 concentrations of alpha-linolenic acid, ranging from 0 to 300 microg/mL. At each concentration, half of the explants were controls and half were challenged with 0.003 microg of LPS as a model of synovial inflammation. Cell inflammatory response was evaluated by measurement of prostaglandin E2 production via an ELISA. Synovial cell viability, function, histomorphologic characteristics, and cell membrane composition were evaluated by use of trypan blue dye exclusion, hexuronic acid assay for hyaluronic acid, objective microscopic scoring, and high-performance liquid chromatography, respectively.

RESULTS

Challenge with LPS significantly increased production of prostaglandin E2 and decreased production of hyaluronic acid. Treatment with alpha-linolenic acid at the highest dose inhibited prostaglandin E2 production. Cell viability and histomorphologic characteristics were not altered by treatment with alpha-linolenic acid or LPS challenge. Treatment with alpha-linolenic acid increased the percentage of this fatty acid in the explant cell membranes.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that investigation of alpha-linolenic acid as an anti-inflammatory medication for equine synovitis is warranted.