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Host-virus associations have co-evolved under ecological and evolutionary selection pressures that shape cross-species transmission and spillover to humans. Observed virus-host associations provide relevant context for newly discovered wildlife viruses to assess knowledge gaps in host-range and estimate pathways for potential human infection. Using models to predict virus-host networks, we predicted the likelihood of humans as hosts for 513 newly discovered viruses detected by large-scale wildlife surveillance at high-risk animal-human interfaces in Africa, Asia, and Latin America. Predictions indicated that novel coronaviruses are likely to infect a greater number of host species than viruses from other families. Our models further characterize novel viruses through prioritization scores and directly inform surveillance targets to identify host ranges for newly discovered viruses.

Emerging infectious diseases in humans are frequently caused by pathogens originating from animal hosts, and zoonotic disease outbreaks present a major challenge to global health. To investigate drivers of virus spillover, we evaluated the number of viruses mammalian species have shared with humans. We discovered that the number of zoonotic viruses detected in mammalian species scales positively with global species abundance, suggesting that virus transmission risk has been highest from animal species that have increased in abundance and even expanded their range by adapting to human-dominated landscapes. Domesticated species, primates and bats were identified as having more zoonotic viruses than other species. Among threatened wildlife species, those with population reductions owing to exploitation and loss of habitat shared more viruses with humans. Exploitation of wildlife through hunting and trade facilitates close contact between wildlife and humans, and our findings provide further evidence that exploitation, as well as anthropogenic activities that have caused losses in wildlife habitat quality, have increased opportunities for animal-human interactions and facilitated zoonotic disease transmission. Our study provides new evidence for assessing spillover risk from mammalian species and highlights convergent processes whereby the causes of wildlife population declines have facilitated the transmission of animal viruses to humans.

Background: The rate of catastrophic musculoskeletal injuries (CMI) in racehorses is high in the United States compared to other countries. Few modifiable risk factors related to lameness, medication, and surgery history have been identified. Objective: To detect management factors that increase risk of CMI by comparing medical histories between horses that sustained, and horses that did not sustain, a CMI. Study design: Case-control. Methods: Racehorse necropsy data (May 2012-June 2013) were obtained through the California Horse Racing Board Postmortem Program. Attending veterinarians of Thoroughbreds (TB) and Quarter Horses (QH) that experienced CMI, and of three matched control horses, were invited to complete an online veterinary medical history survey. We investigated associations between CMI and lameness, medication, surgery, and exercise history using multivariable logistic regression. Results: There were 146 TB (45 cases, 101 controls) and 17 QH (11 cases, 6 controls) surveys completed. TB cases were more likely to show signs of lameness within the 3 months prior to death compared to controls. A high proportion of both cases (64.3%) and controls (76.8%) were administered medications, but unraced TB case horses were more likely to have been administered systemic medications compared to those that previously raced. TB cases were more likely to have raced with greater intensity during their career, but had eased off in the month preceding CMI. For QHs, there was insufficient power to detect significant differences between cases and controls that showed signs of lameness, or that were administered medications. Surgery history was not associated with CMI. Main limitation: Insufficient power to detect small effect sizes. Conclusions: The study provides information that can be used to aid in identification of horses at high risk for catastrophic injury, and management factors that can be modified to reduce the risk for all horses.

Metaphyseal osteopathy (MO) (hypertrophic osteodystrophy) is a developmental disorder of unexplained etiology affecting dogs during rapid growth. Affected dogs experience relapsing episodes of lytic/sclerotic metaphyseal lesions and systemic inflammation. MO is rare in the general dog population; however, some breeds (Weimaraner, Great Dane and Irish Setter) have a much higher incidence, supporting a hereditary etiology. Autoinflammatory childhood disorders of parallel presentation such as chronic recurrent multifocal osteomyelitis (CRMO), and deficiency of interleukin-1 receptor antagonist (DIRA), involve impaired innate immunity pathways and aberrant cytokine production. Given the similarities between these diseases, we hypothesize that MO is an autoinflammatory disease mediated by cytokines involved in innate immunity. To characterize immune dysregulation in MO dogs we measured serum levels of inflammatory markers in 26 MO and 102 control dogs. MO dogs had significantly higher levels (pg/ml) of serum Interleukin-1beta (IL-1β), IL-18, IL-6, Granulocyte-macrophage colony stimulating factor (GM-CSF), C-X-C motif chemokine 10 (CXCL10), tumor necrosis factor (TNF), and IL-10. Notably, recovered MO dogs were not different from dogs during active MO disease, providing a suggestive mechanism for disease predisposition. This is the first documentation of elevated immune markers in MO dogs, uncovering an immune profile similar to comparable autoinflammatory disorders in children.

Most human infectious diseases, especially recently emerging pathogens, originate from animals, and ongoing disease transmission from animals to people presents a significant global health burden. Recognition of the epidemiologic circumstances involved in zoonotic spillover, amplification, and spread of diseases is essential for prioritizing surveillance and predicting future disease emergence risk. We examine the animal hosts and transmission mechanisms involved in spillover of zoonotic viruses to date, and discover that viruses with high host plasticity (i.e. taxonomically and ecologically diverse host range) were more likely to amplify viral spillover by secondary human-to-human transmission and have broader geographic spread. Viruses transmitted to humans during practices that facilitate mixing of diverse animal species had significantly higher host plasticity. Our findings suggest that animal-to-human spillover of new viruses that are capable of infecting diverse host species signal emerging disease events with higher pandemic potential in that these viruses are more likely to amplify by human-to-human transmission with spread on a global scale.

It is currently unclear whether changes in viral communities will ever be predictable. Here we investigate whether viral communities in wildlife are inherently structured (inferring predictability) by looking at whether communities are assembled through deterministic (often predictable) or stochastic (not predictable) processes. We sample macaque faeces across nine sites in Bangladesh and use consensus PCR and sequencing to discover 184 viruses from 14 viral families. We then use network modelling and statistical null-hypothesis testing to show the presence of non-random deterministic patterns at different scales, between sites and within individuals. We show that the effects of determinism are not absolute however, as stochastic patterns are also observed. In showing that determinism is an important process in viral community assembly we conclude that it should be possible to forecast changes to some portion of a viral community, however there will always be some portion for which prediction will be unlikely.

BackgroundDespite the popularity of the horse racing industry in the United States and the wide recognition that horse racing is one of the most hazardous occupations, little focused research into the prevention of falls by and injuries to jockeys has been conducted.PurposeTo describe the incidence rates and characteristics of falls and injuries to Thoroughbred and Quarter Horse racing jockeys in the state of California.Study designDescriptive epidemiology study.MethodsData on race-day falls and injuries were extracted from jockey accident reports submitted to the California Horse Racing Board from January 2007 to December 2011. Denominator data, number of jockey race rides, were obtained from commercial and industry databases. Jockey fall, injury, and fatality incidence rates and ratios in Thoroughbred and Quarter Horse flat races were estimated using Poisson regression. Characteristics of falls and injuries are described and compared.ResultsIn Thoroughbred races, 184 jockey injuries occurred from 360 reported jockey falls, 180,646 race rides, 23,500 races, and 3350 race meetings. In Quarter Horse races, 85 jockey injuries occurred from 145 jockey falls, 46,106 race rides, 6320 races, and 1053 race meetings. Jockey falls occurred at a rate of 1.99 falls per 1000 rides in Thoroughbred races, with 51% of falls resulting in jockey injury, and 3.14 falls per 1000 rides in Quarter Horse races, with 59% of falls resulting in jockey injury. The majority of falls occurred during a race, with catastrophic injury or sudden death of the horse reported as the most common cause in both Thoroughbred (29%) and Quarter Horse (44%) races. During the period studied, 1 jockey fatality resulted from a fall. Jockey fall rates were lower but injury rates were comparable to those reported internationally.ConclusionOn average, a licensed jockey in California can expect to have a fall every 502 rides in Thoroughbred races and every 318 rides in Quarter Horse races. While jockey fall rates were lower, injury rates were similar to those in other racing jurisdictions. The high proportion of jockey falls caused by horse fatalities should be further investigated.

Neural tube defects (NTDs) is a general term for central nervous system malformations secondary to a failure of closure or development of the neural tube. The resulting pathologies may involve the brain, spinal cord and/or vertebral column, in addition to associated structures such as soft tissue or skin. The condition is reported among the more common birth defects in humans, leading to significant infant morbidity and mortality. The etiology remains poorly understood but genetic, nutritional, environmental factors, or a combination of these, are known to play a role in the development of NTDs. The variable conditions associated with NTDs occur naturally in dogs, and have been previously reported in the Weimaraner breed. Taking advantage of the strong linkage-disequilibrium within dog breeds we performed genome-wide association analysis and mapped a genomic region for spinal dysraphism, a presumed NTD, using 4 affected and 96 unaffected Weimaraners. The associated region on canine chromosome 8 (pgenome  =3.0 × 10(-5)), after 100,000 permutations, encodes 18 genes, including NKX2-8, a homeobox gene which is expressed in the developing neural tube. Sequencing NKX2-8 in affected Weimaraners revealed a G to AA frameshift mutation within exon 2 of the gene, resulting in a premature stop codon that is predicted to produce a truncated protein. The exons of NKX2-8 were sequenced in human patients with spina bifida and rare variants (rs61755040 and rs10135525) were found to be significantly over-represented (p=0.036). This is the first documentation of a potential role for NKX2-8 in the etiology of NTDs, made possible by investigating the molecular basis of naturally occurring mutations in dogs.

Objectives: To identify characteristics of jockey falls associated with high-risk landings using a modified Equestrian Fall Assessment Instrument.Design: Cross-sectional study.Methods: Video footage of 22 flat and 58 jump racing falls (N = 80) which occurred in Great Britain, Ireland, and New Zealand from 2013 to 2018 was systematically analysed using the modified Equestrian Fall Assessment Instrument. Race, horse, and jockey-level factors, including the nature of ground contact (landings), were characterised identifying factors associated with high-risk landings. High-risk landings refer to cases where the jockey's head impacted the ground or where there was potential horse impact on the jockey. A multivariable logistic regression model was applied identifying independent variables associated with high-risk landings.Results: In 79 % (63/80) of race falls examined, at least one high-risk landing factor was present. Three independent variables explained 40.3 % of variance in high-risk landings. Lower race class (odds ratio 1.5; 95 % confidence interval 0.96, 2.39; p = 0.054), hanging onto the reins upon ground impact (odds ratio 7.5; 95 % confidence interval 1.04, 53.63; p = 0.028), and no jockey tuck-and-roll behaviour following ground impact (odds ratio 4.9; 95 % confidence interval 1.65, 14.44; p = 0.001) were associated with high-risk landings.Conclusions: Jockeys who ride in lower race classes, who hung onto the reins before landing, and who didn't tuck-and-roll during a fall had increased risk of a high-risk landing. Further examination of relationships between race, jockey experience and fall behaviour characteristics upon injury outcomes, and evaluation of potential protective benefits of fall training are required. [ABSTRACT FROM AUTHOR]

Summary: Background: Musculoskeletal injuries (MSI) in racehorses are commonly due to bone fatigue, a function of the number of cycles (strides) and the magnitude of load applied to the limb. These parameters can be estimated using speed and distance, with greater than 6000 m/month at a gallop (>14 m/s), in combination with canter distances greater than 44,000 m/month, reported to increase fracture risk. Despite their importance, there are limited data on the distances and speeds horses are exposed to during training. Objectives: Estimate training volume at different speeds undertaken by Australian Thoroughbred racehorses. Study design: Cross‐sectional study. Methods: Registered trainers (n = 66) in Victoria, Australia were surveyed. Questions were designed to assess the full training workload from initial pre‐training to training performed to achieve and maintain race fitness, as well as information on rest periods. Descriptive analyses were stratified by trainer‐ and horse‐level factors, with assessment of variance within and between groups. Cluster analyses were used to identify similar workload intensity groups. Results: Horse‐level factors (age, targeted race distance) were associated with workload (younger

Objectives: To investigate the association between air jacket usage and rider injury severity in equestrian eventing competition falls world-wide.Design: Retrospective data analysis.Methods: An analysis was conducted on Fédération Equestre Internationale data for 1819 riders who fell wearing an air jacket and 1486 riders who fell while not wearing an air jacket from 2015 to 2017. Injury data were categorised as either 'no/slight injury' or 'serious/fatal injury'. A chi-square test determined whether an association was present between injury severity category and air jacket usage and binary logistic regression determined the effect size of this association.Results: As a result of falls, 3203 riders sustained no/slight injuries and 102 sustained serious/fatal injuries. While 55.0% of riders who fell were wearing an air jacket, they represented 67.6% of the serious/fatal injury outcomes. Air jacket usage was significantly associated with serious/fatal injuries in falls (X² = 6.76; p = 0.009). Riders wearing an air jacket had 1.7 times (95%CI 1.14-2.64) increased odds of sustaining a serious or fatal injury in a fall compared to riders not wearing an air jacket.Conclusions: Riders wearing an air jacket were over represented in the percentage of serious or fatal injuries in falls compared to riders who only wore a standard body protector. Further research is needed to understand the reason(s) for this finding. It is recommended that additional data on injury outcomes, rider characteristics and the biomechanics of falls be examined in future analyses, and that air jacket and body protector characteristics be further investigated. [ABSTRACT FROM AUTHOR]

Background The risk of falls and injuries in horseracing varies with sex and experience of the jockey. Aims To determine whether the incidence and costs of insurance claims also differ by such factors. Methods A retrospective analysis of compensation claims by flat racing and jumps jockeys injured in a raceday fall in Australia between 2002 and 2009. Claim incidence, costs, absentee days and location, cause and type of injury sustained were described, stratified by jockey sex, age and experience. Results The incidence of claims by flat and jumps racing was 0.6 and 6.5 per 1000 rides, respectively. The mean cost of a claim was 43374 Australian dollars (AUD) (SD 249 612) in flat racing and AUD 52589 (SD 157 808) in jumps racing. The incidence of claims was greater for experienced flat racing jockeys than apprentices but mean costs were higher for apprentices. After adjustment for experience, there were no sex differences in the average cost or incidence of flat racing jockeys' claims. In general, the fall incidence declined, but the claim incidence and median cost of a claim increased, with age. On average, jockeys were absent from work for 9 weeks following a substantive injury. Limb fractures (33%), muscular or soft tissue injuries (28%) and contusions (17%) were the most commonly reported injuries. Conclusions The economic costs of jockey injuries sustained in race-day falls are considerable. Identification of differences in incidence and costs of insurance claims between jockey characteristics will assist decision makers in the development and assessment of targeted safety strategies. [ABSTRACT FROM AUTHOR]

Biomechanical strain is a major stimulus of subchondral bone (SCB) tissue adaptation in joints but may also lead to initiation and propagation of microcracks, highlighting the importance of quantifying the intratissue strain in subchondral bone. In the present study, we used micro computed tomography (μCT) imaging, mechanical testing, and digital image correlation (DIC) techniques to evaluate the biomechanical strains in equine SCB under impact compression applied through the articular surface. We aimed to investigate the effects of in vivo accumulated microdamage in equine SCB on the distribution of mechanical impact strain through the articular cartilage. Under the applied strain of 2.0 ± 0.1% (mean ± standard deviation, n=15) to the articular surface of cartilage-bone plugs, the overall thickness of the SCB developed e S C B O v e r a l l = 0.7 ± 0.2% in all specimens. Contours of high strains in specimens without microdamage (NDmg) aligned parallel to the cartilage-bone interface with peak tensile, ϵ t , and compressive, ϵ c , strains of 0.5 ± 0.3% and 1.2 ± 0.4%, respectively at the time of peak compression (n=7). In damaged specimens (Dmg), contours of high strains aligned with the cracks in the imaged plane with peak strains of ϵ t = 1.2 ± 0.8% and ϵ c = 3.5 ± 2.2%, respectively (n=7). Microdamage was the main predictor of the normalised compressive and tensile strains across the SCB thickness. Results of multivariable analyses revealed presence of microdamage, distance from the articular surface and TMD were the main predictors of normalised compressive and tensile strain. Strain was greater in the superficial bone, particularly for specimens with microdamage. In vivo fatigue-induced microdamage is an important predictor of local subchondral bone strains. [ABSTRACT FROM AUTHOR]

Reasons for performing study If equine conditions with high likelihood of jockey injury can be determined and subsequently prevented, jockey safety can be enhanced. Objectives To identify racehorse injuries or conditions with greatest risk for jockey falls and injuries. Study design Retrospective correlation of race-day jockey fall and injury data with racehorse fatality data. Methods Thoroughbred ( TB) and Quarter Horse ( QH) racehorse cause of death and jockey fall and injury data for California flat races were reviewed for a 6-year period. Race and jockey race ride population data were used to determine jockey fall and injury incidence rates relative to cause of racehorse death, and were assessed using Poisson regression. Differences in proportions were assessed using Fisher's exact, Pearson's χ2, and Cochran- Mantel- Haenszel tests. Results 707 racehorses experienced race-related catastrophic injury or sudden death. 199 jockeys had 601 falls with 325 injuries. Jockeys were 162 times more likely to fall (95% confidence interval 137-192; P<0.001) and 171 times more likely to be injured (95% confidence interval 140-208; P<0.001) when they rode a horse that died in a race. We infer that jockeys were more likely to fall or be injured when riding in QH races than in TB races because of a higher incidence of horse fatalities in QH races. Jockey falls occurred with 24% of TB and 36% of QH race-related horse fatalities, and jockey injury occurred in 64% of falls. Jockey falls were most common with TB fetlock injuries and QH carpal, metacarpal and fetlock injuries; and with axial, bilateral and multiple injuries compared with appendicular, unilateral and singular injuries, respectively. Conclusions Prevention of the most common catastrophic injuries and conditions of the racehorse, e.g. fetlock injuries, may be most effective at decreasing rates of falls and injuries to horseracing jockeys during racing. [ABSTRACT FROM AUTHOR]

Reasons for performing study Knowledge of the site distribution of ligamentous injuries facilitates clinical diagnosis of suspensory apparatus conditions. Objectives To determine if lesions within the suspensory ligament ( SL) and distal ligaments of the proximal sesamoid bones ( DSLs) were associated with suspensory apparatus failure or metacarpal lateral condylar fracture in California Thoroughbred racehorses. Study design Cross-sectional study. Methods Suspensory apparatus specimens from 327 deceased Thoroughbred racehorses were sectioned within the SL body and branches, and oblique and straight DSLs. Purple lesions ≥2 mm in width were categorised as moderate and paler or smaller lesions as mild. Associations between moderate lesions and age, sex, racetrack and cause of death were evaluated using multivariable logistic regression. Results Moderate lesions were evident in 16% and milder lesions in 77% of racehorses. Moderate lesions occurred with similar frequency in SL branches and oblique DSLs. Moderate lesions were more likely to occur in horses that died as a result of suspensory apparatus failure (odds ratio [ OR] = 4.60; 95% confidence interval [ CI] 1.61-13.13; and P = 0.004) or metacarpal lateral condylar fracture ( OR = 5.05; 95% CI 1.42-17.93; and P = 0.012) compared with horses that died from nonmusculoskeletal causes, and in horses aged ≥7 years horses compared with 2-year-old horses ( OR = 5.33; 95% CI 1.44-19.75; and P = 0.012). Conclusions Moderate lesions are common in the SL branches and oblique DSLs of racehorses, and may be associated with risk for suspensory apparatus failure and metacarpal condylar fracture. Monitoring health of the suspensory apparatus ligamentous structures may be a simple means of assessing fatigue in, and preventing more extensive injuries to, the forelimb suspensory apparatus and metacarpal condyles. [ABSTRACT FROM AUTHOR]

Reasons for performing study To gain insight into the pathophysiology of equine lumbar vertebral fractures in racehorses. Objectives To characterise equine lumbar vertebral fractures in California racehorses. Study design Retrospective case series and prospective case-control study. Methods Racehorse post mortem reports and jockey injury reports were retrospectively reviewed. Vertebral specimens from 6 racehorses affected with lumbar vertebral fractures and 4 control racehorses subjected to euthanasia for nonspinal fracture were assessed using visual, radiographic, computed tomography and histological examinations. Results Lumbar vertebral fractures occurred in 38 Quarter Horse and 29 Thoroughbred racehorses over a 22 year period, primarily involving the 5th and/or 6th lumbar vertebrae ( L5- L6; 87% of Quarter Horses and 48% of Thoroughbreds). Lumbar vertebral fractures were the third most common musculoskeletal cause of death in Quarter Horses and frequently involved a jockey injury. Lumbar vertebral specimens contained anatomical variations in the number of vertebrae, dorsal spinous processes and intertransverse articulations. Lumbar vertebral fractures examined in 6 racehorse specimens (5 Quarter Horses and one Thoroughbred) coursed obliquely in a cranioventral to caudodorsal direction across the adjacent L5- L6 vertebral endplates and intervertebral disc, although one case involved only one endplate. All cases had evidence of abnormalities on the ventral aspect of the vertebral bodies consistent with pre-existing, maladaptive pathology. Conclusions Lumbar vertebral fractures occur in racehorses with pre-existing pathology at the L5- L6 vertebral junction that is likely predisposes horses to catastrophic fracture. Knowledge of these findings should encourage assessment of the lumbar vertebrae, therefore increasing detection of mild vertebral injuries and preventing catastrophic racehorse and associated jockey injuries. [ABSTRACT FROM AUTHOR]

• Race day CMI incidence for Thoroughbreds in Uruguay was 0.42 per 1,000 race starts • Incidence of CMI in training was 0.059 per 100 horse months • Catastrophic humeral fractures occurred more frequently during training than racing • The majority of race day CMIs involved the distal limb (71.8%) • CMI risk was greater for horses less intensively raced with more time between starts Catastrophic musculoskeletal injuries (CMI) pose a major welfare concern to horses and their riders, yet limited data are available describing their occurrence in South America. Using a retrospective cohort and case-control design, the objective of the study was to determine the incidence of CMI for Thoroughbreds in training and racing, and associated horse-level risk factors in Uruguay. Seventy-seven Thoroughbreds sustained a CMI, 37 of which were age- and sex-matched to 111 control horses in the same race. Training and racing data from 2011 to 2017 were collected. Incidence of race day CMI per 1,000 race starts and training CMI incidence per 100 horse months were calculated using Poisson regression. Univariable logistic regression was used to assess relationships between race history and occurrence of CMI by fracture location, and multivariable for all fracture locations. Overall race day incidence of CMI was 0.42 per 1,000 race starts (95% CI 0.29, 0.60). The incidence of CMI in training was 0.059 per 100 horse months. Twenty-nine percent (22/77) of horses that sustained a CMI had not raced prior. Most fractures were of the forelimbs (80.3%). There were 32 (41.6%) distal and 39 (50.6%) proximal limb fractures. The risk of CMI was greater for horses with fewer places (P =.001), and greater time between the previous race and the race in which CMI occurred (P =.020). The rate of race day CMI was low, despite Uruguay being a racing jurisdiction with policies and risk factors associated with greater CMI rates compared to other jurisdictions. Lightly raced horses with long periods since their previous race start should be monitored closely. [ABSTRACT FROM AUTHOR]

Reasons for performing study: Identification of exercise history patterns that are related to catastrophic scapular fracture will facilitate prevention of racehorse fatalities. Objectives: To determine if exercise patterns are associated with scapular fracture in Thoroughbred ( TB) and Quarter Horse ( QH) racehorses. Methods: High-speed exercise histories for 65 TB and 26 QH racehorses that had a complete scapular fracture (cases) and 2 matched control racehorses were retrospectively studied. Exercise variables were created from lifetime race and official timed workout reports. Associations between exercise variables and scapular fracture were investigated using conditional logistic regression. Results: Thoroughbreds with a scapular fracture had a greater number of workouts, events (combined works and races), and mean event distances than QHs with a scapular fracture. Quarter Horses worked less frequently and accumulated distance at a lower rate than TBs. Breed differences were not found for career race number or length, time between races or lay-up variables for horses with ≥1 lay-up. For both breeds, cases had fewer events, lower recent accumulated distance and fewer active days in training than controls; however, a subset of TB cases with >10 events since lay-up had a longer active career than controls. For QHs that had a lay-up, total and mean lay-up times were greater for cases than controls. Multivariable models revealed that odds ratios ( OR) of scapular fracture were greater for TBs that had not yet raced ( OR = 23.19; 95% confidence interval (CI) 3.03-177.38) and lower for QHs with more events ( OR = 0.71; 95% CI 0.54-0.94). Conclusions and clinical relevance: Racehorses that are in early high-speed training but behind that of their training cohort should be examined for signs of scapular stress remodelling. Quarter Horses that had a prolonged lay-up and TBs that have endured high-speed training for a longer duration than that of their training cohort also were at greater risk. [ABSTRACT FROM AUTHOR]

The article details a study which described the prevalence of falls, injuries and fatalities among horse-racing jockeys in Australia. The study utilized stewards' reports from the Principal Racing Authority of each Australian territory from August 2002 to July 2006. It found that 34.3 percent of falls during flat races resulted in 61.7 percent sustained injuries. During the period, only five fatalities among jockeys were recorded. Study authors concluded that safety standards in the Australian racing industry should be enhanced.

• Jockey injury surveillance and data collection guidelines have been published for professional horse-racing in Europe. • Substantial variation in jockey injury data collection and reporting practices exists worldwide, with little evidence of use of previously published guidelines. • Recommendations are presented for international horse-racing authorities in support of standardized jockey injury data collection and reporting practices. Jockey injuries are common in professional horse-racing and can result in life-threatening or career-ending outcomes. Robust injury data are essential to understand the circumstances of injury occurrence and ultimately identify prevention opportunities. This study aimed to identify jockey injury surveillance practices of international horse-racing authorities (HRAs) and the specific data items collected and reported by each HRA. A cross-sectional survey of representatives (e.g. Chief Medical Officer) from international HRAs was conducted. An online and paper questionnaire was designed comprised of 32 questions. Questions considered the barriers and facilitators to data collection within each HRA, and where available, what data were collected and reported by HRAs. Representatives from 15 international racing jurisdictions were included, of which 12 reported collection of race day injuries or falls, using varied definitions of medical attention and time loss. Six HRAs did not have a definition for a jockey injury, and eight HRAs had no parameters for describing injury severity. Race day exposure was collected by two HRAs. Results were commonly presented by HRAs as the number of injuries (n = 9/15) or proportion of injured jockeys (n = 6/15). The lack of a designated role for collection, collation and reporting of data was the main barrier for injury surveillance. Twelve HRAs agreed that mandatory collection would be a strong facilitator to improving practice. Enhancement and standardization of international jockey injury surveillance is required to move forward with evidence informed prevention. Concurrent investigation of how reporting practices can be best supported within existing HRA structures is recommended. [ABSTRACT FROM AUTHOR]

Fatigue-induced subchondral bone (SCB) injuries are prevalent among athletes due to the repetitive application of high magnitude loads on joints during intense physical training. Existing fatigue studies on bone utilize a standard fatigue test approach by applying loads of a constant magnitude and frequency even though physiological/realistic loading is a combination of various load magnitudes and frequencies. Metal materials in implant and aerospace applications have been studied for fatigue behavior under physiological or realistic loading, however, no such study has been conducted on biological materials like bones. In this study, we investigated fatigue behavior of SCB under the range of loads likely to occur during a fast-workout of an equine athlete in training. A loading protocol was developed by simulating physiological loads occurring during a fast-workout of a racehorse in training, which consisted of a sequence of compression-compression load cycles, including a warm-up (32, 54, 61 MPa) and cool-down (61, 54, 32 MPa) before and after the slow/fast/slow gallop phase of training, also referred to as a training loop. This loading protocol/training loop was applied at room temperature in load-control mode to cylindrical SCB specimens (n = 12) harvested from third metacarpal medial condyles (MCIII) of twelve thoroughbred racehorses and repeated until fatigue failure. The mean ± standard deviation for total time-to-failure (TTF) was 76,393 ± 64,243 s (equivalent to 18.3 ± 15.7 training workouts) for n = 12 specimens. We observed the highest relative energy loss (REL, hysteresis loss normalized to energy absorbed in a load cycle) under loads equivalent to gallop speeds and all specimens failed under these gallop loads. This demonstrates the importance of the gallop speeds in the development of SCB injury, consistent with observations made in live racehorses. Moreover, specimens with higher mean REL and lower mean stiffness during the first loop had a shorter fatigue life which further confirms the detrimental effect of high energy loss in SCB. Further studies are required to reconcile our results with fatigue injuries among equine athletes and understand the influence of different training programs on the fatigue behavior of subchondral bone. • Fatigue tests on equine subchondral bone were conducted undersimulated physiological loads which occurr in a fast-workout. • The subchondral bone recorded the highest energy loss under loads equivalent to the gallop gait in a racehorse. • Relative energy loss appears to be a useful indicator of fatigue life that can be measured within a single training loop. [ABSTRACT FROM AUTHOR]

Subchondral bone injuries often precede articular cartilage damage in osteoarthritis and are common in thoroughbred racehorses due to the accumulation of fatigue damage from high speed racing and training. Thus, racehorses provide a model to investigate the role of subchondral bone in joint disease. We assessed the association of horse and racing related factors and micro-CT based micromorphology of three separate subchondral bone layers with the initial stiffness and compressive fatigue life of bone plugs. Furthermore, we investigated three different definitions of fatigue failure of subchondral bone during compressive fatigue testing. Initial stiffness was 2,362 ± 443 MPa (mean ± standard deviation). Median compressive fatigue life during cyclic loading to -78 MPa was 16,879 (range 210 to 57,064). Subchondral bone stiffness increased over a median of 24% (range 3%–42%) of fatigue life to a maximum of 3,614 ± 635 MPa. Compressive fatigue life was positively associated with bone volume fraction in the deeper layers of subchondral bone, maximal stiffness, and the number of cycles to maximal stiffness. Initial stiffness was positively associated with tissue mineral density in the deeper layers and bone volume fraction in the superficial layer. Most specimens with a fatigue life of less than 5,500 cycles fractured grossly before reaching 30% reduction of maximal stiffness. Cycles to 10% reduction of maximal stiffness correlated strongly with cycles to lowest recorded stiffness at gross fracture and thus is a valid alternative failure definition for compressive fatigue testing of subchondral bone. Our results show that subchondral bone sclerosis as a result of high speed exercise and measured as bone volume fraction is positively associated with compressive fatigue life and thus has a protective effect on subchondral bone. Further research is required to reconcile this finding with the common collocation of fatigue damage in sclerotic subchondral bone of racehorses. • Subchondral bone fatigue life increases with increasing bone volume fraction. • Subchondral bone stiffness is positively associated with tissue mineral density. • Superficial subchondral bone differs from deeper subchondral bone layers. [ABSTRACT FROM AUTHOR]

The proportion of Thoroughbred (TB) horses that commence training and eventually race, is an important industry-level indicator of how successful it is at producing horses suitable for racing. It is also of interest to the wider community and is central to the issue of whether there is overbreeding in the Australian TB industry. This study investigated the training and racing records for the 2005 and 2010 Victorian TB foal crops to determine the proportion of TBs that train and race, and the age of entering training and first race start. Subsets of the foal crop were also examined to determine if premier yearling sale cohorts would produce selection bias. The Australian Stud Book (ASB) registered 7662 TB horses born in Victoria in 2005 (n = 4116) and 2010 (n = 3546). Of these, 5614 (73%) entered training and 4868 (64%) started in at least one race. Fourteen percent (n = 1045) of the study cohort had their first race start as 2-year-olds and 35% (n = 2644) had their first start as 3-year-olds. A higher proportion of TB horses that attended premier yearling sales entered training (93%) and raced (84%). This study established a baseline for training and racing milestones, such as the proportion and age that horses commenced training, and age of first start using population-level data. It also established that the use of subsets of the population can introduce selection bias., (© 2021 Australian Veterinary Association.)

The number of horses leaving the Australian Thoroughbred (TB) racing industry each year is of concern to animal welfare advocates, public and regulators. A horse's previous athletic performance is a significant driver of retirement from racing. Racehorse performance can be measured in terms of the total number of starts, duration of racing and prize money earned. This study investigated Australian racing records for the 2005 and 2010 Victorian TB foal crops to identify factors associated with total number of starts, racing career duration, prize money earned and age of last race start-up to the 10-year-old racing season. Racing Australia registered 4,577 TB horses born in Victoria in 2005 (n = 2,506) and 2010 (n = 2,071) that raced in Australia. Horses that started racing at 2-years of age had fewer race starts in their first racing season but an increased total number of starts, prize money and duration of racing. The median age of last start (LS) was five (Q1 4; Q3 7) years. Horses that had won a race, had a maximum handicap rating of 61 or above and those racing over distances of more than 2,400 m had an increased racing career duration and an age of last race start greater than 6-years of age. Horses participating in jumps races (n = 63) had the longest careers and older age of LS. These horses were more likely to have had a handicap rating over 80 and were just as likely to start their racing careers as 2-years-olds., (© 2021 Australian Veterinary Association.)

Long bone fractures in racehorses may present as stress fractures which have a good prognosis, or complete fractures, which often result in a fatal outcome. In order to identify differences in modifiable management practices that may contribute to these outcomes, racing histories of horses with humeral or tibial fractures and of matched controls were examined. A retrospective case-control study of Australian Thoroughbred racehorses diagnosed with a fracture of the humerus or tibia by scintigraphy or at post-mortem between 2002 and 2016 was undertaken. Control horses were matched from the same race or trial on age and sex. Statistical analysis was performed using conditional logistic regression, χ 2 and Mann-Whitney U tests. More humeral fractures than tibial fractures were fatal (12/47, 26% vs. 3/35, 8.6%, P = 0.049). No differences in pre-injury racing histories were observed between cases and controls for humeral and tibial fractures. Both humeral and tibial fracture case horses were younger than the registered Thoroughbred racing population (P < 0.001), but horses sustaining humeral fractures were older than those with tibial fractures (3.3 ± 0.9 vs. 2.8 ± 0.8 years, P = 0.005) yet raced fewer times prior to the injury (0.5 ± 1.1 vs. 1.3 ± 1.7 races, P = 0.009). Horses with fatal humeral fractures were less likely to have raced than those with non-fatal humeral fractures (16.7% vs. 55.6%, P = 0.02). In conclusion, tibial and humeral fractures occur in young racehorses, and humeral fractures are more likely to be fatal in those with the least exposure to trialling and racing., (Copyright © 2019. Published by Elsevier Ltd.)

Background: Veterinarians are required to interpret the significance of radiographic findings for sale, soundness and future racing performance of weanling and yearling Thoroughbreds. We investigated the prevalence and radiographic appearance of slab fractures of the third (T3) and central tarsal (Tc) bones., Methods: Weanling and yearling horses with complete or incomplete T3 or Tc fracture were identified by searching a database of radiographs. The prevalence and radiographic appearance at initial diagnosis and after continued pasture turnout, as well as prognosis for racing, of fractures of T3 and Tc were determined., Results: Fractures were identified in 186 tarsi (184 T3 fracture only, 1 Tc fracture only, 1 Tc and T3 fracture) of 157 horses (126 unilateral T3, 29 bilateral T3, 1 contralateral Tc and T3, 1 unilateral Tc and T3) from 7676 examinations. The prevalence of T3 and Tc fractures was 2.40 (95% CI 2.07, 2.76) and 0.04 (95% CI 0.01, 0.11) per 100 radiographic examinations respectively. Fractures were identified on the D556-65°MPlLO view and occurred by survey examination at 11.1 ± 1.3 months in 85.7% horses. At initial diagnosis, 84.3% of T3 fractures appeared incomplete and involved the distal articular surface. Fracture score improved (P < 0.001), and dorsal modelling (P < 0.001) and osteoarthritis score increased in the distal intertarsal joint (P < 0.001), but not the tarsometatarsal joint, between survey and repository examinations. Fractures healed by repository examination in 71.9% of tarsi if there was > 6 months between examinations. There was no difference in sale price, and horses with T3 fractures had fewer trials when 2 and 3 years old (P = 0.023), yet no difference in other parameters of racing success when 2 or 3 years old compared with controls., Conclusion: Tarsal slab fractures can occur in juvenile Thoroughbreds and most heal with continued pasture turnout of > 6 months. Further investigation is required to determine risk factors and before making firm conclusions regarding the optimal management, prognosis for racing and long-term soundness., (© 2019 Australian Veterinary Association.)

Studies of racehorse injury or fatality in various countries have identified common, and in some cases conflicting, risk factors. We conducted a systematic search of the relevant literature published from 1990 to 2017. Peer-reviewed articles were included if they reported the incidence of fatal or catastrophic musculoskeletal injury (CMI) in Thoroughbred flat races (n=21) or risk factors for CMI (n=65). Pooled effect sizes were estimated using the random-effects DerSimonian-Laird model. The pooled incidence of CMI was 1.17 (95% confidence interval 0.90, 1.44) per 1000 race starts. Almost 300 factors have been investigated in epidemiological studies for potential associations with CMI. Factors found to have consistent evidence of increasing risk of CMI are: (1) Horse-level factors such as older horse age and age at first start, male sex, and higher race class or lower claiming price; (2) Race-level factors such as firmer track conditions on turf and wetter conditions on dirt, longer race distance, and a greater number of starters; and (3) Management-related factors including more time since previous start, greater number of starts, longer career length, issues identified at pre-race examination, previous injury, and recent administration of medication or injections. Studies investigating recent cumulative distance of high-speed exercise were conflicting and suggestive of at least two mechanisms of injury related to the accumulation of bone damage: (1) In well adapted bone following a period of intense training; and (2) In poorly adapted bone at relatively low levels of training intensity. Future studies should evaluate success of interventions and mechanisms for injury., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Background: Fragmentation of the dorsal aspect of the distal talus (FDDT), at the dorsolateral articular margin of the proximal intertarsal joint (PITJ) on pre-sale radiographs of yearling Thoroughbreds has not been previously described and data to support decisions made by veterinarians to predict future racing potential of horses with these lesions are lacking., Methods: In this retrospective case-control study we aimed to determine the prevalence of FDDT in juvenile Thoroughbreds and to report their race records. From a database of survey and repository radiographic examinations of 5709 horses, 36 with FDDT were identified., Results: The prevalence of FDDT was 0.63% (36/5709; 95%CI 0.44, 0.87), compared with 5.01% (286/5709; 95%CI 4.46, 5.61) for osteochondrosis of the distal intermediate ridge of the tibia in the same population. In most cases, a single oval-shaped fragment 1-12 mm in diameter was present. When comparing cases with matched controls, there were no significant differences in mean sale price, whether horses started in a trial or race and mean number of starts, wins, places and prize money when 2- and 3-years old., Conclusion: FDDT did not appear to affect racing performance, although a larger-scale study is warranted to confirm this finding., (© 2019 Australian Veterinary Association.)