Disease and pharmacologic risk factors for first and subsequent episodes of equine laminitis: A cohort study of free-text electronic medical records.

Electronic medical records from first opinion equine veterinary practice may represent a unique resource for epidemiologic research. The appropriateness of this resource for risk factor analyses was explored as part of an investigation into clinical and pharmacologic risk factors for laminitis. Amalgamated medical records from seven UK practices were subjected to text mining to identify laminitis episodes, systemic or intra-synovial corticosteroid prescription, diseases known to affect laminitis risk and clinical signs or syndromes likely to lead to corticosteroid use. Cox proportional hazard models and Prentice, Williams, Peterson models for repeated events were used to estimate associations with time to first, or subsequent laminitis episodes, respectively. Over seventy percent of horses that were diagnosed with laminitis suffered at least one recurrence. Risk factors for first and subsequent laminitis episodes were found to vary. Corticosteroid use (prednisolone only) was only significantly associated with subsequent, and not initial laminitis episodes. Electronic medical record use for such analyses is plausible and offers important advantages over more traditional data sources. It does, however, pose challenges and limitations that must be taken into account, and requires a conceptual change to disease diagnosis which should be considered carefully.

Prevalence, survival analysis and multimorbidity of chronic diseases in the general veterinarian-attended horse population of the UK.

The average age of the global human population is increasing, leading to increased interest in the effects of chronic disease and multimorbidity on health resources and patient welfare. It has been posited that the average age of the general veterinarian-attended horse population of the UK is also increasing, and therefore it could be assumed that chronic diseases and multimorbidity would pose an increasing risk here also. However, evidence for this trend in ageing is very limited, and the current prevalence of many chronic diseases, and of multimorbidity, is unknown. Using text mining of first-opinion electronic medical records from seven veterinary practices around the UK, Kaplan-Meier and Cox proportional hazard modelling, we were able to estimate the apparent prevalence among veterinarian-attended horses of nine chronic diseases, and to assess their relative effects on median life expectancy following diagnosis. With these methods we found evidence of increasing population age. Multimorbidity affected 1.2% of the study population, and had a significant effect upon survival times, with co-occurrence of two diseases, and three or more diseases, leading to 6.6 and 21.3 times the hazard ratio compared to no chronic disease, respectively. Laminitis was involved in 74% of cases of multimorbidity. The population of horses attended by UK veterinarians appears to be aging, and chronic diseases and their co-occurrence are common features, and as such warrant further investigation.

Risk factors for epistaxis in jump racing in Great Britain (2001-2009).

The aim of this study was to evaluate risk factors associated with developing epistaxis in jump racing in Great Britain (GB). A retrospective analysis of records from horses running in all hurdle and steeplechase races in GB between 2001 and 2009 identified diagnoses of epistaxis whilst still at the racecourse. Data were used from 603 starts resulting in epistaxis (event) and 169,065 starts resulting in no epistaxis (non-event) in hurdle racing, and from 550 event starts and 102,344 non-event starts in steeplechase racing. Two multivariable logistic regression models to evaluate risk factors associated with epistaxis were produced. The potential effect of clustering of data (within horse, horse dam, horse sire, trainer, jockey, course, race and race meet) on the associations between risk factors and epistaxis was examined using mixed-effects models. Multiple factors associated with increased risk of epistaxis were identified. Those identified in both types of jump racing included running on firmer ground; horses with >75% of career starts in flat racing and a previous episode of epistaxis recorded during racing. Risk factors identified only in hurdle racing included racing in the spring and increased age at first race; and those identified only in steeplechase racing included running in a claiming race and more starts in the previous 3-6 months. The risk factors identified provide important information about the risk of developing epistaxis. Multiple avenues for further investigation are highlighted, including unmeasured variables at the level of the racecourse. The results of this study can be used to guide the development of interventions to minimise the risk of epistaxis in jump racing.

Estimates of genetic parameters of distal limb fracture and superficial digital flexor tendon injury in UK Thoroughbred racehorses.

A retrospective cohort study of distal limb fracture and superficial digital flexor tendon (SDFT) injury in Thoroughbred racehorses was conducted using health records generated by the British Horseracing Authority (BHA) between 2000 and 2010. After excluding records of horses that had both flat and jump racing starts, repeated records were reduced to a single binary record per horse (n = 66,507, 2982 sires), and the heritability of each condition was estimated using residual maximum likelihood (REML) with animal logistic regression models. Similarly, the heritability of each condition was estimated for the flat racing and jump racing populations separately. Bivariate mixed models were used to generate estimates of genetic correlations between SDFT injury and distal limb fracture. The heritability of distal limb fracture ranged from 0.21 to 0.37. The heritability of SDFT injury ranged from 0.31 to 0.34. SDFT injury and distal limb fracture were positively genetically correlated. These findings suggest that reductions in the risk of the conditions studied could be attempted using targeted breeding strategies.

Preliminary genetic analyses of important musculoskeletal conditions of Thoroughbred racehorses in Hong Kong.

A retrospective cohort study of important musculoskeletal conditions of Thoroughbred racehorses was conducted using health records generated over a 15 year period (n=5062, 1296 sires). The prevalence of each condition in the study population was: fracture, 13%; osteoarthritis, 10%; suspensory ligament injury, 10%; and tendon injury, 19%. Linear and logistic sire and animal regression models were built to describe the binary occurrence of these musculoskeletal conditions, and to evaluate the significance of possible environmental risk factors. The heritability of each condition was estimated using residual maximum likelihood (REML). Bivariate mixed models were used to generate estimates of genetic correlations between each pair of conditions. Heritability estimates of fracture, osteoarthritis, suspensory ligament and tendon injury were small to moderate (range: 0.01-0.20). Fracture was found to be positively genetically correlated with both osteoarthritis and suspensory ligament injury. These results suggest that there is a significant genetic component involved in the risk of the studied conditions. Due to positive genetic correlations, a reduction in prevalence of one of the correlated conditions may effect a reduction in risk of the other condition.

Long-term maintenance of arytenoid cartilage abduction and stability during exercise after laryngoplasty in 33 horses.

OBJECTIVES: To (1) assess long-term maintenance of arytenoid cartilage abduction (ACA) after laryngoplasty (LP); and (2) correlate the residual grade of ACA and postoperative abductory loss with arytenoid cartilage stability (ACS) during exercise. STUDY DESIGN: Case series. ANIMALS: Horses re-examined after laryngoplasty (n = 33). METHODS: Of 89 LP horses (2005-2010), 33 had historic ACA data available and upper airway endoscopy at rest and during over-ground exercise (mean, 33 months; range, 4-71 months) after surgery. ACA grade at 1 and 6 weeks postoperatively were correlated to long-term ACA grade. Effects of long-term ACA grade and magnitude of postoperative abductory loss on ACS during exercise were investigated. RESULTS: Median ACA grade at 1 week (n = 33) was 2, reducing to grade 3 by week 6 (n = 16). Grade 3 abduction was maintained in the long-term. Correlation between ACA at 1 week and the long-term was poor (ρ = .43, P = .1), but there was good correlation between week 6 and long-term (ρ = .89, P < .001). Arytenoid cartilage instability was observed during exercise in 7/33 of horses, and not significantly associated with the ACA grade (P = .50), or the number of grades of ACA lost (P = .64). CONCLUSIONS: Limited abductory loss occurs after 6 weeks postoperatively. Resting ACA grade was not a useful predictor of ACS during exercise.

Assessment of the impact of collection temperature and sampler design on the measurement of exhaled breath condensate pH in healthy horses.

The pH measurement of exhaled breath condensate (EBC) may provide a non-invasive method of assessing the lower airways of horses but the methodology used may influence findings. The aim of this study was to investigate the effect of two sampling devices and three methods of condensation surface cooling (ethanol slush, -100°C; dry ice, -75°C; water ice, 0°C) on EBC pH. Each method was tested 30 times using six healthy ponies. Sample pH was determined before and after de-aeration with argon for 10 min. Sampler design was found to significantly affect pH. Samples collected as a liquid had a significantly higher pH than samples frozen during collection (P<0.05). De-aeration resulted in significantly higher pH (P<0.05) with less variation. This study has shown that device design and condensation surface temperature will influence EBC pH, which will prevent a direct comparison of results when different methodologies are used.

Third metacarpal condylar fatigue fractures in equine athletes occur within previously modelled subchondral bone.

Bone modelling and remodelling reduce the risk of fatigue fractures; the former by adapting bone to its loading circumstances, the latter by replacing fatigued bone. Remodelling transiently increases porosity because of the normal delay in onset of the formation phase of the remodelling sequence. Protracted intense loading suppresses remodelling leaving modelling as the only means of maintaining bone strength. We therefore hypothesized that race horses with fatigue fractures of the distal third metacarpal bone (MC3) will have reduced porosity associated with suppressed remodelling while continued adaptive modelling will result in higher volume fraction (BV/TV) at this site. Using high resolution peripheral quantitative computed tomography (HR-pQCT), we measured the distal aspect of the MC3 obtained at postmortem from 13 thoroughbred race horses with condylar fractures of the MC3 (cases), 8 horses without fractures (training controls), 14 horses with a fracture at another site (fractured controls) and 9 horses resting from training (resting controls). Porosity of the subchondral bone of MC3 was lower in cases than resting controls (12±1.4% vs. 18±1.6%, P=0.017) although areas of focal porosity were observed adjacent to fractures in 6/13 horses. BV/TV of the distal metacarpal epiphysis tended to be higher in horses with condylar fractures (0.79±0.015) than training controls (0.74±0.019, P=0.070), but also higher in controls with a fracture elsewhere (0.79±0.014) than the training controls (0.74±0.019, P=0.040). BV/TV was higher in horses over three years of age than those aged two or three years (0.79±0.01 vs. 0.74±0.01, P=0.016). All metacarpal condylar fractures occurred within focal areas of high BV/TV. We infer that intense training in equine athletes suppresses remodelling of third metacarpal subchondral bone limiting damage repair while modelling increases regional bone volume in an attempt to minimise local stresses but may fail to offset bone fragility.