| Popis: |
Thoroughbred horse jump racing is popular in Great Britain (GB). Unfortunately it is associated with inherent risk of injury to the horses involved and it has been shown that the risk is significantly higher in jump than in flat racing. As a result, jump racing has been made a priority in racehorse injury investigation by the racing authorities in GB and is the focus of this thesis. Data about injuries and fatalities collected by veterinary surgeons, from all official race meetings between 2000 and 2009 was made available by the British Horseracing Authority (BHA). Following initial examination of the data, review of the literature and discussion with the BHA, a list of outcomes (injuries and fatality) was defined for further investigation. Multivariable logistic regression modelling was employed to investigate associations between potential risk factors and the outcomes. Model validation techniques were then used for outcomes with the greatest frequencies. In addition, post-mortem (PM) findings from a subset of the available data provided the opportunity to evaluate the accuracy of the information provided. Outcomes selected for further investigation were: fatality, tendon strain, epistaxis, hind limb fracture, pelvic fracture, and proximal forelimb fracture. Multiple risk factors were identified as being significantly associated with each outcome which can be used to guide legislation or further investigation. Risk factors common to many of the outcomes were: season, surface firmness (going), race distance and previous racing history (especially previous flat start history). Notably in some instances the relationships between these common risk factors and the outcomes varied, such that a risk factor might be associated with increased likelihood of one outcome but a decreased likelihood of another. Attempts to validate the models with the most frequent outcomes (fatality, superficial digital flexor tendinopathy and epistaxis) against a novel data set (from the year 2010), demonstrated variable calibration and discrimination and relatively poor predictive ability for all of the models. This was thought to be related to the low outcome frequencies and potentially related to risk factors unaccounted for in the models. Evaluation of the accuracy of the recording system for fatal distal limb fractures using PM findings demonstrated good identification of fracture presence, but relatively poor definition of all affected bones. Frustratingly it was concluded that making policy decisions based on the risk factor models will not be straightforward. Few risk factors had strong associations with all outcomes, not all risk factors are readily modifiable and many potential modifications (such as stopping horses from racing) would have major long term deleterious implications for horses. However, new risk factors for injury were identified providing some additional information about injury aetiology; previously recognised associations (such as firm ground and injury) are supported by the work; and sensible recommendations can be made to the industry, such as: closer monitoring of horses based on their previous racing careers or previous injuries. In addition, further training of racecourse veterinarians and/or provision of diagnostic aids (such as radiography) can be recommended to help with diagnoses made at the racecourses. |
