Exercise-induced pulmonary haemorrhage in Thoroughbred racehorses: a longitudinal study.

BACKGROUND: Exercise-induced pulmonary haemorrhage (EIPH) is considered a progressive disease based on histopathology, but it is unknown if tracheobronchoscopic EIPH severity worsens over time. OBJECTIVES: The aim of this study was to examine tracheobronchoscopic EIPH changes over time in a population of Thoroughbred racehorses. A secondary aim was to identify factors that affect changes in tracheobronchoscopic EIPH severity between observations. STUDY DESIGN: Prospective, longitudinal, observational cross-sectional study. METHODS: Thoroughbred racehorses were examined with tracheobronchoscopy no earlier than 30 min after racing. Examinations were recorded and graded blindly by experienced veterinarians using a 0-4 scale. Horses with 2 or more observations were included in the analysis. The association between the previous and current EIPH score was investigated using a linear mixed effect model. Factors associated with transitioning from a lower to a high EIPH grade and vice versa were examined using multiple ordinal regression. A semi-parametric regression model was used to examine progression using the number of career starts as a marker for time. Models were adjusted for potential confounding variables. RESULTS: There were 2974 tracheobronchoscopic examinations performed on 747 horses. Blood was detected in over half of all examinations (55.6%). The population prevalence of EIPH increased as the number of examinations for each horse increased. The preceding EIPH score was significantly associated with the current EIPH score. Significant variables associated with moving between EIPH grades were the number of days since last racing, ambient temperature and weight carried. Tracheobronchoscopic EIPH is mildly progressive over the first thirty career starts. MAIN LIMITATIONS: Enrolment was voluntary. Horses were not followed for their entire career. CONCLUSION: Limiting the number of days in the current racing preparation and spacing races for horses with moderate to severe EIPH may be beneficial for reducing tracheobronchoscopic EIPH severity. The association between ambient temperature and EIPH warrants further investigation.

Circannual variability in adrenocorticotropic hormone responses to administration of thyrotropin-releasing hormone in clinically normal horses in Australia.

Thyrotropin releasing hormone (TRH)-stimulation testing for pituitary pars intermedia dysfunction (PPID) in horses is only recommended at certain times of the year. Current diagnostic cut-off values reflect testing in the northern hemisphere during this time. The aims of this study were to evaluate TRH stimulation testing during two different phases of the circannual pituitary cycle and to determine whether diagnostic cut-off values developed in the northern hemisphere are appropriate in Australia. Thirteen clinically normal horses at Perth, Western Australia, and 23 horses at Townsville, Queensland, Australia, had TRH stimulation tests performed at two different time points during the circannual pituitary cycle. At both locations, post-TRH adrenocorticotropic hormone (ACTH) concentrations were significantly different between testing time points (Perth: P=0.001; Townsville: P<0.0001). In Perth, the mean ACTH concentrations 10min post-TRH in September and March were 51.4pg/mL (95% confidence interval, CI, 46.4-56.4pg/mL) and 248.5pg/mL (95% CI 170.2-326.9pg/mL), respectively. The median percentage change in ACTH concentrations in March was 361.9%. In Townsville, the mean ACTH concentrations 30min post-TRH in September and April were 35.3pg/mL (95% CI 29.6-40.9pg/mL) and 112.3pg/mL (95% CI 93.4-131.2pg/mL), respectively. The median percentage change in ACTH concentrations in April was 144.7%. The ACTH cut-off value after TRH stimulation in normal horses in September in Perth and Townsville was similar to the values established in the northern hemisphere. However, TRH stimulation testing in March/April was highly variable at both locations.

The association between exercise-induced pulmonary haemorrhage and race-day performance in Thoroughbred racehorses.

BACKGROUND: Exercise-induced pulmonary haemorrhage (EIPH) is commonly implicated as a cause of poor athletic performance but there is limited and conflicting evidence for this association. OBJECTIVES: The aim of this study was to determine if EIPH, based on endoscopic examination after racing, is associated with a variety of novel and established performance parameters. STUDY DESIGN: Prospective, observational cross-sectional study. METHODS: Thoroughbred racehorses competing between 2012 and 2015 were examined on-course no earlier than 30 min after racing. Examinations were recorded and graded blindly by experienced veterinarians using a 0-4 scale. Linear mixed effect models were used for analysis of continuous response variables with horse name incorporated as a random effect to account for repeated sampling and horse variability. Generalised estimating equations were used for analysis of binary responses. Performance variables were examined in 2 models, comparing EIPH grade 0 to grades 1-4, and EIPH grade ≤2 compared with EIPH grades ≥3, controlling race factors that could influence performance. RESULTS: There were 3794 observations collected from 1567 horses. EIPH was detected in 55.1% of observations. Horses with grade 4 EIPH were significantly more likely to have a lower finishing position and finish further behind the winner, less likely to place in the first 3 positions and collect race earnings, collected less earnings per race start and were slower over the last 600 m of the race than horses without EIPH (grade 0). Similar associations were seen in Model 2, with horses with EIPH grade ≥3 having inferior performance when compared to horses with EIPH ≤2. MAIN LIMITATIONS: Enrolment was voluntary. CONCLUSION: Mild to moderate haemorrhage was not associated with inferior race day performance in this population of Thoroughbred racehorses.

Past environmental sun exposure and risk of multiple sclerosis: a role for the Cdx-2 Vitamin D receptor variant in this interaction.

Multiple studies have provided evidence for an association between reduced sun exposure and increased risk of multiple sclerosis (MS), an association likely to be mediated, at least in part, by the vitamin D hormonal pathway. Herein, we examine whether the vitamin D receptor (VDR), an integral component of this pathway, influences MS risk in a population-based sample where winter sun exposure in early childhood has been found to be an important determinant of MS risk. Three polymorphisms within the VDR gene were genotyped in 136 MS cases and 235 controls, and associations with MS and past sun exposure were examined by logistic regression. No significant univariate associations between the polymorphisms, rs11574010 (Cdx-2A > G), rs10735810 (Fok1T > C), or rs731236 (Taq1C > T) and MS risk were observed. However, a significant interaction was observed between winter sun exposure during childhood, genotype at rs11574010, and MS risk (P = 0.012), with the 'G' allele conferring an increased risk of MS in the low sun exposure group (