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Biomedical subjects

R M Christley

Publications and source records attributed to R M Christley.

At least 19 recordsLinked to original sources
PubMed2006

Investigations of the reliability of observational gait analysis for the assessment of lameness in horses.

The objectives of this study were to assess the reliability of a numerical rating scale (NRS) and a verbal rating scale (VRS) for the assessment of lameness in horses and to determine whether they can be used interchangeably. Sixteen independent observers graded the severity of lameness in 20 videotaped horses, and the agreement between and within observers, correlation and bias were determined for each scale. The observers agreed with each other in 56 per cent of the observations with the NRS and in 60 per cent of the observations with the VRS, and the associated Kendall coefficient of concordance was high. Similar trends were evident in the agreement between two observations by each observer. The correlation between and within observers was high for both scales. There were no significant differences (bias) among the observers' mean scores when using either scale. There was a significant correlation between the lameness scores attributed when using the two scales, but the differences between the scores when plotted against their overall mean were unacceptable for clinical purposes. The results indicate that the NRS and VRS are only moderately reliable when used to assess lameness severity in the horse, and that they should not be used interchangeably.

Animals↗
PubMed2005

Effects of changes to the stable environment on the exhalation of ethane, carbon monoxide and hydrogen peroxide by horses with respiratory inflammation.

The aim of this study was to assess the effects of changes to the stable environment on exhaled markers of respiratory inflammation in six horses with clinical histories of recurrent airway obstruction. The horses were maintained for two weeks under conventional stable management (straw bedding and hay) and for two weeks on a reduced-dust regimen (paper bedding and ensiled grass), in a crossover study design. Exhaled ethane and carbon monoxide (CO) and exhaled breath condensate hydrogen peroxide (H(2)O(2)) were measured every three days under each regimen. The presence of clinical signs of airway inflammation (nasal discharge and cough) was monitored daily. The reduced-dust regimen was associated with fewer clinical signs of airway inflammation than the conventional regimen. Exhaled ethane and CO were significantly lower on the reduced-dust regimen and these markers were correlated with clinical signs of respiratory inflammation, but exhaled H(2)O(2) was not affected by the management regimen.

Airway Obstruction↗
PubMed2005

Infection in social networks: using network analysis to identify high-risk individuals.

Simulation studies using susceptible-infectious-recovered models were conducted to estimate individuals' risk of infection and time to infection in small-world and randomly mixing networks. Infection transmitted more rapidly but ultimately resulted in fewer infected individuals in the small-world, compared with the random, network. The ability of measures of network centrality to identify high-risk individuals was also assessed. "Centrality" describes an individual's position in a population; numerous parameters are available to assess this attribute. Here, the authors use the centrality measures degree (number of contacts), random-walk betweenness (a measure of the proportion of times an individual lies on the path between other individuals), shortest-path betweenness (the proportion of times an individual lies on the shortest path between other individuals), and farness (the sum of the number of steps between an individual and all other individuals). Each was associated with time to infection and risk of infection in the simulated outbreaks. In the networks examined, degree (which is the most readily measured) was at least as good as other network parameters in predicting risk of infection. Identification of more central individuals in populations may be used to inform surveillance and infection control strategies.

Community-Acquired Infections↗
PubMed2005

Incidence and risk factors associated with exertional rhabdomyolysis syndrome in National Hunt racehorses in Great Britain.

A telephone survey of 51 National Hunt racing yards with 1140 horses in training was made in April and May 2003 to establish the incidence of exertional rhabdomyolysis syndrome during the previous year. A case-control study was used to investigate the risk factors for the syndrome in eight yards selected on the basis that cases had been confirmed by the analysis of serum muscle enzymes. The overall incidence of syndrome was 6.1 cases per 100 horses per year, and 55 per cent of the yards reported at least one case. The risk factors identified were sex, the average length of the training gallop, and the type of horse (steeplechaser, bumper/unraced or hurdler). There were no significant associations with the horses' temperament, age or Timeform rating.

Animals↗
PubMed2004

Current and future uses of breath analysis as a diagnostic tool.

The analysis of exhaled breath is a potentially useful method for application in veterinary diagnostics. Breath samples can be easily collected from animals by means of a face mask or collection chamber with minimal disturbance to the animal. After the administration of a 13C-labelled compound the recovery of 13C in breath can be used to investigate gastrointestinal and digestive functions. Exhaled hydrogen can be used to assess orocaecal transit time and malabsorption, and exhaled nitric oxide, carbon monoxide and pentane can be used to assess oxidative stress and inflammation. The analysis of compounds dissolved in the aqueous phase of breath (the exhaled breath condensate) can be used to assess airway inflammation. This review summarises the current status of breath analysis in veterinary medicine, and analyses its potential for assessing animal health and disease.

Animals↗
PubMed2004

Seasonal development of Cyathostominae larvae on pasture in a northern temperate region of the United Kingdom.

A study following the development of Cyathostominae from egg to the infective larval third stage was conducted from April to December 2001 in west central Scotland. Duplicate samples (1 kg) of naturally infected faeces were placed on a 78 cm2 plot each week on a cyathostomin-free pasture. Subsamples of the grass surrounding the faecal plot were collected weekly on four occasions and the number of larvae obtained determined. Few larvae were recovered in the first week of development of individual plots, followed by a rise in the numbers of larvae in second, third and fourth weeks of development of each sample. The climatic conditions were seen to have an effect on the rate of development. Specifically, from multilevel, multivariable linear regression models it was evident that the factors associated with numbers of infective larvae recovered from pasture were the time since the faeces samples were laid down, the average temperature and rainfall during the previous week, as well as the interaction between temperature and rainfall. Conversely, from the model, the number of larvae recovered from pasture was associated with neither the number of eggs within the faeces samples placed on the plots nor with the viability of these eggs.

Animals↗
PubMed2004

Validation of a method for collection and assay of pentane in the exhaled breath of the horse.

Oxidative stress refers to an imbalance between the production of oxidising free radicals and the antioxidant defenses of the cell, and is associated with many pathogenic processes. Oxidative damage to cellular lipids results in the evolution of pentane and ethane gas, and detection of these hydrocarbons in the exhaled breath can be used to monitor in vivo oxidative stress. The aim of this study was to validate a gas chromatography (GC) method for measurement of breath pentane in the horse. The GC-system developed showed good specificity for discrimination of pentane from other breath hydrocarbons, and was sensitive to 0.5 ppb pentane. Pentane was detected in the exhaled breath of five horses investigated on two occasions. The results of this preliminary study demonstrate that breath pentane can be measured in the horse, and further work is now justified to investigate the feasibility of applying this method for monitoring in vivo oxidative stress in the horse.

Animals↗
PubMed2003

Factors related to the risk of neonatal mortality, birth-weight and serum immunoglobulin concentration in lambs in the UK.

Neonatal-lamb mortality represents an economic loss and welfare concern. Two factors often associated with the risk of mortality are birth-weight and serum immunoglobulin concentration. We used data from two studies to investigate risk factors for mortality between 2 and 14 days of age and factors affecting birth-weight and serum immunoglobulin concentration at 48h of age. Dataset 1 included 1339 lambs born on eight farms during the 1995 spring lambing season; dataset 2 included 3172 lambs on seven farms during the 1991 spring lambing season. To account for some of the potential clustering within the data, multilevel models were used. Most (>75%) of the variation in the risk of mortality was at the lamb level. In dataset 1, factors significantly associated with increased odds of lamb mortality included low birth-weight and low serum immunoglobulin concentration. In dataset 2, significant risk factors for mortality included low birth-weight, ewe body-condition score, being born late in the season (relative to other lambs on the farm) and being born in multiple litters. There was a significant interaction between the effects of litter size and birth-weight. (Serum immunoglobulin concentration was not available for dataset 2.) More than half of the variation in birth-weight was at the ewe level, 27% at the lamb level, and 18% at the farm level (dataset 1). Single birth and being male were associated with increased birth-weight in both datasets. In dataset 2 only, increasing ewe condition score and birth early in the study period were also associated with increased birth-weight. Fifty-six percent of the variation in immunoglobulin concentration was at the lamb level, 36% at the ewe level and only 7% at the farm level. Factors associated with reduced serum immunoglobulin concentration included early or late birth in the lambing season, being born later than 14 days after the first lamb born on the farm, multiple-birth litters and maternal mastitis.

Animal Husbandry↗
PubMed2003

Small-world topology of UK racing: the potential for rapid spread of infectious agents.

REASONS FOR PERFORMING STUDY: The topology of the network of contacts between individuals has important effects on infectious disease dynamics within a population. Here we examine for the first time a network of contacts between training yards that occurred through racing. OBJECTIVES: To explore the topology of this network and to consider the effects of the network on the potential for disease transmission. METHODS: Race data from one week was analysed. Contacts were defined as occurring between trainers that raced horses in the same race and hence one trainer could contact another trainer several times. A connection was said to exist between trainers who contacted each other at least once. The network of contacts and connections that occurred during the study period was reconstructed and analysed. RESULTS: All 466 trainers formed a single large network. The network of contacts had a short average path length and high clustering and was, therefore, characteristic of a 'small world network'. The probability distribution of the number of contacts was scale-free, whereas that for the number of connections followed a single-scale. The effect of the network would be to increase R0, such that an agent that would tend toward extinction in a homogenously mixing population may persist in the observed network. CONCLUSIONS: The observed small world network topology has important implication for the transmission and, therefore, the control of infectious agents in this population. POTENTIAL RELEVANCE: Effective disease control and surveillance must take account of the contact structure of the population. Further studies investigating other contact definitions and other populations are now required.

Animals↗
PubMed2003

Validation of the 13C-octanoic acid breath test for measurement of equine gastric emptying rate of solids using radioscintigraphy.

REASONS FOR PERFORMING STUDY: Disordered gastric motility may be a significant factor in the pathogenesis of many equine conditions. Although tests for liquid phase emptying rate have been validated in the horse, there are no effective tests for solid phase emptying measurement that can be performed routinely in the field. OBJECTIVES: The objective of this study was the assessment of a novel stable isotope technique, the 13C-octane acid breath test (13C-OABT), for the measurement of gastric emptying of solid ingesta, by direct comparison with the optimum method of gastric scintigraphy. METHODS: To facilitate dual measurement of gastric emptying, a test meal was used containing baked egg yolk labelled with both 13C-octanoic acid and 99mtechnetium sulphur colloid. Simultaneous, serial lateral gastric scintigraphs and expiratory breath samples were obtained in 12 healthy horses after voluntary ingestion of the test meal. Analysis of breath 13CO2:12CO2 ratio was performed by continuous flow isotope ratio mass spectrometry. Power regression was used to determine the gastric emptying coefficient, the gastric half-emptying time (t 1/2) and duration of the lag phase (tlag). RESULTS: Significant correlations (P < 0.001) were found between the 2 techniques for measurement of both t 1/2 and tlag. In addition, scintigraphic left t 1/2 was correlated significantly to breath test gastric emptying coefficient (P < 0.001). CONCLUSIONS: It was concluded that the 13C-octanoic acid breath test is a reliable diagnostic procedure to measure gastric emptying rate of solids in the horse. POTENTIAL RELEVANCE: Being safe, noninvasive and easy to perform, this test has potential value as both sensitive diagnostic modality and humane research tool for motility studies.

Animals↗
PubMed2002

Incidence and risk factors for exertional rhabdomyolysis in thoroughbred racehorses in the United Kingdom.

Telephone surveys of 34 racing yards with 1276 horses in training were made to establish the overall incidence of exertional rhabdomyolysis in the previous year. A case-control study was used to investigate the risk factors for the syndrome in 12 yards selected on the basis of the routine confirmation of diagnoses by the evaluation of the serum activities of creatine kinase and aspartate aminotransferase. The overall incidence of the syndrome was 6.7 per cent and 80 per cent of the trainers had at least one affected horse. In 74 per cent of the affected horses it frequently recurred, with an average of six lost training days per episode. Risk factors identified for the syndrome included being female, having a nervous, excitable temperament, and being two years old.

Aging↗
PubMed2002

Incidence of exertional rhabdomyolysis in polo horses in the USA and the United Kingdom in the 1999/2000 season.

A questionnaire was used to determine the incidence of exertional rhabdomyolysis and the factors that might have contributed to its occurrence among 423 polo horses in 11 yards. The yards were selected at random, six of them with 111 horses, in north-eastern USA, and five with 312 horses in south-east England. During the 1999/2000 season the incidence of the condition was 7.3 per cent (9 per cent in the USA and 6.7 per cent in England). The incidence in mares was similar in the two countries, 8.4 per cent in the USA and 8.0 per cent in England, but the incidence in geldings in the USA (10 per cent) was much higher than in England (1.5 per cent). A more excitable than average temperament was reported in 71 per cent of the horses with the condition, and most cases occurred after a game (chukka) in which the horse was perceived to be not fit enough for the level of play demanded. Sixty-four per cent of the cases occurred early in the season and on average each episode resulted in the loss of 7.6 training days.

Animal Husbandry↗
PubMed2002

The effects of xylazine, detomidine, acepromazine and butorphanol on equine solid phase gastric emptying rate.

The aim of this study was to measure the effects of specific commonly used sedative protocols on equine solid phase gastric emptying rate, using the 13C-octanoic acid breath test (13C-OABT). The gastric emptying of a standard 13C-labelled test meal was measured once weekly in 8 mature horses over two 4 week treatment periods. Each horse acted as its own control. In treatment Period 1, saline (2 ml i.v.), xylazine (0.5 mg/kg i.v.), detomidine (0.01 mg/kg i.v.) or detomidine/butorphanol combination (0.01/0.02 mg/kg i.v.) was administered in randomised order after ingestion of the test meal. During treatment Period 2, test meal consumption was followed by saline, xylazine (1.0 mg/kg i.v.), or detomidine (0.03 mg/kg i.v.) administration, or preceded by acepromazine (0.05 mg/kg i.m.) in randomised order. The 13C:12C ratio of sequential expiratory breath samples was determined by isotope ratio mass spectrometry, and used to measure the gastric half-emptying time, t 1/2, and duration of the lag phase, t lag, for each of the 64 tests. In treatment Period 1, detomidine/butorphanol prolonged both t 1/2 and t lag with respect to xylazine 0.5 mg/kg and the saline control (P < 0.05). In Period 2, detomidine 0.03 mg/kg delayed each parameter with respect to saline, acepromazine and xylazine 1.0 mg/kg (P < 0.001). Xylazine 1.0 mg/kg also lengthened t lag relative to the saline control (P = 0.0004), but did not cause a significant change in t 1/2. Comparison of treatment periods showed that the inhibitory effect of detomidine on gastric emptying rate was dose related (P<0.05). These findings may have clinical significance for case selection when these agents are used for purposes of sedation and/or analgesia.

Acepromazine↗
PubMed2001

Coughing in thoroughbred racehorses: risk factors and tracheal endoscopic and cytological findings.

A matched case-control study was made of 100 thoroughbred horses which were coughing and 148 control horses which were free of clinical signs of respiratory tract disease. The variables identified by multivariable conditional logistic regression as being significantly associated with coughing included age (the risk decreased with age), the stage of training (horses in early training were at greatest risk), the time since the last race (horses that had never raced were at greatest risk) and the time since they were last transported (horses transported more than 14 days previously were more likely to cough than those transported within the last week). The coughing horses were significantly more likely to have high scores for upper and lower tracheal mucus and pharyngeal lymphoid hyperplasia. In addition, the tracheal aspirates of the coughing horses had increased odds of neutrophilia and were more likely to have intracellular bacteria than the control horses. However, a considerable proportion of the control horses had cytological and/or endoscopic evidence of airway inflammation.

Age Factors↗
PubMed2001

The(13)C-octanoic acid breath test for detection of effects of meal composition on the rate of solid-phase gastric emptying in ponies.

The aim of this study was to apply the(13)C-octanoic acid breath test for detection of alterations in the rate of solid-phase gastric emptying, induced by changes in test meal composition, in ponies. After a 14 hour fast the ponies (n = 4) ingested a test meal with 0, 35 or 70 ml soya oil, and labelled with 250 mg(13)C-octanoic acid. Each pony was given each of the three test meals on three separate occasions, in a randomised order. Exhaled breath samples were collected for 12 hours after ingestion of the test meal. Breath samples were analysed by continuous flow isotope ratio mass spectrometry. Three indices of breath(13)C-enrichment were computed, half-dose recovery time (t 1/2), gastric emptying coefficient (GEC) and time to peak breath(13)C-excretion t(max). The(13)C-octanoic acid breath test was a reliable means of assessing the significantly decreased rate of gastric emptying in the pony, associated with addition of soya oil to the test meal.

Animal Feed↗
PubMed2001

A case-control study of respiratory disease in Thoroughbred racehorses in Sydney, Australia.

In order to investigate the role of infectious agents in the aetiology of lower respiratory tract disease in Thoroughbred racehorses, a matched case-control study was conducted. Cases were identified by the presence of coughing, and were compared to a control population matched on time of sample collection and location within the same training establishment. Tracheal wash samples were collected from 100 cases and 148 controls. Case horses were more likely than controls to have endoscopic and cytological evidence of airway inflammation. There was no significant association between serological evidence of infection by commonly implicated respiratory viruses and coughing. Similarly, mycoplasma were rarely isolated and were not associated with disease. In contrast, there was a strong association between isolation of greater than a total of 10(3) colony-forming units/ml of tracheal wash and coughing. Individual bacterial species associated with disease included Streptococcus zooepidemicus, Streptococcus pneumoniae, Streptococcus suis, Streptococcus sanguis, Pasteurella spp and Bordetella bronchiseptica. This study provides evidence of the role of bacterial infection in the aetiology of lower respiratory tract inflammation in racehorses. However, in 58% of cases, few or no bacteria were isolated. Hence, at the time of identification of disease, there was no evidence of viral, bacterial or mycoplasmal infection in the majority of coughing horses. The aetiology of the signs observed in these horses requires further investigation.

Animals↗
PubMed2000

Attitudes of Australian veterinarians about the cause and treatment of lower-respiratory-tract disease in racehorses.

A questionnaire was administered to members of the Australian Equine Veterinary Association to investigate their attitudes and behaviours regarding the cause, diagnosis and treatment of lower-respiratory-tract disease in racehorses. The most-important perceived risk factors related to the level of exposure and resistance to infectious agents, whereas factors associated with racing and climatic factors were lower ranked. By far the most-commonly implicated primary cause of disease was respiratory viruses. However, specific diagnostic tests (such as viral serology or virus isolation) were rarely performed. By far the most-common diagnostic procedure was auscultation (without a rebreathing bag). The relative importance of diagnostic procedures was influenced by the proportion of total workload comprising horse work. Many respondents believed that bacteria become secondarily involved in disease; accordingly, antibiotic therapy was the most-commonly reported therapy. However, bacteriology of lower-airway-fluid samples was not commonly performed. The most-commonly used antibiotics were the potentiated sulphonamides (either alone or in combination with mucolytics or bronchodilators), followed by procaine penicillin and penicillin combined with gentamicin. Mainly, treatment would appear to be based on empirical beliefs rather than exhaustive investigation of individual cases.

Adrenal Cortex Hormones↗