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Biomedical subjects

D P Leadon

Publications and source records attributed to D P Leadon.

At least 19 recordsLinked to original sources
PubMed2006

Comparison of concentrations of Rhodococcus equi and virulent R. equi in air of stables and paddocks on horse breeding farms in a temperate climate.

REASONS FOR PERFORMING STUDY: Rhodococcoccus equi is a significant cause of bronchopneumonia in foals worldwide. Infection of the lungs is believed to result from inhalation of virulent R. equi in dust from contaminated environments. A measure of infectious risk in an environment is the level of airborne contamination. OBJECTIVES: To assess and compare the level of airborne virulent R. equi in paddocks and stables. METHODS: Air samples were collected sequentially over the 2003 foaling season from the paddocks and stables on 3 Irish horse breeding farms affected by R. equi pneumonia. Colony blotting and DNA hybridisation techniques allowed quantitation of virulent R. equi. RESULTS: The odds of detecting airborne virulent R. equi in stables were 173 times greater than in paddocks. The median airborne concentration of virulent R. equi was significantly higher (P < 0.001) in stables than in paddocks on all farms. These observations suggested that stables were high-risk areas for infection. CONCLUSIONS AND POTENTIAL RELEVANCE: Our results indicate that contaminated stables are a significant risk factor in the epidemiology of R. equi pneumonia on horse-breeding farms in a temperate climate, such as in Ireland. Management strategies that improve the air hygiene of stables, through better ventilation, use of less fragile bedding material and the use of fogging agents to reduce the airborne concentration of virulent R. equi, may reduce the incidence and severity of R. equi pneumonia on farms.

Actinomycetales Infections↗
PubMed1991

Relationship between kennel size and stress in greyhounds transported short distances by air.

Greyhounds are usually transported by air between Ireland and England in wooden kennels similar in size to greyhound racing starting traps. These kennels have been criticised in the belief that their small size leads to unnecessary stress. The present study compared plasma ACTH, cortisol, lactate and non-esterified fatty acid concentrations in 12 greyhounds transported either in the existing wooden kennels or in wider perspex kennels, which were stowed either in the belly hold or in the main cargo hold of jet freighter aircraft. Increased kennel size did not appear to result in decreased stress responses but there was a significantly greater stress response in the dogs kept in the belly hold of the aircraft. Individual variation between dogs was the most significant feature of the study.

Aircraft↗
PubMed1991

Maternal and umbilical venous plasma lipid concentrations at delivery in the mare.

The concentrations and fatty acid composition of the plasma free fatty acid, triacylglycerol and phospholipid fractions were determined in maternal and umbilical cord vein blood samples taken at delivery from 17 mares. Maternal and umbilical vein plasma free fatty acid concentrations were of a similar order and a positive correlation was found between the two levels suggesting that the equine placenta is permeable to fatty acid. Substantial amounts of the essential fatty acids and their longer chain derivatives were seen in both umbilical vein plasma free fatty acid and phospholipid fractions supporting this view. Certain long chain polyunsaturated derivatives of the essential fatty acids found in the umbilical venous plasma phospholipid fraction were not seen in the maternal circulating lipids. The precursor fatty acids were readily available to both foetal and placental tissues and therefore must have been elongated and incorporated into phospholipid by either or both. Very small amounts of the essential fatty acids were found in adipose stores in the newborn foal and virtually no fat stores at all in the newborn foal liver.

Adipose Tissue↗
PubMed1987

Comparison of systemic and local respiratory tract cellular immunity in the neonatal foal.

Blood neutrophils from 10 Thoroughbred and 2 Pony foals were evaluated using in-vitro cellular function tests of chemotaxis, chemiluminescence, phagocytosis and intracellular killing. A comparison of the functional capacities of these cells before and 2-4 days after the ingestion of colostrum indicated an improvement in blood neutrophil chemotaxis and chemiluminescence. Bronchopulmonary lavage was carried out on 9 Thoroughbred and 2 Pony 36-h-old foals. The technique used did not require sedation or anaesthesia. Pulmonary alveolar macrophages were the predominant cell type recovered. When comparisons were made between blood neutrophils and pulmonary alveolar macrophages in the same animal fewer pulmonary alveolar macrophages were phagocytic and there was little if any evidence of intracellular killing by pulmonary alveolar macrophages.

Animals↗
PubMed1987

Fatty acid composition of the plasma lipids of the maternal and newborn horse.

The fatty acid composition of the plasma free fatty acid, triacylglycerol and phospholipid fractions was measured in blood and milk samples taken daily from 3 mares and their foals on Days 1-9 post partum inclusive, and from a total of 12 mares and foals on Days 22, 30 and 51. A rise in the plasma concentrations of triacylglycerol and phospholipid similar to that well documented in other species occurred in the neonatal period. Alterations in the composition of the foal plasma phospholipid after birth lend support to the view that the placenta rather than the fetus could be responsible for the elongation and desaturation of the essential fatty acids to provide long-chain polyunsaturated fatty acids for the fetus.

Animals↗
PubMed1986

Behavior and viability of the premature neonatal foal after induced parturition.

Parturition was induced in 2 groups of mares, less than 300 (n = 49) and 300 to 320 days gestation (n = 31), by the administration of prostaglandin F2 alpha or fluprostenol and oxytocin. Foals were categorized into 4 groups according to their ability to adapt in, and survive, the neonatal period. Group A had no demonstrable coordinating reflexes, were weak from birth, and all died within 90 minutes. Group B had some righting reflexes, but had poor coordination and a weak suck reflex. They showed some improvement for about 2 hours, but all died within 9 hours. Group C foals had a good suck reflex and made attempts to stand. After 24 hours, there was a steady deterioration and death occurred within 48 hours. Group D were initially weak, but showed rapid clinical improvement with good adaptation to the environment and survived for at least 7 days. The overall survival rate for the 80 foals born was only 5%. Most group A foals had gestational ages of less than 300 days, but a few (n = 9) were delivered after 300 days and 2 up to 319 days. The youngest survivor was delivered at 318 days and the 3 other survivors were delivered at 320 days. Aspects of the hazards of prematurely induced parturition were considered to be immaturity and stress of parturition.

Animals↗
PubMed1985

A collaborative project in veterinary practice: developing a model of equine prematurity.

The development and design of a project in collaborative research which originated from a problem identified in practice, namely prematurity in the newly born foal, is described here. The project established a model of equine prematurity for the purpose of studying the diagnosis, pathogenesis and treatment of the condition. It involved practitioners and full time research workers in a number of veterinary and medical institutes.

Animals↗
PubMed1984

Mammary secretions in normal spontaneous and induced premature parturition in the mare.

Total calcium, total protein, albumin and globulin content were determined in 49 samples of mammary secretions from 37 crossbred and Thoroughbred mares. The mares were divided into three categories: Group 1--post partum samples from spontaneous full term Thoroughbred deliveries (n = 20); Group 2--pre- and post partum samples from spontaneous full term Thoroughbred deliveries (n = 6); Group 3--pre- and post partum samples from induced premature deliveries in crossbred mares (n = 11). Calcium concentrations of the mammary secretions proved useful in predicting full term and also in assessment of the chances of foal survival in prematurely induced parturition. Mean (+/- se) calcium levels in full term mares that foaled spontaneously (Group 1) were 10.6 +/- 2.7 mmol/litre on the day of parturition. However lower values than this did not necessarily mean parturition would not take place. In Group 2 mares, calcium levels were 4.1 +/- 0.8 mmol/litre just before foaling and rose to 9.2 +/- 1.5 mmol/litre within 20 mins of parturition; an increase of 124 per cent. Group 3 mares, induced prematurely, showed poor foal survival if pre-partum calcium levels were less than 3 mmol/litre. Total protein, albumin and globulin concentrations showed a similar trend but the increase just before or during parturition was much less marked.

Albumins↗
PubMed1984

Studies on equine prematurity 1: Methodology.

This paper describes the general management of mares and foals during the perinatal period and the methodology used in a collaborative research project on equine prematurity. Sixteen mares with dated pregnancies delivered 45 foals over three breeding seasons (1981 to 1983). In the majority, parturition was induced with oxytocin and/or fluprostenol; the remainder were allowed to foal spontaneously. Pre-colostral milk analysis provided a means of assessing the pre-foaling status of the mare. All were observed and monitored before, during and after parturition and the sampling protocol for both mare and newborn foal is discussed in detail. The foals were assessed for their degree of maturity at birth using behavioural, haematological, acid-base status and other criteria; they were then assigned to groups for further study and tests.

Animals↗