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Biomedical subjects

J R Thomson

Publications and source records attributed to J R Thomson.

16 recordsLinked to original sources
PubMed1988

An investigation of mastitis due to S agalactiae, S uberis and M smegmatis in a dairy herd.

Subclinical mastitis caused by streptococcal infections affected 27 of 83 cows in a commercial dairy herd. Between three and six weeks after intramammary treatment of these cows with cloxacillin, 16 (59 per cent) of the treated cows developed acute clinical mastitis associated with Mycobacterium smegmatis. None of the untreated cows was affected. Infected quarters were moderately hypertrophied and fine clots were present in the milk for three to four weeks. No cows showed systemic signs of illness. Studies carried out over 12 months showed that infected cows shed M smegmatis for three to four months and affected quarters remained hypertrophied in all but one cow after 12 months. The mean milk cell count of affected quarters fell slowly from 4,850,000/ml in the acute stage to 810,000/ml five months later and 620,000/ml 12 months later, suggesting that the organism persisted in the udder. The estimated mean loss in lactation yield for cows with M smegmatis mastitis was 10.8 per cent. Losses were greatest when the hind quarters were involved (mean 28 per cent for cows with both hind quarters affected). Ten of the 16 affected cows were ultimately culled owing to serious reductions in yield.

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PubMed1986

A bovine respiratory virus vaccination trial.

A respiratory virus vaccination trial was carried out in a commercial calf-rearing unit with a history of virus pneumonia. The effects of vaccination on the incidence of virus respiratory disease and growth rate were assessed. Forty-four bought-in calves were allocated to groups and treated as follows: A, unvaccinated controls; B, intranasal temperature-sensitive infectious bovine rhinotracheitis (IBR) vaccine at three and 10 weeks; C, intranasal temperature-sensitive combined IBR and parainfluenza-3 (PI3) vaccine at three and 10 weeks; D, intranasal temperature-sensitive combined IBR and PI3 vaccine at three and 10 weeks plus live attenuated bovine respiratory syncytial (BRS) virus vaccine intramuscularly at seven, 10 and 16 weeks. Two outbreaks of virus pneumonia occurred, one at three to four months of age associated with BRS virus and the other at four to five months of age with PI3 virus. During these outbreaks the incidence of pneumonia was lower and the number of days of elevated temperature and the number of treatments were significantly less in groups vaccinated against the associated virus. Despite these findings there were no significant differences between the growth rates of the groups either during the outbreaks of virus pneumonia or during the 10 month period to slaughter.

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PubMed1986

Neurogenic diabetes insipidus in a sheep.

A 7-month-old Suffolk-cross ram was examined because of polydipsia and polyuria of 2 months" duration. Neurogenic diabetes insipidus was diagnosed on the basis of failure to concentrate urine of low specific gravity in response to water deprivation and a positive response to antidiuretic hormone administration. Post-mortem examination of the brain revealed degeneration in the cerebral peduncles, an absence of pituitary neural tissue and evidence suggesting external pressure as the cause.

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PubMed1984

Effects of environmental control on pulmonary function of horses affected with chronic obstructive pulmonary disease.

The effects of environmental control on horses affected with chronic obstructive pulmonary disease was assessed by clinical examination and pulmonary function tests, ie, maximum change in intrathoracic pressure, tidal volume, minute volume, non-elastic work of breathing, dynamic compliance, inspiratory and expiratory flow rates and arterial blood gas analysis. A controlled environment (ie, bedding horses on shredded paper and feeding a complete cubed diet) caused symptomatic COPD affected horses to become asymptomatic within four to 24 days (mean +/- sd 8.4 +/- 4.8 days). When asymptomatic, their pulmonary function values did not differ significantly from those of normal horses, which indicates that the pathophysiological changes occurring in equine COPD are reversible. The time taken for horses to become asymptomatic correlated significantly with age, duration of illness and severity of disease as adjudged by the non-elastic work of breathing.

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PubMed1983

A study on the possible role of chymotrypsin in the aetiology of equine chronic obstructive pulmonary disease (COPD).

The chymotrypsin activity of seven batches of Micropolyspora faeni and of five batches of Aspergillus fumigatus culture extracts, prepared for inhalation challenge in horses, was assayed and was found to range between 0.29 and 1.45 units/mg protein and 0.02 and 0.20 units/mg protein respectively. Horses affected with chronic obstructive pulmonary disease (COPD) were challenged with two batches of each antigen which had different chymotrypsin activities and no significant correlations were found between the degree of response to challenge and the chymotrypsin activity of the antigens. Inhalation of two doses of nebulised, purified chymotrypsin over 4 days did not induce signs of respiratory disease in COPD-affected horses. However, repeated chymotrypsin inhalations after an interval of 3 weeks caused an exacerbation of signs of COPD in one horse. These studies suggest that, although repeated inhalation of purified chymotrypsin may induce respiratory hypersensitivity in horses, the chymotrypsin-like enzymes of M. faeni and A. fumigatus do not play a major role in the precipitation of clinical signs of equine COPD.

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PubMed1983

Chronic obstructive pulmonary disease in the horse. 1: Nature of the disease.

The aetiology, pathophysiological changes, pathology and clinical signs of the disease as presently understood are discussed. The condition appears to be a hypersensitivity of the respiratory system in some horses to poor quality hay and straw. Micropolyspora faeni is the chief agent identified in the northern part of the United Kingdom. In other locations, the chief agent is probably different. The principal changes are spasm of the airways and bronchiolitis of the small airways. Onset may be acute or insidious. The chief clinical signs are well known but the disease process is reversible if the source of the antigen is removed. In early cases, determination of increased maximum intrathoracic pressure changes and co-existent subnormal arterial oxygen pressure are the best objective confirmation of diagnosis. The same measurements may be made on asymptomatic horses if they have been challenged 4 to 5 h earlier by inhalation of the appropriate antigen, or even exposed to poor quality hay or straw. Other methods available to the clinician are discussed.

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PubMed1983

Chronic obstructive pulmonary disease in the horse. 2: Therapy.

The therapy of equine chronic obstructive pulmonary disease (COPD) essentially entails minimising the horse's exposure to the aetiological antigens which are predominantly thermophilic actinomycetes and moulds occurring in hay and straw. This can be achieved, for example, by keeping affected horses permanently out of doors, or when stabled, using shredded paper, wood shavings or peat moss as bedding and feeding a complete cubed diet. There should be no supplementary hay feeding apart from dust-free vacuum-packed hay. Applying such measures generally allows horses to become asymptomatic in seven to 14 days. Bronchodilators and corticosteroids bring about a marked, but temporary, improvement and can be of value in the treatment of acute attacks. The use of oral bronchodilators in combination with environmental control measures may hasten the remission of clinical signs in affected horse. Inhaled sodium cromoglycate can be used prophylactically in asymptomatic horses to prevent the onset of COPD when unavoidable antigen exposure is anticipated.

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PubMed1982

Chronic obstructive pulmonary disease anatomical cardiac studies.

An abattoir survey on horses diagnosed as suffering from chronic obstructive pulmonary disease (COPD) on clinical grounds showed that the right ventricular wall thickness was not significantly different from that of normal horses. However, the weight ratio between the left and right ventricles was found to be significantly (P less than 0.001) different in COPD affected, compared with control, horses in a study of 17 physiologically and pathologically confirmed COPD cases, using ventricular weight measurements. No clinical evidence of right heart failure nor post mortem evidence of right heart dilatation was observed in any COPD affected animals. It is suggested that the low incidence and degree of cor pulmonale in equine COPD may be related to the reversibility of the pulmonary hypertension associated with this disease.

Abattoirs↗
PubMed1981

Prophylactic effects of sodium cromoglycate on chronic obstructive pulmonary disease in the horse.

When stabled in a controlled environment, horses effected with chronic obstructive pulmonary disease (COPD) became clinically asymptomatic in 4 to 32 days (mean [+/-sd] 9.1 +/- 4.9 days), the time being influenced most by the severity of the disease judged on maximum intrathoracic pressure change (Max delta Ppl) and the age of the animal. Sodium cromoglycate, a drug widely used for prophylaxis of allergic respiratory disease in man, was administered by inhalation to 56 COPD-affected horses. The results showed that a linear response existed between the number of successive days treatment with this drug and the duration of remission of clinical signs of COPD while horses were exposed to natural antigen (poor quality straw bedding). Sodium cromoglycate given as a single daily dose (80 mg) on one day and on 4 successive days prevented clinical signs for mean 3.6 days and mean 24.3 days, respectively. These results indicate that prophylactic treatment with inhaled sodium cromoglycate is an effective method of controlling the clinical signs of COPD.

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