Biomedical subjects
Publications and source records attributed to K E Whitwell.
An autopsy study of one dead and two sick hares from an East Anglian estate on which two mares had died of grass sickness revealed that two of the hares were suffering from a polyganglionopathy and alimentary tract changes, remarkably similar to those seen in grass sickness in horses. No such abnormalities were found in two healthy hares from the same locality.
Four out of 12 horses grazing a field in Berkshire, England, suffered a prostrating illness and died within 12 to 72 h. Serum biochemical abnormalities, including markedly elevated muscle enzymes, were demonstrated and at post mortem widespread myodegeneration was found in both skeletal muscle and myocardium. Urine analysis revealed myoglobinuria, and renal changes were seen histologically. Although similar pathologically, the clinical syndrome and circumstances of the outbreak were not typical of equine exertional rhabdomyolysis (EER). The outbreak bore a striking resemblance to other reported sporadic outbreaks of an atypical myoglobinuria occurring in grazing horses. A number of potential aetiological and contributory factors (including herbicide toxicity) were considered, but the aetiology remains unresolved.
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Twenty-five horses, suspected on clinical grounds of having grass sickness, were given a barium swallow. Using image intensification the passage of the barium bolus was followed radiographically from the pharynx to the stomach. All 18 horses in which grass sickness was later confirmed at post mortem examination showed defective oesophageal motility. Although the specificity of the abnormality could not be proven, the technique offers a valuable aid to the ante mortem diagnosis of grass sickness.
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A flexible endoscope was used to obtain 223 tracheal washes from 191 horses in three clinical categories. Total cell counts, cytological and bacteriological examinations are reported and the features of the main cell types encountered described. The presence and degree of inflammatory airway disease was determined by a semiquantitative assessment of the neutrophil response and was an important consideration in the interpretation of the bacteriological results. Potential pathogens were isolated from approximately 30 per cent of samples. Cytological changes suggestive of lungworm infestation, virus infection and chronic airway disease are described. Haemosiderophages, indicative of pulmonary haemorrhage, were found in all horses in full training. The techniques used were rapid and simple and were found to improve the accuracy of diagnosis of pulmonary disease. Sequential samples were useful for monitoring the progress of clinical cases.
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A description is given of the pathological changes present in 8 mares which died or were euthanased in the course of an outbreak of paralysis on a Thoroughbred studfarm. In all cases the principal changes were in the central nervous system (CNS) and consisted of a severe and widespread vaculitis in the brain, cord, sheaths of nerves, capsules of ganglia and occasionally elsewhere in the body. Associated with the damage to vessel walls there was haemorrhage and exudation of plasma into the perivascular tissues. Involvement of neurones was minimal and no neuronophagia was present. Six cases had malacic foci in the brain, related to thrombosis of local arteries. Acinar necrosis in the mammary gland was present in one case. Examinations of the CNS and cerebrospinal fluid (CSF) for the presence of equid herpesvirus 1 (EHV1) or other microbial agents proved negative but EHV1 was isolated from the spleen of one mare and from the pharyngeal mucos membrane in another. The pathogenesis of this type of paralysis is discussed.
The paper describes the assessment and practical implications of a laryngeal adductory reflex in a series of 30 ataxic and 64 non-ataxic horses. The reflex was evoked by slapping the saddle region just caudal to the withers. In normal horses this produced a flickering adductory movement of the contralateral arytenoid cartilage which was observed endoscopically. Abolition of the laryngeal response was encountered in in 3 situations:--(1) Disruption of the afferent impulse occurred in those horses in which there was significant spinal cord pathology affecting the pathway from the cranial thoracic region to the medulla. (2) Disruption of the efferent impulse was manifest when damage to the adductory component of the recurrrent laryngeal nerve prevented normal adduction. (3) The reflex was abolished in tense or frightened horses, possibly due to interference from higher centres. The laryngeal adductory reflex was considered to be a useful diagnostic and prognostic aid in the assessment of ataxia and spinal cord lesions in the horse.
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A rodent pathogen, Bacillus piliformis, has been recognised as causing a rapidly fatal hepatitis in 4 foals in England. The disease in foals has been recognised in America since 1973. A clinico-pathological account of the 4 cases is given and the differential diagnosis discussed. The 4 foals' ages fell within a very narrow range (24-34 days). Some of the properties of this unusual intracellular pathogen are reviewed. For the first time in the equine the bacillus was seen in association with myocardial lesions. There are marked differences in the epidemiology of the disease in the mouse and in the foal, which may result from the very different management practices in the 2 species. It is suggested that the dams of affected foals may be carriers of the disease.
A brief description is given of the morphology of the umbilical cord and some variations encountered. In 95% of normal Thoroughbred foals the cord measures less than 84 cm. Factors which govern cord length are not known. Seven pathological conditions involving the umbilical cord are described. Increased length is the most common abnormality and predisposes to three potentially lethal conditions, strangulation of the cord around the fetus, excessive torsion, and allantochorionic necrosis at the cervical pole.
Of 211 consecutive thoroughbred foalings, 145 satisfied a set of criteria for normal parturition and foal viability. The fetal membranes from these and from 10 pony foalings have been systematically examined morphologically and quantitatively and the findings compared to those of other authors. Five sites on the allantochorion were consistently devoid of villi. Expulsion usually occurred with the non-villous side outermost. In 24 per cent of allantochorions the non-pregant horn was of equal length or longer than the pregnant horn. These placentae tended to be shed with the villous side outermost. All membranes contained a hippomane in the allantoic cavity. Remnants of the yolk sac placenta and extra-embryonic coelom were always present. Large vestigeal yolk sacs have previously been confused with anomalous twins. In most cases the endometrial cup sites were site recognisable, usually arranged around the umbilical cord attachment. This attachment was found on the dorsal aspect of the uterine cavity either at the junction of the horns or within the pregnant hor; rarely, it was in the non-pregnant horn. A degree of twistng of the umbilical cord is normal. In 6.2 per cent of cords small urachal dilatations were noted, resulting from flight stenosis of the urachal luman at the site of a twist. Ninety-five per cent of cords measured between 36 and 83 cm.
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