Clinical Research Abstracts of the British Equine Veterinary Association Congress 2015.

REASONS FOR PERFORMING STUDY: Transcranial magnetic stimulation (TMS) is an electrophysiological technique used to elicit motor evoked potentials (MMEPs) to evaluate the functional integrity of the descending motor fibres in the spinal cord. Successful application of the technique was reported in horses with spinal cord compression. However, limited data are available on the correlation of TMS with histopathological changes. OBJECTIVES: To determine sensitivity of TMS for assessing the integrity of the spinal cord in horses with compressive lesions of the spinal cord. STUDY DESIGN: Case series. METHODS: The study was conducted on 6 horses with spinal ataxia grade III-V/V admitted to the Faculty of Veterinary Medicine, Ghent University. The horses underwent TMS, radiography of the cervical or thoracolumbar vertebral column, and myelography (4/6). All horses were subjected to euthanasia and the spinal cord examined histopathologically. RESULTS: In 5/6 horses MMEPs with abnormal onset latencies in both extensor carpi radialis muscles and cranial tibialis muscles were recorded, suggesting a cervical spinal cord lesion. Radiography revealed cervical vertebral malformation (4/5) with cervical vertebral canal stenosis (3/5) and tumour/osteomyelitis (1/5). In 1/6 horse MMEPs with normal onset latencies in extensor carpi radialis muscles and prolonged onset latencies in tibialis cranialis muscles were recorded, suggesting a thoracolumbar spinal cord lesion. Radiography revealed deformation of the 7th and 8th thoracic vertebrae. Myelography showed reduction in dural diameter and dorsal contrast column (4/4). Histopathological examination of the spinal cord confirmed compressive type lesions in all 6 horses with degenerative changes in the white matter of all funiculi, ballooning of myelin sheets, swollen axons, loss of axons and astroglial activation. CONCLUSIONS: In this case series abnormal function of descending motor pathways as registered by TMS showed 100% sensitivity with the histopathological characteristics of compressive lesions in the spinal cord, but the number of horses is limited and further research is warranted. Ethical animal research: Research ethics committee oversight not currently required by this conference: the study was performed on material collected during clinical procedures. Explicit owner informed consent for participation in this study was not stated. SOURCE OF FUNDING: Not applicable. Competing interests: None declared.

Intramuscular inoculation of cattle with Sarcocystis antigen results in focal eosinophilic myositis.

Bovine eosinophilic myositis (BEM) is a subclinical myopathy characterized by multifocal white to grey-green discolorations in skeletal muscles, heart, tongue and oesophagus. These lesions are found at slaughter or during meat cutting and result in considerable economic losses. The etiology and pathogenesis are unclear, although it has been suggested, that Sarcocystis species are involved. To elucidate their role, two calves were repeatedly injected intramuscularly with adjuvanted Sarcocystis antigen. The morphological changes at the injection sites in these calves were histologically and immunohistochemically compared to spontaneous lesions from 44 BEM condemned carcasses sampled in slaughterhouses. Experimental intramuscular injection of Sarcocystis antigen resulted in lesions at the injection sites that were similar to the lesions of natural cases of BEM. They were characterized by massive infiltration of eosinophilic granulocytes, reactive macrophages (MAC387(+) cells), T-cells (CD3(+)) and B-cells (CD20(+)). Both in the experimental and in the natural cases, COX-2 expression was present in endothelial cells adjacent to lesional areas. MHC class II(+) staining was found amongst others in muscle cells surrounding the lesion. These results show that Sarcocystis antigens can induce an inflammatory response in bovine muscle having the characteristics of natural BEM.

Laryngeal rhinosporidiosis in a Belgian warmblood horse.

In Belgium and even in northern Europe Rhinosporidium seeberi has not been reported in autochtonous people or animals. In this paper, the authors report the first observation of laryngeal masses, caused by Rhinosporidium seeberi, in a Belgian Warmblood horse. Moreover, laryngeal rhinosporidiosis is extremely rare since this localisation is only described in four human cases.

The composition of the inflammatory infiltrate in three cases of polyneuritis equi.

Polyneuritis equi (PNE) is a rare neurological disease in the horse. Because of the suspicion in PNE of a T-lymphocyte mediated immune response against the myelin, the objective of this study was to determine the composition of the inflammatory infiltrate in the involved nerves of 3 horses with PNE, studied retrospectively. T-lymphocytes were demonstrated in the lesions, which suggests a T-lymphocyte mediated immune response against myelin. In addition, the presence of B-lymphocytes indicated a local production of antibodies. More research, involving a prospective study, is needed to determine whether the T-lymphocytes are cytotoxic or T-helper lymphocytes.

Horses on pasture may be affected by equine motor neuron disease.

REASONS FOR PERFORMING STUDY: Equine motor neuron disease (EMND) was diagnosed in 3 horses maintained on lush, grass-based pasture. This contrasted with North American studies which identified limited or no access to green herbage as an important risk factor for EMND. HYPOTHESIS: Grazing horses that have an apparently adequate intake of pasture herbage to meet normal equine vitamin E requirements can develop EMND. METHODS: Owners of 32 European horses diagnosed with EMND completed a questionnaire regarding intrinsic, managemental, nutritional and environmental factors that could potentially be risk factors for EMND, and also regarding clinical signs, treatments and case outcome. Plasma/serum vitamin E data for these horses were supplied by the veterinarians. No control population was studied. RESULTS: Thirteen of 32 horses (termed the 'grazing' group) had part- or full-time access to grass-based pasture at the onset of EMND (median duration at pasture 12 h/day, range 3-24 h). Five of these horses were at pasture for at least 235 h/day at the onset of EMND, 2 of which were at pasture for at least 23.5 h/day throughout the year. Despite grazing, all these horses had a low vitamin E status. The remaining 19 horses resembled those cases reported from North America, in that they had no or limited access to pasture. CONCLUSIONS AND POTENTIAL RELEVANCE: A diagnosis of EMND should not be discounted on the basis that a horse has access, even full-time, to lush grass-based pasture. Inadequate vitamin E intake was probably not the sole cause of either the EMND or the low vitamin E status in the grazing horses; the latter was probably the result of abnormal bioavailability or excessive utilisation of vitamin E.

Role of transcranial magnetic stimulation in differentiating motor nervous tract disorders from other causes of recumbency in four horses and one donkey.

Transcranial magnetic stimulation and measurement of the magnetic motor-evoked potentials (MMEPs) in the thoracic and pelvic limbs of four recumbent horses and one recumbent donkey were used to assess the integrity of the descending motor pathways, in order to confirm or exclude a descending motor tract lesion as the cause of the recumbency. In two of the animals abnormal MMEPs were recorded; in one of the horses a lesion along the cervical spinal cord due to a fracture of the fifth cervical vertebra was diagnosed and confirmed by radiography and postmortem examination; in another horse, damage to the peripheral nerves of the left forelimb was diagnosed and confirmed postmortem when a large abscess was found to have been compressing the peripheral nerves at the level of the last cervical vertebra. In the three other animals, normal MMEPs were recorded, and laminitis, rhabdomyolysis and physitis were diagnosed as the causes of the recumbency.

Hereditary skeletal muscle diseases in the horse. A review.

Since riders nowadays are expecting the highest level of performance from their horses, muscular disorders therefore represent a major problem for the equine athlete. A lot of research has been done to identify muscular disorders and their etiopathogenesis. Both acquired and inherited forms of muscle diseases have been described. In this review only the latter forms will be mentioned. Major signs of all muscle disorders are muscular stiffness, cramping or pain, muscular fasciculations, muscular atrophy and exercise intolerance. Muscle biopsies can help to identify the cause of rhabdomyolysis or muscular atrophy. However, especially in hereditary muscular diseases, a lot of questions are still to be answered. Increasing knowledge of the etiopathogenesis and newer diagnostic tests may lead to a more accurate diagnosis of the individual diseases in future.

Transcranial magnetic stimulation: normal values of magnetic motor evoked potentials in 84 normal horses and influence of height, weight, age and sex.

REASONS FOR PERFORMING STUDY: Cervical spinal cord dysfunction is a common problem in equine medicine and the currently available tests give no objective information about the functionality of the nervous tracts. Therefore, transcranial magnetic stimulation (TMS) was performed in 84 healthy horses of different height in order to have an objective measure for the integrity of the descending motor tracts in normal horses. OBJECTIVES: To obtain reference values for onset latency and peak-to-peak amplitude of magnetic motor evoked potentials (MMEPs) and to evaluate the possible effect of height, age and gender on the neurophysiological measures. METHODS: All horses were sedated and stimulated transcranially by using a magnetic coil placed on the forehead. The stimulator triggered the sweep of an electromyogram machine that recorded MMEPs bilaterally from needle electrodes in the extensor carpi radialis and cranial tibial muscles. In that way, it was possible to measure latency between stimulus and onset of response. RESULTS: A significant difference was found between recordings made in the fore- and hindlimbs; MMEPs recorded in the front legs had a shorter onset latency and higher peak-to-peak amplitude. Mean +/- s.d. normal values for onset latency of 19.32 +/- 2.50 and 30.54 +/- 5.28 msecs and peak-to-peak amplitude values of 9.54 +/- 3.73 and 6.62 +/- 3.62 mV were obtained for extensor carpi radialis and cranial tibial muscles, respectively. The left-to-right difference in onset latency and peak-to-peak amplitude was not significant. In the same horse, differences up to 0.82 and 1.53 msecs for the extensor carpi radialis and cranial tibial muscles, respectively, lie within the 95% confidence limit and are considered normal. In contrast to onset latency, peak-to-peak amplitude showed a very large intra- and interindividual variability, even in the same muscle. To reduce the variability and predict normal values of new individual cases, influence of height, weight, age and sex on the MMEPs were determined. No significant effects of sex were observed on onset latency and peak-to-peak amplitude. The age of the horse had only a small but significant effect on peak-to-peak amplitude, with larger responses in older horses. Height at the withers and weight of the horse, parameters that strongly correlate with the size of the horse, had an important significant influence on onset latency but not on peak-to-peak amplitude. The age of the horse and height at the withers were used to predict peak-to-peak amplitude and onset latency, respectively, in normal horses. CONCLUSIONS AND POTENTIAL RELEVANCE: TMS is an excellent addition to the few tools we have for noninvasive imaging of the equine nervous system. Magnetically evoked potentials are highly reproducible and recent advances suggest that the applications of TMS in horses will continue to grow rapidly.

Standardization of transcranial magnetic stimulation in the horse.

The influence of coil position on the peak-to-peak amplitude and onset latency of transcranial magnetic motor evoked potentials (MMEPs) in the extensor carpi radialis and cranial tibial muscles of horses was evaluated. Seven different stimulating coil positions were obtained by constructing a frame on the forehead. Two stimulation intensities (80% and 100% of maximal stimulator output) and two different coil currents (clockwise and counter-clockwise) were tested. For both recording sites MMEPs with the shortest onset latency and the largest peak-to-peak amplitude were detected when the coil was placed in the median of the forehead. There was no significant difference between left and right side recordings. The direction of the current flow in the coil had no influence on the onset latency of the MMEPs.

Transcranial magnetic stimulation: review of the technique, basic principles and applications.

Transcranial magnetic stimulation is rapidly developing as a powerful, non-invasive tool for studying the descending motor tracts in humans. The applications of the test in animals are for the moment restricted to small animals. However, this non-invasive, sensitive and painless technique appears promising as a test of motor tract function in horses where the neurological examination is mainly restricted to clinical evaluation and some ancillary tests, such as radiography, cerebrospinal fluid analysis and electromyography. In this review, we want to discuss the history, basic principles, technique and applications of transcranial magnetic stimulation in humans and small animals and indicate the possibilities for its use in horses. Since the great portion of this review is based on human studies, it is worthwhile to mention that the reports being described are from humans unless otherwise specified.

Influence of detomidine and buprenorphine on motor-evoked potentials in horses.

Horses need to be sedated before they are investigated by transcranial magnetic stimulation because of the mild discomfort induced by the evoked muscle contraction and the noise of stimulation. This paper describes the influence of a combination of detomidine (10 microg/kg bodyweight) and a low dose of buprenorphine (2.4 microg/kg) on the onset latency and peak-to-peak amplitude of magnetic motor-evoked potentials in normal horses. There were no significant differences between measurements of these parameters made before the horses were sedated and measurements made 10 and 30 minutes after the drugs were administered.

Percutaneous puncture technique for treating persistent retropharyngeal lymph node infections in seven horses.

Between 1999 and 2001, seven horses with fever, dysphagia and a history of chronic upper respiratory tract infection lasting between three weeks and three months were examined. They had been treated unsuccessfully with a variety of antibiotics for three to four weeks. A deep abscess in a retropharyngeal lymph node was diagnosed in each case by clinical examination, endoscopy and echographic examination of the retropharyngeal region. The infected retropharyngeal lymph node of each horse was punctured with a spinal needle under ultrasound guidance. Pus was aspirated from four of the horses, and their abscesses were then rinsed with 0.9 per cent saline solution, and antibiotics (sodium ceftiofur or penicillin) were injected. In the other three horses the pus was too viscous to be aspirated, and the enlarged lymph node was opened along the tract of the needle and rinsed with chlorhexidine. All the horses were treated with penicillin for two weeks and in six of them the clinical signs gradually disappeared. The other horse continued to show fever and the penicillin treatment was continued for another 10 days, after which the signs gradually disappeared over a period of two months.

Development of microbial granules for PCB dechlorination.

The effect of acclimating anaerobic granules from commercial bioreactors with different carbon/electron sources on their ability to reductively dechlorinate a tri- (2,3,4-CB) and heptachlorobiphenyl (2,2',3,3',4,5,6-CB) was studied. The anaerobic granules were first grown in upflow anaerobic sludge blanket (UASB) reactors fed with two different mixtures of carbon/electron sources, i.e., propionate/butyrate/methanol and formate/methanol. Differences in dechlorination patterns for 2,2',3,3',4,5,6-CB were observed in batch experiments inoculated with granules from these two sets of UASB reactors. The reductive dechlorination of 2,2',3,3',4,5,6-CB for propionate/butyrate/methanol acclimated granules proceeded via 2,2',3,3',4,5-CB for all 2,2',3,3',4,5-CB for all 2,2',3',4,5-CB + 2,2',3',4-CB for all 2,4-CB + 2,3-CB + 2,4'-CB and 2,2',3,3',5,6-CB for all 2,2',3,5,6-CB for all 2,2',3,5-CB for all 2',3,5-CB. The dechlorination pathway for formate/methanol acclimated granules followed: 2,2',3,3',4,5-CB + 2,2',3,3',5,6-CB for all 2,2',3,3',4-CB + 2,2',3,3',6-CB for all 2,2',3,3'-CB for all 2,2',3-CB for all 2,2'-CB. This research demonstrates a successful strategy for the development of biocatalysts to serve as the inoculum of partially decontaminated sites in order to provide microorganisms with specificities complementary to those of naturally occuring dechlorinators.

Reductive biodegradation of 1,2-dichloroethane by methanogenic granular sludge: perspectives for in situ remediation.

Granular methanogenic sludge was able to dechlorinate 1,2-dichloroethane (1,2-DCA) to ethene in UASB reactors. Ethanol served as the sole carbon and energy source. The average dechlorination rate measured on the basis of ethene production varied between 1.7 and 2.1 micromol 1,2-DCA/(h.gVSS) (46.7 and 57.4 mg/L.d). In order to elucidate the microbial origin of this bioconversion, enrichment cultures of the methanogenic sludge were prepared with different carbon and electron sources: pyruvate, lactate, H2/CO2, ethanol and formate. Dithiothreitol (DTT) was the strong reductant in order to increase the negative redox potential in the media. A homo-acetogenic gram-positive strain could be isolated in the presence of formate. 16S rRNA of the isolated strain showed that the bacterium was closely related (99.7%) to Acetobacterium wieringae. The strain also grew on pyruvate, lactate, H2/CO2 and ethanol, although dechlorination rates of 1,2-DCA were at least 5 times higher when formate was the (only) electron source. Average conversion rates reached 3 micromol/(h.g(dry cells)) and appeared t relate to cometabolic biocatalysis on the corrinoid centers of the homo-acetogenic strain. Some perspectives of anaerobic in situ bioremediation of groundwater polluted with chloroethanes are presented.

The use of magnetic motor evoked potentials in horses with cervical spinal cord disease.

The aim of this study was to investigate the use of magnetic motor evoked potentials as an ancillary diagnostic test in horses with cervical cord lesions. Transcranial magnetic stimulation was performed in 12 ataxic horses and the results of the evoked responses were compared to those found in normal horses. The latency and peak-to-peak amplitude of the potentials in the 12 ataxic horses were significantly different from those measured in normal horses. The configuration of the abnormal potentials was also polyphasic. Normalisation of the evoked potentials occurred in none of the horses, presented after a period of clinical improvement. These findings demonstrate that the technique is also able to detect lesions in horses with subtle clinical signs of incoordination. Magnetic transcranial stimulation is a valuable ancillary test to assess the integrity of the motor tracts. The technique is painless and safe and shows good sensitivity to detect lesions along the descending motor pathways.

The use of non-immune plasma powder in the prophylaxis of neonatal Escherichia coli diarrhoea in calves.

The protective use of plasma powder from cattle and swine against experimentally induced neonatal E. coli diarrhoea in colostrum-deprived calves was examined. Diarrhoea was induced with a strain expressing F5+ fimbriae and a strain expressing F17+ fimbriae. In all groups supplemented with bovine plasma powder, diarrhoea and fever were less severe than in the control groups. For the groups infected with the F5+ E. coli strain, a reduction in excretion of the challenge strain by 2-4 orders of magnitude and by 1-2 orders of magnitude was seen when supplemented with bovine plasma powder at a dose of 25 g/l milk and 10 g/l milk, respectively. The bovine plasma powder showed also beneficial effects in the F17+ infected groups. No mortality, no septicaemia and no severe clinical signs were observed. Concerning the excretion of the E. coli F17+ strain in the faeces, no significant difference with the control group was found. Swine plasma powder showed little beneficial effect on E. coli diarrhoea in calves in this study.

Protection of just weaned pigs against infection with F18+ Escherichia coli by non-immune plasma powder.

The anti-colonization effect of porcine plasma powder against experimentally induced postweaning diarrhoea and oedema disease in just weaned piglets was examined. Piglets were infected with an Escherichia coli strain expressing F18ac fimbriae and producing SLTIIv- and LT-toxins. Reduced fecal excretion of the challenge strain and protection against clinical symptoms was obtained by daily supplementation of the feed with either 90 or 45 g of plasma powder. However, the piglets receiving 90 g of plasma powder a day showed diarrhoea and reduced weight gain compared to the piglets receiving 45 g of plasma powder a day. The diarrhoea was attributed to biogenic amines released from excessive protein in the diet.

Use of right ventricular pressure increase rate to evaluate cardiac contractility in horses.

OBJECTIVE: To establish reference values for right ventricular maximal rate of increase in pressure (dP/dt(max)) in horses and determine the usefulness of this variable to evaluate cardiac contractility. ANIMALS: 15 crossbred horses, 3 to 20 years old. PROCEDURE: Cardiac catheterization was performed, using a high-fidelity catheter tip micromanometer, to determine right ventricular dP/dt(max). The following mathematic corrections were made: for preload, (dP/dt(max))/instantaneous total pressure, (dP/dt(max))/instantaneous developed pressure, and (dP/dt(max))/end diastolic pressure; for afterload, (dP/dtCPIP)/common peak isovolumic pressure. Wedge pressure was measured simultaneously, using a Swan-Ganz catheter. A negative inotropic drug, detomidine hydrochloride, was administered to 6 horses to examine the effect of the negative inotropic drug on right ventricular dP/dt(max) and derived variables. RESULTS: The mean right ventricular dP/dt(max) was 477 (+/- 84.1) mm Hg/s in 15 horses. A 40% decrease in dP/dt(max) was found for 30 minutes after detomidine administration. Variables that correct for preload and afterload were influenced similarly. Detomidine administration also caused a 24% increase in mean wedge pressure, probably indicating reduced left-sided cardiac contractility. CONCLUSIONS AND CLINICAL RELEVANCE: Right ventricular dP/dt(max) may be a useful clinical variable for determining acute changes in cardiac contractility in horses.

Intracardiac overdrive pacing as a treatment of atrial flutter in a horse.

A five-year-old warmblood mare with atrial fibrillation was treated with quinidine sulphate. The atrial rhythm changed to atrial flutter and, because there were toxic effects, the treatment was discontinued. Seven months after the occurrence of the atrial flutter, treatment with a rapid atrial pacing technique restored a normal sinus rhythm. One year after the pacing therapy the horse was still in sinus rhythm and had been brought back into training.