Short‐term outcome of equine emergency admissions at a university referral hospital

Reasons for performing study: Obtaining data on emergency admission survival rates is important to provide clients with an estimate of prognosis and to identify areas in which improvements in case management can be achieved. Objective: To determine the short‐term outcome of equine emergency admissions to a university referral hospital during a 12 month period. Methods: Short‐term outcome was defined as survival to discharge or died/euthanasia during hospitalisation. The overall death (euthanasia) rate was calculated; and rate for horses with different categories of: age; admission month, day and time; presenting complaint (PC); duration of clinical signs prior to presentation; clinical pathology abnormalities; and therapy/therapeutic‐related procedures performed was recorded. Results: There were 918 admissions. The overall death rate was 24%. Foals (34%) and geriatric (40%) subjects had a death rate that was higher than that for mature horses (21%, referent). The death rate was highest in March (37%). Horses with a PC categorised as neurological (46%) or neonatal (41%) had the highest and as ophthalmological (5%) or trauma/skin (13%) the lowest death rates. There was no difference in death rate between different admission days or times or the duration of clinical signs prior to presentation. The death rates for horses with abnormal peritoneal fluid (71%), coagulopathy (63%), acid‐base abnormalities (52%), hypoproteinaemia (47%), dehydration (43%), hypoxia/hypercapnia (48%), leucopenia (44%), electrolyte abnormalities (39%), hyperlactataemia (39%) or azotaemia (35%) were high. The death rate for horses treated with intranasal oxygen (57%), plasma (34%) or polymixin B (35%) was high and for horses undergoing laceration repair/joint (0%) or synovial cavity lavage (4%) was low. Conclusions: Age and critical illness were important contributing factors to a higher death rate. Potential relevance: Improving the understanding of disease processes in and developing treatment strategies for neonatal and geriatric patients as well as critically ill patients is required.     

Short‐ and long‐term results following standing fracture repair in 34 horses

Reasons for performing study: Standing fracture repair in the horse is a recently described surgical procedure and currently there are few follow‐up data. This case series contains 2 novel aspects in the standing horse: repair of incomplete sagittal fractures of the proximal phalanx and medial condylar repair from a lateral aspect. Objectives: To describe outcome in a case series of horses that had lower limb fractures repaired under standing sedation at Rossdales Equine Hospital. Method: Case records for all horses that had a fracture surgically repaired, by one surgeon at Rossdales Equine Hospital, under standing sedation and local anaesthesia up until June 2011, were retrieved. Hospital records, owner/trainer telephone questionnaire and the Racing Post website were used to evaluate follow‐up. Results: Thirty‐four horses satisfied the inclusion criteria. Fracture sites included the proximal phalanx (incomplete sagittal fracture, n = 14); the third metacarpal bone (lateral condyle, n = 12, and medial condyle, n = 7); and the third metatarsal bone (lateral condyle, n = 1). One horse required euthanasia due to caecal rupture 10 days post operatively. Twenty horses (66.7% of those with available follow‐up) have returned to racing. Where available, mean time from operation to return to racing was 226 days (range 143–433 days). Conclusions: Standing fracture repair produced similar results to fracture repair under general anaesthesia in terms of both the number of horses that returned to racing and the time between surgery and race. Potential relevance: Repair of lower limb fracture in the horse under standing sedation is a procedure that has the potential for tangible benefits, including avoidance of the inherent risks of general anaesthesia. The preliminary findings in this series of horses are encouraging and informative when discussing options available prior to fracture repair.     

Haematogenous septic arthritis in foals: Short‐ and long‐term outcome and analysis of factors affecting prognosis

Synovial sepsis represents a major cause of morbidity and mortality in foals; however, there are no studies focusing on foals particularly at risk during the first 2 months of life. Our objective was to analyse outcome in foals aged <2 months with haematogenous septic arthritis and to identify prognostic factors and compare the effects of two different lavage procedures on outcome. Sixty foals with synovial sepsis were used for our retrospective study in which medical records, online data and telephone interviews were utilised to analyse prognostic factors, and determine short‐ and long‐term survival and athletic performance of foals treated at Evidensia Equine Specialist Hospital, Helsingborg, between 2008 and 2014. Overall survival to discharge was 80% (48/60). Time to long‐term follow‐up ranged from 6 months to 6.5 years. Forty/60 (67%) horses survived long‐term. Four/8 (50%) of the nonsurvivors at long‐term follow‐up had been subjected to euthanasia due to sequelae of joint sepsis. Of the long‐term survivors, 37/40 (92.5%) achieved athletic soundness. Overall long‐term outcome for athletic soundness was 37/60 (62%). Prognostic factors based on historical, clinical or laboratory data, or the use of through‐and‐through needle lavage compared to endoscopic lavage as the first procedure, could not be identified. The present study demonstrates a more favourable prognosis than previously reported, with 80% of foals with synovial sepsis surviving to discharge, and approximately 60% achieving athletic soundness. However, the study was limited by a small population size, which may account for the failure to verify statistically significant prognostic factors.     

Liposome-mediated uptake of exogenous DNA by equine spermatozoa and applications in sperm-mediated gene transfer

REASON FOR PERFORMING STUDY: Sperm-mediated gene transfer has been reported as a method for production of transgenic animals in a variety of species, and this technique represents a possible method for production of transgenic equids. OBJECTIVES: To evaluate the uptake of exogenous DNA (enhanced green fluorescent protein; pEGFP) by equine spermatozoa and to assess the ability of transfected spermatozoa to introduce this transgene into early equine embryos. METHODS: To evaluate incorporation of pEGFP into equine spermatozoa, washed spermatozoa were incubated with 32P-pEGFP, with or without lipofection. Spermatozoa were also transfected with fluorescently-labelled DNA (Alexa647-pEGFP) and changes in sperm viability and DNA uptake were assessed. Mares were inseminated with pEGFP-transfected spermatozoa and embryos recovered. Expression of pEGFP was assessed by epifluorescence microscopy of embryos, and the presence of pEGFP DNA and mRNA was assessed by PCR and RT-PCR, respectively. RESULTS: Liposome-mediated transfection increased the incorporation of 32P-pEGFP into spermatozoa compared to controls. Flow cytometric evaluation of spermatozoa after transfection with Alexa647-pEGFP revealed a linear increase in the proportion of live, Alexa647+ spermatozoa with increasing DNA concentrations. After insemination with transfected spermatozoa, 8 embryos were recovered. There was no evidence of EGFP expression in the recovered embryos; however, PCR analysis revealed evidence of the pEGFP transgene in 2 of 5 embryos analysed. CONCLUSIONS: The incorporation of exogenous DNA by equine spermatozoa was enhanced by liposome-mediated transfection and this did not adversely affect sperm viability, acrosomal integrity or fertility. Although the EGFP transgene was detected in a proportion of Day 7-10 embryos, there was no evidence of expression of EGFP in these embryos. POTENTIAL RELEVANCE: Sperm-mediated gene transfer offers a potential technique for the generation of transgenic equids.     

Comparison of two different centrifugation extenders for preservation of frozen equine semen

This study compares a commercial semen extender (control group) to ultra high temperature (UHT) skimmed milk (treatment group) used during centrifugation for subsequent cryopreservation of equine semen. Following post‐thawing of semen samples parameters measured included motility, sperm motion kinetics (using computerised assisted semen analysis) as well as acrosome and plasmatic membrane integrity (using fluorescent dyes). After collection and analysis, the sperm‐rich fraction was divided and diluted with either: control (1:1 dilution in a skimmed milk‐glucose extender) or treatment (1:1 dilution in UHT skimmed milk). The milk used in this experiment was of the same source, commercial brand, of only one lot. After dilution, samples were subjected to centrifugation at 600 g for 10 min and sperm pellets were resuspended in a freezing extender to a concentration of 200 × 10⁶ cells/ml. Aliquots were packed into 0.5 ml straws placed in a stainless steel support and kept inside the refrigerator (5°C) for 20 min. Subsequently, these straws were placed at a height of 6 cm over liquid nitrogen for 20 min in an isotherm box. No significant differences were observed in total sperm motility (42.71 vs. 38.29%), progressive sperm motility (12.29 vs. 7.86%), plasma membrane integrity (53.43 vs. 60.14%) or acrosomal membrane integrity (93.29 vs. 93.71%) with a P>0.05 calculated between the control and the treatment groups, respectively. Considering that UHT skimmed milk has a lower cost than the commercial semen extender, this could be an option used during the centrifugation protocol to decrease the expense of the equine semen cryopreservation process and increase shelf life.     

Short‐term anaesthesia with xylazine,diazepam/ketamine for castration in horses under field conditions: Use of intravenous lidocaine

Reasons for performing study: Lidocaine single boluses and/or constant rate infusions are commonly administered intraoperatively during inhalant anaesthesia to lower inhalant concentrations, promote or maintain gastrointestinal motility, and potentially supplement analgesia. The benefits of using lidocaine with injectable anaesthesia for field surgeries has not been fully explored to determine advantages and disadvantages of lidocaine as an anaesthetic and analgesic adjunct in these conditions and impact on recovery quality. Objectives: To evaluate the use of systemic lidocaine with a standard field injectable anaesthetic protocol related to the need for additional drug administration as well as overall recovery score and quality. Hypothesis: The administration of systemic lidocaine with xylazine‐diazepam/ketamine anaesthesia for castration in the field decreases the need for additional injectable doses required for maintenance, but prolong and potentially impact the overall recovery score and quality in horses. Methods: Thirty client‐owned horses underwent standard injectable anaesthesia for field castration. Fifteen horses received lidocaine 3 mg/kg bwt, i.v. as a single bolus, and 15 received saline equal volume. The horses were monitored for the need for additional injectable anaesthetics and scored for overall recovery and quality by a blinded anaesthetist. Results: There were no statistically significant differences in the overall recovery score and quality, or need for additional injectable anaesthetic between horses receiving lidocaine and those receiving saline. There was a significantly longer time for the horses to stand after induction in the lidocaine group (mean 30.7 min) vs. saline group (mean 22.5 min) (P<0.04). Conclusions: Lidocaine, 3 mg/kg bwt i.v., does not adversely affect recovery using injectable field regimes, but the overall recovery period was longer. Lidocaine does not appear to reduce the need for additional injectable administration during surgery. Potential relevance: Further research is warranted to define the benefit of systemic lidocaine with field anaesthesia in horses by exploring the ideal dose and plasma level of lidocaine with injectable anaesthesia.     

Time‐related changes in post‐operative equine morbidity: A single‐centre study

Our objective was to test the hypothesis that the prevalence and type of post‐operative equine morbidity at a single centre does not change over time with a retrospective and prospective observational study. The post‐operative case records of 92 (of 96) horses undergoing nonabdominal procedures, and surviving to discharge, were compared with previous data from the same centre. Predefined morbidities were recorded from horses undergoing surgery between August 2013 and July 2014. This was compared with data collected from the same institute from April 2004 to June 2005 and published in a previous study. The overall prevalence of morbidities increased from 13.4% to 25%. The prevalence of post‐anaesthetic colic, thrombophlebitis, pyrexia, lameness, neuropathy and myopathy increased while the proportion of incidence of diarrhoea, respiratory distress and wounds sustained in recovery decreased. There was a statistically significant association (P = 0.045) between the duration of surgery and the prevalence of post‐anaesthetic colic. Geldings were less likely (odds ratio 0.12, 95% confidence interval 0.02–0.84) to develop swelling at the catheter site and the likelihood of thrombophlebitis increased by 1.20 (95% confidence interval 1.01–1.41) for every year of life. Tracking morbidities and changes in their prevalence may elucidate their possible causation and allow prophylactic measures to be taken.     

Comparison of density gradient and single layer centrifugation of stallion spermatozoa: Yield,motility and survival

Reasons for performing study: A new, simpler, technique of colloidal centrifugation has recently been developed, designated single layer centrifugation (SLC). This technique requires evaluation by comparison with a density gradient for its ability to select the best quality spermatozoa and its practicality of use on studfarms. Objective: To compare the effect of 2 methods of colloidal centrifugation, density gradient centrifugation and single layer centrifugation, on stallion sperm motility, yield and survival, using freshly collected extended stallion semen. Methods: Aliquots of extended stallion semen from 10 stallions (38 ejaculates) were processed by the 2 methods of colloidal centrifugation. For both uncentrifuged and centrifuged samples, sperm yield was calculated and subjective sperm motility assessed over several days to provide an estimate of sperm survival. Some stored semen samples, held at 4°C overnight, were also available for testing. Results: For fresh, extended semen, a similar recovery yield of motile spermatozoa was seen for the 2 methods of preparation for single layers and density gradients, respectively. Sperm motility and survival rate were significantly improved by colloidal centrifugation compared to unprocessed ejaculate, without any significant difference between methods (SLC vs. gradient). However, the yield was reduced by 18–20% when cold‐stored semen was used for centrifugation compared to fresh semen; and more variation between ejaculates was observed than for fresh ejaculates. Again, sperm motility and sperm survival were improved in the centrifuged sperm preparations compared to stored, unprocessed ejaculates. Potential relevance: The 2 colloid centrifugation techniques produce equivalent sperm preparations in terms of sperm quality. However, the SLC method would be more practical and convenient for use in the field.     

Short‐term incubation of equine laminar veins with cortisol and insulin alters contractility in vitro: possible implications for the pathogenesis of equine laminitis

This study investigated the effects of cortisol and insulin, hormones that affect both glycaemic status and vascular function, on the in vitro contractility of isolated healthy equine small laminar veins. Small veins (150–500 μm) draining the digital laminae from healthy horses or ponies were investigated by wire myography. Concentration response curves were constructed for noradrenaline (NA), phenylephrine (PE), endothelin‐1 (ET‐1) and 5‐hydroxytryptamine (5‐HT) in the presence of either cortisol (10^?6 m ) or insulin (1000 μIU/mL). Cortisol significantly increased the maximum contractility of laminar veins to the vasoconstrictors NA and 5‐HT but decreased the maximal contraction to ET‐1. Insulin decreased the contractility of vessels to PE and ET‐1. It is possible that short‐term cortisol excess could enhance venoconstrictor responses to 5‐HT and NA in laminar veins in vivo, thereby predisposing to laminitis. Additionally, a reduction in the ability of insulin to counteract alpha‐adrenoreceptor and ET‐1‐mediated contraction, likely to occur in subjects with insulin resistance, may further exacerbate venoconstriction in animals prone to laminitis. These mechanisms may also predispose horses with disorders such as equine Cushing's disease and equine metabolic syndrome to laminitis.     

Undetectable vitamin D3 in equine skin irradiated with ultraviolet light

Vitamin D requirements for most animals are expected to be fulfilled through daily exposure of the skin to solar ultraviolet B radiation. The synthesis of vitamin D₃ in skin depends on different factors including melanin pigmentation, the amount of UVB radiation reaching the skin, type of clothing/hair coat, latitude and altitude, season, and time of day. Alternatively vitamin D₂ may be obtained from UVB irradiated pasture species. Recent studies have shown that in unsupplemented grazing horses 25-hydroxyvitamin D₂ is the predominant form of vitamin D in plasma, and that 25OHD₃ is undetectable suggesting horses may rely on diet to obtain vitamin D. In order to mimic the natural environment of skin to sunlight exposure, five equine and two ovine devitalized skin samples were irradiated with 5 J/cm² of UVB light followed by measurement of 7-dehydrocholesterol (7-DHC) and vitamin D₃ concentrations using reverse-phase high pressure liquid chromatography (HPLC). HPLC revealed the presence of 7-DHC in the skin of both horses and sheep. Vitamin D₃ was undetectable in both ovine and equine skin prior to irradiation, but after irradiation with UVB light, ovine skin showed an increase in vitamin D₃ concentration (mean 0.16 ± 0.07 µg/g), whereas vitamin D₃ was undetectable in equine skin. These results provide additional evidence that horses make negligible quantities of vitamin D₃ in their skin after exposure to UVB light and may therefore rely on their diet as a primary source of vitamin D.     

Antimicrobial‐associated diarrhoea in three equine referral practices

Reasons for performing study: Although antimicrobial‐associated diarrhoea (AAD) is the most frequently observed adverse effect of antimicrobial therapy in horses, few multicentred studies on the prevalence of AAD have been performed. Objectives: To determine the prevalence of AAD in horses that developed diarrhoea after antimicrobial treatment for nondiarrhoeic conditions and identify the antimicrobials used. Methods: The 2009 database of 3 referral hospitals was searched to identify nonhospitalised horses (weanling age or older) treated with antimicrobials for nongastrointestinal conditions. Horses with these criteria that presented with diarrhoea during 2009 were included in the study. Additional information, including antimicrobial administered and results of faecal pathogen testing, was gathered on each hospitalised case. Results: Of the 5251 horses treated with antimicrobials for nongastrointestinal signs, 32 were diagnosed with probable AAD, a prevalence of 0.6% (95% confidence interval: 0.43–0.86%). The AAD‐diagnosed horses had an 18.8% (6/32) mortality rate. Horses with AAD had been treated for an average of 4.2 days. The most frequently used antimicrobials in horses with AAD were gentamicin in combination with penicillin (n = 7), enrofloxacin (n = 7) and doxycycline (n = 4). Clostridium difficile was identified in faecal samples from 4 horses, 2 of which died and Salmonella from 3 horses. Conclusions: Results indicated that the prevalence of AAD is low. Any antimicrobial class commonly used in equine practice is a potential cause of equine AAD. Other risk factors, such as opportunistic enteropathogens, may play a part in the development of diarrhoea secondary to antimicrobial usage. Potential relevance: Although the risk of equine AAD is low, this sequela of antimicrobial treatment is possible especially when opportunistic enteropathogens or other risk factors are present. Because drugs from any antimicrobial class can be potentially involved in AAD, clinicians have additional incentive to ensure the judicious use of antimicrobial agents.     

Management and environmental factors involved in equine influenza outbreaks in Ireland 2007-2010

Reasons for performing study: Outbreaks of equine influenza (EI) in endemic populations continue to cause economic loss despite widespread vaccination. Hypothesis: To identify the key management and environmental factors that determine the risk of horses contracting EI in an endemic country and to identify control strategies. Methods: Real time‐polymerase chain reaction (RT‐PCR), virus isolation and haemagglutination inhibition were carried out on nasopharyngeal swabs and clotted blood samples collected from horses and ponies showing signs of respiratory disease. On premises where a diagnosis of EI was confirmed, the attending veterinary surgeon was asked to participate in an epidemiological investigation. Results: Between June 2007 and January 2010, EI outbreaks were diagnosed on 28 premises located in 13 of the 32 counties of Ireland. Veterinary advice was sought on average more than 5 days after the first clinical signs were observed. The majority of diagnoses were made by RT‐PCR. Data from 404 horses on 16 premises were used in the epidemiological analysis. In 15 premises, EI was identified following movement of horses. Housing type, teaser stallions or fomites/personnel contributed to virus spread. Vaccination status, number of years vaccination, time since last vaccination and age influenced disease expression. Isolation and vaccination were effective control measures on the premises where they were implemented. Conclusions: Preventative measures include: isolation, clinical monitoring, serological testing and vaccination of new arrivals, booster vaccination of horses at 6 monthly intervals, maintenance of effective boundaries between equine premises and avoidance of stabling in single air spaces. Control measures include: prompt isolation of suspected cases, rapid diagnosis by RT‐PCR, booster vaccination of cohorts and implementation of biosecurity measures to avoid transmission by fomites and personnel. Potential relevance: Implementation of these preventative and control measures should reduce the economic losses associated with outbreaks of EI.     

Storage‐associated artefact in equine muscle biopsy samples

Reasons for performing study: Muscle biopsy is increasingly used in equine veterinary practice for investigating exertional, inflammatory or immune mediated myopathies and unexplained muscle atrophy. Although formalin‐fixed samples are often used, for complete evaluation, fresh‐frozen tissue is required. Freezing muscle in veterinary practice is impractical: samples sent to specialist laboratories for processing are therefore susceptible to delays, potentially leading to artefact and compromising histological interpretation. Hypothesis: Altered temperature, duration and hydration status influence the severity of storage‐induced artefact in equine muscle. Methods: Skeletal muscle obtained immediately post euthanasia was divided into 6 independent samples from each of 8 horses. One sample per horse was frozen immediately in isopentane precooled in liquid nitrogen. Additional samples were stored in conditions designed to mimic possible situations encountered in practice, including increased storage times, temperature and hydration status. Following storage, stored samples were frozen as before. Cryosections were stained using haematoxylin and eosin and ranked for artefact on 2 occasions by 2 blinded observers. The best samples were processed subsequently with a panel of routine stains and immunolabelled for collagen V to enable the measurement of minimum fibre diameters. Results: Both prolonged storage and increased hydration resulted in more storage‐associated artefact. Samples stored for 24 h chilled on dry gauze were ranked higher than those stored on damp gauze; however, a panel of routinely‐used histochemical staining techniques was unaffected by chilled 24 h storage. There was no significant effect of storage on mean fibre diameter; however, both chilled dry and damp storage for 24 h caused a significant increase in fibre‐size variability. Conclusion and potential relevance: Caution should be exercised when interpreting fibre size profiles in shipped samples. Equine muscle biopsy samples are optimally shipped in dry gauze, sealed in plastic containers and shipped on ice packs to be processed within 24 h and can thus be interpreted by the receiving laboratory with minimal artefact.     

Diagnostic and prognostic use of L‐lactate measurement in equine practice

Lactate concentrations can now be measured rapidly and inexpensively in equine hospitals or in the field with a degree of accuracy that is acceptable when compared to laboratory analysers. Arterial or venous blood samples can be used. Short‐term storage of samples for up to 4 h at room temperature does not appear to affect the result. Taking a sample in the field and returning to the practice to analyse it is therefore feasible. Lactate measurement is useful in horses with colic to aid in the diagnosis of an ischaemic lesion and to determine the probability of a successful outcome if surgery is undertaken. Lactate concentrations are also useful as an indicator of hypoxia and/or circulatory disturbances associated with intra‐, or post partum abnormalities including dystocia, prematurity, dysmaturity, neonatal encephalopathy, sepsis, systemic inflammatory response syndrome or enteritis. Measuring lactate concentrations may assist in determining the severity of these conditions and the need for intensive care. Initial lactate concentration and increases or decreases in blood lactate concentration following a period of treatment can provide useful prognostic information. Lactate may also be measured during training to monitor fitness and performance.