EQUINE VETERINARY EDUCATION / AE / MARCH 2015


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Highlights of recent clinically relevant papers


Faecal microbiota and colic Recent studies have explored the complex nature of the equine faecal microbiota; this study by Scott Weese and colleagues in Canada and the USA aimed to determine if there were consistent changes in the microbiota preceding an episode of colic. A population of pregnant mares was used; faecal samples


were collected from 221 mares, of which 24 developed post partum colic. Thirteen samples were suitable for microbiota analysis, 13 time-matched controls from pregnant mares were used and 5 non-pregnant mares were used as an additional control group. Pre and post foaling faecal samples were analysed by next generation sequencing following DNA extraction. The faecal microbiota during late pregnancy was different from that of non-pregnant control mares, but only in the microbial community membership and structure, rather than differences in phyla. There was no significant impact of foaling on the faecal microbiome; however, faecal samples collected prior to colic episodes had a significantly higher relative abundance of Proteobacteria. Samples with a relative abundance of Firmicutes of <50% all preceded a colic episode. The consistent changes in faecal microbiota which


preceded episodes of colic found in this study may lead to identification of higher risk mares and manipulation of the microbiota in order to reduce the risk of colic.


Eosinophilic keratitis


Mary Lassaline-Utter and colleagues in the USA have recently reviewed the medical records of horses with eosinophilic keratitis (EK) in the Mid-Atlantic United States in order to document the characteristics, treatment and outcome of the cases and also to evaluate the effects of different treatments and the likelihood of recurrence. A retrospective medical records review identified 27 horses


(46 eyes) diagnosed with EK over a 5-year period. Recurrence data was obtained by phone interview. As well as documenting the characteristics, treatment and


outcome of these cases the authors aimed to evaluate the effects of topical or systemic corticosteroid treatment, oral cetirizine treatment and secondary corneal infection on disease duration; and also to evaluate the association between corticosteroid and cetirizine treatment and likelihood of recurrence. Eosinophilic keratitis was found to be seasonal with 92% of


cases developing clinical signs between June and October. The most cases were diagnosed in July (41%). Forty-four percent of the affected horses had been affected in previous years. Time to resolution averaged 3.7 months. Ten horses (18 eyes) were treated with systemic dexamethasone, with a significantly shorter time to resolution (average 2.23 months) than horses not so treated (average 4.20 months). Secondary infection led to a significant increase in time to resolution (average 4.1 months) compared with horses without secondary infection (average 3.0 months). All eyes were visual at resolution. Horses treated with cetirizine were less likely to have recurrence during the follow-up period (8%) than horses not so treated (57%).


The authors concluded that EK has a seasonal occurrence


in summer in the Mid-Atlantic United States. Systemic but not topical corticosteroid treatment may decrease therapy duration. Treatment with cetirizine may be associated with a decreased risk of recurrence.


Comparison of sedation protocols


In this recent study Charlotte Marly and colleagues in Switzerland have compared the clinical usefulness of constant rate infusion (CRI) protocols of romifidine with or without butorphanol for sedation of horses. Two treatments were used in this trial which used 40 healthy


Freiberger stallions. Twenty horses received intravenous (i.v.) romifidine (loading dose: 80 μg/kg bwt; infusion: 30 μg/kg bwt/h) (treatment R) and 20 horses received romifidine combined with butorphanol (romifidine loading: 80 μg/kg bwt; infusion: 29 μg/kg bwt/h, and butorphanol loading: 18 μg/kg bwt; infusion: 25 μg/kg bwt/h) (treatment RB). Dentistry and ophthalmic procedures were performed on 21 horses and opthalmic procedures and buccal examination only on 19 horses. Physiological parameters and occurrence of head/muzzle shaking or twitching and forward movement were recorded during the procedures. Additional romifidine (20 μg/kg bwt, i.v.) was given whenever sedation was insufficient. Recovery time was evaluated by assessing head height above ground and both the dentist and anaesthetist scored the overall quality of sedation using a visual analogue scale.


Median sedation quality scores assessed by the anaesthetist were R: 7.55 and RB: 8.8, and by the dentist R: 6.6, RB: 7.9. Horses receiving RB showed clinically more effective sedation as demonstrated by fewer poor scores and lower additional drug requirements. More horses showed forward movement and head shaking in treatment RB than treatment R. Three horses (2 RB, 1 R) had signs of colic following sedation. These protocols provide effective sedation under clinical


conditions but the addition of butorphanol is advantageous for dentistry procedures.


Effects of epidural morphine in horses after laparoscopic surgery


In this randomised clinical trial, Manuel Martin-Flores and colleagues at Cornell University, USA, evaluated their hypothesis that epidural morphine decreases pain in horses after laparoscopic surgery without adversely affecting gastrointestinal (GI) motility. Eighteen


horses undergoing laparoscopic


cryptorchidectomy under general anaesthesia were randomly assigned to receive either epidural morphine (0.1 mg/kg bwt) or no epidural before the start of surgery. Pain behaviour was rated during the first 2 days following surgery using a numerical scale. Barium-filled spheres were administered through a nasogastric tube before anaesthesia. Gastrointestinal motility was assessed by recording manure production and the number of spheres in the manure, and by abdominal auscultation of intestinal sounds. Heart rates and cortisol concentrations were also measured during the post operative period.


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