Background: The survival of horses diagnosed with critical colic relies on rapid and effective decision-making by owner and veterinary practitioner. Objectives: To explore horse owners’ and veterinary practitioners’ experiences of decision-making for critical cases of equine colic. Methods: A phenomenological approach was taken. Individual, semi-structured telephone interviews were conducted with 14 horse owners and 13 veterinary practitioners (vets) who had experienced a critical decision (referral or euthanasia) for a horse with colic. A purposive, convenience sample of participants was recruited. Sessions explored participant’s experience of colic, including recognition, help-seeking behaviour, and challenges. Thematic analysis was performed on collected data. Results: Four over-arching themes were identified; ‘head’, ‘heart’, ‘practicalities’ and ‘impact’. Owners acknowledged responsibility for their horse’s welfare but had different perspectives to vets on the importance of finance (‘head’). Both vets and owners described how the horse-human relationship (‘heart’) often led to conflict during decision-making. The vet-client relationship was influential on decision-making for both owners and vets; involving other people in decision-making was described both positively and negatively by participants (‘heart’). ‘Practicalities’, such as lack of preparedness, transport issues and adverse weather conditions, were identified by both owners and vets as barriers. Owners described a ‘rollercoaster’ of emotions after a critical decision, with profound impacts on their mental wellbeing, feelings of guilt, and long term changes in behaviour (‘impact’), and a lack of support to manage these feelings. Main Limitations: Small sample size. Conclusions: This study describes stakeholder decision-making during critical cases of equine colic. Factors that commonly influenced decisions included an owner’s previous knowledge and beliefs, social pressures, logistics, and the relationship between owner and vet. The study highlighted long term impacts on the owner, including their management and decisions for subsequent horses. These factors should be considered and included in shared decision-making for critical cases of colic.

Background: Equine trigeminal-mediated (TGM) headshaking (HS) is a facial pain syndrome characterised by varying intensity and frequencies of head movements and nasal irritation. An accurate method for quantification and/or characterisation of severity is lacking. Objectives: To develop and validate an objective measure of TGMHS. Study design: Prospective case control study. Methods: Horses presenting for HS were recruited alongside those presenting for forelimb lameness (LAME) and pre-purchase examination as well as healthy controls (CONTROL). Head movement data were collected for five minutes whilst trotting on the lunge using a tri-axial accelerometer (range ±16g, sampling rate of 800Hz) on the bridle headpiece. Recordings were exported and peak detection performed using minimum and maximum thresholds of -1g and +1g (corrected for gravity) and a minimum peak width of 10 samples. Results: Fifty-six horses were included in the study; 18 TGMHS, 10 non-TGMHS, 12 LAME and 16 CONTROL. Characteristics and frequency of vertical (Z axis) head movements of TGMHS horses differed significantly from other horses. TGMHS horses had peaks with greater mean and maximum positive g-force (P<0.005) and lower mean and minimum negative g-force (P<0.001), greater frequency of peaks/min (P<0.001), and over twelve times greater percentage of peaks >+2g compared to other horses (P<0.001). Receiver operator curve characteristics of percentage of peaks >+2g (CI 0.72-0.95), percentage of peaks <-2g (CI 0.66-0.92), and percentage of peaks <-2g and >+2g (CI 0.72-0.96) showed excellent discrimination of TGMHS horses from LAME, CONTROL and non-TGMHS horses. Main limitations: Referral population of horses, small sample size, and control horses were not evaluated for orthopaedic disease. Conclusions: Accelerometer data from trotting exercise on the lunge gives an objective measure of HS and can differentiate between TGMHS, non-TGMHS, normal head movements, and those associated with forelimb lameness. Accelerometer use may aid HS diagnosis and monitoring of management strategies.

The current study aims to investigate the complication rate of equine appendicular magnetic resonance imaging (MRI) performed under general anesthesia at a tertiary referral center. 1655 horses, donkeys, and mules were included in the study. A complication rate of 1.5% was found in this 9-year study period. The most common complication was post-anesthetic fever with 11 horses becoming pyrexic in the immediate post-anesthetic period. Four of these horses went on to develop clinical pneumonia and one horse had an outbreak of respiratory herpesvirus. The incidence of neuropathy was 0.4% and colic was 0.4%. This study concludes that peri-anesthetic antimicrobial administration would not decrease the risk of complications in horses or donkeys undergoing general anesthesia for MRI of the appendicular skeleton at this tertiary referral center.

Background: Limited literature exists regarding equine Immune Mediated Keratitis (IMMK) in Europe. North America-based publications describe minimal blepharospasm, rare corneal ulceration and no uveitis; clinical impression suggests that these signs are common in Europe. Objectives. Assess the prevalence of blepharospasm, corneal ulceration and uveitis and their impact on outcome in horses diagnosed with IMMK in European countries. Study design: Retrospective case series of 95 horses with IMMK in the UK and Finland. Methods. Clinical records of horses with IMMK were retrospectively evaluated. The UK and Finland populations were comparable; therefore, descriptive statistics were performed on combined data on subtypes of IMMK and clinical features. Odds ratios (OR) and confidence intervals (CI) were calculated for impact of blepharospasm, ulceration or presence of uveitis on the outcome of enucleation and treatment duration. Results. IMMK subtype was classified as 10/95 (10.5%) epithelial, 50/95 (52.6%) anterior stromal, 15/95 (15.8%) mid-stromal, 4/95 (4.2%) endothelial cases and 16/19 (16.8%) unrecorded. Blepharospasm was documented in 35/95 (36.8%), corneal ulceration in 28/95 (29.5%), and signs of uveitis in 24/95 (25.4%) of horses. Increased odds of enucleation were associated with the presence of blepharospasm (OR 5.9, 95% CI 1.7-20.8), corneal ulceration (OR 3.3, 95% CI 1.0-10.5) and signs of uveitis (OR 8.6, 95% CI 2.5-29.6). The presence of blepharospasm, corneal ulceration or uveitis did not significantly alter the odds of ongoing medication. Main limitations: Data were collected over a wide timeframe and the diagnosis was mainly made without histopathology. A broad definition of uveitis was used and there was a bias towards complicated cases being retained for follow up. Conclusions. The clinical features of IMMK were similar between two geographically distinct European countries but different to findings described in the USA. Blepharospasm, corneal ulceration and signs of uveitis can occur with IMMK and increase the odds of enucleation.

Background: Selective anthelmintic treatment, advocated due to evolving anthelmintic resistance, has been associated with an increase in Strongylus vulgaris prevalence. Reverting to routine interval anthelmintic treatments is not viable and therefore, identifying other management factors correlated with S. vulgaris infection is vital. Objectives: To investigate possible risk factors associated with the presence of S. vulgaris infection in residing horses on Swedish horse establishments. Study design: Internet-based questionnaire survey. Methods: A questionnaire, created using the internet-based survey platform Netigate, was distributed to owners of equine establishments throughout Sweden via established equine platforms and social media channels. The survey was available for response from May 21 until September 1 2022. Questions were closed ended with branching logic paths. Results: Four factors were significantly associated with S. vulgaris infection, with an increased odds of infection seen in livery yards (OR 1.67, 95% CI 1.18-2.36, p = 0.004) and premises with more than ten residing horses (OR 2.42, 95% CI 1.64-3.56, p < 0.001). A lower odds of infection was seen in establishments using quarantine routines (OR 0.69, 95% CI 0.50-0.96, p = 0.03) and anthelmintic treatment of new horses prior to arrival at the premise (OR 0.37, 95% CI 0.18-0.74, p = 0.005). Main limitation: Due to the presence of S. vulgaris infection in the present study being based on S. vulgaris diagnostics performed at the farm level, any association between faecal diagnostic use and risk of infection could not be investigated. Conclusions: Although the use of diagnostics for S. vulgaris can keep infection rates low, large farms or livery yards with many different horse owners, and those with low use of biosecurity measures as regards to new horses arriving at the premise, are associated with a higher risk of infection.

Rhodococcus equi causes pyogranulomatous pneumonia in foals and immunocompromised people. Despite decades of research efforts, no vaccine is available against this common cause of disease and death in foals. The purpose of this narrative review was to summarize the current understanding of interactions between R. equi and the host innate immune system, to describe features of the immune response that are associated with resistance or susceptibility to R. equi infection, and help guide strategies for developing novel approaches for preventing R. equi infections. Virulence of R. equi in foals has been attributed to the virulence associated protein A which allows intracellular survival in macrophages by preventing acidification of R. equi-containing vacuole. Additionally, foal susceptibility to R. equi infection is associated with immaturity and naivety of innate and adaptive immune systems, while adult horses with fully functional immune system are resistant to pneumonia. Specific interaction between R. equi and innate immune cells can result in bacterial survival or death; learning how to manipulate these responses to control infection is critical to prevent pneumonia in foals. Administration of live vaccines and stimulation of innate immune responses appears to improve foals’ immune response and has the potential to overcome the challenges of foal active vaccination and elicit protection against pneumonia.

Background: Few studies have investigated the adequate contrast enhancement (CE) evaluation depending on concentration, volume, and rate of contrast media (CM) and the scan parameters in equine contrast enhanced computed tomography (CECT). Objectives: We investigated CE of the deep digital flexor tendon (DDFT) and arteries depending on voltage, concentration, volume, and rate of CM during intra-arterial CECT of equine distal forelimbs. Study design: This is a prospective study. Methods: Six horses underwent fifty-four CT scans. First, the CE of DDFT and arteries was evaluated depending on the voltage (80 or 120 kV) and CM concentration (150, 120, or 90 mg I/mL in 50 mL of CM). Second, CE of DDFT and vessels was evaluated depending on the CM volume (50, 100, or 150 mL) and administration rate (2, 4, or 6 mL/s) with a fixed iodine delivery rate (IDR) (300 or 180 mg I/s). Results: CE of DDFT significantly increased at 80 kV of voltage and 150 mg I/mL of CM concentration (Median: 29.65; IQR: 1.74; P < 0.05). CE of the DDFT positively correlated with CM concentration (P = 0.0004; r = 0.75). At 180 mg I/s of IDR, an increase in rate and volume (6 mL/s and 150 mL) led to low contrast attenuation in the medial and lateral palmar arteries (median and IQR: 985.93 and 71.8 Hounsfield units [HU] and 988.73 and 41.16 HU, respectively); the CE was sufficient to distinguish the artery from the adjacent structures. Main limitations: The number of animals was small for parametric statistical analysis. Conclusions: Our results suggest that a low CM concentration could yield sufficient CE of the DDFT and arteries with adjusted CT scanning parameters or volume and injection rate of CM.

Background: Equine obesity is a growing concern, much of the current management advice centres on dietary restrictions, including the removal or limitation of grazing. Little is known about the effectiveness and impact of this approach on the overall welfare of the horse. Objective: This study investigates the impact of two commonly used grazing systems advocated for the control of weight – the ‘strip-grazing’ system and the ‘track’ system - on the behaviour and welfare of outdoor living ponies. Study design: A within-subject cross-over experimental design was used with four groups of pasture kept ponies experiencing each system for 4 weeks in a random order. Methods: Time budgets and behavioural indicators of welfare were measured using 24-hour electronic surveillance, morphometric parameters including weight, body condition score and cresty neck score were measured weekly and activity levels were tracked using GPS tracking units. Results: Ponies moved more (median (IQR), track: 3.23% (2.08%), strip: 2.02% (0.90%); P = 0.001) and travelled a greater distance in 24-hour period (median (IQR), track: 7013.47m (1761.49m), strip: 5331.91m (494.16m); P < 0.001) and engaged in less overt agonistic behaviour on the track system compared with the strip system (median IQR; track: 0.14 (0.30), strip: 0.21 (0.37) P = 0.02). Main Limitations: A relatively short time period of exposure to each grazing system. Conclusions: Track systems resulted in a significant increase in ambulatory behaviour compared with the strip system. Increased levels of agonistic interactions on the strip system maybe the result of perceived reduction of space or a spatial concentration of resources compared to the track system, although the actual accessible area was the same. These results suggest that there may be physical health benefits to the track system as the ponies engaged in more voluntary low intensity exercise as well as improvements to overall welfare.

Background: Data on equine thoracic pathology hardly exist in other breeds than Thoroughbreds. Objectives: To describe pathological changes of the osseous thoracic vertebral column in Warmblood horses, Shetland ponies and Konik horses, and to compare prevalence and severity. Study design: Descriptive post-mortem study. Methods: Computed tomography examined the thoracic vertebral column of 34 Warmblood horses, 28 Shetland ponies, and 18 Konik horses. Osteoarthritis (OA), periarticular osteolysis (PO), cyst-like lesions (CLL) and fragments of articular processes (APJs), costovertebral (CVJs) and costotransverse (CTJs) joints, soft tissue (ST) mineralisation surrounding these joints, intervertebral disc (IVD) mineralisation, impingement of spinous processes (SPs) and spondylosis were scored. Results: APJ aplasia (98%; 58/ 59) occurred in 14 Shetland ponies. OA predominated in Warmblood horses across all joints (45% vs. 29 and 32%, p<0.001). OA and PO were particularly found in CTJs (p<0.001) across all breeds. Warmblood and Konik horses showed more and severe ST mineralisation than Shetland ponies (2.3%, score 1.5 and 3.2%, score 1.3, respectively, vs. 0.3%, score 0.9, p<0.01). Mid location was most often affected with highest severity score (4.2%, 1.5, p=0.001). Konik horses displayed the highest IVD mineralisation (20%, p<0.001), which notably increased with age (p<0.001) compared to Warmblood horses (4.5%) and Shetland ponies (1.1%). SPs impingement was absent in Shetland ponies, and most prevalent in Warmblood horses (11.2%, p=0.0004) compared to Konik horses (2.2%). CLL, fragments and spondylosis were minimal in all breeds, nearly absent in Shetland ponies. Main limitations: Clinical histories were unavailable. Conclusions: Distinct breed differences exist in prevalence and severity of thoracic vertebral column osseous pathologies. CTJ pathology prevails over APJ in all breeds. Warmblood horses are prone to OA, spondylosis and SPs impingement; Konik horses exhibit significant IVD mineralisation, and Shetland ponies demonstrate high APJ aplasia . PO, CLL, fragments and ST mineralisation are notably low in Shetland ponies.

TitleUpper appendicular, pelvic and axial skeletal pathology with poor performance

Background: Obesity has been associated with human obstructive sleep apnoea and canine brachycephalic obstructive airway syndrome. To the authors’ knowledge the effect of body condition score (BCS) on structures of the oropharynx , nasopharynx and upper airway of the horse has not been investigated. Objectives: To investigate the effect of BCS on tongue area and height, soft palate angle and basihyoid depth in the horse. Study Design: Retrospective, analytical, cross-sectional. Methods: Computed tomographic (CT) images of the head of 44 horses were assessed. DICOM viewing software was used to measure head length, basihyoid-skin depth, soft palate angle (SPA), midline tongue area and dorsoventral height (DVH) of the tongue in two locations. BCS were assigned at the time of CT examinations. Results: Increased BCS led to an increased mean SPA (mean difference=2.56 ˚ ; P=0.019) and increased median basihyoid depth (mean difference=0.246cm; P=0.006). Following adjustments made for the effect of head length on tongue measures, significant correlation was identified between SPA and tongue area (Spearman’s r=0.544; P=0.007); SPA and DVH of the tongue at the level of the hard palate (Spearman’s r=0.562; P=0.004) and SPA and DVH of the tongue at the lingual process of the basihyoid bone (Spearman’s r=0.690; P<0.001). No significant correlation was identified between variables with sex or age of horses. Conclusions: Increased BCS increases SPA and basihyoid bone depth. Increases in tongue size measurements increase SPA. Results from this study warrant further investigation into the clinical significance of the effects of BCS on the upper airways of the horse.