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: 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.

Background: There is no objective information reporting the effect of unilateral laser ventriculocordectomy (VeC) on arytenoid abduction or stability. Objectives: To evaluate arytenoid stability and abduction in horses with severe recurrent laryngeal neuropathy (RLN) before and after unilateral laser VeC. Study design: Prospective study in clinically affected client-owned horses. Methods: Sample size calculations indicated ≥7 horses were required. Horses with grade C or D exercising laryngeal function that underwent unilateral laser VeC were included. Exercising endoscopy was performed before and ≥6 weeks after left-sided laser VeC. Arytenoid stability at maximal exercise was calculated by measuring the left-to-right quotient angle ratio (LRQ) of the corniculate processes at the points of maximal arytenoid abduction (expiration) and maximal arytenoid collapse (inspiration). For each horse, means of measurements obtained for four breaths pre- and post-operatively were used for statistical analysis. Results: Eight horses were included: 5 grade C and 3 grade D laryngeal function. The difference in LRQ between inspiration and expiration was lower post-operatively (median 0.039; interquartile range [IQR] 0.032-0.047) compared to pre-operatively (median 0.158; IQR 0.083-0.249; p=0.01) confirming the left arytenoid was more stable following unilateral laser VeC. The degree of improvement was significantly greater for grade D horses compared to grade C horses (p=0.04). The LRQ measured on maximal abduction was also lower post-operatively (median 0.467; IQR 0.444-0.506) compared to pre-operatively (median 0.578; IQR 0.554-0.655; p=0.02) indicating the left arytenoid was less abducted following surgery. Main study limitations: The sample size was small, no racehorses were included and post-operative assessment was conducted at a variable time after surgery. Conclusion: Unilateral laser VeC in grade C and D RLN-affected horses results in slightly reduced left arytenoid abduction but increased arytenoid stability.

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.

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.

The renal resistivity index is a tool to evaluate the hemodynamics through arterial resistance. Considering perfusion as one of the first aspects to be affected upon kidney injury, alterations in renal blood flow could be especially important for the early detection of kidney damage. The aim of this systematic review was to retrieve published studies on equine renal resistivity index (RI) in order to develop a standardized method of renal ultrasound examination through a transabdominal approach as well as to evaluate current reference range for renal RI value in horses. An electronic search in Science Direct, PubMed, Scopus and Web of Science databases was performed in February 2023 using the terms “RI” OR “resistivity index” OR “IP” OR “pulsatility index” AND (kidney OR renal) AND (equine OR horse) in titles, keywords and abstracts. The studies were screened based on inclusion criteria and variables of interest were extracted. To assess the methodological quality, the SYRCLES‘s risk of bias tool was used. From the search, a total of 134 studies were identified and five of them were considered eligible. The selected studies had been conducted in healthy non-sedated horses through transabdominal technique. The upper limit of normality for renal RI was 0.58 ± 0.06 for the right kidney of untrained horses, which is considerably lower than the value of 0.70 currently used for humans, cats and dogs. There were heterogenous outcomes among studies, where two out of the five demonstrated difference between RI value of left and right kidneys and one out of the five showed increased renal RI value in the elderly compared to foals and adult animals. Data of RI in horses is still scarce; a normality standard for renal RI studies in horses would greatly improve comparison and good quality results to allow clinical application.

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: 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.