Jennifer Burns

Summary: Lymphoma in horses is uncommon and rarely diagnosed as a cause of ataxia. This case report describes a 2‐year‐old Standardbred cryptorchid colt who presented with acute onset of grade 3–4/5 spinal ataxia in all four limbs, with the hindlimbs more severely affected than forelimbs and severe proprioceptive deficits. Due to the severity of the ataxia, a full neurologic examination could not be completed, and the colt was humanely euthanised. Post‐mortem examination revealed multiple osteochondritis dissecans lesions in the cervical and lumbar spine. Initially, this was thought to be the cause of the ataxia; however, histopathology revealed multifocal areas where the spinal nerve roots and epidural surface of the dura mater of the meninges were surrounded or covered by plaques of neoplastic round cells which infiltrated the adipose tissue surrounding the spinal tissues. Atypical round cells similar to those observed in the spinal meningeal tissues were also found in the kidneys, lungs, liver, testes and one lymph node. Immunohistochemical staining of meningeal tissue samples revealed moderate‐to‐intense cytoplasmic/membranous immunoreactivity for CD20 and a diagnosis of multicentric diffuse large B cell lymphoma was made. These results indicate that lymphoma should be included as a differential diagnosis for a horse presenting with acute ataxia that does not have evidence of spinal cord compression, equine protozoal myeloencephalitis, equine herpesvirus‐1 myeloencephalopathy, equine degenerative myeloencephalopathy, equine motor neuron disease, trauma or other more common sources of ataxia.

Background: Donkeys ( Equus asinus ) in East Africa are recognised as working with poorly designed harnesses and carts. The donkey cart used in regions of Africa, specifically Meru County, Kenya, appears to place the cart's weight solely on the donkey's mid‐cervical region. The ventral area of the neck is vulnerable to external pressure on the trachea, which is superficially located. Objectives: To compare the presence and severity of endoscopic abnormalities in the upper airway and trachea of Meru County working cart donkeys compared to pack donkeys. To determine associations between endoscopic and physical evidence of harness injury. Study Design: Cross‐sectional. Methods: At voluntary health clinics, physical examination and endoscopy of the upper airway and trachea were evaluated and recorded at rest on 66 donkeys (38 cart donkeys and 28 pack donkeys). The presence and grade of tracheal collapse, tracheal ring abnormalities, tracheal mucus, and pharyngitis were subsequently determined on the endoscopy recordings by blinded evaluators. Results: Significant associations were identified between work type and tracheal collapse severity, ring abnormalities, pharyngitis, hairless skin, and thickened skin, with these findings more common in cart than pack donkeys (all p < 0.03). Moderate tracheal collapse (grade 3) was present in 40% (95% CI: 24%–57%) of cart and 0% (0%–12%) of pack donkeys. Intra‐tracheal ring abnormalities were noted in 45% (29%–62%) of cart and 0% (0%–12%) of pack donkeys. Physical examination findings were significantly and positively associated with endoscopy findings (all p < 0.002). Main Limitations: Standing endoscopy was performed at rest and dynamic endoscopy during the pulling of carts was not performed. Conclusion: Moderate tracheal collapse was seen in cart donkeys when compared to pack donkeys. Physical examination findings at rest were associated with and moderately predictive of tracheal collapse.

Summary: Background: Apical proximal sesamoid bone (PSB) fractures are a common occurrence in Standardbred racehorses due to the high‐intensity nature of their work. Several studies have evaluated the racing performance after surgical removal of apical fracture fragments in Thoroughbred horses, however information pertaining to Standardbred racehorses is limited. Objectives: To (i) describe the distribution of apical PSB fractures in a population of Standardbred racehorses; and (ii) measure return to athletic ability in these horses following surgical removal of apical PSB fracture fragments. Study design: Retrospective. Methods: Medical records of Standardbred racehorses presenting to the Atlantic Veterinary College (AVC) for surgical treatment of an apical PSB fracture were reviewed. Lifetime racing records were obtained, and the five race starts before injury and the five race starts following surgical treatment were analysed for total earnings and number of top‐3 placings for each horse. Results: Thirty‐three horses raced following surgery; 22 of which were racing prior to injury. No significant differences were found in top‐3 placings or monetary earnings for the 22 horses which had raced prior to and after surgery. There was no significant difference in limb or sesamoid affected and return to racing. No associations were found between type of surgery performed or degree of suspensory desmitis and whether the horse returned to racing. Main limitations: Small sample size. Conclusions: 88% of horses that were racing prior to injury also raced following surgical treatment of an apical PSB fracture. Surgical removal of apical PSB fractures in Standardbred racehorses does not appear to affect their future athletic ability.

Lymphoma in horses is uncommon and rarely diagnosed as the cause of ataxia in horses. This case report describes a two-year-old Standardbred cryptorchid colt who presented with acute onset of grade 3.5/5 ataxia. Due to the severity of the ataxia, a full neurologic examination could not be completed, and the colt was humanely euthanized. Post-mortem examination revealed multiple osteochondritis dissecans lesions in the cervical and lumbar spine. Initially this was thought to be the cause of the ataxia, however histopathology revealed multifocal areas where the spinal nerve roots and epidural surface of the dural mater of the meninges were surrounded or covered by plaques of neoplastic round cells which infiltrated the adipose tissue surrounding the spinal tissues. Atypical round cells similar to those observed in the spinal meningeal tissues were also found in the kidneys, lungs, liver, testes and one lymph node. Immunohistochemical staining of meningeal tissue samples revealed moderate to intense cytoplasmic/membranous immunoreactivity for CD20 and a diagnosis of multicentric diffuse large B cell lymphoma was made. Lymphoma should be included in the differential diagnoses for a horse presenting with ataxia and neurologic deficits

Background: Donkeys in East Africa are recognized as working with poorly designed harnesses and carts. The donkey cart used in regions of Africa, specifically Meru County, Kenya, appears to place the cart’s weight solely on the donkey’s mid-cervical region where the trachea is superficially located. Objectives: To compare the presence and severity of endoscopic abnormalities in the upper airway and trachea of Meru County working cart donkeys compared to pack donkeys. To determine associations between endoscopic and external physical exam findings. Study design: Cross-sectional Methods: At voluntary health clinics, physical examination and endoscopy of the upper airway and trachea were evaluated and recorded at rest on 66 donkeys (38 cart donkeys and 28 pack donkeys). The presence and grade of tracheal collapse, tracheal ring abnormalities, tracheal mucous and pharyngitis were subsequently determined on the endoscopy recordings by blinded evaluators. Mann–Whitney and Chi-square/Fisher’s exact tests were used to investigate associations between work type and physical exam and endoscopy findings. Results: Significant associations were identified between work type and tracheal collapse severity, ring abnormalities, pharyngitis, skin lesions, and skin hypertrophy with these findings more common in cart than pack donkeys (all P<0.03). Moderate tracheal collapse (grade 3) was present in 40% (95% CI: 24-57%) of cart and 0% (0-12%) of pack donkeys. Exam findings were significantly and positively associated with endoscopy findings (all P<0.002). Main limitations: Standing endoscopy was performed at rest, not dynamic endoscopy during the pulling of carts. Conclusion: Moderate tracheal collapse was seen in cart donkeys when compared to pack donkeys. Physical exam findings at rest were associated with tracheal collapse and tracheal ring abnormalities. This work may help identify by physical examination donkeys that are at greatest need of improved harnesses.

Summary: A 3‐year‐old Standardbred trotting gelding presented to the Atlantic Veterinary College for diagnostic work‐up of poor performance and abnormal respiratory noise during exercise. Physical examination was unremarkable, and no significant findings were identified on standing endoscopic examination of the upper respiratory tract. Treadmill endoscopy was utilised for dynamic evaluation of the upper respiratory tract; a diagnosis of epiglottic retroversion was confirmed. The owner requested euthanasia of the gelding, and a post‐mortem evaluation was completed. Despite thorough gross and histological examination of the head and neck on post‐mortem examination, no evidence was identified to support the postulated aetiologies for epiglottic retroversion currently found in the literature. This case represents the first reported findings from a post‐mortem examination of a horse with epiglottic retroversion.

Background: Rapid, economical, and quantitative assays for measurement of camelid serum immunoglobulin G (IgG) are limited. In camelids, failure of transfer of maternal immunoglobulins has a reported prevalence of up to 20.5%. An accurate method for quantifying serum IgG concentrations is required. Objective: To develop an infrared spectroscopy-based assay for measurement of alpaca serum IgG and compare its performance to the reference standard radial immunodiffusion (RID) assay. Animals: One hundred and seventy-five privately owned, healthy alpacas. Methods: Eighty-two serum samples were collected as convenience samples during routine herd visits whereas 93 samples were recruited from a separate study. Serum IgG concentrations were determined by RID assays and midinfrared spectra were collected for each sample. Fifty samples were set aside as the test set and the remaining 125 training samples were employed to build a calibration model using partial least squares (PLS) regression with Monte Carlo cross validation to determine the optimum number of PLS factors. The predictive performance of the calibration model was evaluated by the test set. Results: Correlation coefficients for the IR-based assay were 0.93 and 0.87, respectively, for the entire data set and test set. Sensitivity in the diagnosis of failure of transfer of passive immunity (FTPI) ([IgG] <1,000 mg/dL) was 71.4% and specificity was 100% for the IR-based method (test set) as gauged relative to the RID reference method assay. Conclusions and Clinical Importance: This study indicated that infrared spectroscopy, in combination with chemometrics, is an effective method for measurement of IgG in alpaca serum.

A stallion presenting for surgical correction of an acquired inguinal hernia was also diagnosed with a nephrosplenic entrapment (NSE) intraoperatively. Surgical intervention resulted in a successful outcome. To date, these conditions have not been reported to occur simultaneously.

Atrial fibrillation (AF) is the most clinically relevant cardiac arrhythmia identified in the Standardbred racehorse. However, there is limited literature regarding athletic ability in Standardbred racehorses following AF conversion. To investigate this issue, the objectives of this review were to: i) determine the success rate in using quinidine sulphate to treat AF in a population of hospitalized equine patients in Atlantic Canada between January 2008 and December 2019; and ii) measure return to athletic ability (using racetrack earnings and top-3 finishes) following cardioversion with quinidine sulphate in a population of Standardbred racehorses. Overall, 73% (16/22) of AF instances in this study were successfully treated with enteral quinidine sulphate. No significant difference was detected in racetrack earnings or number of top-3 finishes for each horse that raced at least 5 times pre- and post-conversion. Key clinical message: To the authors' knowledge, this is the first published review to assess the athletic ability of Standardbred racehorses following cardioversion with enteral quinidine sulphate. Based on the current information, it does not appear that treatment of AF with quinidine sulphate affects future athletic performance in horses that achieved cardioversion.