Elizabeth Halliwell

Background: Integumentary manifestations of Rhodococcus equi infection in foals are infrequently reported in the literature. Subcutaneous abscessation as the primary clinical presentation in temporally clustered cases of foal rhodococcosis in an equine farm has not, to the authors' knowledge, been previously described. Objectives: To describe an outbreak of R. equi infection where foals presented with subcutaneous abscessation as the primary clinical sign. Study Design: Clinical case series. Clinical Summary: Three Thoroughbred foals aged 6–11 weeks developed subcutaneous abscesses over a 3‐week period in July 2024, out of a cohort of 11 foals. Thoracic ultrasound examination was performed on all foals on the farm, and 6/11 (54%) had evidence of subclinical pneumonia. No foals other than the three cases with subcutaneous abscesses were clinically affected. Purulent aspirates from abscesses in two foals were subjected to microbiological diagnosis and yielded a pure culture of R. equi. Two of the three clinically affected foals received 4 weeks of systemic antimicrobial treatment, and all abscesses resolved. Whole‐genome sequencing of one isolate demonstrated near identity to a previous UK isolate associated with pulmonary rhodococcosis, and did not reveal genetic features that could explain the atypical presentation. Main Limitations: Financial constraints on the farm precluded microbiological confirmation of diagnosis in the third foal. Sequencing of a single isolate precluded assessment of strain relatedness within the outbreak. Conclusions: R. equi infection should be considered in foals presenting with subcutaneous abscesses, even in the absence of overt respiratory signs. Exposure‐related factors likely contributed to this presentation, and the possibility of a transcutaneous route of entry should be considered.

Background: Broodmares are at increased risk of gastrointestinal colic. However, colic risk factors specific to this population have not been investigated. Objective: To investigate horse‐ and management‐level risk factors for post‐partum colic in a cohort of Thoroughbred broodmares in the United Kingdom and Ireland. Study Design: Prospective, nested case–control study. Methods: Twenty‐nine Thoroughbred stud farms in the United Kingdom and Ireland were recruited, and 1044 mares were followed over the 2021 and/or 2022 foaling seasons. Data were collected on signalment, medical and management history for post‐partum colic mares and matched (3:1) controls. Multivariable analysis was conducted using conditional logistic regression. Results: Due to strong collinearity between days post‐partum and time spent stabled, two multivariable models were built. Days post‐partum (Model 1: OR 0.9, 95% CI 0.8–0.9; p < 0.001) and increasing hours stabled (Model 2: OR 1.2, 95% CI 1.1–1.3; p < 0.001) were strongly associated with increased risk of post‐partum colic. Colic risk was highest immediately post‐partum, with reduction in likelihood of colic up to 50 days after foaling. NSAID use in the previous 28 days (Model 1: OR 6.2, 95% CI 2.0–65.5; Model 2: OR 4.1, 95% CI 1.1–15.0; p = 0.048) and a history of previous colic (Model 1: OR 7.4, 95% CI 1.2–7.9; Model 2: OR 5.3, 95% CI 1.7–17.1; p = 0.01) were also associated with increased colic risk. Calcium supplementation was associated with increased likelihood of post‐partum colic in Model 1 only (OR 4.4, 95% CI 1.3–15.7; p = 0.04). Main Limitations: Mares comprised a small sub‐population of UK and Irish Thoroughbred broodmares. Pre‐partum colic was not investigated. Conclusions: Maximising turnout in post‐partum broodmares may reduce colic risk, immediately post‐partum and up to 50 days. Broodmares who have recently received NSAIDs, have a history of colic or are receiving a calcium‐based supplement may be at increased risk of post‐partum colic.

Summary: Background: Few reports describe the aetiology, presentation and diagnosis of retinal detachment in horses. Equine recurrent uveitis (ERU) and trauma are the most common causes of equine retinal detachment in the United States, but no studies have characterised the disease within the United Kingdom. Objectives: To describe clinical presentation, aetiology and diagnostic examination findings of horses with retinal detachment within a UK‐based population. Study design: Retrospective case series. Methods: Medical records of horses presented to a single UK referral centre between 2010 and 2020 were reviewed. Horses were diagnosed with retinal detachment by clinical examination and/or ultrasonography, and details of clinical presentation, aetiology and examination findings were recorded. Results: A total of 23 horses were included. There were 13 geldings and 10 mares with a median age of 9 at presentation (range 4 days to 17 years). Warmbloods were the most common breed ( n = 8). Unilateral cases ( n = 21) were more common than bilateral ( n = 2). ERU was the most common aetiology ( n = 10) followed by trauma ( n = 8). Three cases presented post‐intraocular surgery, one congenital and one secondary to primary glaucoma. Ultrasound confirmed diagnosis in 23 (100%) cases, but only nine could be visualised by direct ophthalmoscopy. Cataracts, posterior synechiae and vitreal debris were found commonly in both the ipsilateral and contralateral eye affected. Main limitations: Small sample size. Single‐centre retrospective study which may not be representative of the entire UK population. Histological confirmation of cases was not obtained. Conclusions: Causes of retinal detachment in the studied population are like those previously reported in the USA and most cases presented with complete detachment. Ocular ultrasound is useful in the diagnosis of retinal detachment when the fundus cannot be directly assessed. The presence of retinal detachment should be considered in non‐visual eyes presenting with cataracts, vitreal debris and posterior synechiae.

Summary: This report describes four cases of intraocular melanoma which were treated with a course of human tyrosine DNA canine melanoma vaccine. Two cases continued to show progression of the tumour. One case presented with bilateral intraocular melanomas and demonstrated clinical progression in one eye within 5 months, and apparent quiescence of disease in the other, though subtle deterioration was noted at a 2‐year follow‐up. The final case presented with recurrent ulceration due to an intraocular melanoma and demonstrated a good clinical response with a reduction in the frequency and severity of the episodes of ulceration. The small number of cases in this report precludes firm conclusions, but these reported outcomes suggest limited justification for the routine recommendation of melanoma vaccines to horses with intraocular melanomas.