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Africanized crossbred bees (Apis mellifera) originated in Brazil in 1957, and since then, the number of accidents involving humans and animals has significantly increased. Although they are considered clinical emergencies, there are few reports describing the clinical and pathological aspects of bee envenomation in horses. In this context, this report aims to describe the clinical and pathological features of bee toxicity after massive bee envenomation in three horses. The horses were referred to the veterinary hospital the day following the attack, and after clinical and laboratory examination, they presented with vascular, muscular, pulmonary, hepatic, and renal impairment. Even after the initiation of therapy immediately upon admission, the clinical condition of the two horses worsened, and they died within two days of hospitalization, with pathological analysis confirming the previously observed clinical alterations of generalized vasculopathy, liver degeneration, pulmonary edema, and renal tubular necrosis. Many cases of massive bee envenomation have been documented in both humans and animals, particularly in dogs. Understanding the mechanism of action of apitoxin, its effects on various tissues, and the ideal therapy for each patient has proven crucial for improving survival rates., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Vascular hamartoma is an abnormal development of endothelial tissue that rarely affects horses. Histopathological examination remains the gold standard for definitive diagnosis, yet the presence of abnormal vascular structures must be carefully differentiated from other vascular anomalies and neoplasms. This report describes two cases of vascular proliferation affecting the skin on the lateral side over the left tarsus and the dorsolateral region over the fetlock joint of two fillies. The clinical history, presentation, and radiographic and sonographic findings in both patients suggested a neoplasm of unknown origin. Surgical excision of the mass was successfully performed in both patients. In one patient, a second surgery was performed six months after the first surgery because of the recurrence of the mass. Histopathological examination revealed a disorganized proliferation of well-differentiated, tortuous, and varied-sized blood vessels hemmed in myxoid tissue with abundant fibrocollagenous bands. Immunohistochemical examination of the endothelium markers factor VIII and ERG revealed positive staining of the mass samples in both cases, confirming their vascular origin. The combination of these markers was effective, providing a reliable option for differentiating vascular proliferation in horses. To the best of the author's knowledge, this is the first report applying the ERG endothelial marker to horse vascular malformations., Competing Interests: Declarations Competing interests The authors declare no competing interests. Ethical approval The study described in this manuscript involved the use of non-experimental horses. The owners have provided consent for veterinary clinical care for the individual patient at the São Paulo State University —School of Veterinary Medicine and Animal Science (FMVZ/UNESP), Botucatu, Brazil, and for the publication of their pet’s data. Therefore, ethical approval from a committee was not specifically required for publication., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

The association between aural plaques, Equus caballus papillomavirus (EcPV), and the different breeds of horses and risk factors is poorly described. The objective of this study was to determine the clinical prevalence of aural plaques in Mangalarga Marchador (MM) and Quarter Horse (QH) horses in Brazil, to evaluate the association of this prevalence with some risk factors, and to detect the presence of EcPV DNA (types 1-10) in aural plaques biopsies. A total of 400 MM and 425 QH horses, were clinically evaluated. For each horse, an identification form was completed, containing information on breeding, sex, age, presence, and classification of aural plaque lesions, presence of ectoparasites, management type, ear clipping performed, and sensitivity to ear palpation. Biopsies of the lesions were taken from 30 horses and assessed for the presence of EcPV DNA using PCR. Among the MM and QH horses evaluated, 41.5% and 33.6%, respectively, had aural plaques. The MM horses showed a higher frequency of plaques than QH (p = 0.02). At least one viral type was identified in 90% of all aural plaque biopsies, with EcPV4 being the most frequently detected in both breeds, followed by EcPV6, EcVP5, EcVP3 and EcPV1 respectively. In one sample, EcPV1 was detected alone, although it had previously been described only in copresence. The copresence of viral DNA the MM 73% (11/15) QH 27% (4/15) horses. Aural plaques are widely distributed, with a higher prevalence of EcPV4. Additionally, MM horses have higher susceptibility and frequency of the disease than QH horses., Competing Interests: Declarations Ethics statement All procedures were approved by the Ethics Committee for the Use of Animals in Research (CEUA) of the School of Veterinary Medicine of Uberlândia Federal University– UFU (nº 23117.041869/2022-16). All methods were performed in accordance with the guidelines and regulations of the CEUA. Competing interests The authors declare no competing interests. Conflict of interest The authors declare no conflict of interest., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

An 18-y-old American Saddlebred mare was admitted with fever and acute onset of neurologic signs including grade 3 of 5 ataxia, difficulty in prehension, and dull mentation. Because of financial restraints, desired testing could not be performed; the horse's condition declined despite supportive treatment, and euthanasia was elected. Postmortem examination revealed petechiae and ecchymoses in the meninges and neuroparenchyma of the encephalon. Blast-like neoplastic round cells were identified within the vasculature and areas of hemorrhage in the neuroparenchyma, the intestinal submucosa, and other organs, including the liver, kidney, lung, and mesenteric lymph node. Necrotizing enterocolitis and acute fibrinonecrotizing bacterial pneumonia were also noted. Of the atypical round cells in the encephalon, >70% expressed ionized calcium-binding adapter molecule 1 (Iba1), 10-20% expressed myeloperoxidase (MPO), and <10% expressed PAX5, CD3, CD20, CD79a, or MUM1. The bone marrow was diffusely effaced by neoplastic round cells expressing Iba1, and ~70% of these cells expressed MPO with no expression of CD3 or CD20. CD172a also immunolabeled a portion of the neoplastic cells. These findings were consistent with the diagnosis of acute myeloid leukemia-M1 with an unusual neurologic presentation., Competing Interests: Declaration of conflicting interestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Lipofuscin is a complex mixture of highly oxidized, cross-linked macromolecules that accumulates in neurons with age and some neurodegenerative diseases. Equine dysautonomia (ED) is a polyneuropathy that mainly affects autonomic and enteric nervous systems, resulting in alimentary tract dysfunction. Our main aim was to determine whether neuronal lipofuscin increased with increasing duration of ED. We investigated the prevalence of lipofuscin in cranial cervical ganglia of horses with acute (AED), subacute (SED), and chronic ED (CED), young controls (of similar age to ED cases), and aged controls ( n  = 8 per group). We used Schmorl stain for histologic detection of lipofuscin and assessed its accumulation in neurons using image analysis software. The percentage of neurons positive for lipofuscin increased with age in individual groups and all groups combined ( p  < 0.001). There were fewer positive neurons in AED and SED compared to aged controls ( p  < 0.001) and more in CED than AED cases ( p  = 0.042) and young controls ( p  = 0.012). We found a strong positive correlation between percentage positive neurons and percentage positive area of the neuron containing lipofuscin for combined groups ( p  < 0.001). Although neuronal lipofuscin increased in cranial cervical ganglion in CED cases, it remains to be determined whether this is a cause or consequence of neuronal degeneration., Competing Interests: Declaration of conflicting interestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

The equine digital cushion (DC) has been a poorly understood structure regarding its mechanical properties and composition. The objective of this study was to develop a sampling technique and to compare the biomechanical and histologic properties of DC between lame and non-lame forelimbs. Both forefeet from horses with induced carpal lameness were radiographed prior to humane euthanasia. Radiographs were used to guide sample collection of two, post-mortem, midline DC samples, palmar and dorsal, via an 8mm biopsy punch. Samples were subjected to compressive testing to determine elastic modulus. Histological evaluation was used to quantify collagen, adipose, ground substance, elastic fibers, and blood vessels. Comparisons of variables between palmar and dorsal DC sites and lame and non-lame limbs were made using student's t-tests or Wilcoxon signed rank tests with P < 0.05. There were no differences in histologic or biomechanical properties in DCs of lame and non-lame forelimbs. The dorsal DC sampling site had a significantly higher median elastic modulus (median: 0.054 MPa, range: 0.001 - 2.110 MPa) and a larger median percentage of ground substance (median: 15 %, 95 % CI: 3 - 30 %) compared to the palmar DC site (elastic modulus: median: 0.023 MPa, range: 0 - 0.576 MPa; ground substance: median 5 %, 95 % CI: 3 - 25 %) (P = 0.03, <0.001; respectively). This study demonstrated that adequate samples could be collected from the DC for biomechanical and histological analysis. Differences in elastic modulus and ground substance between palmar and dorsal samples may reflect different roles of these sites within the DC., Competing Interests: Declaration of competing interest None of the authors has any financial or personal relationships that could inappropriately influence or bias the content of the paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background: Large colon volvulus is a cause of colic in horses with high morbidity and mortality when not promptly treated. More treatment options are needed to improve the outcome of these cases by protecting against the damage caused by ischaemia and reperfusion injury., Objectives: To determine the effect of preconditioning with dexmedetomidine prior to induction of ischaemia-reperfusion (IR) injury in a large colon volvulus model in the horse., Study Design: Randomised blinded in vivo experiments., Methods: Horses received either a dexmedetomidine (DEX) or saline (CON) constant rate infusion (CRI) immediately following induction of anaesthesia. Venous, arterial, and transmural occlusion of a section of the large colon was performed for 3 h, after which the ligatures and clamps were removed to allow for reperfusion for 3 h. Biopsies of the large colon were taken at baseline, 1 and 3 h of ischaemia, and at 1 and 3 h of reperfusion., Results: The severity of crypt epithelial loss (DEX = 2.1 [0.8-2.8], CON = 3.1 [2.5-4], p = 0.03) and mucosal haemorrhage was decreased (DEX = 2.1 [1.3-3], CON = 3.5 [2.5-4], p = 0.03) in group DEX compared to group CON when graded on a scale of 0-4. Crypt length remained longer (DEX = 369.5 ± 91.7 μm, CON = 238.5 ± 72.6 μm, p = 0.02) and interstitium to crypt (I:C) ratio remained lower (DEX = 1.4 (1-1.7), CON = 2.6 [1.8-5.9], p = 0.03) in group DEX compared to group CON during reperfusion., Main Limitations: Clinical applicability of pharmacologic preconditioning is limited., Conclusion: Preconditioning with a dexmedetomidine CRI prior to IR injury demonstrated a protective effect histologically on the large colon in the horse. Further investigation into postconditioning with dexmedetomidine is warranted as a possible intervention in colic cases suspected of being large colon volvulus., (© 2024 The Author(s). Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Ancillary diagnostic methods to enhance the accuracy of viability assessment have not been established for use in clinical practice., Objectives: To assess intestinal microperfusion measured by Laser Doppler Flowmetry and Spectrophotometry (LDFS) in naturally occurring small intestinal strangulations of different origins and to compare this between viable and non-viable segments., Study Design: Prospective clinical trial., Methods: Forty horses undergoing colic surgery for naturally occurring small intestinal strangulations were included. Tissue oxygen saturation (tSO 2 ), haemoglobin (tHB) and blood flow (tBF) were determined by LDFS before and after release of the strangulation. Intestinal biopsies were taken in cases that underwent intestinal resection or intraoperative euthanasia and assessed using a semi-quantitative mucosal injury score (MIS). The LDFS measurements were compared between the different categories of strangulation causes and histopathological injury using parametric and non-parametric tests (p < 0.05)., Results: Strangulations by pedunculated lipomas had lower tBF (13.9 ± 18 arbitrary units [AU]) than epiploic foramen entrapments (65.2 ± 61 AU; CI -1.697 to -0.2498; p = 0.005). Segments with MIS > 5 showed lower tBF during strangulation than segments with MIS < 4 (mean difference 61.1 AU; CI -1.119 to -0.07361; p = 0.03). This did not differ significantly following release of strangulation. Furthermore, there was a positive correlation between the inflammatory cell count and tBF during strangulation (r 0.34; CI 0.01 to 0.60; p = 0.04). The tSO 2 and tHB did not differ between the different categories of lesions or injury., Main Limitations: No biopsies could be taken from the intestinal segments that did not undergo resection. The duration of strangulation could not reliably be ascertained., Conclusions: Blood flow measurements in naturally occurring strangulating lesions show a varying degree of ischaemia in different causes of strangulation. Intestinal blood flow measurements prior to release of the strangulation could potentially contribute to the identification of mucosal injury, yet a high individual variability and other contributing factors need to be considered., (© 2024 The Author(s). Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Osteochondral fragments within equine joints are commonly encountered and may predispose to lameness and limitation to sport purposes. Factors leading to this condition include genetic, nutritional and environmental conditions. However, few studies have evaluated the impact of conformation traits and their correlation with osteochondrosis. This study, based on the radiographic screenings of young horses born in Wallonia (266 individuals, 532 forelimbs), evaluated the correlation between foot, fetlock conformations of the front limb, height at the withers and presence of osteochondral fragments. Moreover, for all traits significantly associated with the presence of osteochondral fragments, a Receiver Operator Characteristic (ROC) curve, area under the curve and optimal cut-off value were calculated to predict the occurrence of fragments. Mean dorsal hoof wall angle was 52.36°, dorsal and palmar angle of the third phalanx were respectively 49.83° and 2.99°, and dorsal metacarpophalangeal angle 147.99°. Moreover, the prevalence of upright feet, defined as having an inclined profile of >2° steeper in relation to its contralateral counterpart, was 24%. Increased palmar angle of the distal phalanx was significantly correlated (P < 0.05) with presence of fragments located at the dorso-proximal margin of the proximal phalanx. The associated area under the curve was 0.623 (95% CI: 0528-0.717, P < 0.05) and the optimal cut-off value to predict fragment occurrence was 2.95° (sensitivity 77.3%; specificity 52.9%). Furthermore, the third metacarpal bone diameter of the left forelimb and height at the withers were significantly (P < 0.05) correlated with the presence of osteochondral fragments in general and within tarsocrural and metatarsophalangeal joints specifically. The area under the curve was 0.585 (95% CI: 0.513-0.656, P < 0.05) with an optimal cut-off value of 152.5 cm (sensitivity 85.1%; specificity 31.2%) for height at the withers to predict presence of osteochondral fragment; to predict the occurrence of osteochondral fragment in any joint on the basis of the third metacarpal bone diameter, the area under the curve was 0.595 (95% CI: 0.524-0.667, P <0.05) and the optimal cut-off value 34.9 mm (sensitivity 52.5%; specificity 64.9%). This study provides information about phenotypic traits associated with osteochondral fragments in horses. Although the diagnostic accuracy of these traits to detect osteochondral fragment was limited, the identification of more phenotypic characteristics could, in the future, make it possible to generate models for accurately identifying individuals at high risk of osteochondral fragments on the basis of their phenotype., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Van Cauter et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Kenney-Doig scale is considered the international standard method for classifying uterine biopsies in mares; however, its objectivity has been questioned by various studies. In the present study, we analysed the degree of agreement between two pathologists when assessing the same set of 201 uterine biopsies, obtaining a slight to moderate level of agreement (κ = .34/κ w  = .57). Subsequently, we developed a numerical scale based on the evaluation of histological parameters, including inflammation, fibrosis, glandular density and lymphatic lacunae. Partial scores were summed to obtain a fifth parameter called Summation. The correlation between both scales was demonstrated (p < .0001), and their combined use resulted in a notable increase in the degree of agreement between the two pathologists (κ = .53/κ w  = .67)., (© 2024 The Author(s). Reproduction in Domestic Animals published by Wiley‐VCH GmbH.)

Increased synthesis and deposition of collagen (COL) in the extracellular matrix (ECM) of equine endometrium contributes to endometrosis. Toll-like receptors (TLRs) are transmembrane receptors involved in the innate immune response, recognized for their role in antigen recognition and previously associated with equine endometritis. The TLRs not only recognize pathogen-associated molecular patterns but also regulate inflammations, fibrosis and cancer. The aim of this study was to explore the relationship between TLR expression at different stages of Kenney and Doig's (K-D) grading and COL1 expression during the follicular phase of the oestrous cycle. Forty samples of endometrial tissues were collected post-mortem from mares on the follicular phase of the oestrous cycle (10 samples of each K-D category). Relative mRNA transcription of TLR-2, TLR-4 and COL1A2 genes was assessed using qPCR, and COL1 protein expression by Western blot analysis. The COL1A2 transcription increased in category IIB when compared to categories I, IIA and III endometria (p < .01). The relative protein abundance of COL1 showed no significant differences between endometrial categories (p > .05). As for the TLRs mRNA transcription, TLR-2/-4 transcripts increased in IIA when compared to the other K-D endometria categories (p < .05). Our findings suggest that TLRs may be involved in the initiation of the endometrial inflammatory response. Additional studies are needed to explore TLRs' potential role as diagnostic markers for monitoring inflammation progression and fibrosis development, as well as their involvement in the mechanisms underlying fibrotic pathways., (© 2024 Wiley‐VCH GmbH. Published by John Wiley & Sons Ltd.)

Objective: To describe the clinical appearance, histopathology, and treatment of equine intraocular melanocytic neoplasia in adult horses., Animals and Procedure: A retrospective review of medical records was conducted. Data recorded included signalment, ocular examination findings, physical examination findings, therapeutic interventions, and case outcomes. Histopathologic characteristics of enucleated globes were evaluated. A Student's t -test was used to evaluate differences in the interval from diagnosis to last known outcome between horses receiving therapeutic interventions and horses undergoing monitoring alone., Results: Of the 55 horses included, Arabian was the most common breed (15/55, 27%). Gray was the most common coat color (85%). Physical examination was completed for 75% of horses at time of diagnosis, and of those, 67% had cutaneous melanoma. The interval from diagnosis to last known outcome was not different ( P = 0.312) between horses that underwent monitoring alone (median: 2.0 y) and those that received treatment (mean: 2.25 y)., Conclusion: Equine intraocular melanocytic neoplasms are highly associated with cutaneous melanoma and gray coat color, and they are more prevalent than previously published reports suggest., Clinical Relevance: A complete ophthalmic examination is indicated for all horses with cutaneous melanoma. Additional research into the timing and rationale for treatment of intraocular melanocytic neoplasia is necessary., (Copyright and/or publishing rights held by the Canadian Veterinary Medical Association.)

Background: This case report details a long-term follow-up of a hoof melanoma with dermo-epidermal activity (resembling Spreading Superficial Melanoma (SSM)) in a bay horse with a history of a right front hoof keratoma. Melanomas involving the horse's foot are seldom reported and usually diagnosed as anaplastic melanomas based on signalment and post-mortem examination. The clinical-pathological characteristics of the foot melanoma in this bay horse are consistent with SSM-like described in humans, which is considered an intermediate malignant tumour attending their biological behaviour. However, a definitive diagnosis is limited by the single case and the lack of references in horses., Case Presentation: A 12-year-old bay Andalusian gelding underwent keratoma removal on the lateral aspect of the hoof wall. A partial resection of the hoof wall was performed for this purpose. Additionally, a plaque-like, hyperkeratotic pigmented lesion, 2 × 2X0,4 cm in size, was observed at the lateral aspect of the coronary band and was also resected for histopathological examination. Microscopically, a melanocytic tumour, characterised by small nests of large polygonal or epithelioid cells infiltrating the basal and suprabasal epidermis, the dermo - epidermal junction, and the superficial dermis, was observed. The neoplastic cells exhibited large euchromatic nuclei, prominent nucleoli, moderate pleomorphism and 4 mitotic figures per 2,37mm 2 ; variable amounts of dark granules (melanin) were present in the cytoplasm, as well as in numerous peritumoral macrophages. The immunophenotype of the tumour cells was PNL2 +  +  + , S100 +  + , AE1/AE3-. A diagnosis of melanoma with dermo-epidermal junction and marked intraepidermal activity (consistent with superficial spreading melanoma) was made. A magnetic resonance imaging (MRI) performed, revealed no further invasion into surrounding structures. Treatment was based on surgical resection and multiple local chemotherapy sessions with cisplatin were applied. The biopsies obtained after treatment showed partial regression of the tumour and different stages of healing. After 26 months of follow-up, there was no signs of malignant spreading into surrounding structures including the pedal bone and distal metastasis but a dark - coloured area persists over the lateral aspect of the coronary band., Conclusions: This case presents a concomitant keratoma and melanoma with dermo - epidermal activity, resembling a spreading superficial melanoma. After a follow - up of 26 months the horse remains healthy and sound providing new information for clinicians and pathologists. Despite the poor prognosis associated with foot malignant melanocytic tumours, it is important that an early and accurate diagnosis is reached through different diagnostic modalities such as advanced imaging techniques and histopathology. Additionally, these findings demonstrate that the current classification and prognosis for equine foot melanomas are insufficient., (© 2024. The Author(s).)

The parotid duct has been reported to be the most common site of sialoliths in horses. In this case report, we described the first confirmed case of the equine sialolithiasis in Slovakia. The work was aimed to describe the transcutaneous approach to removing the sialolith, which manifested as a hard painless mass in the area of the maxillary cheek teeth, in a 14-year-old Slovakian warmblood mare. Pathological-anatomical and histological examination after extirpation confirmed the presence of parotid duct ectasia resulting from calculus. The mineral composition of the sialolith was determined with atomic absorption spectroscopy using X-ray powder diffraction. The sialolith was successfully extirpated transcutaneously, without complications or recurrence., (© 2024. The Author(s).)

Prostaglandins have many roles in the equine reproductive tract, including but not limited to luteolysis, luteal support, ovulation, transport through the uterine tube, uterine contraction, embryonic mobility, inflammation, and fibrosis. Altered secretion of inflammatory proteins are likely to disrupt the balance of endometrial function and could impair fertility. Our overall goal was to measure the expression of several prostaglandin- and inflammation-related genes in mares with different degrees of endometrial histological changes. Our hypothesis was that mares with neutrophilic and lymphocytic plasmocytic inflammation, fibrosis, or different biopsy grades would have altered concentrations of prostaglandin E2 (PGE2) and F2α (PGF2α), as well as altered expression of inflammation- and prostaglandin-related genes, compared to mares with minimal to no histological changes on biopsy evaluation. Forty-five endometrial biopsies from estrous mares were assessed by a reproductive pathologist for the degree of neutrophilic inflammation, lymphocytic and plasmocytic inflammation, and fibrosis, and a biopsy grade was assigned based on the Kenney-Doig system. A low-volume uterine lavage was collected from a subset of twenty-six mares prior to biopsy collection and was used to measure PGE2 and PGF2α concentrations via ELISA. Total RNA was extracted from biopsies and mRNA expression was evaluated for twenty-five genes of interest. A restricted maximum likelihood linear model was used to compare differences of mRNA expression, with a statistical significance set at P < 0.05. There was no difference in the abundance of PGE2 or PGF2α between any of the variables tested. Mares with endometrial biopsy grade I had lower expression of NF-kB, PTGS1 and HPGD compared to grade IIA or IIB (P < 0.05). Mares with neutrophilic inflammation had decreased expression of NF-kB, PTGS1, PTGER4, CBR1, mPGES2 and PTGIS compared to mares without inflammation. Mares with mild or minimal endometrial fibrosis had increased expression of mPGES2 and PTGIS, compared to mares with moderate endometrial fibrosis. In conclusion, several genes were identified to be differentially expressed in mares with histological changes compared to mares with no to minimal histological changes. The presence of inflammation and fibrosis may alter the concentration of prostaglandins in endometrial tissue, which could impair many of the uterine reproductive and immune functions during estrus, affecting early embryo survival., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

This article describes the development of the pathogenic dimorphic fungus Histoplasma capsulatum var. farciminosum (HCF), which is the causative agent of Equine epizootic lymphangitis (EEL), from the mycelial form in the soil to the yeast form in the horse. In this study, the stages and morphology of HCF were identified through histopathological analysis and culture with various samples collected in Ethiopia from 15 horses showing clinical signs of EEL. In equids, especially cart horses in Ethiopia, poor-quality harnesses cause cutaneous wounds, which often attract flies facilitating the transmission of the fungus. Also, HCF infection occurs through open wounds or ocular mucous membranes when horses roll on contaminated damp soil. Respiratory histoplasmosis can occur through inhaling fungal spores, which is rare. HCF microconidia enter the lungs and skin wounds and are phagocytized by tissue-resident macrophages. The spores undergo intracellular replication within the macrophages transitioning into yeasts. The infected macrophages undergo lysis releasing pathogenic yeast cells into the surrounding tissue. Consequently, yeast-rich purulent exudate is produced, contaminating the soil in stables where yeast cells germinate into the mycelial form, and the entire process starts from the beginning., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Objective: The objective of this Case Report was to describe the clinical manifestation and postmortem findings of a horse evaluated for recurrent colic diagnosed with pyloric aplasia and an ectopic duodenal papilla., Animal: 13-year-old Quarter Horse gelding., Clinical Presentation, Progression, and Procedures: The horse was presented to a referral center for signs of colic that were unresponsive to management on the farm. No abnormalities were noted on rectal palpation; however, upon passage of a nasogastric tube, 31 L of net gastric reflux was obtained. Gastroscopy noted grade IV squamous ulceration and moderate glandular ulceration, severe gastric dilatation, an abnormally positioned gastric outflow tract, and an ectopic duodenal papilla leaking bile-like fluid directly into the stomach., Treatment and Outcome: The horse was initially treated with gastroprotectants, promotility agents, and dietary modifications. Following treatment failure and repeated episodes of colic with increasing severity, the horse was euthanized and a necropsy performed. At necropsy, it was confirmed that the aboral aspect of the stomach formed a dilated pouch and continued directly into the proximal duodenum with no discernible pyloric sphincter. The area of the pylorus was delineated by a faint indentation. The ectopic duodenal papilla was traced to the liver., Clinical Relevance: Congenital gastric abnormalities, even in adult horses, should be considered as differential diagnoses when investigating horses presenting with a history of chronic colic. Neither pyloric aplasia nor an ectopic duodenal papilla have been described in the equine literature, and this Case Report raises awareness of the presence of such malformations and their manifestations.

Background: Equine asthma is a common, non-infectious, chronic lung disease that affects up to 80% of the horse population. Strict phenotyping and identification of subclinically asthmatic horses can be challenging. The aim of this study was to describe equine asthma phenotypes (mild, moderate, and severe asthma) defined by BALF cytology and occurrence of clinical signs in a population of privately owned horses and to identify the variables and examination steps with best discriminative potential. The standardised examination protocol included clinical examinations, blood work, airway endoscopy with bronchoalveolar lavage fluid analysis, arterial blood gas analysis and radiography under clinical conditions performed by one veterinarian., Results: Out of 26 horses, four were diagnosed with mild (subclinical), seven with moderate, and seven with severe asthma based on clinical examination and BALF cytology. Eight horses served as controls. Cough with history of coughing was the strongest variable in phenotype differentiation. Factor analysis revealed an increasing clinical variability with disease severity and an overlapping of clinical presentations between phenotypes. Elevated mast cell (4/4 horses) and neutrophil counts (3/4 horses) in bronchoalveolar lavage cytology differentiated mild asthmatic horses from healthy horses. Moderate and severe asthmatic horses were characterised by clinical signs and neutrophil counts., Conclusions: The results indicate that medical history, clinical examination and bronchoalveolar lavage cytology are minimum indispensable steps to diagnose equine asthma and that phenotypes are clinically overlapping. A differentiation of three phenotypes without neutrophil and mast cell counts in bronchoalveolar lavage cytology is not sufficient for clinical diagnostics. A comparably exact diagnosis cannot be achieved by relying on alternative examinations used in this study. Screenings of inconspicuous horses with bronchoalveolar lavage can aid in diagnosing subclinically affected animals, however, group size was small, the procedure is invasive and clinical relevance of slightly elevated cells in bronchoalveolar lavage remains unclear. Clinical relevance could not be clarified in this study, since follow-up examinations or lung function testing were not performed., (© 2024. The Author(s).)

A 16-year-old pony gelding presented with epistaxis and a head tilt. Referral skull radiographs suggested an ethmoid hematoma. Concurrent neurologic abnormalities prompted contrast-enhanced CT of the head and cranial neck, revealing numerous hyperattenuating masses throughout the brain and paranasal sinuses, along with a large osteolytic mass in the second cervical vertebra. The vertebral mass extended into the vertebral canal, causing focal extradural compressive myelopathy. These findings were inconsistent with ethmoid hematoma and metastatic hemangiosarcoma or malignant melanoma were prioritized as potential causes for the clinical signs. Postmortem examination confirmed the sinonasal, intracranial, and vertebral masses as hemangiosarcoma, and additionally revealed innumerable thoracoabdominal metastatic lesions and hemorrhagic foci. A final diagnosis of disseminated hemangiosarcoma was made. In this study, CT proved invaluable for evaluating the severity and characterizing regional disease and neural involvement, directly affecting case management decisions., (© 2024 The Authors. Veterinary Radiology & Ultrasound published by Wiley Periodicals LLC on behalf of American College of Veterinary Radiology.)

Background: Palmar/plantar osteochondral disease (POD) of the metacarpal/tarsal condyles is a common pathological finding in racehorses., Objective: To compare diagnoses, imaging details, and measurements of POD lesions between cone-beam computed tomography CT (CBCT), fan-beam CT (FBCT), and low-field magnetic resonance imaging (MRI) using macroscopic pathology as a gold standard., Study Design: Cross-sectional study., Methods: Thirty-five cadaver limbs from 10 horses underwent CBCT, FBCT, MRI, and macroscopic examination. CT and MR images were examined for presence of POD, imaging details of POD, and measurements of POD dimensions and areas. Imaging diagnoses, details, and measurements were compared with macroscopic examination and between modalities., Results: Forty-eight POD lesions were seen over 70 condyles. Compared with macroscopic examination the sensitivity and specificity of diagnosis were 95.8% (CI95 = 88%-99%) and 63.6% (CI95 = 43%-81%) for FBCT, 85.4% (CI95 = 74%-94%) and 81.8% (CI95 = 63%-94%) for CBCT, and 69.0% (CI95 = 54%-82%) and 71.4% (CI95 = 46%-90%) for MRI. Inter-modality agreement on diagnosis was moderate between CBCT and FBCT (κ = 0.56, p < 0.001). POD was identified on CT as hypoattenuating lesions with surrounding hyperattenuation and on MRI as either T1W, T2*W, T2W, and STIR hyperintense lesions or T1W and T2*W heterogeneous hypointense lesions with surrounding hypointensity. Agreement on imaging details between CBCT and FBCT was substantial for subchondral irregularity (κ = 0.61, p < 0.001). Macroscopic POD width strongly correlated with MRI (r = 0.81, p < 0.001) and CBCT (r = 0.79, p < 0.001) and moderately correlated with FBCT (r = 0.69, p < 0.001). Macroscopic POD width was greater than all imaging modality (p < 0.001)., Main Limitations: Effect of motion artefact in live horse imaging could not be assessed., Conclusions: All imaging modalities were able to detect POD lesions, but underestimated lesion size. The CT systems were more sensitive, but the differing patterns of signal intensity may suggest that MRI can detect changes associated with POD pathological status or severity. The image features observed by CBCT and FBCT were similar., (© 2023 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Transrectal ultrasonography is the best technique for evaluating the ventral aspect of the lumbosacral and sacroiliac regions yet this diagnostic technique does not always lead to a final diagnosis of back pain in horses., Objectives: To describe anatomical variations and acquired pathological bony changes (APBCs) in the lumbosacral and sacroiliac regions detected by ultrasonography (US) and computed tomography (CT) examinations on specimens. We hypothesised that age, body mass, previous use and anatomical variations may be correlated with the presence and/or severity of APBCs., Study Design: Descriptive cadaver study., Methods: Lumbosacroiliac specimens were obtained from 51 horses that died or were euthanised for reasons other than the study and underwent US and CT examinations post-mortem., Results: Forty-two specimens were analysed. The most prevalent lumbosacral disc morphology was type 2 (21/42), and protrusions were found in 15/42 specimens. Abnormal echogenicity of the L5-L6 and lumbosacral discs was detected in 11/42 and 30/42 specimens, respectively. Abnormalities in the size of the L5-L6 disc were found in 10/42 specimens and correlated with promontorium localisation (Cramér's V coefficient [V] = 0.42) and lumbosacral disc morphology (type 1: V = 0.41; type 5: V = 0.69). The most prevalent orientation of the L6 spinous process (SP) was convergent (24/42). The promontoria were mostly located between L6 and S1 (36/42). Lumbosacral spondylosis was detected in 24/42 specimens and spondylolisthesis in one. Age was associated with the severity of APBCs in the sacroiliac joints, lumbosacral intertransverse joints, articular process joints, spondylosis and L6 or S1 bone plate irregularities. Lumbosacral spondylosis or L6 extremitas caudalis irregularity was associated with lumbosacral angulation, variability in the size of the L5-L6 disc and localisation of the promontorium, L6 SP orientation and L6 extremitas caudalis irregularity with abnormal echogenicity of the LS disc., Main Limitations: Lack of information on clinical signs., Conclusions: High variability and prevalence of the anatomical variations and APBCs in the lumbosacroiliac region were observed, and correlations between some anatomical variations and APBCs and between APBCs and age were reported., (© 2023 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Nocardioform placentitis is a poorly understood disease of equine late gestation. The presence of nocardioform, filamentous branching gram-positive bacteria, has been linked to the disease, with Crossiella equi, Amycolatopsis spp., and Streptomyces spp. being the most frequently identified bacteria. However, these bacteria are not found in all clinical cases in addition to being isolated from healthy, normal postpartum placentas. To better understand this form of placentitis, we analyzed the microbial composition in the equine placenta (chorioallantois) of both healthy postpartum (control; n = 11) and nocardioform-affected samples (n = 22) using 16S rDNA sequencing. We found a lower Shannon index in nocardioform samples, a higher Chao1 index in nocardioform samples, and a difference in beta diversity between control and nocardioform samples (p < 0.05), suggesting the presence of dysbiosis during the disease. In the majority of the NP samples (77 %), one of the following genera-Amycolatopsis, Crossiella, Lentzea, an unidentified member of the Pseudonocardiaceae family, Mycobacterium, or Enterococcus -represented over 70 % of the relative abundance. Overall, the data suggest that a broader spectrum of potential opportunistic pathogens could be involved in nocardioform placentitis, extending beyond the traditionally recognized bacteria, resulting in a similar histomorphological profile., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Equine Gastric Ulcer Syndrome (EGUS) occurs with variable prevalence in horses, donkeys, and mules. Due to the particularities of the mucous membranes, the syndrome is made up of Squamous Gastric Disease (ESGD) and Glandular Gastric Disease (EGGD). Given the multifactorial nature and multiple classification systems of the syndrome, significant differences have been reported between prevalence studies performed ante mortem, which are even more remarkable when compared with postmortem evaluations. This study aimed to determine the presence and grade of squamous gastric disease in horses, donkeys and mules immediately after slaughter. The postmortem examination considered the inspection of the squamous region (cardia, dorsal fundus, and margo plicatus) and the classification of the observed lesions. The general prevalence of ESGD in the entire population of study was 83.3 % (78 %, 89 %, and 83 % for horses, donkeys, and mules, respectively), compromising the margo plicatus in all cases. 75 % had more than 5 lesions and 50 % had deep lesions, lesions of varying severity and/or evidence of recent/active bleeding. The prevalence of ESGD was similar in horses, donkeys, and mules subjected to similar handling conditions prior to slaughter, including long-distance traveling, fasting, and stress factors., Competing Interests: Declaration of competing interest The authors declare that they have no know competing financial interest or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Background: Desmitis of the accessory ligament of the deep digital flexor tendon (ALDDFT) is a commonly reported injury. Despite the commonality of this injury, the literature is limited to small case series, with the reported success following treatment varying from 18% to 75%., Objectives: To identify the prognosis and factors associated with a return to work following ALDDFT injury., Study Design: Retrospective case series., Methods: Medical records of horses from four equine hospitals (January 2000 and December 2018) with a diagnosis of desmitis of ALDDFT were reviewed. Data retrieved included case detail, use, history, lameness treatment and follow-up. Success was defined as returning to work. Backward stepwise logistic regression was used to identify variables significantly associated with return to work., Results: Ninety-one horses were included. The mean age was 13.5 years (standard deviation 4.9 years). Thirty-four percent (28/91) of horses were sound at the initial presentation. Sixty-eight percent (62/91) of horses were managed using controlled exercise alone, 28% (29/91) were treated with intra-lesional injection, therapeutic ultrasound, extracorporeal shockwave therapy or desmectomy of the ALDDFT and 3% (3/91) were euthanased without treatment. Sixty-four percent (54/85) of horses returned to work. Horses that were lame at follow-up were less likely to return to work (odds ratio [OR] 107.93, 95% confidence interval [CI] 20.06-580.61, p < 0.001) than those that returned to soundness. Identification of adhesions on ultrasonography was also associated with having reduced odds for return to work when compared to horses without adhesions (OR 0.10, 95% CI 0.01-0.76, p = 0.03)., Main Limitations: Retrospective nature of the study, the potential of selection bias with regards to follow-up., Conclusion: Sixty-four percent (54/85) of horses returned to work following injury of the ALDDFT. Persistence of lameness and adhesion formation were significantly associated with a poor outcome., (© 2023 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Clinicopathological findings and their association with the outcome and development of laminitis in horses with acute diarrhoea has not been investigated in a multicentre study across different geographic regions., Objectives: Describe and compare clinicopathologic findings of diarrhoeic horses between different geographic regions, survival rates and factors associated with non-survival and laminitis., Study Design: Multicentre retrospective case series., Methods: Information from horses with acute diarrhoea presenting to participating institutions between 2016 and 2020 was collected, and clinicopathological data were compared between surviving and non-surviving horses and horses that did and did not develop laminitis. Survival rates and seasonal and geographic differences were also investigated., Results: One thousand four hundred thirty-eight horses from 26 participating institutions from 4 continents were included; 76% survived to discharge with no differences identified between geographic regions. The survival proportion of horses with SIRS and creatinine concentrations > 159 μmol/L was 55% (154/279) compared with 81% (358/437) for those with SIRS and creatinine concentrations < 159 μmol/L (p < 0.001). The survival proportion of horses with SIRS that had an L-lactate concentration > 2.8 mmol/L was 59% (175/298) compared with 81% (240/296) in horses with SIRS and L-lactate concentration < 2.8 mmol/L (p < 0.001). The proportion of horses that developed laminitis was lower in Europe (4%, 19/479) compared with North America (8%, 52/619), Australia (8%, 12/138) and Latin America (11%, 16/146) (p < 0.05). More horses developed laminitis in the summer (46%, 39/85) compared with winter (18%, 15/85), spring (18%, 15/85) and fall (19%, 16/85) (p < 0.01). Horses with laminitis had greater odds of non-survival than those without laminitis (OR: 3.73, 95% CI: 2.47-5.65)., Main Limitations: Not all variables were available for all horses due to the retrospective nature., Conclusions: Clinicopathological findings in horses with acute diarrhoea and their association with survival are similar across geographic regions. However, developing laminitis secondary to diarrhoea is less common in Europe. In addition, factors associated with non-survival were indicative of disease severity and subsequent cardiovascular compromise., (© 2023 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Data on equine lumbar pathology hardly exist in breeds other than Thoroughbreds., Objectives: To describe pathological changes of the osseous lumbar vertebral column in Warmblood horses, Shetland ponies and Konik horses., Study Design: Descriptive post-mortem study., Methods: The lumbar vertebral columns of 34 Warmblood horses, 28 Shetland ponies, and 18 Konik horses were examined by computed tomography (CT). Osteoarthritis (OA) of articular processes (APJs), OA of intertransverse joints (ITJs), intervertebral disc (IVD) mineralisation, impingement of spinous (SPs) and transverse (TPs) processes and spondylosis were scored. Breed differences in prevalence and severity of pathologies were analysed by linear regression analysis and by calculating Spearman's rank correlation coefficients (r s )., Results: In Warmblood horses, the prevalence of OA of APJs, impingement of SPs and TPs was respectively 90%, 36%, and 35%, significantly higher than in the other breeds (p < 0.001). In Konik horses, IVD mineralisation (40%) and spondylosis (10%) were more frequent than in Warmbloods and Shetland ponies (p = 0.03). Severity score for OA of ITJs was highest in Shetland ponies (p < 0.001). For impingement of SPs, severity score was highest in Warmbloods (p = 0.03), and of TPs lowest in Shetland ponies (p = 0.003). For all parameters, except for spondylosis in Shetland ponies, there was a positive correlation between percentage of vertebrae affected and age, with IVD mineralisation scores increasing faster in Konik horses (p < 0.001). In all breeds, there was also a positive relation between scores of severity and age for OA of APJs and ITJs and for IVD mineralisation, with severity scores increasing faster in Shetland ponies (p = 0.04). Strong left/right correlations of the severity scores were seen for OA of the APJ, ITJ, impingement of TPs, and paramedian spondylosis (r s  = 0.74-0.86, all p < 0.001)., Main Limitations: Clinical histories were not available., Conclusions: There are distinct breed differences between prevalence and severity of osseous pathologies of the lumbar spine. Warmblood horses have higher scores for most pathologies with IVD mineralisation being more important in Konik horses and OA of ITJs in Shetland ponies., (© 2023 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

A 3-year-old American Saddlebred gelding presented for progressive tetraparesis, ataxia, and cervical hyperaesthesia. Radiographic myelography identified spinal cord compression at C6-7 in neutral, extended, and flexed positions and at C4-5 in the flexed position. CT myelography and postmortem MRI identified severe vertebral canal stenosis/compression at C6-7. MRI further identified severe intervertebral disc herniation at C6-7 with intramedullary changes. Disc protrusion was confirmed macroscopically at postmortem. Lesions consistent with compressive myelopathy were confirmed microscopically at C6-7. This is the first report of equine disc protrusion and myelocompression confirmed by multiple advanced imaging modalities and postmortem examination., (© 2024 American College of Veterinary Radiology.)

Background: Focal hyperintense lesions within the navicular bursa emanating from the dorsal border of the deep digital flexor tendon (DDFT) can be recognised on T1-weighted magnetic resonance images (MRI) and have been attributed to lameness in horses. Removal of these lesions, also referred to as synovial masses, by navicular bursoscopy is currently recommended., Objectives: To investigate the correlation between MRI and navicular bursoscopic findings. It is hypothesised that the prognosis following surgery is proportional to the size of the DDFT lesion., Study Design: Retrospective analysis of clinical records., Methods: Horses undergoing standing low-field MRI and navicular bursoscopy with >1 year follow-up were included. A grading system was developed to classify the size of synovial mass(es) and lesion(s) of the DDFT on MRI and at surgery. Generalised estimating equations were used to evaluate the association between MRI findings and surgery and between outcome and severity of the tendon injury., Results: Fifty-nine horses presenting over a 15-year period (2006-2021) fulfilled inclusion criteria. Ninety navicular bursae were examined both on MRI and endoscopically. There was strong correlation between the size of synovial masses and tendon lesions on MRI and bursoscopy (p < 0.001, OR: 25.61, 95% CI 8.71-75.29 and p < 0.001, OR: 7.34, 95% CI 2.70-19.92, respectively). Size of tendon lesion and synovial mass had no impact on prognosis (p = 0.3, OR: 1, 95% CI 1-1 and p = 0.1, OR: 1, 95% CI 1-1, respectively), which was guarded (30.5% return to previous level of exercise)., Main Limitations: Performance data for conservatively treated horses with MRI-detected synovial masses was not considered, nor was the effect of navicular bursal effusion. Horses were not randomly assigned to treatment protocols., Conclusion: There is good correlation between MRI and bursoscopic findings of DDFT lesions and synovial masses within the navicular bursa, with no false positives. Size of the synovial masses and DDFT lesions does not influence prognosis following navicular bursoscopy., (© 2023 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Non-septic tenosynovitis is a clinically relevant and often performance limiting musculoskeletal injury in the horse., Objectives: To review the published literature to determine which tendon sheaths are commonly affected by non-septic tenosynovitis and to describe the most frequently reported pathological lesions, outcomes, and surgical complications in equine non-septic tenosynovitis., Study Design: Systematic review., Methods: Literature searches were conducted in July 2021 from the online search engines PubMed, Scopus, Web of Science Core, VetMed Resource and ProQuest Theses & Dissertations. The inclusion criteria followed a participants, interventions, comparisons, outcome and study design (PICOS) approach. For inclusion, studies had to include live equids with non-septic tenosynovitis of any tendon sheath. Studies were excluded if they only described non-equine species, if they included data only on non-tendon sheath structures, or if they included data exclusively on cases of septic or contaminated tendon sheaths. Determination of non-sepsis relied on the diagnosis of the original authors; however, if non-sepsis was not explicitly specified, then cases that had a history of contamination of the sheath, a wound near the sheath or a positive bacterial culture were excluded from analysis. Data analysed included the distribution of structures affected by non-septic tenosynovitis, the most common pathological lesions identified within each sheath, and the most frequently reported surgical complications of non-septic tenosynovitis. The quality of each study was assessed using a methodological quality analysis., Results: A total of 85 studies describing non-septic tenosynovitis in the horse were included. Across all 85 studies, there were a total of 2449 tendon sheaths in 2101 horses reported to be affected by non-septic tenosynovitis. The digital flexor sheath was the most reported structure to be diagnosed with non-septic tenosynovitis: 41/85 (48%) studies examined the digital flexor sheath exclusively, followed by the carpal flexor sheath, tarsal flexor sheath, carpal extensor sheaths, tarsal extensor sheaths, and one case of biceps brachii non-septic tenosynovitis. For most tendon sheaths, the most common pathological lesion was an intrathecal tear of a soft tissue structure, including tears of the deep digital flexor tendon and tears of the manica flexoria. Bilateral disease was most common in the carpal flexor sheath, where distal radial physeal exostoses were the most common pathological lesions. Less common causes of non-septic tenosynovitis included neoplasia, fracture of a bone adjacent to a tendon sheath, and mineralisation of an intrathecal tendon. The likelihood of return to previous level of athletic function following non-septic tenosynovitis of most structures was approximately 50%, and the most common complication was persistent effusion following tenoscopy. While iatrogenic infection following surgery was uncommon, it was most likely following tenoscopy of the digital flexor sheath., Conclusion: Non-septic tenosynovitis is commonly reported in equine athletes, with intra-thecal tears of the deep digital flexor tendon, superficial digital flexor tendon and manica flexoria frequently reported. Directions for future research include more thorough assessment of and reporting of complications following non-septic tenosynovitis and correlation of characteristics of intrathecal pathological lesions with clinical outcomes., (© 2023 EVJ Ltd.)

Background: Reports of leptospirosis in horses are limited., Objectives: To describe the clinical and diagnostic findings of acute systemic leptospirosis in horses., Animals: Eleven client-owned horses presented to an equine hospital because of acute onset of disease between 2015 and 2023., Methods: Retrospective case series. Horses diagnosed with leptospirosis by 1 or more of urine PCR, serologic microscopic agglutination test (MAT), and histopathology., Results: Common clinical signs included lethargy (10), anorexia (10), fever (9), tachypnea (9), abnormal lung sounds (9), and epistaxis (6). Acute kidney injury was present in all cases. Evidence of pulmonary hemorrhage and liver disease was found in 8 (73%) and 6 (55%) horses, respectively. In 6 (55%) horses, kidneys, lungs, and liver were affected. Urine quantitative polymerase chain reaction for detection of pathogenic Leptospira spp. was positive in 6 (55%) cases. On serology Leptospira interrogans serovar Australis, Autumnalis, and Bratislava accounted for 86% of all titers ≥1 : 800. Overall case fatality rate was 4/11 (36%). Main findings on necropsy were tubular necrosis, interstitial nephritis, hemorrhage in the alveoli, pulmonary edema, periportal hepatitis and necrosis, cholestasis, and cholangitis., Conclusions and Clinical Importance: Leptospirosis should be considered as a differential diagnosis in horses with evidence of acute systemic inflammation and acute renal injury, epistaxis, or hepatic disease. For increased likelihood of identifying positive cases, both MAT serology and urine PCR should be performed., (© 2024 The Author(s). Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.)

The diagnosis of neoplasia in the horse is both simple and extremely challenging, depending on the type of neoplasm and its location. Obtaining an accurate diagnosis of a neoplastic condition is key to formulating an appropriate treatment plan if possible or developing a palliative plan if curative treatment options do not exist. A combination of historical features, clinical examination findings, and diagnostic testing typically allow a working diagnosis of neoplasia to be made, with a definitive diagnosis requiring the identification of neoplastic cells in a sample or tissue., Competing Interests: Disclosure No conflicts of interest of funding declared by either author., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Lymphoma and myeloproliferative diseases in horses are relatively uncommon. The clinical signs, prognosis, and treatment options depend upon the anatomic location and subtype. Significant gaps in knowledge remain regarding prevalence, pathogenesis of different subtypes, antemortem diagnostic tests, response to treatment, and standardized treatment protocols. However, treatment options are available, accessible on the farm, and could improve quality of life and prolong survival., Competing Interests: Disclosure The authors declare no conflict of interest., (Copyright © 2024 Elsevier Inc. All rights reserved.)

There are a number of unusual tumors in the horse. Gross tumor characteristics, anatomical location, and signalment may assist with identification. Clinical pathology is often unrewarding with non-specific findings, while fine needle aspirates may not obtain sufficient tissue material to confirm a diagnosis. Although regular staining of biopsy material may be sufficient, immunohistochemistry markers may be required, especially in less differentiated tumors. The prognosis is dependent on the type, location, tumor size as well as on metastatic spread. A selection of unusual and rare tumors that the clinician is more likely to encounter is discussed., Competing Interests: Disclosure The authors have nothing to disclose., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Thoracic neoplasia often presents with generalized and nonspecific clinical signs and should be considered as a differential especially when patients are nonresponsive to therapeutic intervention for more common differential diagnoses of respiratory disease (such as equine asthma) and where there is evidence thoracic and/or abdominal effusion upon examination. Antemortem diagnosis can be challenging and working closely with a pathologist to differentiate the respective neoplasia is helpful. Early recognition and appropriate management of thoracic neoplasia are vital for patient welfare as rapid disease progression can be relatively quick, and/or the relatively advanced stage of disease in which these patients frequently present., Competing Interests: Disclosure The authors have nothing to disclose., (Copyright © 2024 Elsevier Inc. All rights reserved.)

This article reviews the different types of equine non-neoplastic and neoplastic oral and sinonasal tumors and describes their known prevalence and general characteristics. The clinical and ancillary diagnostic findings (primarily radiography and endoscopy, and increasingly computed tomography) for each type of growth that can aid diagnosis are described. Most lesions require a histopathological confirmation of the diagnosed growth. The possible treatments and prognosis for these growths are briefly described., Competing Interests: Disclosure The author has nothing to disclose., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Neoplasia has been reported to involve the majority of the urinary system of the horse, with tumors affecting the kidneys and bladder most comprehensively described. Primary tumors of the external genitalia are relatively common in the horse and are easily identified on clinical examination while primary tumors of the upper urogenital tract are uncommon. This article will highlight the common tumors, their clinical presentations, and discuss potential medical and surgical treatment options available. The less common neoplasms will be mentioned but not discussed in depth., Competing Interests: Disclosure The authors have nothing to disclose., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Gastrointestinal neoplasia is uncommon in horses. Clinical signs can be vague and advanced testing, including biopsy, exploratory surgery, and/or advanced imaging may be required for diagnosis. Prognosis varies by location, organ involved and is frequently poor to grave., Competing Interests: Disclosure No conflicts of interest to declare., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Cancer is disease of the genome. The Hallmarks of cancer are a way of thinking of cancer to help rationalize what occurs in this disease process. A solid tumor is a complex of normal and neoplastic cells, arising through an evolutionary process to survive and grow. By understanding how normal cellular mechanisms are subverted to promote cancer we can refine our approach to improve outcomes. It gives us opportunities to prevent some cancers and allowing earlier diagnosis. We can refine conventional diagnostic tools and give more accurate prognoses. It offers novel targets to improve treatment of cancers, allowing personalized medicine., Competing Interests: Disclosure There are no affiliations other than I (S. Murphy) work for the University of Edinburgh., (Copyright © 2024 Elsevier Inc. All rights reserved.)

A 16-year-old warmblood mare was referred with a progressive history of behavioral changes and left-sided blindness. Following neuroanatomical localization to the forebrain, magnetic resonance imaging of the head revealed a well-delineated, 4.5 cm in diameter, round pituitary mass causing marked compression of the midbrain and optic chiasm. Euthanasia was recommended but declined by the owners. Veterinary specialists and a human neurosurgeon collaboratively prepared for surgical case management. A novel navigated transmandibular lateral transsphenoidal approach was developed to access the region of the sella turcica and practiced on cadaver specimens. The horse was anesthetized and placed in sternal recumbency with the head above the heart line. Using a cone beam computed tomography (CBCT)-coupled navigation system, a navigated pin traversing the vertical ramus of the mandible and the lateral pterygoid muscle was placed in a direct trajectory to the predetermined osteotomy site of the basisphenoid bone. A safe corridor to the osteotomy site was established using sequential tubular dilators bypassing the guttural pouch, internal and external carotid arteries. Despite the use of microsurgical techniques, visualization of critical structures was limited by the long and narrow working channel. Whilst partial resection of the mass was achieved, iatrogenic trauma to the normal brain parenchyma was identified by intraoperative imaging. With consent of the owner the mare was euthanized under the same general anesthesia. Post-mortem magnetic resonance imaging and gross anatomical examination confirmed partial removal of a pituitary adenoma, but also iatrogenic damage to the surrounding brain parenchyma, including the thalamus.

Squamous cell carcinomas are a very common tumor type in horses, and are found in a variety of dermatologic and non-dermatologic locations. Metastasis is common, even at the first presentation of the disease, and a full staging workup is therefore strongly recommended to direct treatment and assist with prognostication. Wide surgical excision remains the treatment of choice in most cases, but recurrence is common, and adjunctive therapy may be indicated to improve the long-term prognosis., Competing Interests: Disclosure The author has no affiliations other than I work for the University of Cambridge., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Lymphoma is the most common tumor of hematopoietic origin in horses. The course of the disease and clinical signs vary greatly, depending on tumor location and extent. The aim of this report is to describe the occurrence of T-cell-rich oral large B-cell lymphoma with marked local infiltration in a 25-year-old Crioula mare. The mare showed an increase in volume on the right side of its face, dyspnea, anorexia, and progressive weight loss. The clinical assessment showed that the lesion was located in the rostral and caudal sinuses and was markedly invasive to adjacent structures. The autopsy revealed a yellow mass with a soft to firm consistency, infiltrating multiple bones in the skull, and extensively invading the hard palate and masseter muscle. Histologically the mass comprised an undifferentiated malignant neoplasm characterized by a densely cellular neoplasm composed of large CD20 + neoplastic B-lymphocytes admixed with sheets of small, CD3 + reactive T-lymphocytes supported by delicate fibrovascular stroma leading to the diagnosis of oral T-cell-rich large B-cell lymphoma., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Penile squamous cell carcinomas (SCCs) are common, potentially life-threatening neoplasms of horses. They are well-recognized to be caused by Equus caballus papillomavirus (EcPV) type 2, although EcPV2 cannot be detected in all cases. A 23-year-old standardbred gelding developed multiple penile in situ and invasive SCCs that contained histological evidence of PV infection. By using both consensus and specific PCR primers, these lesions were found to contain EcPV7 DNA, but not DNA from EcPV2 or any other PV type. To determine how frequently EcPV7 is present in equine penile SCCs, specific primers were used to detect EcPV2 and EcPV7 in a series of 20 archived samples. EcPV7 was the only PV detected in one, both EcPV2 and 7 were detected in five, and only EcPV2 was detected in 14 SCCs. EcPV7 DNA was also detected in three of 10 archived oropharyngeal SCCs, although only as a co- infection with EcPV2. This is the first report of EcPV7 causing disease in horses. These results suggest EcPV7 could cause a subset of equine penile SCCs, and this is the first evidence that PV types other than EcPV2 can cause these neoplasms. The detection of EcPV7 in the oropharyngeal SCCs suggests a potential role of this PV type in the development of these SCCs. There were no clinical or histological features that differentiated lesions containing EcPV7 DNA from those containing EcPV2 DNA. If EcPV7 causes a proportion of equine penile SCCs, vaccines to prevent EcPV2 infection may not prevent all equine penile SCCs., Competing Interests: Declaration of Competing Interest None of the authors of this paper has a financial or personal relationship with other people or organisations that could inappropriately influence or bias the content of the paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Inflammatory bowel disease (IBD) in the horse encompasses a group of infiltrative gastrointestinal disorders resulting in malabsorption, maldigestion, weight loss, colic, and sometimes diarrhea. The type of IBD can be classified as granulomatous, lymphocytic-plasmacytic, or eosinophilic enterocolitis. The diagnosis of IBD in equids is based on consistent clinical signs and clinicopathologic findings in conjunction with confirmatory histopathology from a gastrointestinal biopsy. Treatment usually consists of a combination of immunosuppressive medications, anthelmintics, and dietary modifications. The prognosis of IBD in horses is variable and dependent on the horse's response to treatment; however, horses can show improvement or resolution of clinical signs., Competing Interests: Disclosure The author has nothing to disclose., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The present study describes the morphological and immunohistochemical characteristics of a case of diffuse seminoma in a 16-year-old male mixed-breed horse. According to the owner, the animal's left testicle had been gradually increasing in size over a period of 2 months. On palpation, the testicle had a firm consistency, with no sensitivity to digital pressure, was adhered to the scrotum and measuring 16 cm × 8 cm. In the ultrasound examination, it presented a heterogeneous texture and areas of hypoechogenic echogenicity without visualization of the mediastinum. Therefore, the bilateral orchiectomy was performed. After the surgical procedure, it was found that the affected testicle presented a firm mass measuring 9 cm × 7 cm × 3.5 cm. Histologically, a multilobulated, non-encapsulated and invasive tumour mass was found, which replaced the seminiferous tubules, consisting of polygonal cells arranged in a mantle that varied from cohesive to loosely cohesive, supported by a scarce fibrous stroma. In the immunohistochemical examination, the neoplastic cells showed positive immunolabelling for OCT4 and C-KIT. In this report, the physical examination combined with the ultrasonographic examination were fundamental to the therapeutic management of the case, and the final diagnosis was made after histopathological and immunohistochemical tests., (© 2024 Wiley‐VCH GmbH. Published by John Wiley & Sons Ltd.)

A study comprising 74 colic and 74 control horses admitted to an animal hospital was performed. Faecal samples were collected and analysed for dry matter concentration, particle size distribution using wet-sieving, and sand presence through a sand sedimentation test. Data on horse breed, age, gender and basic feeding variables was collected and analysed using χ 2 -tests. Faecal dry matter concentration, particle size distribution and sand score was compared between colic and non-colic horses, and between horses with different colic types, using one-way ANOVA. Results showed that colic and non-colic horse groups were similar in breed, age, gender and basic feeding variables. Faecal dry matter concentration, particle size distribution and sand score were similar among colic and non-colic horses. Horses diagnosed with "unknown colic cause" had higher proportion of particles >0.5 <1.0 mm size compared to horses with colic due to impactions in caecum or colon, torsion or gas accumulation (P<0.05), but this difference was very small and most likely not of biological importance. Faecal dry matter concentration and sand score were similar among horses with different types of colic. Increased knowledge of the composition of particles of different size in equine faeces may enhance our understanding of digesta passage rate in colic and non-colic horses, which is needed to develop preventative measures of certain types of colic., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author. Published by Elsevier Inc. All rights reserved.)

Objective: To establish racing prognosis in Thoroughbred yearlings with proximal sagittal ridge osteochondral lesions and compare them to dorsoproximal and palmar/plantar first phalanx osteochondral lesions., Animals: A total of 47 horses had proximal sagittal ridge lesions, 34 had palmar/plantar first phalanx lesions, and 115 had dorsoproximal first phalanx lesions., Study Design: Retrospective case series., Methods: Medical records of Thoroughbred yearling racing prospects treated arthroscopically for fetlock osteochondral lesions were reviewed. Data were collected from a public database, including the ability to train and race, earnings, starts, wins, and placed races. Racing prognosis was analyzed and compared between three lesion locations., Results: Of the proximal sagittal ridge group, 76.6% raced, 65.71% of the palmar/plantar first phalanx group, and 74.58% of the dorsoproximal first phalanx group. Career length was similar for all lesions. A lower number of "starts" in the group "five years old and older" was found for the dorsoproximal first phalanx group compared to the cohort with proximal sagittal ridge lesions. Mares had more "earnings" at two years old but fewer "starts" at "five years old" compared to colts and geldings. Forelimb lesions were predictive for fewer total career starts., Conclusion: Proximal sagittal ridge lesions had similar prognoses to dorsoproximal and palmar/plantar first phalanx lesions. In older horses, there was an increase in the number of starts for the proximal sagittal ridge group compared to the dorsoproximal first phalanx group. Mares and forelimb lesions were associated with decreased racing starts., Clinical Significance: These findings aid in prognostication for Thoroughbreds with osteochondral lesions removed arthroscopically in the fetlock joint., (© 2024 American College of Veterinary Surgeons.)

Approximately 1-2 per 100,000 young athletes die from sudden cardiac death (SCD) and extreme exercise may be associated with myocardial scar and arrhythmias. Racehorses have a high prevalence of atrial fibrillation (AF) and SCD but the presence of myocardial scar and inflammation has not been evaluated. Cardiac tissues from the left (LAA) and right (RAA) atrial appendages, left ventricular anterior (LVAPM) and posterior (LVPPM) papillary muscles, and right side of the interventricular septum (IVS-R) were harvested from racehorses with sudden cardiac death (SCD, n = 16) or other fatal injuries (OFI, n = 17), constituting the athletic group (ATH, n = 33), and compared to sedentary horses (SED, n = 10). Horses in the ATH group had myocyte hypertrophy at all sites; increased fibrosis at all sites other than the LAA; increased fibroblast infiltration but a reduction in the overall extracellular matrix (ECM) volume in the RAA, LVAPM, and IVS-R compared to SED horses. In this horse model, athletic conditioning was associated with myocyte hypertrophy and a reduction in ECM. There was an excess of fibrocyte infiltration and focal fibrosis that was not present in non-athletic horses, raising the possibility of an exercise-induced pro-fibrotic substrate., (© 2024. The Author(s).)

Objective: To describe the treatment of subcutaneous lipomas in the horse., Animals: 3 horses., Clinical Presentation: The horses were aged 1 to 2 years old, with lipoma of the abdomen, prepuce, and tarsus., Results: All cases had surgical removal of the masses under general anesthesia. Recurrence of an invasive abdominal lipoma occurred in case 1 at the exit site of a passive drain. The recurrence was treated unsuccessfully with injectable cisplatin, and a second revision surgery with the use of an active drain resulted in resolution. In case 2, complete resection of an encapsulated lipoma of the lateral prepuce was successful with no recurrence. In case 3, incomplete resection of a tarsal lipoma resulted in a sound horse, with no further growth. Histopathologic analysis revealed that all masses were composed of well-differentiated adipocytes with no evidence of malignancy., Clinical Relevance: Subcutaneous lipomas are relatively rare and affect horses primarily ≤ 2 years of age. They are benign, although their presence can be deleterious due to invasion of local structures or the impact on normal locomotion. The margins of invasive tumors are difficult to identify due to their integration with normal tissue. Incomplete removal may allow for mass recurrence. Active suctions drains are beneficial if dead space is a concern.

Background: Vulvar squamous cell carcinoma (VSCC) has been recently associated with Equus caballus papillomavirus type 2 (EcPV2) infection. Still, few reports concerning this disease are present in the literature., Objective: To describe a case of naturally occurring EcPV2-induced VSCC, by investigating tumour ability in undergoing the epithelial-to-mesenchymal transition (EMT)., Study Design: Case report., Methods: A 13-year-old Haflinger mare was referred for a rapidly growing vulvar mass. After surgical excision, the mass was submitted to histopathology and molecular analysis. Histopathological diagnosis was consistent with a VSCC. Real-time qPCR, real-time reverse transcriptase (RT)-qPCR and RNAscope were carried out to detect EcPV2 infection and to evaluate E6/E7 oncogenes expression. To highlight the EMT, immunohistochemistry (IHC) was performed. Expression of EMT-related and innate immunity-related genes was investigated through RT-qPCR., Results: Real-time qPCR, RT-qPCR and RNAscope confirmed EcPV2 DNA presence and expression of EcPV2 oncoproteins (E6 and E7) within the neoplastic vulvar lesion. IHC highlighted a cadherin switch together with the expression of the EMT-related transcription factor HIF1α. With RT-qPCR, significantly increased gene expression of EBI3 (45.0 ± 1.62, p < 0.01), CDH2 (2445.3 ± 0.39, p < 0.001), CXCL8 (288.7 ± 0.40, p < 0.001) and decreased gene expression of CDH1 (0.3 ± 0.57, p < 0.05), IL12A (0.04 ± 1.06, p < 0.01) and IL17 (0.2 ± 0.64, p < 0.05) were detected., Main Limitations: Lack of ability to generalise and danger of over-interpretation., Conclusion: The results obtained were suggestive of an EMT event occurring within the neoplastic lesion., (© 2023 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

A newborn Thoroughbred filly presented with a large mass located on the ventro-rostral aspect of the mandible. The mass was surgically removed under general anaesthesia. Upon gross examination, the mass was well circumscribed with a heterogeneous lobulated appearance. The results of histopathology and immunohistochemistry were consistent with a diagnosis of congenital fetal rhabdomyoma. On follow-up at six months post-surgical excision, no abnormalities were noted on clinical examination., (© 2024 The Author(s). Veterinary Medicine and Science published by John Wiley & Sons Ltd.)