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Topic:Histopathology
Histopathology in horses involves the microscopic examination of tissue samples to study the manifestations of disease. This field provides insights into the structural and cellular changes that occur in equine tissues as a result of various pathological conditions. Common applications of histopathology in equine medicine include the diagnosis of neoplastic, inflammatory, and degenerative diseases. Techniques such as tissue staining and immunohistochemistry are employed to identify specific cellular components and pathological markers. This page aggregates peer-reviewed research studies and scholarly articles that explore the methodologies, findings, and implications of histopathological investigations in equine health.
Pulmonary cryptococcosis with an endobronchial cryptococcoma in a Warmblood mare. This report describes pulmonary cryptococcosis with a large endobronchial cryptococcoma in an 8-year-old Warmblood mare. The mare was presented initially with fever and lethargy, and clinical signs typical of bacterial pneumonia. Markedly elevated serum amyloid A (SAA) concentrations indicated a severe systemic inflammatory response. Over a period of 6 wk, the condition progressively worsened and was refractory to multiple courses of broad-spectrum antimicrobial therapy as administered in a field setting. Diagnostic imaging following referral revealed extensive consolidation of the left lung a...
Surgical Management of Unilateral Maxillary Molar Teeth Impaction in a Horse. Impaction of equine permanent cheek teeth is most commonly reported in the mandible, whereas maxillary involvement is rare. This report describes an uncommon presentation of congenital impaction of 3 successive maxillary molar teeth in a 4-year-old mare. Computed tomography revealed complex spatial relationships between the impacted teeth, the sinus floor and adjacent structures, which were not fully appreciated on conventional radiography and were essential for surgical planning. Surgical extraction via a maxillary sinus bone flap permitted controlled sectioning and subsequent removal of all ...
Multi-Detector Helical Computer Tomography, Transrectal Ultrasonography and Histology of the Lumbosacral Area: A Comparative Study in Warmblood Horse Cadavers. Pain arising from the lumbosacral region is a recognized cause of poor performance and impaired welfare in horses. However, structural changes in the intertransverse joints (ITJs), lumbar articular process joints (APJs), and lumbosacral intervertebral discs (LSDs) may also occur in asymptomatic horses, complicating interpretation of imaging findings.This study evaluated these structures in 14 middle-aged Warmblood cadavers that were not lame according to the owners prior the onset of the problem that resulted in euthanasia or slaughter and correlated ultrasonographic (US) and computed tomograp...
Histomorphometric and Histochemical Changes in the Mare Tuba Uterina During the Oestrous Cycle and Follicular Cyst Condition. This study evaluated histomorphometric and histochemical changes in the mare tuba uterina during different reproductive stages and under follicular cyst conditions. Forty nonpregnant mares were classified into follicular, luteal, post-ovulation and follicular cyst groups (n = 10/group). Histological evaluation of the isthmus, ampulla and infundibulum was performed using haematoxylin and eosin staining, while periodic acid-Schiff (PAS) staining was used to assess epithelial secretory activity. Morphometric parameters included number of primary mucosal folds, fold length, epithelial height a...
Wound healing of experimental cutaneous wounds in horses: comparison between a topical formulation containing powdered coconut water and an antimicrobial ointment. Skin wounds in horses often present prolonged healing, stimulating the search for alternative topical therapies. To date, there are no experimental studies in horses evaluating topical formulations containing powdered coconut water. Objective: To compare the early macroscopic and morphometric wound-healing outcomes and the histopathological findings at day 14 in experimental cutaneous wounds in horses treated with a topical formulation containing powdered coconut water versus a reference antimicrobial ointment. Methods: Eight clinically healthy horses received two standardized circular skin wo...
Intratracheal Leiomyosarcoma in a 13-Year-Old German Riding Pony Mare. A 13-year-old German Riding Pony mare was referred for evaluation of progressive respiratory noise and mixed dyspnoea, which rapidly deteriorated to respiratory distress. Clinical examination revealed marked rattling inspiratory and expiratory tracheal sounds and severe, rattling, vesicular lung sounds. Arterial blood gas analysis demonstrated moderate hypoxaemia (partial pressure of arterial oxygen 76 mmHg at rest). Upper airway endoscopy identified a pink, cauliflower-like pedunculated mass originating from the dorsal tracheal wall approximately 15 cm cranial to the tracheal bifurcation, cau...
Concurrent Small Intestinal Neoplasia And Large Colon Volvulus In A Standardbred Yearling. Large colon volvulus is a common, life-threatening cause of colic in horses. Gastrointestinal neoplasia is a rare cause of abdominal pain in young horses. A 1-year-old Standardbred colt presented with acute colic unresponsive to medical treatment. An exploratory laparotomy identified extensive gastrointestinal pathology, and euthanasia was elected due to a poor prognosis. Necropsy revealed a 360-degree volvulus of the caecum and large colon with adhesions, enterotyphlocolitis, and a well-circumscribed mesenteric mass arising from the small intestine. Histopathology in combination with immunohi...
Testicular Disorders in Equids: A Case Series. Equine testicular disorders represent a diverse group of conditions that impact the longevity of a stallion's breeding career. Stud farm veterinarians should be familiar with the variety of clinical presentations and diagnostic options for these conditions. This retrospective case series reports 57 cases of testicular abnormalities in stallions and donkeys presented to the clinic for further diagnostics and treatment. These disorders included neoplasia (three unilateral and one bilateral seminoma; two Sertoli cell tumors; two Leydig cell tumors; and one malignant mixed sex cord-stromal tumor),...
Clinical outcomes of a novel flowable calcium silicate cement in equine endodontic treatment. Orthograde endodontic treatment of equine cheek teeth is performed infrequently with variable success rates of obturation with calcium hydroxide paste (CHP). A novel flowable calcium silicate cement (eCSC) formulated for use as an obturation material in equine teeth has demonstrated acceptable canal filling volumes and evidence of dentinal tubule penetration. However, clinical outcomes of eCSC-obturated equine teeth have not been reported. Objective: To report the clinical outcomes of orthograde endodontic treatment using eCSC. Methods: Retrospective case series. Methods: Horses that underwent...
Rethinking Equine Cystitis: Evidence from Four Atypical Clinical Presentations. In this case series, four equines were diagnosed with cystitis, resulting in divergent clinical outcomes. Three animals achieved complete clinical resolution without recurrence, whereas one required euthanasia due to progressive clinical deterioration. All diagnoses were established through a dual-modality investigative protocol comprising cystoscopic evaluation and histopathological examination of bladder mucosal biopsies. The cohort exhibited considerable etiological heterogeneity. One case was classified as chronic idiopathic cystitis, while another was attributed to an opportunistic bacter...
Hepatic encephalopathy associated with extensive hepatic diaphragmatic herniation in an adult horse. Diaphragmatic hernia in horses is a rare condition, most commonly presenting with signs of colic and, less frequently, respiratory compromise. Hepatic herniation through a diaphragmatic defect with secondary hepatic failure and encephalopathy has rarely been documented in horses. Methods: A 5-year-old Mangalarga Marchador stallion was evaluated for progressive neurological deterioration, including obtundation, head pressing, ataxia, and circling. Serum biochemistry revealed severe hepatobiliary dysfunction, characterised by increased gamma-glutamyl transferase and alkaline phosphatase activiti...
Penile and preputial pythiosis in Saudi Arabian horses: clinicopathological features and surgical outcomes. Pythiosis, caused by , is a chronic granulomatous disease of horses characterized by invasive, ulcerative, and pyogranulomatous cutaneous lesions. Involvement of the external genitalia is uncommon and remains poorly characterized, particularly regarding environmental exposure and treatment outcomes. This study aimed to describe the epidemiological pattern, clinicopathological features, diagnostic findings, and surgical outcomes of penile and preputial genital pythiosis in a hospital-presented horse cohort. Unassigned: A retrospective study was conducted on 123 horses presented with cutaneous u...
Clinical and pathologic findings of splenic tumours in four horses: a case series. Splenic tumours are rare in horses, with limited published literature consisting primarily of individual case reports and one hepato-splenic lymphoma case series. This case series analyses the clinical presentation, diagnostic findings and clinical outcomes of four cases of splenic neoplasia that presented to a university referral hospital over a three year period (2022-2025). Methods: Presented are two cases of primary splenic lymphoma, and two cases of metastatic melanoma. Three cases (75%) presented with chronic, non-specific clinical signs including weight loss, colic and ventral oedema. O...
Morphological investigation of myocardial sleeves with potential relevance to atrial fibrillation in Norwegian-Swedish Coldblooded Trotters. Myocardial sleeves (MSs) are thin layers of cardiac muscle that extend from the atria into the caval and pulmonary veins. They are recognised as important structures in both initiating and maintaining atrial tachycardia, and especially atrial fibrillation (AF), which is the most clinically important cardiac arrhythmia in horses with a reported prevalence of 1.3-2% in Standardbred racehorses. In contrast, the Norwegian-Swedish Coldblooded Trotter (NSCT) has a much lower prevalence of AF despite experiencing similar physical demands. The purpose of this study was to describe the macro-, and micr...
MUSCULAR SARCOCYSTIS INFECTIONS IN HORSES IN NORTH AMERICA: ETIOLOGY, CLINICAL DISEASE, PERSONAL PERCEPTION, AND DEPOSITION OF SPECIMENS IN THE SMITHSONIAN MUSEUM. Uncertainty shrouds the number and identity of the species of Sarcocystis infecting horses in the United States. Horses are intermediate hosts for Sarcocystis fayeri, for which the domestic dog is the definitive host. Clinical signs and lesions associated with S. fayeri are not defined. Granulomatous myositis, especially involving the chest and dysphagia, is one of the clinical presentations associated with S. fayeri infections. Whether S. fayeri is the sole species that forms sarcocysts in equine muscles in the United States is not clear. Little is known of the molecular diagnosis of Sarcocys...
Gastroscopic Evaluation of Gastric Mucosa in Horses Treated With Flunixin Meglumine or High-Dose Firocoxib: A Descriptive Pilot Study. Equine Gastric Ulcer Syndrome (EGUS) is common in horses, and nonsteroidal anti-inflammatory drugs (NSAIDs) are a known risk factor for gastrointestinal ulceration. Although COX-2 selective NSAIDs such as firocoxib theoretically offer a better safety profile, endoscopic evidence for their mucosal safety at high off-label doses is lacking. Objective: To compare the effects of label-dose flunixin meglumine and high-dose firocoxib on the gastric mucosa of a small selected group of horses using serial gastroscopy and histopathology in a descriptive pilot study. Methods: Twenty mixed-breed horses w...
Testicular seminoma: clinical, imaging, and histologic features in nine horses. Testicular seminomas in horses are infrequently reported in the veterinary literature and long-term survival and metastatic potential are not well documented. Objective: Describe the clinical, imaging, and histologic features in 9 horses with testicular seminoma. Methods: Medical records of 9 horses diagnosed with testicular seminoma at a referral hospital between 2000 and 2024 were reviewed. Methods: Horses were included if seminoma was confirmed on histopathology from biopsy or necropsy. Information retrieved included signalment, history, clinical pathology, ultrasonographic findings, treatm...
Cutaneous Equine Sarcoidosis: A Case Series and Investigation Into a Potential Association With Equine Gammaherpesviruses-2 and -5 in 30 Equids. Gammaherpesviruses have been associated with granulomatous inflammation in the skin of various species. Equine sarcoidosis (idiopathic granulomatous disease) can cause granulomatous dermatitis, and its cause remains unknown. Objective: This retrospective study aimed to investigate the possible association between equine gammaherpesviruses-2 and -5 (EHV-2, -5) and cutaneous equine sarcoidosis (cES). Methods: Thirty client-owned equids. Methods: All animals had histologically and clinically confirmed cES. Signalment, geographical location and clinical features were recorded. Gram, Ziehl-Nielsen ...
Mammary neuroendocrine tumor in a mare. A 10-y-old American Paint Horse mare was presented to the Equine Field Services at Virginia-Maryland College of Veterinary Medicine (Blacksburg, VA, USA) for evaluation of mastitis and a possible abscess in the right mamma. Histologic evaluation of a mammary biopsy revealed a densely cellular, infiltrative neoplasm with cells arranged in packets supported by thin stroma. In a neuroendocrine immunohistochemistry panel, the neoplastic cells did not immunolabel for neuron-specific enolase or synaptophysin, positively immunolabeled for chromogranin A, and had moderate scattered immunolabeling for ...
Gross and Histopathologic Comparison of the Distal Third Metacarpal Bone and the Proximal First Phalanx with Sodium Fluoride Positron Emission Tomography Radiopharmaceutical Uptake in Five Horses. Injuries of the metacarpophalangeal joint are a major cause of morbidity and catastrophic fracture in racing horses, yet early osseous pathology is often difficult to detect using conventional imaging. This pilot study aimed to correlate sodium fluoride Positron Emission Tomography (F-NaF PET) radiopharmaceutical uptake with gross and histopathologic changes in the distal third metacarpal bone (MC3) and proximal first phalanx (P1). Five horses (three racing Thoroughbreds with fetlock injury and two non-racing controls) underwent ante-mortem F-NaF PET and cone-beam CT imaging (CBCT), followed b...
Signal-averaged electrocardiography in horses: characteristics of ventricular late potentials in healthy Thoroughbreds and horses with cardiac abnormalities. Sudden death in horses, often attributed to lethal arrhythmias, poses significant welfare and economic risks, yet its prediction remains challenging. This study aimed to characterize ventricular micro-potentials using signal-averaged electrocardiography (SAECG) and evaluate their potential for assessing sudden death risk. High-resolution orthogonal X-, Y-, and Z-lead ECGs were recorded in 24 healthy Thoroughbreds (aged 2-31 years), one horse with bupivacaine-induced myocardial injury, and three horses with persistent pathological murmurs. SAECG parameters, including filtered QRS duration (fQRS...
Vital bone and increased osteoid in equine osteochondrosis dissecans of the proximal phalanx: A controlled study indicating a mineralization deficit rather than vascular failure. Osteochondrosis and osteochondrosis dissecans (OCD) are among the most common orthopaedic disorders in young horses. Although traditionally explained by vascular failure and ischaemic necrosis, recent findings in human juvenile OCD suggest that impaired bone mineralization may play an important role. Horses are known to have relatively low circulating vitamin D metabolites, raising the question of whether insufficient mineralization contributes to equine OCD. This study investigated the bone vitality and mineralization status of osteochondrosis dissecans fragments (OCDFs) collected from the do...
Comparative cardiac histopathology and toxicology screens in horses succumbing to exercise-associated sudden cardiac death and control horses. Horse racing has faced increased scrutiny because of concerns about equine welfare and the safety of both equine and human participants. Sudden death (SD) in racehorses is relatively uncommon, and its causes are still unclear. Little information and considerable confusion exist regarding the clinical significance of microscopic lesions in the hearts of horses with SD. We examined the hearts of 29 horses that suffered exercise-associated sudden cardiac death (EASCD) and 29 clinically healthy control horses that were euthanized because of catastrophic musculoskeletal injuries. Acute cardiomyocyt...
Infection by Strongylus edentatus and Strongylus vulgaris in a warmblood crossbred foal in Ontario. A 6-month-old warmblood-cross filly was presented to the Ontario Veterinary College Large Animal Hospital (Guelph, Ontario) because of acute profuse diarrhea unresponsive to treatment and severe wasting. The filly progressed to obtundation over 4 d and was euthanized. Postmortem examination revealed multifocal hemorrhage within the extraperitoneal fascia and diaphragm with intralesional, 4-centimeter-long, white nematodes. In addition, verminous arteritis of the cranial mesenteric artery, right colic artery thrombosis with segmental colonic infarction, ulcerative colitis, and segmental fibrino...
Use of computer-assisted tomography for diagnosis and standing surgical reduction of progressive ethmoidal hematoma in a mare. Progressive ethmoidal hematoma (PEH) is a rare, nonneoplastic mass occurring in the sinonasal passages of horses. An 11-year-old, pregnant Thoroughbred mare was presented with a history of intermittent nasal discharge and stertorous respiration. On examination, radiography revealed increased opacity in the sinus and nasal cavities and endoscopy identified a mass emerging from the left ethmoidal turbinate. Computed tomography (CT) showed the range and origin of the mass, indicative of PEH. A standing frontonasal flap was made under sedation, following temporary tracheostomy to secure the airway...
Pathology of sudden death in racehorses: a review. Sudden death (SD) is the second most important syndrome associated with death in racehorses. The cause of SD in a large number of horses remains undetermined, and, in many of these cases, causes are not found by gross or microscopic postmortem examinations. Among the known causes of SD are traumatic injuries, including fractures of skull, neck, and pelvis; intoxications (e.g., anticoagulant rodenticides); and others. For many cases of SD in which no significant lesions are found, heart failure, probably associated with arrhythmias, is suspected. Precise phenotypic characterization of SD in hor...
Prognosis of Equine Liver Diseases. Prognostic information in equine liver disease can be gleaned from historical, clinical, clinicopathological, ultrasonographic, and histopathological features. However, given the multiple causes and subtypes of liver disease affecting horses worldwide, prognostic data might not be suitable for universal application across all cases. Most evidence has been established for horses with chronic hepatopathies and extrapolation to acute cases should be avoided. In chronic liver disease the presence and severity of clinical signs and serum markers including total globulins, albumin, and bile acids ar...
Equine Liver Histopathology. This review summarizes best practices for equine liver biopsy, including when to perform a biopsy, techniques for sample collection and handling, and strategies to optimize diagnostic yield. It discusses the interpretive framework used by pathologists, common diagnostic challenges, and prognostic scoring systems. Limitations such as sampling error and variability among observers are considered alongside ancillary testing, immunohistochemistry, and in situ hybridization. Emphasis is placed on the importance of communication between clinicians and pathologists to maximize diagnostic and prognost...
Combined PRP and CCP Therapy Suppresses Inflammation and Protects Cartilage in Post-Traumatic Osteoarthritis. This study aimed to evaluate the therapeutic effects of platelet-rich plasma (PRP) and Cervus and Cucumis polypeptide (CCP) injections in rats with post-traumatic osteoarthritis (OA). The model was established by transection of the anterior cruciate ligament, and the animals were subsequently treated with PRP and CCP. Articular cartilage degeneration was assessed through gross morphological observation, histopathological staining, and a standardized scoring system. Concurrently, pain-related behaviors, joint swelling, levels of inflammatory cytokines, and markers associated with extracellular ...
