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Topic:Pathology
Pathology in horses involves the study of diseases and abnormalities affecting equine health, encompassing a range of conditions that can impact various systems within the horse's body. This field examines the causes, mechanisms, and effects of diseases, as well as the structural and functional changes they induce in equine tissues and organs. Common pathological conditions in horses include laminitis, colic, equine infectious anemia, and respiratory disorders. Understanding these diseases involves evaluating clinical signs, diagnostic methods, and treatment options. This page compiles peer-reviewed research studies and scholarly articles that explore the etiology, pathogenesis, and clinical implications of pathological conditions in horses.
[Cutaneous vascular hamartoma in a foal]. Vascular hamartomas are rare malformations in foals that typically present as painless masses of the skin or subcutaneous tissue. This case report describes a newborn foal with a vascular mass over the right shoulder. Complete surgical excision was performed at seven days of age. Histologically, the lesion was found to be a well-defined dermal vascular proliferation consistent with a vascular hamartoma. The healing process was uneventful, and no recurrence occurred six months postoperatively. This case adds a rare location on the scapula to the literature and confirms surgical removal as an ef...
Leptomeningeal dissemination of a poorly differentiated carcinoma involving the trigeminal ganglion in a horse: a case report. Neoplastic conditions involving cranial nerves are uncommon in horses and represent a significant diagnostic challenge. Leptomeningeal dissemination is a recognized mechanism of tumor progression in aggressive neoplasms but is rarely reported in this species. A 15-year-old mixed-breed horse with a history of periocular squamous cell carcinoma treated by enucleation three years earlier developed progressive neurological signs. Initial differential diagnoses included metastatic neoplasia and equine protozoal myeloencephalitis. Due to rapid neurological deterioration, euthanasia and necropsy were...
Risk Factors for Disease in Military Working Equines. Diseases can impact Military Working Equids (MWEs) readiness and limit days in service. The objectives of this study are to categorize diseases in MWEs and evaluate potential risk factors for disease. Methods: Pathology reports from MWEs from 2005 to 2025 were retrieved from the Joint Pathology Center archives. Disease processes with ≥5 cases were evaluated for potential risk factors, including MWE breed, sex, neuter status, geographic location, and age at sampling. Results: Diagnoses included inflammation (n = 30), neoplasia/proliferation (n = 24), within normal limits (n = 12),...
Technical note on cervical epidural catheterization in two adult horses: Injectate distribution and epidural space effects. To determine the caudalmost extent of diffusion of contrast media administered through a cervical epidural catheter (CEC) and to describe pathologic changes associated with maintaining an indwelling CEC for up to 17 days. Methods: Pilot study. Methods: Two mature horses. Methods: CECs were placed under ultrasound guidance in two horses. Both horses were injected with 5 mL 50% Iohexol contrast solution, followed by radiographs of catheter insertion site to confirm placement. A total volume of 15 mL contrast solution was injected in 5 mL aliquots up to 25 min post-initial injection. La...
A postmortem grading system for articular cartilage loss of the dorsoproximal aspect of the proximal phalanx of Thoroughbred racehorses. The metacarpophalangeal and metatarsophalangeal joints in Thoroughbred racehorses are common injury sites, given their high range of motion and compression during galloping. In New Zealand, the proximal phalanx (P1) is a common site for race-day fracture, but the lesions of this bone have not been described. Therefore, we created a scoring system to describe cartilage on the dorsoproximal aspect of P1 in New Zealand Thoroughbred racehorses. We collected 102 P1s from racehorses submitted for postmortem examination. Horses were categorized into 2 cohorts: 1) fracture (18 horses euthanized becaus...
Central nervous system lymphoma and neurolymphomatosis in equids. Lymphoma affecting the central and peripheral nervous systems in equids is rarely reported. Objective: To describe the clinical presentation, neuroanatomical localization, laboratory and pathologic features, type of lymphoma, and outcome to further current knowledge. Methods: Fourteen equids (13 horses, 1 mule). Methods: Retrospective study. Medical records from a veterinary teaching hospital were reviewed (1993-2025). The inclusion criteria consisted of a definitive diagnosis of lymphoma of the nervous system. Data collected included signalment, neurologic findings, laboratory results, imagin...
Oxidative Stress and Immunomarkers in Equine Dermal Melanomatosis: Single-Case Comparison with Healthy Individual. Dermal melanomatosis is a common tumor in grey horses, characterized by cutaneous/subcutaneous lesions with metastatic potential. While clinically well-described, oxidative stress involvement remains poorly understood. This case report compared oxidative stress markers and antioxidant enzymes' activities in total protein extracts from melanomatosis lesions (grey horse) versus healthy control skin (black horse), alongside histopathology and immunohistochemistry, to correlate oxidative imbalance and tumor behavior. Melanomatosis tissue exhibited decreased antioxidant defenses confirmed by catala...
Nonsteroidal anti-inflammatory drug administration alters crypt distribution of the peroxisomal marker acyl-coenzyme A oxidase 1 in the equine right dorsal colon. To characterize and compare the distribution of peroxisomal markers in the right dorsal colon (RDC) and left ventral colon (LVC) of healthy horses and horses treated with NSAIDs. Unassigned: Archived colonic tissues were evaluated from 10 horses (n = 5/group) administered phenylbutazone (4.4 mg/kg, PO, twice daily for 10 days) or placebo prior to euthanasia. Samples from the RDC and LVC were analyzed using immunofluorescence to assess peroxisomal biogenesis factor 14 (PEX14) and acyl-coenzyme A oxidase 1 (ACOX1) distribution. Marker abundance was quantified within colonic crypts and compared b...
Bacteremia in horses undergoing routine dental prophylaxis: Before, during, and after the procedure. Transient bacteremia after dental procedures is well-documented in the literature, but the prevalence and clinical significance in horses remains largely unexplored. Objective: To assess whether routine dental prophylaxis in clinically healthy horses is associated with detection of bacteria in blood, using culture and 16S rDNA sequencing. Our central hypothesis is that a percentage of horses would demonstrate detectable but transient bacteremia in the immediate post-procedural period following dental prophylaxis. Methods: Prospective, observational study. Methods: Venous blood samples from 20 ...
The Transcriptomic and Proteomic Molecular Signatures of Equine Multiple-System Neuropathy (Grass Sickness). Equine grass sickness (EGS or equine dysautonomia) is a predominantly fatal multi-system neuropathy affecting grazing horses, likely caused by a neurotoxic phospholipase A2 (nPLA2) derived from a plant or microorganism. We studied neuronal tissue gene and protein expression patterns in EGS to elucidate the possible mechanisms of neurotoxicity and neurodegeneration. Tissue from the cranial cervical ganglion of eight EGS horses and six controls was examined histologically and used for transcriptomic analysis. These transcriptomic data were compared with previously published EGS-related proteomic...
Anatomopathological aspects of osteoarticular lesions associated with Rhodococcus equi infection in two foals. Rhodococcus equi is an important bacterium that affects foals up to six months of age, especially those that are immunocompromised. The main manifestation is pyogranulomatous pneumonia; nevertheless, extrapulmonary lesions have not only been reported, but are not uncommon, including arthritis and osteomyelitis. Despite the widespread occurrence of rhodococcosis, the macro- and microscopic lesions in the musculoskeletal system are still poorly understood, and a detailed study is needed to better understand the pathogenic potential of the organism. The aim of this report is to present the anatom...
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...
The Peridental Structures of Equine Cheek Teeth: An Age-Dependent Anatomical Study of Maxilla and Mandible. Sequestration is the most common complication following equine cheek tooth extraction, occurring predominantly in the mandible of younger horses. Extraction-related trauma to the peridental region may impair healing. Despite its clinical relevance, detailed knowledge of peridental anatomy remains limited. This study investigated age-related differences in the peridental region of maxillary and mandibular equine cheek teeth 07 to 09. The peridental region of 24 cheek teeth rows from six cadaver heads was sectioned horizontally at approximately 10 mm intervals. Sections were photographed and the...
Preliminary Assessment on Pathogenicity of an African Horse Sickness Virus Serotype 1 Strain in Guinea Pigs and Horses. African horse sickness (AHS), a noncontagious insect-borne disease affecting equids, is caused by the African horse sickness virus (AHSV) and is associated with extremely high morbidity and mortality. AHSV has nine distinct serotypes (AHSV-1 to AHSV-9). In a previous study, we characterized the genome and in vitro growth properties of AHSV/C, a cell-adapted derivative of an AHSV-1 strain imported into China 60 years ago, and verified its safety in mice. This study preliminarily explored the pathogenicity of AHSV/C in guinea pigs and horses (its natural host). Six groups of guinea pigs were ino...
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...
Alphavirus madariaga-associated encephalomyelitis in equines from the Brazilian Pantanal reveals arbovirus circulation in a peri-urban environment. Alphavirus madariaga (MADV), a member of the eastern equine encephalitis virus complex, is an emerging arbovirus in South America, with limited information regarding its occurrence and molecular characterization in equine populations. This study reports the detection and genetic characterization of MADV in equines from the state of Mato Grosso, Brazil. Two horses presenting acute neurological disease with a clinical course of approximately two days were evaluated. Histopathological examination revealed nonsuppurative meningoencephalomyelitis. Molecular screening for neurotropic viruses using T...
Diagnostic Ultrasound of the Equine Liver. Ultrasound is readily available to most practitioners and can be used in a straightforward manner to assess the liver. The liver can be assessed for size, shape, echogenicity, and architecture. Findings such as masses, cysts, granulomas, and biliary distention can be relatively specific as to suspected disease process. Other findings may be nonspecific but are useful to confirm concerns and aid in refining differential diagnosis. Findings should be interpreted considering the clinicopathologic picture and sampling performed when appropriate. Ultrasound can and should be used to identify optima...
Case report: exercise-associated sudden death in a Thoroughbred racehorse with cardiac lesions. Exercise-associated sudden death (EASD), defined as acute collapse and death in an apparently healthy racehorse during or within ~1 h after exercise, is currently among the top concerns in the racing industry. Cases of EASD with no cause of death identified at necropsy are frequently presumed to be of cardiac origin. In such cases, in addition to a regular necropsy, a cardiac examination protocol is performed that includes a detailed gross examination and microscopic evaluation of 11 regions of the heart. Very often this protocol is unrewarding because there are no microscopic lesions to expl...
Tick-borne bacterial and protozoal pathogens in horses in Austria – A cross-sectional study on current and past infections and potential risk factors. Tick-borne bacterial and protozoal pathogens are a major threat to equine health worldwide. In Austria, studies on pathogens such as piroplasms, Anaplasma phagocytophilum and Borrelia spp. in horses are scarce and do not cover the countrywide horse population. To address this, blood samples from horses without prior record of infection with tick-borne pathogens (n = 588) were tested for the presence of Theileria equi, Babesia caballi or A. phagocytophilum DNA by PCR and for specific antibodies against these pathogens and Borrelia burgdorferi with commercially available assays. While no DNA of ...
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 ...
Diagnosis of bacteraemia in neonatal foals using 16S rRNA high-throughput sequencing. Sepsis is an important cause of morbidity and mortality in foals. Early diagnosis can improve outcome but is complicated by non-specific clinical signs and delayed confirmation of infection via blood culture. Molecular assays represent a rapid and more sensitive alternative. Objective: To evaluate and compare bacterial load and composition in blood and blood culture media (BCM) of sick and healthy foals using molecular assays and to compare results with traditional bacterial culture. Methods: Cross-sectional observational clinical study. Methods: Thirteen septic foals, 10 sick non-septic and 8...
Computed tomography long-term follow-up of a facial fracture involving the orbit and paranasal sinus. Fractures of the facial bones involving the orbit are challenging conditions that require surgical treatment. Objective: To describe preoperative and postoperative clinical and computed tomographic findings of an orbital rim fracture repaired using a reconstruction plate. Methods: Case report. Methods: A 14-year-old Haflinger mare was presented with an open, depressed and comminuted fracture involving the frontal, nasal, lacrimal and maxillary bone, sinus system and the medial aspect of the orbital rim and wall on the right side, as diagnosed by CT. Fracture repair included orbital rim reconst...
Ulcerative dermatitis, tendinitis, tenosynovitis, and desmitis caused by chronic infection with Serratia odorifera in a racehorse. We investigated a case of severe infection in a racehorse. The horse had developed progressive lameness associated with swelling of the left tarsal region, which progressed to ulcerative dermatitis, tendinitis, tenosynovitis, and desmitis. The plantar side of the superficial digital flexor (SDF) tendon was visible through the skin ulcer, and coalescing nodules were present in the dermis. The horse was euthanized and an autopsy was performed. Grossly, in addition to the changes described above, severe edema of the soft tissues was associated with the ulcer. Microscopically, necrotizing and ulc...
Integrated transcriptomic profiling reveals oncogenic pathways and chimeric transcripts in equine sarcoid lesions with predominant BPV1 detection. Sarcoids are the most common cutaneous tumors in horses, representing up to 90% (35%-90%) of skin neoplasms. Mostly caused by Bovine Papillomavirus (BPVs) infections, sarcoids are highly resistant to therapy and prone to recurring, posing a significant threat to equine health. The aim of this study is to explore molecular pathogenetic mechanisms underlying the development of equine sarcoids, by applying transcriptomic approach. After testing samples for viral DNA, both mRNA and small RNA expression was analyzed via high-throughput Illumina sequencing comparing 12 sarcoids and 12 healthy skin s...
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...
Glandular gastric disease prevalence in equids (horses, donkeys, and mules) and other gastric findings: post-mortem comparative study. Equine glandular gastric disease (EGGD) has limited prevalence studies and scarce understanding of the predisposing factors and pathophysiological mechanisms involved. The objectives of this study were to determine and compare the post-mortem prevalence of EGGD and other gastric lesions in Colombian equids, specifically horses, donkeys, and mules. The study utilized a sample of 300 equids stomachs, with 100 specimens from each group, collected immediately after slaughter. The post-mortem examination included a thorough inspection of the ventral fundus, adjacent area of the margo plicatus, and ...
Development of a rapid and highly accurate diagnostic test for detecting Theileria equi in horses using recombinase polymerase amplification (RPA) combined with nucleic acid lateral flow immunoassay. Equine piroplasmosis (EP) is a protozoan disease in horses, mainly caused by Theileria equi, and is associated with non-specific signs such as fever, anemia, and edema. The lack of specific clinical signs, coupled with the high prevalence of carrier horses, highlights the critical need for a rapid and highly accurate diagnostic test for the detection of Theileria equi. Existing methods, including molecular, serological, and microscopic techniques, require specialized equipment, skilled personnel, and considerable time. The current study aims to develop a rapid and accurate assay for the detect...
