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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.
Prevalence and Genetic Characterization of Giardia duodenalis and Blastocystis sp. in Horses in Shanxi Province, North China. (synonyms and ) and sp. are prevalent zoonotic intestinal protozoans with significant public health and economic importance. Both parasites infect various hosts, including humans and most livestock. can cause infections ranging from asymptomatic carriage to clinical manifestations such as acute diarrheal disease, growth stunting and malabsorption, whereas sp. infection is often asymptomatic and its pathogenicity remains debated. Following the rapid expansion of modern equine industries (horse racing, equestrian sports, production, and tourism), concern about the spread of parasitic diseas...
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...
An unusual presentation of a sarcoid in Australia. Sarcoids are a common skin tumour affecting all equids. To date, only one case of a sarcoid in the oral cavity of the horse has been reported. In the present case, an oral sarcoid was identified using histology and polymerase chain reaction to detect bovine papillomavirus type 2 DNA. The lesion was known to be incompletely surgically excised and did not recur over a 15-month period. This case report describes the first oral sarcoid identified in Australia.
Clinical Signs of Liver Disease in Horses. Clinical signs associated with liver disease in horses are often a reflection of underlying hepatic dysfunction but typically vague rather than pathognomonic. Many observed clinical signs are subtle or not recognizable in the early stages of liver disease and thus may appear acute in onset despite an underlying chronic condition. Clinical signs reported in horses with liver disease include hyporexia or anorexia, weight loss, changes in demeanor, hepatic encephalopathy, colic signs, icterus, photosensitization, diarrhea, clinical coagulopathies, ascites, peripheral edema, steatorrhea, pruritus,...
Radiographic identification and description of the equine middle conchal sinus (ethmoidal sinus): Implications for diagnosing middle conchal sinusitis. The middle conchal sinus (MCS) (ethmoidal sinus) remains one of the least understood equine paranasal compartments. Despite recognition of its involvement in sinonasal disease, disorders of the MCS often remain underdiagnosed in the absence of computed tomographic (CT) imaging due to limited anatomical understanding and challenges with radiographic visualisation. Objective: The objectives of the study were (1) to characterise the radiographic features and anatomical location of the MCS in horses and (2) to illustrate the practical relevance of the anatomical and radiographic findings in two cl...
Comparison of Magnetic Resonance Imaging and Computed Tomography for Evaluation of Cervical Vertebral Nerves and Synovial Tissues in Horses with Cervical Spinal Disease. Pathology of the cervical spine is an important cause of poor performance in sport horses. Computed tomography (CT) and magnetic resonance imaging (MRI) have improved musculoskeletal diagnostic capabilities. CT is well-suited to assess osseous pathology, although it is limited for assessing soft tissues. MRI, the gold standard for imaging soft tissues, cannot be used for antemortem imaging of the equine cervical spine. The diagnostic potential of CT for evaluating soft tissues of the equine cervical spine compared to MRI is not well-defined and warrants investigation. Postmortem MRI was perfor...
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...
Molecular and parasitological evidence of Leishmania (Mundinia) martiniquensis infection in a horse from Brazil. Leishmania (Mundinia) martiniquensis is an emerging human pathogen with increasing reports of infection in domestic animals. This study describes a naturally infected mare from Brazil with no history of international travel, presenting with persistent nodular cutaneous lesions and cervical lymph node enlargement, without evidence of systemic involvement. Considering the endemicity of cutaneous and visceral leishmaniasis in the study area, as well as previous reports of equine leishmaniasis, infection by Leishmania (Leishmania) infantum was initially suspected. Anti-L. (L.) infantum antibodies ...
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...
Miscellaneous Equine Liver Conditions. Miscellaneous equine liver conditions not covered in other chapters include chronic active hepatitis, Tyzzer's disease, seasonal idiopathic hepatitis, neoplasia, and idiopathic persistent hyperbilirubinemia. Chronic active hepatitis refers to inflammatory and fibrotic liver disease with an unknown cause. Treatment is aimed at reducing inflammation. Tyzzer's disease is caused by Clostridium piliforme infection and causes acute necrotizing hepatitis in foals. Successful treatment with antimicrobial therapy and supportive care is rare. Seasonal idiopathic hepatitis is a winter disease of Midweste...
Biliary Disorders in Horses. This review will mainly focus on the presentation, diagnosis, and treatment of cholangiohepatitis in adult horses. The condition is often accompanied by some degree of intrahepatic and/or extrahepatic biliary obstruction with "sludgy" bile or actual choleliths. In horses, these calculi are typically composed of calcium bilirubinate, rather than cholesterol. There is a propensity for cholangiohepatitis to become a recurrent, chronic condition and patient management should reflect this. Although much rarer, foreign body obstruction, neoplasia and, in some parts of the world, liver flukes can als...
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...
Accuracy of Computed Tomography in Diagnosing Temporomandibular Joint Osteoarthritis Relative to Histopathological Findings-An Ex Vivo Study of 41 Horses. Computed tomography (CT) is used to support the diagnosis of equine temporomandibular joint (TMJ) disease; however, its diagnostic accuracy remains unclear. This study aimed to evaluate the relationship between CT findings and histopathological manifestations of osteoarthritis (OA) in equine TMJs. A total of 82 TMJs were CT-imaged, sampled, grouped into age-related and OA-related groups, and analyzed for frequency distributions, correlations, and CT-based TMJ OA diagnosis. CT findings were observed in 79% of joints, including 'CT anatomical variations' considering to reflect age-related remode...
An intronic variant in Ferredoxin Reductase (FDXR) creates a cryptic exon in Quarter Horses with Equine Juvenile Spinocerebellar Ataxia. Equine Juvenile Spinocerebellar Ataxia (EJSCA) is a novel autosomal recessive neurologic disease in Quarter Horses. Affected foals display a progressive proprioceptive ataxia by 1-5 weeks of age, leading to recumbency and necessitating euthanasia. Whole genome sequencing was performed on 7 EJSCA cases and unaffected horses that included 4 obligate carriers, 4 unaffected half or full-siblings, and 28 unrelated, unaffected control Quarter Horses. An 82 kb region of association was identified (EquCab3.0, chr11: 6963986-7045999), containing 9 candidate SNPs across four genes (FADS6, FDXR, GRIN2C a...
Verminous mastitis caused by Cephalobus cubaensis infection in a mare. A 7-y-old American Quarter Horse mare was presented to a veterinary hospital for ongoing reproductive monitoring and management of endometritis. During physical evaluation, several nodular lesions of unknown origin and duration were discovered in the mammae. Histologically, biopsies from the lesions were confirmed as severe granulomatous mastitis with intralesional rhabditid nematodes. A putative diagnosis of or infection was assigned, and ivermectin (1.2 mg/kg PO) treatment was given every 2 wk. When lesions persisted after the initial dose of ivermectin, PCR testing of and gene targe...
Possible Effects of C-Reactive Protein in the Central Nervous System During Venezuelan Equine Encephalitis Virus Infection. Venezuelan equine encephalitis virus (VEEV) is an alphavirus vectored by mosquitos. It can cause disease in equines and humans characterised by a febrile illness that may progress into encephalitis. Replication of VEEV in the central nervous system induces activation of glial cells and neurons, compromising the blood-brain barrier (BBB) and inducing a state of neuroinflammation. This inflammation can lead to symptoms such as confusion, seizures, and coma, and sustained inflammation contributes to neurodegeneration. C-reactive protein (CRP) is a biomarker that has previously been associated wit...
Alkaline-Promoted Hydrothermal Liquefaction of Polo Horse Manure for Biocrude Production. Horse manure (collected as pure feces) is a high-moisture, nutrient-dense organic waste stream with potential for valorization via hydrothermal liquefaction (HTL). However, catalyst selection is often reported without direct catalyst-class comparisons under identical conditions. In this study, manure collected in Thailand was characterized and converted via noncatalytic and catalytic HTL in a batch reactor at 300 °C for 40 min (feedstock/water = 1:10, w/w; heating rate 10 °C min). Four catalysts (KOH, NaOH, HPO, NH·HO) were evaluated at 10 and 20 wt % (dry feed basis), with biocrude recover...
Molecular prevalence of equine parvovirus hepatitis in healthy horses from the Northern region of the state of Rio Grande do Sul, Brazil. The equine parvovirus hepatitis (EqPV-H) was initially linked to fatal cases of equine serum hepatitis but, more recently, it has also been detected in sick or asymptomatic horses around the world, including in a limited number of horses in southeastern Brazil. In this study we aimed to assess the prevalence of EqPV-H DNA in the serum of healthy horses in the northern region of Rio Grande do Sul state, Brazil. For this purpose, we used 1000 serum samples collected from horses from 40 municipalities and organized them into 200 pools of five samples each, based on origin and age. Using a nested ...
First confirmed report of equine coital exanthema in Uruguayan horses. Equine Coital Exanthema (ECE) is a contagious venereal disease caused by Equid alphaherpesvirus 3 (EHV‑3). Although ECE is self-limiting, it causes significant economic losses to the global equine industry due to the temporary segregation of affected mares and stallions from breeding activities. This report describes the epidemiological, clinical, histological, and molecular findings from an outbreak of ECE in Uruguayan horses. Seven days following the introduction of a stallion, five mares developed extensive papular and vesicular dermatitis in the vaginal and perineal regions. The stallion...
Unusual, fatal neck cancer in a foal: immunohistological investigations and differential diagnosis. Neck masses may represent a diagnostic challenge for equine veterinarians, since they may involve different structures with a similar clinical appearance. Whereas neck masses in foals mostly result from non-neoplastic conditions, including various congenital abnormalities, neoplastic cervical masses have been rarely documented. This report describes the unusual case of a rapidly growing neck cancer in a four-month-old colt, resulting in a fatal outcome. Gross and immunohistological findings were most consistent with a poorly differentiated thymic carcinoma with sarcomatoid features and multifo...
Retrospective assessment of equine herpesvirus type 1 (EHV-1) genotype-associated clinical disease in Ontario. Equine herpesvirus type 1 (EHV-1) is an important viral pathogen in horses, associated with diverse clinical manifestations including fever, upper and lower respiratory disease, neurological signs, ocular disease, and abortion. Currently, EHV-1 variants (genotypes) are classified based on a single nucleotide polymorphism mutation of the open reading frame 30 (ORF30). Unassigned: The aim of this retrospective study was to evaluate the EHV-1 genotypes present in horses with various clinical presentations, including respiratory disease, abortion, and neurological disease, at a referral center in ...
Rostral hard palate swelling (lampas) in horses: true or fiction? This study aimed to determine the occurrence of swellings (lampas) in the rostral portion of the hard palate in young, adult, and elderly horses and to characterize them histologically. One hundred and twenty horses of different ages were evaluated by oral inspection. Horses were classified with lampas when the mucosa of the hard palate extended beyond the occlusal surface of the upper incisors and samples of palatal mucosa were collected. Ten other horses without rostral hard palate alterations, euthanized for unrelated causes, were included as the control group. Histological analysis include...
Germline Pathogenic Variant in the APC Gene Suggestive of Gardner Syndrome in a Pony. A 12-year-old pony mare was presented for evaluation of dental disease and nasal discharge. At presentation, clinical signs included bilateral nasal discharge, cutaneous masses, and numerous hard enlargements involving the bones of the skull, maxilla, mandible, and cervical vertebrae. Oral exam revealed advanced dental disease with hard enlargements adjacent to and between numerous cheek teeth. Radiographs and computed tomography confirmed the presence of severe dental disease and proliferative bone lesions disseminated along the skull, hyoid apparatus, and cranial cervical vertebrae. The bony...
Epidemiology of open and closed diastemata in equine cheek teeth and associations with periodontal pathology. Cheek-tooth diastemata are a common dental abnormality in horses and are considered a major predisposing factor for periodontal disease. However, the influence of diastema type and anatomical location on disease severity remains incompletely understood. To determine the prevalence and distribution of open and closed cheek-tooth diastemata and evaluate their association with periodontal disease severity in horses, while assessing the influence of age, sex, jaw location and laterality, fifty equine cadaver heads obtained from an abattoir were examined. Diastemata were identified through visual a...
Diffuse idiopathic skeletal hyperostosis in a Roman-period horse from Gerulata (Bratislava-Rusovce, Slovakia): Diagnostic Considerations. To evaluate pathological changes identified in a skeleton of a horse from Roman-period Gerulata, Slovakia. Methods: The remains consist of a partially preserved, articulated skeleton of an adult horse from today's southern urban district of Bratislava-Rusovce in southwestern Slovakia. Methods: The specimen underwent macroscopic analysis to assess taxonomic identification, biological profile, and pathological changes. Thoracolumbar lesions were further evaluated using computed tomography (CT). Radiocarbon dating determined the absolute age of the remains. Results: Species determination indicate...
Klossiella equi, an underreported parasite of equids in the Americas. Klossiella equi Baumann, 1946 (Apicomplexa: Coccidia) is a globally distributed adeleorinid parasite that infects the kidneys of equid hosts. Considered an uncommon parasite, when K. equi is detected, it is typically an incidental finding during histologic examination of the kidneys as part of routine necropsy. In the present study, kidney was collected opportunistically from 3 different equine populations: 1) routine necropsies at the Ontario Veterinary College (OVC; n = 48); 2) natural mortalities from the Sable Island wild horse herd (n = 25); and 3) routine necropsies of animals fr...
Persistence of Sarcocystis neurona and histopathology in horses with equine protozoal myeloencephalitis. Currently, little is known about the exact role of immunopathology in equine protozoal myeloencephalitis (EPM), including the ability to persist after anti-protozoal treatment. The main objectives of this study were to determine whether is present in the CNS in horses with EPM, including previously treated cases, and to evaluate the associated histopathology and immune response. For this study, control ( = 10) and horses with EPM ( = 9) were confirmed based on our inclusion criteria. Based on our preliminary data, we classified horses with EPM and clinical signs for >6 months as...
Modified mucosal digestion procedure improves precision of encysted larval cyathostomin counts in horses. With rising anthelmintic resistance in adult cyathostomins, the most pervasive equine parasites, the need to assess larvicidal efficacy has increased, yet available methods remain limited. Encysted larvae are quantified using mucosal digestion, wherein a 5% subsample of intestinal mucosa is processed, and a 2% aliquot is counted for early third stage (EL3) and late third stage/mucosal fourth stage (LL3/L4) larvae. This method is imprecise and post-treatment larval differences are often not observed. The following study aimed to assess standard and modified protocol precision and sensitivity. I...
