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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.
Target animal safety and tolerance study of pyrantel pamoate paste (19.13% w/w pyrantel base) administered orally to horses. Pyrantel pamoate paste (19.13% w/w pyrantel base) for the treatment of tapeworm, Anoplocephala spp was evaluated for target animal safety and tolerance in horses treated orally at 0, 1, 3, 5, and 10 times the clinical dose of 13.2 mg pyrantel base/kg body weight administered daily for six consecutive days. Parameters evaluated included clinical signs, food and water consumption, body weights, physical examinations, clinical pathology (hematology, coagulation, serum chemistry, urinalyses, and fecal examinations), complete necropsy, organ weights, and histopathology. No adverse events or test ar...
Cerebral listeriosis in an adult Freiberger gelding. Listeria monocytogenes infection, although rare in horses, can lead to septicaemia, gastroenteritis and abortion or stillborn foals. Equine cerebral listeriosis has been reported, but only in newborn animals. This report describes a Freiberger gelding with severe neuronal symptoms of sudden onset. The animal collapsed within 24 h and was humanely killed. Necropsy revealed multiple small brown to reddish foci within the brain stem and pons. Histopathology demonstrated multifocal suppurative meningoencephalitis with microabscesses and occasional intra-lesional, coccoid to rod-shaped, bacteria. T...
Severe pulmonary disease due to multisystemic eosinophilic epitheliotropic disease in a horse. Multisystemic eosinophilic epitheliotropic disease was diagnosed histologically in a 17-year-old Quarter Horse intact mare that was presented with a chronic history of respiratory distress. At necropsy, the lungs were poorly collapsed and the pulmonary parenchyma contained innumerable, discrete, spherical nodules in a miliary pattern. A few similar nodules were scattered in the liver and the renal lymph nodes. Histologically, these nodules consisted of fibrosing eosinophilic granulomas. Based on histologic findings and the absence of an etiologic agent, a diagnosis of multisystemic eosinophili...
Severe combined immunodeficiency in a Fell pony foal. Five days after birth of a viable Fell pony filly, yellow watery diarrhoea appeared without any signs of systemic disease. Four days later the diarrhoea ceased. On 11th day, the animal showed apathy, and a few days later, the foal was very lethargic, suffered from muscular weakness and severe watery diarrhoea that reappeared. The illness did not respond to therapy. At the age of 21 days the filly spontaneously died under symptoms of intestinal colic and pneumonia. Haematological examinations revealed lower numbers of erythrocytes as well as non-selective lymphopenia. Phagocytic activity was sl...
How does magnetic resonance imaging represent histologic findings in the equine digit? Magnetic resonance (MR) imaging is increasingly used in the diagnosis of equine foot pain, but improved understanding of how MR images represent tissue-level changes in the equine foot is required. We hypothesized that alterations in signal intensity and tissue contour would represent changes in tissue structure detected using histologic evaluation. The study objectives were to determine the significance of MR signal alterations in feet from horses with and without lameness, by comparison with histopathologic changes. Fifty-one cadaver feet from horses with a history of lameness improved by pa...
Histopathology in horses with chronic palmar foot pain and age-matched controls. Part 1: Navicular bone and related structures. Causes of palmar foot pain and the aetiopathogenesis of navicular disease remain poorly understood, despite the high incidence of foot-related lameness. Objective: Abnormalities of the collateral sesamoidean ligaments (CSLs), distal sesamoidean impar ligament (DSIL), deep digital flexor tendon (DDFT), navicular bone, navicular bursa, distal interphalangeal (DIP) joint or collateral ligaments (CLs) of the DIP joint may contribute to palmar foot pain. Methods: Feet were selected from horses with a history of unilateral or bilateral forelimb lameness of at least 2 months' duration that was improv...
Histopathology in horses with chronic palmar foot pain and age-matched controls. Part 2: The deep digital flexor tendon. Causes of palmar foot pain and the aetiopathogenesis of navicular disease remain poorly understood, despite the high incidence of foot-related lameness. Objective: Abnormalities of the deep digital flexor tendon (DDFT) may contribute to palmar foot pain; ageing degenerative changes may be seen in horses free from lameness; and horses with lameness are likely to have a greater severity of abnormalities than age-matched horses with no history of foot pain. Methods: Feet were selected from horses with a history of uni- or bilateral forelimb lameness of at least 2 months' duration. Histology of th...
A retrospective study of cutaneous equine sarcoidosis and its potential infectious aetiological agents. Nine horses from ages 5 to 21 years were diagnosed with cutaneous equine sarcoidosis (ES) over an 18-year period. In addition to skin, the lungs were frequently involved, with other organ systems affected less commonly. A predisposition for thoroughbreds and geldings was noted. Cutaneous lesions and signs included crusts, scales, alopecia and pruritus. These were found at various sites, particularly the legs/thighs/elbows, thorax, neck, face and ventral abdomen. Three horses were euthanized shortly after hospitalization; others survived as long as 12 years. Histopathologic stains, immunohistoc...
SRY negative 64,XX intersex phenotype in an American saddlebred horse. A female American saddlebred horse was presented for surgical correction of a possible pseudohermaphrodite condition. The horse had abnormal external genitalia and exhibited stallion-like behaviour. No evidence of uterine or ovarian tissue was identified on laparoscopic examination, but hypoplastic testicular-like tissue was removed, although this was found to contain no spermatogonia upon histopathological examination. A karyotype was performed and showed the normal chromosomal complement for a female horse (64,XX). Polymerase chain reaction to detect the SRY gene was negative in peripheral b...
Ovarian teratoma and endometritis in a mare. An 8-year-old Arabian mare was admitted for a large ovarian anovulatory follicle. A clinical diagnosis of ovarian tumor and endometritis was established. Histological examinations revealed an ovarian teratoma and a grade II endometritis. Three months after unilateral ovariectomy, the mare was confirmed pregnant and eventually gave birth uneventfully. Une jument Arabe de 8 ans fut présentée pour un gros ovaire. Un diagnostic de tumeur ovarienne et d’endométrite fut posé. L’examen histologique confirma un tératoma ovarien et une endométrite grade II. Trois mois après une ovariectomie...
Congenital stationary night blindness in a Thoroughbred and a Paso Fino. This report documents congenital stationary night blindness (CSNB) in two non-Appaloosa horse breeds (Thoroughbred and Paso Fino). History of vision impairment since birth, normal ocular structures on ophthalmic examination, and electroretinographic findings were consistent with CSNB. In one horse (Thoroughbred), a 9-year follow-up was carried out. In the Paso Fino, severe vision impairment from birth to approximately 1 year of age in both dim and bright light situations led to humane euthanasia and histopathologic confirmation of the disorder.
Alterations of epidermal proliferation and cytokeratin expression in skin biopsies from heavy draught horses with chronic pastern dermatitis. We report the historical, clinical and histopathological characteristics of skin lesions in biopsies from 37 heavy draught horses with chronic pastern dermatitis. The skin lesions were divided into four macroscopic groups: scaling (group I, n=5), hyperkeratotic and hyperplastic plaque-like lesions (group II, n=14), nodular skin masses (group III, n=16) and verrucous skin lesions (group IV, n=2). The principal histological findings were hyperkeratosis and epidermal hyperplasia. There was a gradual increase in epidermal hyperplasia from groups I to IV, suggesting that the lesions represent diffe...
Equine cutaneous non-neoplastic nodular and proliferative lesions in the Pacific Northwest. A retrospective study examined data on cutaneous nodular and proliferative lesions in horses, donkeys and mules submitted to the Veterinary Diagnostic Laboratory at Oregon State University in a 3.5-year period. One hundred and sixteen non-neoplastic nodular and proliferative lesions were identified, comprising 18% of all lesions studied and 6.4% of total equine pathology accessions. Exuberant granulation tissue, eosinophilic granuloma, fungal granuloma, cysts and habronaemiasis were most common, and constituted 91% of non-neoplastic lesions, 16% of all lesions studied, and 5.85% of total equin...
Articular / epiphyseal osteochondrosis in Thoroughbred foals at 5 months of age: influences of growth of the foal and prenatal copper supplementation of the dam. To determine the influence of copper (Cu) supplementation by injection of mares in late gestation on the frequency and severity of osteochondrosis (OC) lesions in their foals at around 160 days of age. To determine if there was any influence of the concentration of Cu in the liver, growth rate, birthweight, weight at 160 days of age, fatness, sex, or year of birth of the foal on the frequency and severity of OC lesions. To determine the influence of dam's age, and sex and birthweight of the foal on the growth rate from birth to 160 days of age, and weight at 160 days of age. Methods: Thirty-th...
Incidence of polysaccharide storage myopathy: necropsy study of 225 horses. Muscle samples were obtained at necropsy from 225 horses and ponies 1 year of age or older. Samples were processed in routine manner and were stained with hematoxylin and eosin and with periodic acid-Schiff for glycogen. Sections were examined for abnormal glycogen content and amylase-resistant complex polysaccharide and for chronic myopathic change (excessive fiber size variation, increase in number of internal nuclei). A total of 101 horses and ponies with lesions of polysaccharide storage myopathy were identified. Age of affected horses ranged from one to 30 years, with a mean of 14.7 years...
Cutaneous lymphosarcoma in a stallion. Multiple cutaneous lymphosarcomas were diagnosed in an 8-year-old Thoroughbred stallion presented for evaluation of lumps on its scrotum. Histological examination of skin biopsy samples showed a homogenous pattern of lymphoid tissue suggestive of a T-cell lymphosarcoma. Immuno-histochemical tests showed a positive reaction to Rabbit/Anti-Human T-Cell, CD3 antibodies confirming T-cell lymphosarcoma. The animal was not treated and was subsequently euthanased.
Review of 15 cases of pemphigus foliaceus in horses and a survey of the literature. The records of 15 horses with pemphigus foliaceus diagnosed on the basis of their history, clinical signs, histopathology and the exclusion of differential diagnoses were evaluated with respect to the age of onset, the clinical signs and the diagnostic tests used. There was no apparent breed predisposition. The horses' mean age was nine years, with a range from three months to 25.5 years, three were foals up to six months old and eight were nine years old or older. The most frequent lesions were scaling in 11, crusting in 10 and alopecia in 10, and they appeared most commonly on the face, neck...
Misregulated Wnt/beta-catenin signaling leads to ovarian granulosa cell tumor development. Misregulation of the Wnt/beta-catenin signaling pathway is a hallmark of several forms of cancer. Components of the Wnt/beta-catenin pathway are expressed in ovarian granulosa cells; nevertheless, its potential involvement in granulosa cell tumorigenesis has not been examined. To this end, human (n = 6) and equine (n = 18) granulosa cell tumors (GCT) were analyzed for beta-catenin expression by immunohistochemistry. Unlike granulosa cells of normal ovaries, most (15 of 24) GCT samples showed nuclear localization of beta-catenin, suggesting that activation of the Wnt/beta-catenin pathway plays ...
Changes in structure of lymphatic organs in foals died due to Rhodococcus equi infection. The aim of this study was to investigate the structure of lymphatic organs in foals which died due to Rhodococcus equi infection. The material for this study consisted of 9 foals, of both genders, various breeds, 6-14 weeks old. The routine histopathological examination and immunocytochemical reaction for cytokeratine-3 receptors revealed the disturbances in the thymus epithelial cells development. This was manifested by a complete lack of cells expressing cytokeratine-3 receptors, as well as absence of normal thymocytes differentiation. The supposed thymus epithelial cells were very few, expr...
Diagnosis and surgical removal of a granulosa-theca cell tumor in a mare. An 8-year-old mare showed stallion-like behavior and aggressiveness. A granulosa-theca cell tumor was tentatively diagnosed based on history, transrectal palpation, and ultrasonography, and surgically removed. Serological levels of testosterone and inhibin were elevated. Histopathological examination confirmed the diagnosis. The mare recovered and by day 45 could be turned out with other horses. Une jument de 8 ans a manifesté un comportement et de l’agressivité semblables à ceux d’un étalon. Une tumeur de cellule de la granulosa-theca a été provisoirement diagnostiquée, en se fond...
Funisitis associated with leptospiral abortion in an equine placenta. Funisitis, inflammation of the umbilical cord, is well recognized in human placentas. This report describes a case of funisitis associated with leptospiral infection in the placenta of a Thoroughbred foal born prematurely. The umbilical cord had diffuse superficial yellow discoloration along its entire length. Microscopic evaluation showed an exudate of neutrophils admixed with fibrin on the surface. Warthin-Starry staining showed spirochetes in the Wharton's jelly of the umbilical cord. A locally extensive, severe placentitis not involving the star and allantoic cystic hyperplasia were the ot...
First observation of an Hashimoto thyroiditis-like disease in horses from Eastern Europe: histopathological and immunological findings. Among 622 slaughtered horses from eastern Europe, 156 thyroid glands were selected on the basis of macroscopic alterations (e.g., determination of volume and weight). In the 80% of these thyroids, microscopic alterations consistent with a diagnosis of Hashimoto thyroiditis-like disease were found. In particular, a subverted architecture of the thyroid gland with colloid rarefaction, lymphocytic infiltration, and fibrosis was noted. The confirmation of the histopathological diagnosis of an equine Hashimoto thyroiditis-like disease was provided by the increased serum concentration of thyroglobul...
Hemangiosarcoma in 11 young horses. Hemangiosarcoma is a rare neoplasm of horses and hemangiosarcoma in young horses might behave differently than in mature horses. The purpose of this study was to identify the characteristics of hemangiosarcoma occurring in horses < or = 3 years of age. Medical records from 1982 to 2004 were searched for horses < or = 3 years of age with a histopathologic diagnosis of hemangiosarcoma. Eleven records were identified. Thoroughbred and Thoroughbred crosses predominated. Age ranged from 9 days to 3 years. All horses presented with cutaneous or leg swellings or joint effusion. Physical examina...
Sudden death due to thoracic lymphoma in a standardbred racing horse. During training, a 6-year-old standardbred gelding collapsed, exhibiting severe epistaxis and agonal breathing and was euthanized. The horse had a recent history of poor performance, lethargy, and unilateral eyelid swelling with serous ocular discharge. Postmortem and histopathologic examination findings revealed thoracic lymphosarcoma and concurrent exercise-induced pulmonary hemorrhage. Résumé — Mort subite d’un cheval de course de race standardbred causée par un lymphome thoracique. En cours d’entraînement, un standardbred hongre âgé de 6 ans s’est effondré, présentant des s...
Immune-mediated keratitis in horses: 19 cases (1998-2004). The purpose of this study is to describe clinical and histologic findings, treatment, and outcome of horses with suspected immune-mediated keratitis (IMMK). Methods: Retrospective study. Methods: Nineteen horses that presented to NCSU-VTH from 1998 to 2004 with IMMK. Procedures Information retrieved from the medical records included signalment, duration of clinical signs, therapy prior to initial examination, ophthalmic abnormalities, diagnostics performed, therapy instituted, and long-term vision. Results: Nineteen horses (22 eyes) were diagnosed with IMMK. Three distinct clinical groups were...
Macroscopical and histopathological changes in regressing primary and recurrent equine sarcoids during active specific bio-immunotherapy. Healing sarcoids were followed in 18 horses which had taken part in previous clinical studies on a total of 29 horses suffering from either primary or recurrent sarcoids, treated with bio-immunotherapy. In the present study, attention was paid to changes observed in these fibroblastic skin tumours during their regression. The tumours were surgically debulked leaving the base in the skin. The horses were immunized according to bio-immunotherapy at 2- to 4-week intervals with an autogenous vaccine made from the excised part of the tumour until the base had visibly regressed. Healing was followed...
Comparison of topical lidocaine/prilocaine anesthetic cream and local infiltration of 2% lidocaine for episioplasty in mares. Local anesthesia and tissue inflammation associated with lidocaine infiltration and lidocaine/prilocaine topical anesthetic cream for episioplasty in mares were compared. Twenty-two mares were randomly assigned to lidocaine or lidocaine/prilocaine topical anesthetic cream treatment groups. Perineum and vulva were cleaned, 8-12 g (approximately 1 g/cm per side of vulva) of topical anesthetic cream was applied, and the area was covered by plastic wrap 30 min prior to beginning procedure. Alternately, lidocaine was injected (1 mL) every centimeter just prior to the procedure. Episioplasty was con...
Leucocytoclastic vasculitis associated with Staphylococcus intermedius in the pastern of a horse. A pregnant quarterhorse mare became acutely lame as a result of severe swelling of its right hind leg, thought to have been caused by a fracture or a muscle tear. Diagnostic procedures ruled out a traumatic musculoskeletal cause and a physical examination revealed chronic pastern dermatitis ('scratches'/'grease heel'). Histopathological evaluation of biopsy samples from the right hind leg was consistent with a leucocytoclastic vasculitis, and culture yielded Staphylococcus intermedius. The treatment and infectious causes of pastern dermatitis are discussed.
[Pemphigus foliaceus in a Haflinger gelding]. A 10-year-old Haflinger gelding was presented with severe generalized chronic dermatitis characterized by scales, crusts and widespread alopecia with a partially diffuse and partially circumscribed pattern. Pemphigus foliaceus was diagnosed based on history, clinical signs and histological examination of skin biopsies. Typical histological findings were subcorneal pustules with accumulations of intact neutrophil granulocytes and acantholytic keratinocytes. The gelding was treated with glucocorticoids and gold salts. The skin lesions resolved completely after 8 weeks of treatment. No recurrence...
Ectopic cilium in seven horses. Ectopic cilium was diagnosed by slit-lamp biomicroscopy and treated surgically by transconjunctival excision in seven adult horses. All cases presented with a common history of blepharospasm, ocular discharge and keratitis. Ophthalmic examination revealed a single translucent cilium in the upper eyelid palpebral conjunctiva, emerging approximately 5 mm from the eyelid margin. Corneal ulceration was not observed in any horse. Most horses responded well to transconjunctival surgical excision. There was recurrence of ectopic cilium 6 weeks postoperatively in one horse. Histopathologic examination...
