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.
Mycosis fungoides in a horse. A 17-year-old Quarter Horse mare was examined to determine the cause of a vulvar mass. Differential diagnoses for the swollen, ulcerated tissue included hypersensitivity reaction to insect stings or bites and cutaneous neoplasia. During the next 4 months, the mass enlarged involving the skin of the perineum and ventral aspect of the abdomen with secondary dependent edema of both hind limbs. Histologic examination of biopsy and necropsy specimens revealed changes consistent with a diagnosis of mycosis fungoides (cutaneous T-cell lymphoma). Diagnostic features included invasion of neoplastic lym...
Emericella nidulans as an agent of guttural pouch mycosis in a horse. A case is reported in a 9-year-old Anglo-Arab horse with guttural pouch mycosis caused by Emericella nidulans. Acute death occurred by exsanguination following erosion of the external carotid artery. Histopathological examination of the mycotic plaque demonstrated septate hyphae, conidial heads, hülle cells and mature cleistothecia containing characteristic ascospores. Specific identification was confirmed by culture. In accordance with previous reports, Emericella nidulans should be considered as the major agent of guttural pouch mycosis in Equidae.
Pseudocyst of the spermatic cord of a gelding. Clinical, echographic, and histopathological features of an unusual enlarging scrotal mass in a 5-year-old gelding are described. Echography of the scrotal mass in this case provided valuable information concerning the nature of the tissue present, and assisted in narrowing the differential diagnosis.
Cardio-histopathological observations on aborted equine fetuses infected with equid herpesvirus 1 (EHV-1). Twenty-five aborted equine fetuses infected with equid herpesvirus 1 (EHV-1) were examined cardio-histopathologically. The main changes in the heart consisted of interstitial myocarditis and intramyocardial vascular lesions accompanied by degeneration and necrosis of the cardiac myocytes. Vascular pathology of intramyocardial small arteries and arterioles was characterized by endothelial cell necrosis and fibrinoid changes in the media. Eosinophilic intranuclear inclusion bodies characteristic of herpesvirus infection were detected in the myocardial cells and macrophages within and around the ...
Severe polysaccharide storage myopathy in Belgian and Percheron draught horses. A severe myopathy leading to death or euthanasia was identified in 4 Belgian and 4 Percheron draught horses age 2-21 years. Clinical signs ranged from overt weakness and muscle atrophy in 2 horses age 2 and 3 years, to recumbency with inability to rise in 6 horses age 4-21 years. In 5 horses there was mild to severe increases in muscle enzyme levels. Clinical diagnoses included equine motor neuron disease (2 horses), post anaesthetic myopathy (2 horses), exertional myopathy (2 horses), myopathy due to unknown (one horse), and equine protozoal myelitis (one horse). Characteristic histopathology...
Equine babesiosis associated with strenuous exercise: clinical and pathological studies in Jordan. Clinical, haematological and pathological studies were undertaken in Jordan in a stud of 103 racing horses clinically suffering from babesiosis and apparently healthy animals. Out of 47 horses which participated in strenuous exercise, three mares showed sudden onset of immobility and reluctance to move and two mares died. Clinical examination revealed that these five horses (group 1) had fever, anorexia, weakness and severe icterus and, in two mares, haemoglobinuria. Haematological examination revealed that all five horses were heavily parasitized with Babesia equi. This was also found in four...
Corneal concentrations and preliminary toxicological evaluation of an itraconazole/dimethyl sulphoxide ophthalmic ointment. The objectives of this study were to determine the concentration of itraconazole achieved in corneal tissue and aqueous humour after topical application of a 1% itraconazole ointment: to determine the effect of including dimethyl sulphoxide (DMSO) in the ointment on achievable ocular tissue itraconazole concentrations; and to assess if any gross or histopathologic ocular toxicity results from the topical application of 1% itraconazole with or without the addition of DMSO. The experimental trial consisted of 6 horses considered to have normal eyes. Each horse had one eye treated with 0.3 mL of ...
[A case of cutaneous epitheliotropic malignant lymphoma (mycosis fungoides) in a horse]. This article describes an eleven year old mare with apathy, fever, enlarged mandibular lymph nodes, skin lesions on the upper lip and edematous, grey-red mucous membranes in the nose, mouth and vulva. Histopathology revealed infiltrates with atypical lymphocytes forming Pautrier's microabscesses. The neoplastic cells had large, often indented nuclei. Immunohistology showed that some cells were CD3-positive (Pan T-cell-marker). The diagnosis of cutaneous epitheliotropic malignant lymphoma (Mycosis fungoides) was made. The etiology in the horse is unknown.
Orbital neuroendocrine tumors in three horses. Three horses were examined because of exophthalmos and others signs indicative of a space-occupying orbital mass. In 2 horses, exenteration was used to remove the orbital mass. In a third horse, an orbital tumor and lung metastases were found at necropsy. Routine histologic and Grimelius' histochemical staining were used on fixed tissues; immunohistochemical staining for chromogranin and electron microscopy also were performed. Masses were orbital neuroendocrine tumors. Horses that underwent exenteration were alive 19 and 24 months after surgery. Hypotension was encountered at surgery in both ...
Acute arsenic toxicosis in five horses. Five adult horses presented with acute clinical signs of watery diarrhea, excessive salivation, muscle tremors, ataxia, and depression. Four died within 24 hours and the fifth was euthanatized approximately 48 hours after onset of clinical signs. Necropsy finds in two of the horses included hyperemia of gastric mucosa, intestines filled with green to black watery fluid, and multifocal to coalescing, hemorrhagic 1.0-2.0-cm-diameter ulcers of the mucosa of the cecum and large colon. Histopathologic changes in the cecum and large colon consisted of mucosal necrosis and ulceration, vascular thromb...
Removal of a nasal polyp in a standing horse. Diagnosis and removal of a nasal polyp in a horse using standing chemical restraint and readily available equipment are described. Histopathology of the polyp and differential diagnoses are discussed.
Pathomorphological findings in a case of onychomycosis of a racehorse. The hooves of a racehorse which were affected with white line disease and hoof wall disorders on both forelimbs were histopathologically investigated using thin ground section and standard paraffin section techniques. On both hooves, large quantities of fungus were found to have invaded the white line tissues, especially in the terminal horn which were markedly damaged. The fungus was also present among the cellular debris in the fissures of horny tissues. The morphological characteristics of the fungus were brown (its natural color), PAS-positive, mold-like shape with septa inside the tissues...
Cutaneous leishmaniasis in two horses. This report contains the clinical, histologic, immunohistochemical, and electron microscopic findings in two cases of equine cutaneous leishmaniasis. Nodular, sometimes crusty or ulcerated lesions were confined to the pinna and adjacent neck in both animals. The dermal inflammatory infiltrate was lymphohistiocytic in horse No. 1 and pyogranulomatous with formation of tuberculoid granulomas in horse No. 2. Numerous Leishmania organisms were found within macrophages in both animals. There was moderate to intense and specific reaction by immunoperoxidase using a polyclonal antiserum against Leish...
Multiple peripheral nerve sheath tumors in the small intestine of a horse. Multiple neurofibromas, schwannomas, and hyperplastic enteric plexuses were observed in the distal jejunum and ileum of a 6-year-old pinto gelding. The animal was presented because of an acute episode of colic. Three meters of distal small intestine, partially incarcerated in the epiploic foramen, were surgically removed. Numerous tumor nodules up to 10 mm in diameter were found adjacent to a Meckel's diverticulum, predominantly located in the subserosa of a hypertrophic segment. Histologically, tumors were well demarcated and composed of interlacing fascicles formed by spindloid cells. Adjace...
Histomorphological endometrial status and influence of oxytocin on the uterine drainage and pregnancy rate in mares. The aim of this field study was to examine the influence of the uterotonic substance oxytocin in 2 different therapeutic dosages of 15 and 25 i.u., respectively on the uterine drainage of oestrous mares and on their fertility. In addition endometrial biopsies of mares with and without intrauterine fluid accumulations around the time of ovulation were evaluated histomorphologically regarding the aetiology of susceptibility to uterine infection. A population of 59 Hanoverian Warmblood mares was used in this study. The mares were divided into Group A (mares with intrauterine fluid accumulations [...
Experimental inoculation of foals and pigs with an enterotoxigenic E. coli isolated from a foal. Hemolytic E. coli strain 807-13, O149:NM:K88(STb+, LT+), was isolated from the feces of a neonatal diarrheic foal. E. coli 807-13 was examined for adhesion to brush border membranes (BBM) from foals, adult horses and pigs, and its pathogenicity was assessed in neonatal foals and pigs. E. coli 807-13 did not adhere to equine BBM but adhered to pig BBM. It did not cause diarrhea nor did it colonize the intestinal epithelium of 3 colostrum-deprived and 3 suckled foals challenged at 24 h of age. Acute ulcerative gastritis and acute suppurative gastritis were observed in 2 colostrum-deprived challe...
Clinical presentation of experimentally induced rabies in horses. Twelve naive and nine test-vaccinated horses which developed clinical signs of rabies as a result of the required protocol of a vaccine trial were prospectively observed. Nineteen of the 21 cases were confirmed positive for rabies infection of the brain by fluorescent antibody test. The two horses with negative results had ganglioneuritis of the trigeminal ganglion or lymphocytic perivascular cuffing in the brain stem in addition to clinical signs. Average incubation period was 12.3 days and average morbidity was 5.5 days. Naive animals had significantly shorter incubation and morbidity period...
Nasal obstruction caused by nutritional osteodystrophia fibrosa in a group of Ethiopian horses. A severe, advanced case of nutritional osteodystrophia fibrosa is described in a 10-year-old gelding with primary upper respiratory obstruction and chronic weight loss, which was one of a group of similarly affected horses in Ethiopia. The diagnosis was based on the clinical signs, gross lesions, histopathology and management history. The affected bones had suffered severe mineral depletion.
Papillary ductal adenocarcinoma in the mammary glands of two horses. Mammary gland neoplasms in horses are uncommon and may initially be confused with mastitis. Masses from the mammary glands of two horses with chronic discharges were examined by cytology and histopathology. Both masses were diagnosed as papillary ductal adenocarcinomas with extensive intraductal and intralobular involvement and only focal infiltration of the adjacent stroma. Complementary immunohistochemical studies were made of both fresh and formalin-fixed tumour tissue, and attempts were made to assess the steroid receptor status of fresh tissue biochemically to assess the possibility of ho...
Equine adenocarcinomas of the large intestine with osseous metaplasia. Large intestinal adenocarcinoma with osseous metaplasia was diagnosed in two horses, a 15-year-old standard bred gelding and a 9-year-old Haflinger mare. Clinically, both animals had displayed weight loss and anaemia. A presumptive diagnosis of abdominal neoplasia was made and the horses were humanely killed. At necropsy, the gelding and the mare were found to have ulcerated tumours growing into the lumen of the caecum and colon, respectively. In the mare, the mass extended through the mesocolon and was evident in the left dorsal and ventral colon. Histopathologically, the tumours consisted of...
Influence of chronic degenerative endometritis (endometrosis) on placental development in the mare. Placentation between 80 and 220 days of gestation was studied by measurement of fetal dimensions and gross, light and transmission and scanning electron microscopic examinations of the allantochorion and endometrium from 4 fertile mares with no, or very mild, endometrial histopathology and 6 subfertile Thoroughbred mares suffering varying degrees of age-related chronic degenerative endometritis (endometrosis). Spontaneously occurring twin gestation was observed in 3 animals. Several of the subfertile mares had endometrial cysts which showed 2 distinct features during pregnancy: those located n...
Clinical and pathological features of Nigerian equine encephalitis. Thirteen cases of a disease with a low morbidity and very high mortality in horses in Nigeria are described; the disease is characterised by fever (rectal temperature > or = 40 degrees C), generalised muscle spasms, ataxia, increased respiratory and heart rates and terminal lateral recumbency. The illness generally lasts three to five days but durations of 12 to 30 hours have been observed. Laboratory investigations, including histopathology and serology suggest a viral aetiology, possibly an alphavirus of the equine encephalitis group.
Histopathological and immunofluorescent studies on transplacental infection in experimentally induced abortion by equine arteritis virus. Five pregnant mares, at between 6 and 8 months gestation, were experimentally infected with the Bucyrus strain of equine arteritis virus (EAV). Of the five mares, four aborted and one died. The pathogenesis of the abortions was studied, using histopathologic techniques, tissue immunofluorescence and virus isolation. Common microscopic lesions in the maternal reproductive organs indicated myometritis with a degeneration of the myocytes and an infiltration of the mononuclear cells. Epithelial cells of the endometrial gland showed sporadic degeneration. Lesions in the fetal tissue included an atr...
Immunohistochemical diagnosis of eastern equine encephalomyelitis. An immunohistochemical (IHC) assay was developed for the detection of eastern equine encephalomyelitis (EEE) virus antigen in formalin-fixed, paraffin-embedded tissues. All cases of EEE diagnosed at the Michigan State University Animal Health Diagnostic Laboratory from 1991 through 1994 were evaluated. The diagnosis was based on histopathologic examination of the brain and confirmatory virus, isolation. Sections of cerebrum from 26 equids and 5 birds were assessed by IHC. Histologically normal brain tissues from 2 horses and 1 pheasant and brain tissues from 2 cases of equine neurologic diseas...
Eosinophilic colitis and hepatitis in a horse with colonic intramucosal ciliated protozoa. Tissues from a 9-year-old American Standardbred gelding with a history of anorexia, mild colic, and unexpected death were submitted to the Laboratories of Veterinary Diagnostic Medicine at the University of Illinois for histopathologic examination. Microscopic diagnoses were severe subacute, diffuse eosinophilic colitis with intralesional protozoa and a subacute to chronic eosinophilic portal hepatitis with granuloma formation. Two tissue-invading, ciliated protozoa were identified in large numbers within the colonic mucosa. The ciliates were Polymorphella ampulla and Cycloposthium sp., Phylum...
Malignant mast cell neoplasia with local metastasis in a horse. A 12-year-old Arab stallion was presented with a chronically swollen right carpus resulting in profound lameness of the same leg. An incisional biopsy of subcutaneous tissue from the right carpus submitted for cytology and histopathology revealed large numbers of eosinophils interspersed by substantial numbers of variably sized and granulated mast cells. Fungal culture of a subcutaneous tissue sample taken from the right carpus was negative. Serial full blood counts revealed persistent mature eosinophilia, not accompanied by a mastocytaemia, neutrophilia without left shift and persistent hyper...
Basement membrane pathology: a feature of acute equine laminitis. Thirty-two dorsal, mid-hoof wall, lamellar sections from 8 Standardbred horses, humanely killed 48 h after the administration of an alimentary carbohydrate overload, were sectioned and examined by light microscopy. Sections were stained with the connective tissue and basement membrane stains periodic acid-Schiff (PAS), Azan and periodic acid silver methanamine (PASM) and with routine haematoxylin and eosin (H&E). Lesions of the epidermal lamellae, attributable to laminitis, were graded in order of increasing severity from Grade N (normal), Grade 1 (mild), Grade 2 (moderate) to Grade 3 (severe ...
Equine papillary ependymoma. A 17-year-old Arabian gelding with progressive neurologic signs had a velvety, reddish brain tumor protruding from the ventral midline caudal to the optic chiasma. Histologically, the tumor had a papillary formation with a single layer of elongate cells radially oriented around a central fibrovascular core. Intracytoplasmic globular inclusions were positive for glial fibrillary acidic protein and weakly positive for vimentin. Ultrastructurally, these inclusions were comprised of whorling intermediate filaments. Neoplastic cells also had cytoplasmic interdigitations and numerous zona adherens a...
Nasopharyngeal conidiobolomycosis in a horse. Nasopharyngeal conidiobolomycosis caused by Conidiobolus coronatus was diagnosed in a horse after endoscopic and histopathologic examinations of a biopsy specimen. The fungal lesions in the nasopharynx were substantially reduced in size after intralesional injection of amphotericin B through the biopsy channel of a videoendoscope in combination with i.v. administration of sodium iodide and oral administration of potassium iodide during a 2-month period. Endoscopy performed 15 months after initial examination revealed regression of the granulomatous masses in the nasopharynx and complete disapp...