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.
Shefstad DK.The lesions caused by larvae of Gasterophilus intestinalis in the cardiac region of the equine stomach were funnel-shaped ulcers surrounded by a rim of hyperplastic epithelial cells. Bacteria were commonly seen on the rim of epithelial cells, at the base of some ulcers, and within the cavities produced by the hooks of the larvae. Cellular debris and mucus were within the ulcer.
Meuten DJ, Butler DG, Thomson GW, Lumsden JH.Chronic granulomatous enteritis associated with weight loss and hypoproteinemia was identified in 2 horses. Both horses continued to have normally formed feces. Malabsorption of carbohydrate and lipid, with concomitant gastrointestinal protein loss was demonstrated in 1 case. One horse was treated symptomatically and gained 108 kg. In both cases, principal gastrointestinal lesions were partial to total villus atrophy and transmural mononuclear leukocytosis, with lymphocytes and histiocytes predominating. The cause of the condition was not identified in either case.
McPherson EA, Lawson GH, Murphy JR, Nicholson JM, Fraser JA, Breeze RG, Pirie HM.Mean normal values for PaO, and max A Ppl for horses were determined. Using 2 standard deviations below (Pa0,) and above (max A Ppl) the mean normal values as a guide, horses affected with COPD were satisfactorily distinguished from other horses in a series of 100 animals. The frequency of occurrence of 20 different clinical parameters in affected, not affected and possibly affected horses was examined statistically. Poor work performance and a history of previous febrile illness occurred more often in COPD horses than in others. The presence of a chronic cough, dyspnoea, double expiratory eff...
Firth EC.The findings in 6 experimental and 1 natural case of Horner's Syndrome (HS) are presented. The experimental cases were induced by unilateral surgical section of the cervical sympathetic trunk in the middle third of the neck. The naturally occurring case was seen in a 17 year old gelding with a mediastinal tumour. The signs of HS in these horses included ptosis, miosis, enophthalmos, hemilateral sweating and temperature increase of the face and cranial cervical region on the affected side. The intensity of these signs was variable between and within animals. Miosis, enophthalmos and temperature...
Boomker J, Coetzer JA, Scott DB.Black grain mycetoma occurred in two horses, one a cross-bred pony and the other a Thoroughbred racehorse. Lesions were limited to wart-like growths in one case and a deep-seated girth gall in the other. In both cases the granules in the affected tissues were similar in pigmentation and structure to those produced by Curvularia geniculata in dogs. Since all the specimens were received in formalin, the causative fungus could not be isolated. These are the first cases of maduromycosis in animals to be recorded in South Africa.
Goulden BE.Any condition which leads to a diminution in the size or alteration of the shape of the lumen of the respiratory tract in the horse may result in the production of abnormal respiratory noises at exercise.
Merritt AM, Kohn CW, Ramberg CF, Cimprich RE, Reid CF, Bolton JR.Five clinically normal, mature horses and 11 with chronic diarrhea were given 51Cr-tagged Cohn fraction V equine albumin intravenously. All urine and feces were collected separately, and blood for plasma analysis was taken periodically for 5 to 8 days after injection of the isotope. Plasma clearance of albumin into the intestinal tract of normal horses was calculated as 0.67 +/- 0.23 (SD) ml/kg of body weight/day, with 1.33 +/- 0.69% of the 51Cr dose appearing in the feces in 5 days. Of the 11 diarrheal horses, 8 had a plasma clearance of 0.49 +/- 0.21 ml/kg/day with 1.12 +/- 0.68% of the dose...
Cho DY, Leipold HW.The report describes a case of myelodysplasia involing spinal cord segments C7 to T8 of a 5 month old part-Thoroughbred foal. There was a single extensive syringomyelic and hydromyelic cavity which extended from the seventh cervical segment (C7), to the seventh thoracic segment (T7), abnormal size and shape of central canal, and disorderly differentiation of the grey and white matter. The cause of the defect is unknown.
Duncan ID, Baker GJ, Heffron CJ, Griffiths IR.The larynges of 6 horses were examined endoscopically and the findings correlated with the gross and histological appearance of the intrinsic laryngeal muscles and their nerve supply. In all cases it appeared that the balance between abductor and adductor muscle groups had been lost due to preferential atrophy of individual muscles or groups of muscles. The laryngeal abnormalities recorded were asymmetry of the larynx with asynchronous left sided abduction and fluttering or trembling of the left vocal cord and arytenoid cartilage. It is suggested that these changes represent the early signs of...
Blackmore DJ, Palmer A.Examination of tissues obtained from thoroughbred horses showed that the 'intestinal' phosphatase activity could be differentiated from other phosphatases by analysis at a pH of 9-5 and inhibition with 15 mM L-phenylalanine. A simple method for the measurement of 'intestinal' phosphatase in heparinised plasma or serum is described. Application of the technique to serum or plasma from normal and diseased horses indicates that the increase in the activity of 'intestinal' phosphatase is associated with cases showing clinical, biochemical and haematological evidence of intestinal damage.
Banerjee DP, Singh B, Gautam OP, Sarup S.An intradermal skin test, to demonstrate a delayed cutaneous hypersensitivity reaction in Babesia equi infection in donkeys, was developed. A skin reaction to B. equi antigen was elicited in vaccinnated, infected and carrier intact and splenectomised donkeys. The histopathological examination of the skin biopsy revealed infiltration of mononuclear cells and accumulation of oedematous fluid in the deeper layers of the dermis. A leucocyte migration inhibition test was developed and its specificity as an in vitro measure of cell-mediated immunity to B. equi antigen was established. The results of...
Gebhart W, Niebauer GW.The morphological substrates of pigmented and depigmented skin as well as the structural characteristics of spontaneously developing melanomas were revealed by clinical, light- and electron microscopic methods in gray horses (Lipizzaner breed) from the Vienna Spanish Riding School. On clinical investigations in a group of 31 older horses (more than 10 years old) 20 exhibited melanomas, whereas 23 younger animals (less than 10 years of age) had no evidence for visuable melanotic tumors. Concomitantly with the progressive graying of the hair a depigmentation of the skin was frequently observed. ...
Dubey JP, Streitel RH, Stromberg PC, Toussant MJ.Hearts, diaphragms, esophagi, and spinal cords from 266 horses were obtained at slaughter in Creston, Ohio. Tissues were examined microscopically for Sarcocystis in sections, digested in trypsin to obtain bradyzoites, and fed to 10 dogs and 10 cats. Intramuscular cysts were found in selections of two hearts from 57 horses and four esophagi from 107 horses. The cysts were up to 900 micron long and up to 70 micron wide. The cyst wall was 1 to 2 micron thick and cross-striated. The enclosed bradyzoites were banana-shaped, 15 to 20 by 20 to 3 micron, and contained several PAS-positive granules. Br...
Adrian M, Grant B, Ratzlaff M, Ray J, Boulton C.Electrogoniometry was used qualitively and quantitatively to assess the movements of the normal and pathologic metacarpophalangeal joints of selected horses. A total of 4 Thoroughbreds, 1 normal and 3 with clinical and radiographic changes in the metacarpophalangeal joints of 1 limb, were evaluated at the walk and trot. Goniograms of the affected joints were compared with those of the normal horse and the normal contralateral metacarpophangeal joint. Qualitative asymmetry was recognized on the goniograms, and the ranges of motion were quantified and related to the clinical and radiologic obser...
Webbon PM.The results of a survey are presented in which 589 limbs from 206 horses were dissected. In174 of the limbs lesions were found in either the superficial (131) or deep (43) digital flexor tendons. Changes occurring with age were also recorded. The sites of the abnormalities and their macroscopical appearance are described and the value of the results is considered in relation to the diagnosis and the treatment of clinical lesions.
Orzan F, Angelini P, Oglietti J, Leachman RD, Cooley DA.Two cases of horseshoe lung are described; one was suspected and the other was diagnosed preoperatively. Both underwent successful surgical treatment. The embryology of this anomaly is briefly reviewed with reference to the closely related scimitar syndrome (anomalous venous return of right lung to inferior atriocaval junction). Diagnostic studies are discussed with stress on the need for a thorough functional evaluation of both the heart and lungs before the surgical indication is made.
Cimprich RE, Rooney JR.Corynebacterium equi is a pathogen associated with respiratory disease in the foal. This paper discusses two cases of Corynebacterium equi infection, one acute and one chronic, in which the major damage was intestinal. Necrosis of Peyer's patches was the only lesion seen in the small intestine of both foals. The foal with acute disease had distinct green-tan focal necrosis and thickened mucosa of the large intestine. In the foal with chronic disease, the mucosa of the large intestine was thickened, rugose, and mottled red-tan. Histologically, the predominant lesions were villous atrophy, mucos...
Sundberg JP, Burnstein T, Page EH, Kirkham WW, Robinson FR.In a retrospective study of neoplasms in Equidae pre;ented to the Animal Disease Diagnostic Laboratory, Purdue University, from Jan 1, 1970, to Dec 31, 1974, data were compiled on numbers and anatomic sites of neoplasms as well as on age, sex, and breed of subjects from which the neoplasms were taken. During this 5-year period, 21 neoplasms were diagnosed from 687 equine necropsies (3.1%) and 215 from 635 biopsies (33.9%), totaling 236 neoplasms from 1,322 cases (17.9%). The most common neoplasms were sarcoids (43.6%) and squamous cell carcinomas (24.6%). Papillomas (5.5%), nerve sheath tumors...
Cotchin E.Published figures from veterinary schools indicate that tumours may account for about 1 to 3 per cent of surgical cases. In this paper an account is given of clinical and pathological aspects of the tumours that are most likely to be encountered in practice, either as visibly or palpably detectable masses of tissue, or as internal tumours responsible for clinical signs. Amongst the common and important tumours dealt with, the most prominent are "equine sarcoid", squamous-cell carcinoma (of eye region and of glans penis), granulosa-cell tumours and melanomas. Well over a hundred references prov...
Bertone JJ, Traub-Dargatz JL, Trotter GW.Endoscopic examination of a 7-year-old gelding with weight loss indicated a palatal defect with a prominent tissue mass at the caudomedial margin of the defect. At necropsy, the condition was determined to be bilateral hypoplasia of the soft palate.
Spoormakers TJP, Veraa S, Graat EAM, van Weeren PR, Brommer H.Data on equine thoracic pathology hardly exist in breeds other than Thoroughbreds. Objective: To describe pathological changes of the osseous thoracic vertebral column in Warmblood horses, Shetland ponies and Konik horses, and to compare prevalence and severity. Methods: Descriptive post-mortem study. Methods: Computed tomography was used to examine the thoracic vertebral column of 34 Warmblood horses, 28 Shetland ponies, and 18 Konik horses. Osteoarthritis (OA), periarticular osteolysis, osseous cyst-like lesions and fragments of articular processes (APJs), costovertebral and costotransverse ...
van Heule M, Verstraete M, Norris JK, Graniczkowsa KB, Scoggin KE, Ali HE, Ball BA, De Spiegelaere W, Daels P, Weimer BC, Dini P.Nocardioform placentitis (NP) is an understudied form of equine placentitis historically attributed to nocardioform bacteria, yet it remains uncertain whether these organisms are the sole pathogens involved. Objective: To elucidate the pathophysiology of NP and the host-pathogen interaction. Methods: In vivo clinical multi-omics study. Methods: Dual RNA sequencing was performed to profile transcriptionally active microbial communities and concurrent placental transcriptome responses in samples from 31 placentas with and without NP. Untargeted metabolomics was performed to study the associated ...
Guadalupi M, Girelli CR, Della Tommasa S, Corte FD, Crovace AM, Fanizzi FP, Brehm W, Lacitignola L.Joint and tendon sheath diseases are a major cause of lameness and reduced performance in horses. Synovial fluid composition changes in response to pathological processes and metabolomic profiling offers a promising approach to detect these alterations. While equine joint metabolomics has been explored, little is known about the metabolomic profile of tendon sheaths. This study aimed to characterize and compare the synovial fluid metabolomic profiles of healthy and pathological joints and tendon sheaths in horses using high-resolution H Nuclear Magnetic Resonance spectroscopy, and to identify ...
Logas D, Kunkle G, Calderwood-Mays M, Frank L.An 8-year-old gelding, with a 1-year history of intense pruritus only after exercise, was diagnosed as having cholinergic pruritus. Provocative testing, using exercise and hot-water baths to increase core body temperature, assisted in the diagnosis. Cholinergic pruritus in human beings is a variant of the more common syndrome, cholinergic urticaria, which is characterized by intense pruritus and pinpoint urticaria. With cholinergic pruritus, intense itching results without urticaria. Specific diagnostic laboratory tests have not been developed.
Nap RC, Wouda W, Firth EC, Dik K, von Dijk P.The case of a horse affected with frontal sinusitis, in which neurological complications occurred following trepanation, is reported. The previous history of the animal as well as the clinical, radiological and pathological findings are discussed.
Townsend M, Fowler B, Aulakh GK, Singh B.Endotoxin-induced diseases cause significant mortality and morbidity in the horse, leading to enormous economic damage to the equine industry. Neutrophils play a critical role in initiating the immune response in the lung. Pattern recognition receptors (PRRs) are programmed to recognize microbial structures unique to pathogens and mount an immune response. Pentraxin 3 (PTX3) is a PRR that is produced at sites of inflammation by many cell types upon stimulation by pro-inflammatory cytokines and agonists, such as endotoxins [also known as lipopolysaccharides (LPS)]. Pentraxin 3 recognizes and bi...
Valentine BA, Rousselle SD, Sams AE, Edwards RB 3drd .Three horses with fibrotic myopathy were examined for neuromuscular disease. In 2 horses, concentric needle electromyography was performed. Dense spontaneous activity suggestive of denervation, was found in multiple thigh muscles of 1 of the 2 horses. All 3 horses were euthanatized. Histochemical and histologic examination of tissue specimens was performed. All horses had degenerative lesions in peripheral and intramuscular nerves. Angular atrophy of type-1 and type-2 muscle fibers, indicative of denervation atrophy, was seen in multiple muscle specimens from all 3 horses. One horse was found ...
Winder NC, Pellegrini A, von Fellenberg R.A peroxidase antiperoxidase technique was used to identify alpha 2-macroglobulin in formalin-fixed sections of normal equine lung and liver and in tissue sections and bronchoalveolar lavage fluid from horses with various lung diseases. Equine peripheral blood leucocytes and bronchoalveolar lavage samples from clinically normal horses were negative for alpha 2-macroglobulin. It was concluded that liver and pulmonary macrophages may be potential sources of alpha 2-macroglobulin. Although alpha 2-macroglobulin may play a role in various chronic bronchointerstitial pneumonias of the horse, it is d...
Wilson DG, Peyton LC, Wolf G.Three horses with equine sarcoids were treated with radical surgical excision and immediate split-thickness skin grafts. Graft take ranged from 50 to 100%, and the epithelial coverage attained resulted in an early functional repair. In no instance was there a recurrence of the sarcoid.
Baxter GM, Allen D, Farrell RL.LARYNGEAL haemiplegia is common in horses and most often
involves the left haemilarynx (Baker 1983; Haynes 1984).
Although specific processes have been incriminated in the
pathogenesis of laryngeal haemiplegia, most cases involve an
idiopathic distal axonopathy of the recurrent laryngeal nerve. The
purpose of this report is to describe a case of laryngeal
haemiplegia associated with an anomalous respiratory cyst. A
description of the lesion, method of surgical repair of the
laryngeal collapse and a proposed term to describe the
abnormality based on pathological and functional consider...
Cheetham J, Witte TH, Rawlinson JJ, Soderholm LV, Mohammed HO, Ducharme NG.The success of laryngoplasty is limited by abduction loss in the early post operative period. Objective: To determine the efficacy of polymethylmethacrylate (PMMA) in stabilising the cricoarytenoid joint (CAJ) and reducing the force on the laryngoplasty suture. Objective: Injection into the cricoarytenoid joint resists the forces produced by physiological laryngeal air flows and pressures thereby reducing the force experienced by the laryngoplasty suture. Methods: Ten cadaver larynges were collected at necropsy and PMMA was injected into one CAJ at selected random. Each larynx was subjected to...
Attenburrow DP, Goss VA.A case of acute destabilization of the right stifle joint associated with rupture of the anterior cruciate ligament and avulsion fracture of the tibial spine in a horse is reported. The diagnosis was obtained by scintigraphy and radiography. Post mortem investigations 6 weeks after injury demonstrated fibrillation of surface cartilage in regions unprotected by tibial menisci. No pathological change was demonstrated in the subchondral bone of the tibia in regions associated with loss of cartilage integrity.
Leifsson PS, Olsen SN, Larsen S.This paper is the first report of systemic tuberculosis involving the eyes in a horse. The animal lost condition and gradually became increasingly blind in both eyes; it was eventually euthanased. The pathological findings included bilateral, mycobacterial granulomatous uveitis with unilateral retinal detachment and necrosis, and disseminated, mycobacterial granulomatous foci in the myocardium, lungs, bronchial lymph nodes, kidneys, liver, pancreas, colon and visceral serosal surfaces, with the most extensive lesions in the myocardium. The mycobacteria were identified as Mycobacterium avium.
McGivney CL, Sweeney J, Gough KF, Hill EW, Katz LM.Endoscopic tip placement in the pharynx and water flushing interval (FI) may affect exercising upper respiratory tract (URT) endoscopic results. Objective: To determine associations between the endoscopic tip position in the pharynx and automated FI with overground endoscopic (OGE) results. Methods: Randomised balanced 2X5 factorial design. Methods: A total of n = 200 horses undergoing OGE were randomly assigned into 10 groups (n = 20/group) of different automated endoscopic FIs (no flushing, 60, 120, 180, 240 s) with the endoscope tip positioned either rostrally (position A) or caudally ...
Kim DY, Cho DY, Snider TG.A case of mucinous hyperplasia in the right renal pelvis and ureter is reported in a 23-year-old, male, Quarter horse. The affected right renal pelvis was markedly distended and filled with inspissated yellowish-green mucous material compressing the adjacent cortical and medullary parenchyma. Multiple, similar masses were present protruding from the right urethral mucosa. Histologically, the masses were characterized by a cystic glandular and papillary hyperplasia of the mucosa of the renal pelvis and ureter. This is believed to be the first reported case in an equine species.
