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Topic:Disease Etiology
Disease etiology in horses refers to the study of the causes and development of diseases within equine populations. It encompasses various factors, including genetic predisposition, environmental influences, infectious agents, and nutritional imbalances, that contribute to the onset and progression of diseases in horses. Understanding disease etiology is essential for identifying risk factors and implementing preventative measures in equine health management. This topic includes research on pathogen-host interactions, the impact of management practices on disease incidence, and the role of genetic and environmental factors in disease susceptibility. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanisms, contributing factors, and implications of disease etiology in horses.
Pathology of lethal peripartum broad ligament haematoma in 31 Thoroughbred mares. Broad ligament haemorrhage in peripartum mares is a life-threatening disease and there are few reports on the aetiology and pathogenesis of broad ligament haematoma. Objective: To obtain information regarding the sites for the early diagnosis and pathogenesis of broad ligament haematoma of mares. Methods: Thirty-one mares that died of broad ligament haematoma peripartum were examined pathologically for bleeding sites. The arterial distribution of 5 young mares with several parities served as negative controls. Results: Age and/or multiparity were the predisposing factors for the disease. Arter...
Prevalence of Clostridium perfringens in faeces and ileal contents from grass sickness affected horses: comparisons with 3 control populations. While previous studies have demonstrated an association between equine grass sickness (EGS) and the presence of Clostridium botulinum within ileal contents and faeces, no such associations with other intestinal-derived anaerobic bacteria have been extensively investigated. Objective: The prevalence of C. perfringens in the ileal contents and faeces of EGS horses is greater than control horses; the detection of C. perfringens in faeces by ELISA could be diagnostically beneficial in a clinical setting. Methods: The prevalence of C. perfringens in faeces from EGS horses and healthy grazing contro...
Clinical presentation, diagnosis, and prognosis of chronic laminitis in Europe. The terminology relating to laminitis is confusing. This article describes how equine veterinarians, by using their eyes and fingers alone, can diagnose and evaluate a case of chronic laminitis. This evaluation will enable veterinarians to give a statistically significant prognosis that can be further refined by measurements taken from plain, weight-bearing lateromedial radiographs of the affected hooves. Should invasive techniques such as digital venography also be used, the results of both techniques are complementary.
Supporting limb laminitis. Supporting limb laminitis poses a threat to all horses suffering from severe unilateral lameness. Despite its devastating effects, relatively little is known about the precise pathologic processes that lead to its development. This article reviews the potential mechanisms of supporting limb laminitis, and the authors present some preliminary data based on advanced imaging and computer-based modeling techniques aimed at further elucidating the etiology of this unique form of laminitis. Gaining a better understanding of the pathologic processes that lead to supporting limb laminitis is essential...
Supporting limb laminitis. Supporting limb laminitis poses a threat to all horses suffering from severe unilateral lameness. Despite its devastating effects, relatively little is known about the precise pathologic processes that lead to its development. This article reviews the potential mechanisms of supporting limb laminitis, and the authors present some preliminary data based on advanced imaging and computer-based modeling techniques aimed at further elucidating the etiology of this unique form of laminitis. Gaining a better understanding of the pathologic processes that lead to supporting limb laminitis is essential...
Current concepts on the pathophysiology of pasture-associated laminitis. Epidemiologic studies indicate that most laminitis cases occur in horses and ponies kept at pasture, hence the term 'pasture-associated laminitis'. Clinical cases of laminitis most often occur under conditions that favor accumulation of rapidly fermentable nonstructural carbohydrates (fructans, simple sugars, or starches) in pasture, and animals with an equine metabolic syndrome (EMS) phenotype (insulin resistance, abnormal insulin dynamics, +/- obesity) seem to be at highest risk for developing the condition. Although the mechanisms linking consumption of pasture forage with development of la...
Extended phylogeny of the equine arteritis virus sequences including South American sequences. To perform genetic analysis of the ORF5 of equine arteritis virus (EAV) may provide new insights into the genetic evolution and origin of the Argentinean EAV sequences. Methods: A total of 76 sequences were analyzed by neighbor joining (NJ), maximum parsimony and maximum likelihood algorithms. The analysis of the selective pressures was performed using the Tajima's test. Results: The trees showed similar topologies. Two clades were identified: the first clade was formed by strains isolated mainly from a donkey, whereas the second clade presented four large groups from different geographic regi...
In vitro comparison of two centrally threaded, positive-profile transfixation pin designs for use in third metacarpal bones in horses. To compare heat generation during insertion, pullout strength, and associated microdamage between a self-tapping positive profile transfixation pin (STTP) and nontapping positive profile transfixation pin (NTTP). Methods: 30 pairs of third metacarpal bones (MC3s) from adult equine cadavers. Methods: One MC3 of each pair was assigned to the STTP group; the other was assigned to the NTTP group. The assigned pin was inserted into the diaphysis in a lateral to medial direction. Bone temperature increase during pilot-hole drilling and pin insertion was recorded at 1 mm from the final thread positio...
Expression of inflammation-associated genes in circulating leukocytes collected from horses with gastrointestinal tract disease. To investigate whether expression of inflammation-associated genes in leukocytes from horses with gastrointestinal tract (GIT) diseases correlated with the type of disease and outcome. Methods: 10 healthy horses and 50 horses with GIT disease. Methods: A blood sample was collected from each healthy horse or horse with GIT disease (during admission to the hospital). Leukocytes were isolated, diluted to a standard concentration, and frozen until RNA extraction. Expression of 14 genes associated with inflammation was quantified by use of a real-time quantitative reverse transcription PCR assay. R...
Primary epitheliotropic intestinal T-cell lymphoma as a cause of diarrhea in a horse. A 25-year-old Appaloosa gelding was evaluated for chronic weight loss and diarrhea. A clinical diagnosis of protein loosing enteropathy was made and the gelding was euthanized. Histology revealed neoplastic lymphocytes infiltrating the mucosa of the small and large intestine. Immunohistochemistry was positive for CD3, consistent with epitheliotropic T-cell lymphoma. Lymphome T intestinal épithéliotrope primaire comme cause de diarrhée chez un cheval. Un hongre appaloosa âgé de 25 ans a été évalué pour perte de poids et diarrhée chronique. Un diagnostic clinique d’entéropathie avec...
Proinflammatory cytokine and chemokine gene expression profiles in subcutaneous and visceral adipose tissue depots of insulin-resistant and insulin-sensitive light breed horses. Insulin resistance has been associated with risk of laminitis in horses. Genes coding for proinflammatory cytokines and chemokines are expressed more in visceral adipose tissue than in subcutaneous adipose tissue of insulin-resistant (IR) humans and rodents. Objective: To investigate adipose depot-specific cytokine and chemokine gene expression in horses and its relationship to insulin sensitivity (SI). Methods: Eleven light breed mares. Methods: Animals were classified as IR (SI=0.58+/-0.31x10(-4) L/min/mU; n=5) or insulin sensitive (IS; SI=2.59+/-1.21x10(-4) L/min/mU; n=6) based on results o...
The role of activated neutrophils in the early stage of equine laminitis. Despite ongoing research and a widening range of treatment options, laminitis remains a severely damaging condition with poorly understood pathophysiology. Results obtained from cytokine regulation studies during the last decade have highlighted the inflammatory nature of laminitis. This review will describe the role of systemic activation and local infiltration of neutrophils in laminar tissues in the induction of laminitis. Particular emphasis is placed on the role of neutrophil activation in subsequent vascular dysfunction and oxidative and proteolysis imbalances that are pathways previousl...
EcPV2 DNA in equine squamous cell carcinomas and normal genital and ocular mucosa. Squamous cell carcinoma (SCC) represents the most common malignant tumour of the eye and external genitals in horses. Comparable to humans, papillomaviruses (PV) have been proposed as etiological agents of cancer in horses and recently, Equine papillomavirus type 2 (EcPV2) has been identified in genital SCCs. Hitherto it had never been demonstrated in ocular SCCs. The first goal of this study was to determine the prevalence of EcPV2 DNA in tissue samples from equine genital and ocular SCCs, genital papillomas and penile intraepithelial neoplasia (PIN) lesions, using EcPV2-specific PCR. The sec...
Catastrophic biaxial proximal sesamoid bone fractures in UK Thoroughbred races (1999-2004): horse characteristics and racing history. Catastrophic biaxial proximal sesamoid bone fractures (PSBF) have not yet been described in detail in the UK racing population. Objective: To determine the incidence and relative risk (RR) of PSBF in different types of racing in the UK; and to describe horse-level characteristics and racing histories of horses sustaining these injuries. Methods: Distal limbs were collected from all racehorses suffering catastrophic fractures during racing at all 59 racecourses in the UK, in a prospective study from February 1999 to December 2004. Post mortem investigation identified the anatomical location and...
Histopathology and computed tomography of age-associated degeneration of the equine temporohyoid joint. The aetiology of temporohyoid osteoarthropathy (THO) is unknown; both primary infectious and degenerative causes have been suggested. Objective: There is a significant association between increasing age and severity of temporohyoid joint degeneration. To examine the histopathology of the temporohyoid articulation in aged horses and to compare the appearance of the joint with computed tomography (CT) and peripheral quantitative CT (pQCT). Methods: pQCT scans of the temporohyoid articulations were obtained bilaterally from 31 horses (range age 1-44 years) post mortem and images were graded by 2 ...
Advances in the diagnosis and treatment of chronic infectious and post-mating-induced endometritis in the mare. Rapid physical uterine clearance is paramount for fertility. Mares that are unable to clear the by-products of insemination or foaling quickly may develop post-mating-induced or acute endometritis. If endometritis is not promptly resolved, the infection can become chronic. Endometritis can be difficult to identify because clinical signs, ultrasonographic and laboratory findings can vary between uterine pathogens. Some micro-organisms are associated with an influx of neutrophils and fluid into the uterine lumen while others are associated with only heavy debris on cytological specimens. Identif...
IL-4 activates equine neutrophils and induces a mixed inflammatory cytokine expression profile with enhanced neutrophil chemotactic mediator release ex vivo. Neutrophils are potent contributors to the lung pathophysiological changes occurring in allergic airway inflammation, which typically involve T helper type 2 (Th2) cytokine overexpression. We have previously reported that equine pulmonary endothelial cells are activated by the Th2 cytokine IL-4 and express chemotactic factors for neutrophils after stimulation. We have further explored the possible mechanisms linking Th2-driven inflammation and neutrophilia by studying the effects of recombinant equine IL-4, a prototypical Th2 cytokine, on peripheral blood neutrophils (PBN) isolated from normal...
Toxicological effects of aflatoxins in horses. Aflatoxins are a group of mycotoxins principally produced by Aspergillus flavus and A. parasiticus, which are both natural contaminants of food and feedstuff. Aflatoxin B(1) is the most prevalent member of this group that is normally detected and is the most powerful hepatocarcinogen known. Few naturally occurring episodes of aflatoxicosis in horses have been reported in the literature. Indeed, the published information about aflatoxin exposure, metabolism and the effects on horses is limited and controversial, possibly indicating a lack of awareness rather than the rarity of the occurrence. T...
Genetic heterogeneity and variation in viral load during equid herpesvirus-2 infection of foals. Equine herpesvirus-2 (EHV-2) infection has been implicated as a cause of a variety of clinical disorders in young horses, including upper respiratory tract disease, generalized malaise, fever, pharyngeal lymphoid hyperplasia, and lymphadenopathy. Considerable sequence heterogeneity has been demonstrated previously among EHV-2 strains, and individual horses can be concurrently infected with more than one virus strain. In this study, the temporal variation of the viral load and genomic diversity of the glycoprotein B (gB) gene of EHV-2 in the nasal secretions of a cohort of foals was characteriz...
Deciphering membrane-associated molecular processes in target tissue of autoimmune uveitis by label-free quantitative mass spectrometry. Autoimmune uveitis is a blinding disease presenting with autoantibodies against eye-specific proteins as well as autoagressive T cells invading and attacking the immune-privileged target tissue retina. The molecular events enabling T cells to invade and attack the tissue have remained elusive. Changes in membrane protein expression patterns between diseased and healthy stages are especially interesting because initiating events of disease will most likely occur at membranes. Since disease progression is accompanied with a break-down of the blood-retinal barrier, serum-derived proteins mask the...
Evaluation of the role of superoxide anions in endotoxin-induced impairment of beta-adrenoceptor-mediated vasodilation in equine digital veins. To investigate the role of superoxide anions in the lipopolysaccharide (LPS)-induced impairment of beta-adrenoceptor-mediated equine digital vein (EDV) vasodilation. Methods: EDVs isolated from forelimbs of 24 healthy adult horses. Methods: Endothelium-intact or endothelium-denuded EDV rings were incubated with or without LPS (10 microg/mL) of Escherichia coli (O55:B5) for 4 hours. Cumulative concentration-relaxation curves resulting from administration of isoprenaline, a nonselective beta-adrenoceptor agonist, or from administration of SR 58611A, a selective beta(3)-adrenoceptor agonist, were...
Comparison of macrostructural and microstructural bone features in Thoroughbred racehorses with and without midbody fracture of the proximal sesamoid bone. To compare macrostructural and microstructural features of proximal sesamoid bones (PSBs) from horses with and without PSB midbody fracture to gain insight into the pathogenesis of PSB fracture. Methods: PSBs from 16 Thoroughbred racehorses (8 with and 8 without a PSB midbody fracture). Methods: Parasagittal sections of fractured and contralateral intact PSBs from horses with a PSB fracture and an intact PSB from age- and sex-matched control horses without a PSB fracture were evaluated for visual, radiographic, microradiographic, histologic, and his-tomorphometric differences in bone porosity,...
Ventricular arrhythmias during race recovery in Standardbred Racehorses and associations with autonomic activity. A lack of information on normal heart rhythm at maximal effort hampers investigation of poor performance and sudden death in Standardbred racing. Objective: To characterize rhythm variations during scheduled racing in clinically normal Standardbred horses. Methods: Two hundred and eighty-eight Standardbred horses competing in 40 scheduled races at a Southern Ontario racetrack. Methods: Observational study, convenience sampling: Heart rhythm was monitored by ECG from harnessing to postrace recovery and assessed visually and by examining heart rate intervals. Rhythm variations were used as respo...
Age-related differences in prostaglandin E2 synthesis by equine cartilage explants and synoviocytes. Time- and concentration-related actions of lipopolysaccharide (LPS) on the synthesis of prostaglandin E(2) (PGE(2)) were investigated in cartilage explants and synoviocytes harvested from 3 age groups of horses, all with clinically normal joint function: group A 20 years. Cartilage explants from group A horses were least and those from group C were most sensitive to LPS. Significant increases in PGE(2) concentration (P <or= 0.01) were obtained in group C horses in response to LPS concentrations of 1.0 microg/mL (and higher) after exposure for 24, 36 and 48 h, whereas explants from group A h...
