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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.
Blood arginine vasopressin, adrenocorticotropin hormone, and cortisol concentrations at admission in septic and critically ill foals and their association with survival. Sepsis is an important cause for neonatal foal mortality. The hypothalamic-pituitary-adrenal axis (HPAA) responses to sepsis are well documented in critically ill humans, but limited data exist in foals. The purpose of this study was to evaluate the HPAA response to sepsis in foals, and to associate these endocrine changes with survival. Objective: Blood concentrations of arginine vasopressin (AVP), adrenocorticotropin hormone (ACTH), and cortisol will be higher in septic foals as compared with sick nonseptic and healthy foals. The magnitude of increase in hormone concentration will be negativ...
Risk factors for owner-reported occurrence of equine protozoal myeloencephalitis in the US equine population. Equine protozoal myeloencephalitis (EPM) is a serious and often fatal neurologic disease of horses, but few studies have investigated risk factors. Objective: To evaluate operation- and individual-level factors associated with likelihood of the occurrence of EPM. Methods: Data were collected as part of a study of the US equine industry from 1,178 operations representing 83.9% of horses and 51.6% of operations with > or =3 horses in 28 states. Methods: Probability-based sampling was used to enroll representative operations in a cross-sectional study. Interviews were conducted to collect info...
Equine recurrent uveitis–a spontaneous horse model of uveitis. Equine recurrent uveitis (ERU) is an autoimmune disease that occurs with a high prevalence (10%) in horses. ERU represents the only reliable spontaneous model for human autoimmune uveitis. We already identified and characterized novel autoantigens (malate dehydrogenase, recoverin, CRALBP) by analyzing the autoantibody-binding pattern of horses affected by spontaneous recurrent uveitis (ERU) to the retinal proteome. CRALBP also seems to be relevant to human autoimmune uveitis. Proteomic screening of vitreous and retinal samples from ERU diseased cases in comparison to healthy controls has led t...
Evaluation of dietary and management risk factors for enterolithiasis among horses in California. Enteroliths are intestinal calculi that result in intestinal obstruction and colic in horses. Equine enterolithiasis occurs worldwide, but the disease is particularly prevalent in some geographic locations, including California. The objectives of this study were to evaluate dietary and environmental risk factors for the disease. This was accomplished through a case-control study by comparing horses with colic from enterolithiasis presenting to the University of California, Davis VMTH, to horses with colic of other causes. Data were collected on 61 horses with enterolithiasis and 75 controls vi...
A subset of equine sarcoids harbours BPV-1 DNA in a complex with L1 major capsid protein. Bovine papillomavirus type 1 or 2 (BPV-1, BPV-2) are accepted causal factors in equine sarcoid pathogenesis. Whereas viral genomes are consistently found and expressed within lesions, intact virions have never been detected, thus permissiveness of sarcoids for BPV-1 replication remains unclear. To reassess this issue, an immunocapture PCR (IC/PCR) was established using L1-specific antibodies to capture L1-DNA complexes followed by amplification of the viral genome. Following validation of the assay, 13 sarcoid-bearing horses were evaluated by IC/PCR. Samples were derived from 21 tumours, 4 per...
Acquired multiple Acyl-CoA dehydrogenase deficiency in 10 horses with atypical myopathy. The aim of the current study was to assess lipid metabolism in horses with atypical myopathy. Urine samples from 10 cases were subjected to analysis of organic acids, glycine conjugates, and acylcarnitines revealing increased mean excretion of lactic acid, ethylmalonic acid, 2-methylsuccinic acid, butyrylglycine, (iso)valerylglycine, hexanoylglycine, free carnitine, C2-, C3-, C4-, C5-, C6-, C8-, C8:1-, C10:1-, and C10:2-carnitine as compared with 15 control horses (12 healthy and three with acute myopathy due to other causes). Analysis of plasma revealed similar results for these predominantly...
A review of equine muscle disorders. Muscle disorders are a common cause of disability in horses. For many years, clinical manifestations such as muscle pain, exercise intolerance, weakness, and stiffness were believed to be caused by a single syndrome. However, in the past years a broad spectrum of muscle disorders have been recognized including glycogen and polysaccharide storage myopathies, malignant hyperthermia, mitochondrial myopathy, hyperkalemic periodic paralysis and others. For some, a specific mutation has been identified. Recognition of the myopathic clinical phenotype and thorough clinical, electrodiagnostic, and his...
Atypical myopathy in grazing horses: a first exploratory data analysis. Over the last decade, atypical myopathy (AM) in grazing horses has emerged in several European countries. An exploratory analysis was conducted to determine horse- and pasture-level indicators or factors associated with AM in Belgium. Belgian cases of AM confirmed by histology (n=57) were compared to their healthy co-grazing horses (n=77) and to pastured horses not involved with AM as controls (n=386). The pastures where confirmed cases were grazing (42 pastures; 38 sites; 44 incidences of AM) were compared with those of the controls (216 pastures; 96 sites; no incidence of AM). Statistically ...
MT3-MMP (MMP-16) is downregulated by in vitro cytokine stimulation of cartilage, but unaltered in naturally occurring equine osteoarthritis and osteochondrosis. Matrix degradation by metalloproteinases is considered a key feature in the loss of articular cartilage seen in many joint diseases. Membrane-type matrix metalloproteinase-3 (MT3-MMP) expression is elevated in human cartilage in end-stage osteoarthritis. We investigated whether MT3-MMP is similarly regulated in cartilage in two naturally occurring arthropathies in vivo and whether proinflammatory cytokines regulate its expression in vitro. MT3-MMP expression was evaluated in cartilage from horses with osteoarthritis and osteochondrosis and compared with age- and site-matched normal cartilage. ...
Fate of equine pericardial roll conduit for Rastelli operation during long-term follow-up. Right ventricular outflow tract obstruction is a frequent condition after Rastelli operation. Although several modifications have been reported elsewhere, ideal conduit has not been developed yet during long-term follow-up. We reviewed our experiences over 15-year long-term follow-up with patients who underwent Rastelli operation using house-made equine pericardial roll graft. Methods: Since June 1981, 16 patients underwent Rastelli operation with the pericardial roll graft. Median follow-up time was 15.6 years (7.3-26.8 years). Results: Twelve out of 16 patients using pericardial roll graft w...
The equine endometrosis: new insights into the pathogenesis. This paper describes the histomorphological and immunohistochemical characterisation of phenotypic variations of endometrosis as well as potential etiological factors which may influence disease progression. In total, 779 endometrial biopsies were examined. These biopsies were taken in the breeding and non-breeding season (n=509), on defined days during the estrous cycle (n=70) and before and after experimentally induced bacterial endometritis (n=200). In addition to conventional histopathology, selected biopsies were investigated using alcianblue staining as well as immunohistochemical method...
Cytokine dysregulation in aged horses and horses with pituitary pars intermedia dysfunction. Equine pituitary pars intermedia dysfunction (PPID) is the result of a loss of dopaminergic inhibition of the pars intermedia secondary to neurodegeneration of periventricular hypothalamic neurons. The pathologic events contributing to development of neurodegeneration or clinical signs in equids with PPID are unknown. Chronic inflammation may contribute to initiation or progression of PPID. Objective: Horses with PPID have a distinct systemic cytokine profile compared with that of normal adult or aged horses. The cytokine profile of healthy aged horses differs from that of adult horses. Method...
Suspected primary scapulohumeral osteoarthritis in two Miniature ponies. Two cases of severe scapulohumeral osteoarthritis in Miniature ponies are described, one bilateral and the other unilateral. The condition is thought to occur in miniature breeds as a result of scapulohumeral dysplasia. The presentation in one of the ponies was unusal: it refused to pick up either fore limb, with progression to a uniquely bizarre gait with narrow forelimb placement, an arched back and widely placed hindlimbs camped well forward under the body. The other pony was presented for an acute unilateral non-weight bearing forelimb lameness. Response to analgesia in both cases was poor...
Equine atypical myopathy: a review. Atypical myopathy (AM) is an acute rhabdomyolysis syndrome that occurs at irregular intervals in grazing equines. An increasing number of outbreaks have been reported in recent years, including some from countries where the disease has not previously been diagnosed. In this review, clinical and other details of outbreaks of AM are analysed to better define its epidemiological profile. Potential aetiologies are discussed, the short clinical course of AM is described and the main biochemical and pathological findings are considered. Recommendations for medical management are suggested, based on ...
Hormone profiles of mares affected by the mare reproductive loss syndrome. While searching for the cause of the Mare Reproductive Loss syndrome (MRLS), we postulated that 1 of 3 tissues in 40-120 D pregnant mares was the likely primary target of the noxious factor that caused early abortions: The corpora lutea (CL), the endometrium or the fetus and/or its membranes. At this stage of gestation, progesterone (P4) is solely produced by luteal tissue, eCG by endometrial cups in the endometrium and oestrogens by the feto-placental unit. We determined whether concentrations of P4, eCG and/or total conjugated oestrogens (CE) would indicate which tissue was targeted during t...
Effect of a novel solution for organ preservation on equine large colon in an isolated pulsatile perfusion system. Several therapeutic agents have been tested in models of ischaemia and reperfusion injury (IRI) in equine jejunum, with mixed results. This study was based on the use of an organ perfusion solution (OPS) designed to protect human allografts from IRI. Objective: A modified OPS can preserve the integrity of equine large colon during 12 h of isolated pulsatile perfusion, in the absence of oxygen and blood. Methods: Segments of large colon were removed from anaesthetised horses, the contents removed and the mucosa rinsed with 0.9% saline. Experimental segments were perfused for 12 h with one litre...
Unexplained underperformance syndrome in sport horses: classification, potential causes and recognition. When inadequate training stress is applied and recovery time is insufficient, performance reduction and chronic maladaptation occurs. Known as overtraining syndrome (OTS), this complex condition afflicts horses in top training. The name of the syndrome implies causation and it is necessary to differentiate it from over-reaching, a term used in horses that, after suffering a loss of performance without an obvious clinical reason, recover their performance within 1 or 2 weeks. The term OTS should be used for horses in heavy training losing performance without an obvious clinical reason and which...
Transmission dynamics and changing epidemiology of West Nile virus. West Nile virus (WNV) is a flavivirus that is maintained in a bird-mosquito transmission cycle. Humans, horses and other non-avian vertebrates are usually incidental hosts, but evidence is accumulating that this might not always be the case. Historically, WNV has been associated with asymptomatic infections and sporadic disease outbreaks in humans and horses in Africa, Europe, Asia and Australia. However, since 1994, the virus has caused frequent outbreaks of severe neuroinvasive disease in humans and horses in Europe and the Mediterranean Basin. In 1999, WNV underwent a dramatic expansion of ...
Naturally arising point mutations in non-essential domains of equine infectious anemia virus Rev alter Rev-dependent nuclear-export activity. Equine infectious anemia virus (EIAV) exhibits a high rate of genetic variation in vivo, and results in a clinically variable disease in infected horses. In vivo populations of EIAV have been characterized by the presence of distinct, genetic subpopulations of Rev that differ in phenotype and fluctuate in dominance in a manner coincident with each clinical stage of disease. This study examined the specific mutations that arose in vivo and altered the phenotype. The Rev protein was found to be highly conserved, and only 10 aa mutations were observed at a frequency greater than 10 % in the sampl...
Health management of horses under high challenge from trypanosomes: a case study from Serengeti, Tanzania. Horses kept for recreational riding purposes by a wildlife tourism company in a heavily tsetse fly-infested region of north-western Tanzania were systematically monitored to investigate the occurrence, presentation and management of tsetse-transmitted trypanosomosis. During a 23-month period, 18 clinical cases were diagnosed (Trypanosoma brucei or Trypanosoma congolense were identified) and treated and trypanosomes were implicated of involvement in four deaths. Pyrexia consistently aided early detection (17 cases). Ataxia, weight loss and anaemia were seen in chronic cases and conferred a poor...
American cutaneous leishmaniasis in horses from endemic areas in the north-central mesoregion of Paraná state, Brazil. American cutaneous leishmaniasis (ACL) is an endemic disease in the north-west of Paraná state, Brazil, where it occurs in humans and dogs. Few studies have been undertaken on the occurrence of the disease in other domestic animals and horses. In this study we investigated the infection of horses by Leishmania in ACL-endemic rural areas. Direct agglutination test (DAT) and polymerase chain reaction (PCR) were employed. Fifty-five horses from rural areas in the municipalities of Doutor Camargo, Ourizona, São Jorge do Ivaí, Ivatuba and Santa Fé (Agua do O) were analysed. DAT-detected antibod...
Retrospective study assessing efficacy of treatment of large colonic impactions. Cases with a history of colic due to a large colonic impaction were recruited retrospectively to assess the treatment efficacy and complications of oral and parenteral fluid therapy regimes for correction of primary large colon impactions. Oral isotonic fluids had been administered at varying intervals following initial treatment with magnesium sulphate and water. There was no significant difference in complication rates between groups. Considering complication rates with impaction clearance, hourly administration of oral fluids appears to be the most appropriate treatment regime of those inve...
The pathology of bronchointerstitial pneumonia in young foals associated with the first outbreak of equine influenza in Australia. The first outbreak of equine influenza virus (EIV) infection was confirmed in Australia in 2007. Some EIV-positive young foals died with bronchointerstitial pneumonia, an rare disease process in this age group that is often postulated to be caused by viral infection. Objective: The aim of this study was to describe post mortem lesions in EIV-infected foals. Methods: Post mortem examinations were conducted on 11 young foals (age 2-12 days) submitted to the Scone Veterinary Hospital, NSW over a 2-month period in 2007. The foals had presented with or developed fatal pneumonia, and were known or s...
High resolution microscopic survey of third metacarpal articular calcified cartilage and subchondral bone in the juvenile horse: possible implications in chondro-osseous disease. The aim was to survey articular calcified cartilage (ACC) and subchondral bone in the palmar and dorsal regions of the condyles of the third metacarpal bone (Mc3) of young horses with minimal or no signs of musculo-skeletal abnormality. Back-scattered electron scanning electron microscopy (BSE SEM) was conducted on polymethyl methacrylate-embedded mediolateral slices and macerated wedges of the right distal Mc3 from seven each of trained and untrained 2-year-old Thoroughbred horses. Furrows or grooves visible to the naked eye in the mineralizing front (MF) of ACC are the commonest "lesion" and...
