Pathogenesis in horses refers to the biological mechanisms that lead to the development and progression of diseases within equine species. This process involves a complex interaction between the horse's immune system, genetic predispositions, environmental factors, and infectious agents such as bacteria, viruses, or parasites. Understanding pathogenesis is essential for identifying how diseases manifest and progress in horses, which can inform diagnostic and therapeutic strategies. Research in this area often focuses on specific diseases, examining factors such as pathogen entry, immune response, tissue damage, and recovery processes. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanisms, contributing factors, and implications of pathogenesis in equine health.
Jeffcott LB, Dalin G.The functional anatomy of the thoracolumbar (TL) spine is considered in relation to the horse's ability to perform at speed and to jump. The morphological features quite clearly show the relative inflexibility of the equine back and this was confirmed by some experimental studies. Fresh post mortem specimens from 5 Thoroughbreds were used to estimate the limits of dorsoventral movement of the TL spine from mid-thoracic to the cranial lumbar (T10-L2). The individual spinous processes could be moved a mean 1.1-6.0 mm on maximum ventroflexion and 0.8-3.8 mm on dorsiflexion. The overall flexibilit...
Swerczek TW.Four experiments were performed to elucidate the pathogenesis of toxicoinfectious botulism in horses and foals. Groups of horses and foals were inoculated with one of the following: (1) crude toxin of Clostridium botulinum, type B, given IV, (2) C botulinum spores, given IM, (3) C botulinum spores, given IM, in necrotic lesions, and (4) C botulinum spores, given orally with and without dexamethasone. Toxin of C botulinum in minute amounts is toxic to horses. Clostridium botulinum spores produced toxicosis only when necrotic lesions were present. When C botulinum spores were given orally, they ...
Barclay WP, White KK, Williams A.Nineteen cases of villonodular synovitis as identified in 14 horses are presented. Physical and radiographic findings are discussed and the surgical correction described. Case histories indicate that surgical extirpation of the lesion is corrective and that rest without surgical intervention is ineffective. Radiation therapy following surgery does not appear to be necessary.
Keeler RF, Balls LD, Shupe JL, Crowe MW.Cows, ewes, and mares varied considerably in susceptibility to toxicoses from the oral administration of the piperidine alkaloid, coniine. Cows were most susceptible and ewes least. Only calves had teratogenic effects from maternal administration of coniine during gestation; lambs and foals were apparently resistant. Results suggest that the marked differences between cattle and sheep are probably not due to variation in gut absorption or rumen metabolism.
van Nie CJ, van der Kamp JS.A case of tricuspid atresia in a premature foal associated with large atrial septal and ventricular septal defects is reported. This anomaly is compared with other cases in horses as reported in the literature. As tricuspid atresia in horses is usually not diagnosed so that relatively few cases have been reported, a classification similar to that of human anomalies is not possible. It is suggested that the present malformation is due to abnormal development of the atrioventricular canal. The factors involved in the pathogenesis of this abnormal development are obscure.
Roumillat LF, Feorino PM, Lukert PD.Infection of a human lymphoblastoid cell line (Jijoye line derived from a Burkitt lymphoma which contains Epstein-Barr virus) with equine herpesvirus 1, maintained and observed for 53 days, was characterized by the continuous production of infectious extracellular and intracellular virus. Maximum virus production correlated with active cell multiplication. Less than 15% of the cells possessed viral capsid antigen at any one time. Five percent of the cells in the Jijoye line possess Epstein-Barr viral capsid antigen; 80% of the Epstein-Barr viral caspid-containing cells also contained equine he...
Clayton HM, Duncan JL.Following infection with 8000 Parascaris equorum eggs in two- to four-week-old foals reared under worm-free conditions a high percentage of the infective dose completed its tissue migration and returned to the small intestine. Patent infections were establisehd between 81 and 104 days after infection and high faecal egg counts were recorded. A group of six- to 12-month-old foals, which had been either reared under worm-free conditions or exposed to natural ascarid and strongyle infections on pasture, received a similar infection of 8000 P equorum eggs. Compared with the younger foals there was...
Jackson DS.This paper reviews some of the biochemical modifications involved in fibrous tissue formation and discusses possible ways of controlling fibrosis in clinical conditions. The lathyritic agents, beta-aminoproprionitrile (BAPN) and penicillamine, appear in certain situations to be able to control fibrosis by blocking the biosynthesis of collagen. There are no compounds that are yet known which are capable of reversing pre-existing fibrosis and future research may perhaps be more profitably directed towards the stimulation of collagen catabolism rather than the inhibition of its synthesis.
Slauson DO, Lewis RM.Glomerulonephritis constitutes an important category of renal diseases in animals and has been recognized with increasing frequency in the last decade. We report here the comparative morphologic aspects of glomerulonephritis as a naturally occurring disease of animals. We briefly review the immunopathogenesis of glomerulonephritis. The morphology of renal lesions occurring in glomerulonephritis in dogs, cats, cattle, sheep, horses and swine has been reviewed with emphasis on the range and specificity of various glomerular lesions and on the comparison of lesions between various species. A dist...
Klevjer-Anderson P, Cheevers WP, Crawford TB.Equine dermal fibroblasts persistently infected with equine infectious anemia virus (EIAV) show no alterations in cell morphology or growth kinetics when compared to uninfected cells. The percentage of cells immunofluorescent positive for viral proteins fluctuated, depending upon the stage of the cell cycle, while production of extracellular virus was uniform throughout the cell cycle, increasing only as the cell number increased. This was shown in log versus stationary phase cultures as well as in cultures synchronized by sterum starvation. The establishment of productive infection did not re...
Lancaster WD, Theilen GH, Olson C.DNAs from bovine papilloma virus(BPV)-induced hamster tumors and from equine connective tissue tumors of unknown etiology were examined for BPV DNA sequences by molecular hybridization. DNA from two distinct classes of BPV (type 1 and type 2) was labeled in vitro and used as probes. Analysis of DNA-DNA reassociation kinetics indicated that both virus types were capable of tumor induction in the hamster. DNA isolated from 6 of 7 equine tumors accelerated the reassociation of the BPV DNA probes. BPV type 1 or type 2 DNA hybridized extensively to DNA from 3 tumors, while 3 other tumors contained ...
Bennett D.The gross and histological features of multiple bone infection in two foals are described. In both cases the lesions were confined to the region of the growth plate. Bone and, in some cases, growth plate cartilage destruction has occurred associated with an extensive inflammatory cell infiltration. The significance of the pathological observation is discussed in relation to the pathogenesis of bone infection in the foal.
Srihakim S, Swerczek TW.Parasite-free pony foals (n = 10) were infected orally with 1000,000 Parascaris equorum embryonated eggs. One pony foal each was euthanatized on days 1, 3, 5, 7, 11, 16, 23, 27, 42, or 80 after infection. Foals infected for more than 7 days showed signs of coughing, anorexia, rough coat, and weight loss. Cellular changes in the blood were mild anemia, marked eosinophilia, and leukopenia. Gross postmortem lesions included hemorrhage, edema, and white-to-yellow necrotic foci (0.5 to 1.00 mm) in lungs, liver, and bronchial and hepatic lymph nodes. Microscopically, the liver was hemorrhagic and ha...
Kiryu K, Kaneko M, Satoh H.Histopathololgical observations were performed on the heart and cardiac nervous system of 5 horses affected with wandering pacemaker. The histopathological lesions common to all the animals were as follows: (1) Focal fibrosis in the atrial myocardium just beneath the subendocardium and/or in the endo- and subendocardium, and existence of atrial Purkinje-like fibers within the fibrotic lesions, (2) Microvascular altetation, characterized by edematous-loosening and/or fibrous swelling of the walls of the small and minute arteries, in both the atria, (3) Edema in the intracadiac nerves of both th...
Davies ME.A detailed study was made of 194 equine strains of E. coli, involving biochemical and serological characters. In these, the equine strains closely resembled E. coli from other sources, and shared antigenic characters with strains isolated from different animal species.
Jackson DS.This paper reviews some of the biochemical modifications involved in fibrous tissue formation and discusses possible ways of controlling fibrosis in clinical conditions. The lathyritic agents, beta-aminoproprionitrile (BAPN) and penicillamine, appear in certain situations to be able to control fibrosis by blocking the biosynthesis of collagen. There are no compounds that are yet known which are capable of reversing pre-existing fibrosis and future research may perhaps be more profitably directed towards the stimulation of collagen catabolism rather than the inhibition of its synthesis.
Young KM, Lunn DP.Technologic advances in immunodiagnostic testing have enhanced our understanding of the pathogenesis of a broad array of diseases, including infectious diseases, immunodeficiency disorders, and immune-mediated disorders. If applied rationally, with an understanding of the questions the tests answer as well as the limitations that constrain their use, these tests can serve as valuable aids in the diagnosis and management of equine diseases.
Fatemi-Nainie S, Anderson LW, Cheevers WP.MC-1 is an equine sarcoid-derived cell line which spontaneously releases a retrovirus possessing genomic sequence homology with an inducible endogenous retrovirus of normal equine cells. A complete characterization of MC-1 tumor cells was undertaken, including morphology, growth kinetics, and saturation density, selective growth in semisolid media, uptake of 2-deoxyglucose, and tumorigenicity in athymic nude mice. MC-1 cells, in contrast to normal equine dermal fibroblasts, exhibit all of the characteristics of malignantly transformed cells.
This section includes clinical conditions which have unique characteristics which make them unsuitable for inclusion in the first six sections. The clinical description, aetiology and histopathologic findings of the unusual ear lesion, aural plaques, are described. Dermatoses complicated by, or caused by, photosensitivity are discussed in regards to their aetiology and pathogenesis as well as clinical features. The suggestion that photosensitization plays a role in the development of the lesions seen in pastern leukocytoclastic vasculitis is made. This section ends with an in depth discussion ...
Gothe R.This paper gives a survey on biology and ecology of equine tapeworms as well as on pathogenesis, clinics, diagnosis, therapy, and prophylaxis of tapeworm infections.
Stitz L, Richt JA, Rott R.An overview of the pathogenesis of Borna disease (BD) in rats as a model for the naturally occurring infection in horses and sheep is presented. Our findings revealed a virus infection in which a virus-specific T cell-mediated immune response leads to disease. The immune cells capable of mediating this immunopathological reaction were defined as helper/inducer T cells. In all, the described observations indicate that CD4+ T cells and macrophages trigger a delayed-type hypersensitivity reaction and cause BD together with other cells of the immune system.
Mele M, Ramseyer A, Burger D, Leeb T, Gerber V.Overall, monogenetic hereditary diseases are less important for the breeding industry than polygenetic diseases because they are relatively rare. For the individual animal, however, these diseases have often a dramatic outcome and many of these diseases presently known are lethal. For several of them the exact pathogenesis is known and DNA-tests are available to confirm the exact diagnosis.
Jaeschke G, Rudolph R.Clinicopathological aspects of equine leukosis are discussed in a review. Among various other findings, only hypercalcaemia accompanied by paraneoplastic syndrome in the course of equine leukosis, increased values of alkaline phosphatase as usual in tumorous diseases, and hypalbuminaemia and hypergammaglobulinaemia in mesentric and intestinal forms of equine leukosis seem to have some diagnostic and pathogenetic significance. Changed values of further parameters are more or less non-specific concomitant signs, indicating that other organs or organ systems have been affected. However, in case o...
Svalastoga E.Microangiographical investigations of the navicular bone in horses with navicular disease show, compared to similar investigations of normal navicular bones, that, in general, the vascular pattern is preserved but the vessels are dilated with "pooling" of the contrast medium subchondrally under facies flexoria. Similar changes may be observed in cases of human arthrosis. The present investigation therefore supports the view that navicular disease is a disease which resembles arthrosis.
Iqbal J, Purewal AS, Edington N.The aim of this study was to investigate the role of immediate early gene (gene63) in the pathogenesis of equine herpesvirus 1 (EHV-1) acute and latent infections in equine and murine models. EHV-1 gene63 mutant virus (g63mut) along with EHV-1 (Ab4) was used for intracerebral and intranasal infection of 3 and 17-day-old mice. Both viruses were recovered at the same frequency from tissues after infection. Two Welsh ponies were infected via the intranasal route with each of the viruses. Acute infection was monitored by virus isolation from nasal swabs and peripheral blood leukocytes. Six weeks p...
Don-van't Slot HP, van der Kolk JH.Severe-Combined-Immunodeficiency-Disease (SCID) is discussed with special reference to its pathogenesis, clinical symptoms, pathology, and diagnosis. The disorder has been observed in the USA, Canada, Great Britain, and Australia and is characterized by an autosomal recessive mode of inheritance. The clinical features of the disease seen in Arab foals under 46 days of age are intermittent fever, (adenoviral) pneumonia, and weight loss sometimes associated with diarrhoea. From 1998 on, the SCID gene can be detected in the Netherlands by means of DNA analysis.
Rosser EJ.Although there are numerous dermatoses in the horse in which the formation of crusts occurs, there are two relatively common and important infectious crusting dermatoses, namely, dermatophytosis and dermatophilosis. This article reviews the current concepts regarding the etiology and pathogenesis of each disease, as well as the more common clinical presentations, methods of diagnosis, and treatment.
Allen AL.Postmortem radiography can be a valuable supplement to traditional necropsy. This article provides examples where postmortem radiographs have been useful in diagnosing and documenting lesions in animals, and have helped demonstrate important principles of the pathology and the pathogenesis of lesions identified at necropsy. This article also discusses additional circumstances where the application of postmortem radiography might be worthwhile.
Marr KA, Lees P, Page CP, Cunningham FM.The leukotrienes (LT) LTD4 and LTB4 have been shown to cause bronchoconstriction and neutrophil accumulation, respectively, in horse lungs. Such changes are characteristic of the equine allergic respiratory disease, chronic obstructive pulmonary disease (COPD). To further investigate the role of these putative mediators in the pathogenesis of equine COPD the effect of a 5-lipoxygenase inhibitor, fenleuton, on antigen-induced changes in horses with this condition has been examined. Six horses with COPD underwent a series of four antigen challenges, one month apart, with placebo pre-treatment on...
Szczerba-Turek A, Siemionek J, Wasowicz K, Szweda W, Raś A, Platt-Samoraj A.BPV-1 is now recognized as a main etiological agent of equine sarcoids. The etiopathogenesis of the equine sarcoids is equivocal and is not yet fully understood. The aim of the present study was to analyse a partial sequence of the L1 gene of BPV associated with equine sarcoids in Polish horses. After clinical diagnosis, 40 skin lesions obtained from 29 horses were collected. The amplicons of a fragment of BPV L1 DNA were detected using PCR with MY09/MY11 primers in 31 specimens. All of them were recognized as BPV-1. Phylogenetic analysis has allowed the amplicons of partial L1 gene to be divi...
Mair TS, Pearson GR.A 3 1/2-year-old bay gelding of the cob type showed nervous signs and coughing associated with breaking-in and exercise. At post-mortem examination, heavy melanin pigmentation of the meninges of the hind brain and the medulla was identified and, on histological examination, melanin-containing cells were found within connective tissue extending into the medulla. The lesion was considered to be a melanotic hamartoma.
Holbrook TC, Gilliam LL, Stein FP, Morgan SE, Avery AL, Confer AW, Panciera RJ.Caley Pea (Lathyrus hirsutus) is potentially toxic to horses, but large case series are not reported. Objective: To describe the clinical signs of horses intoxicated with Lathyrus hirsutus and speculate on the neuroanatomical lesion localization and pathogenesis based upon the observed clinical signs. Methods: Twenty-two of 25 horses ranging in age from 6 to 34 months were affected. Five affected horses were presented to the OSUCHVS for evaluation and treatment after having been attended at the ranch by a local veterinarian (ALA). An additional horse that had been euthanized was also presented...
Karamendin K, Abishov A, Kydyrmanov A, Akhmetzhanova M.In 2011, there was an outbreak of a disease with mass abortions among horses in southeastern Kazakhstan. The AK-2011 strain was isolated from an aborted fetus and subsequently identified as equid alphaherpesvirus 1. Here, we describe the nearly complete genome sequence of the AK-2011 strain, attenuated for vaccine development.
Malekinejad H, Alizadeh-Tabrizi N, Ostadi A, Fink-Gremmels J.The pathogenesis of equine grass sickness (EGS) has not fully understood. A better understanding of the exact pathogenesis of diseases can help to make an accurate diagnosis. Previous studies reported some pathological damage of neuronal cells in EGS patients. In this study, primarily cytotoxicity of serum from three clinically EGS-diagnosed horses on PC12 Tet-off (PTO) cells was assessed. Subsequently, the apoptotic tests including cytochrome C release, caspase-3/7 activity measurement and DNA fragmentation assay were conducted to clarify the apoptotic effect of serum from EGS patients. Addit...
Bergman HJ, de Kruif A, van Dessel S.A review is given of treatment for 'problem' mares that do not become pregnant. To determine the best therapy, it is necessary to understand the defence mechanisms of the uterus and the pathogenesis of not getting in foal. A thorough clinical examination is absolutely necessary to come to a correct diagnosis. This examination will be explained in a practical way. In the second article the different therapies for treating problem mares are discussed. The therapeutic possibilities vary widely. They can be classified in: anatomical corrections, anti-infectious therapy, and treatment to enhance th...
Musselman EE, LoGuidice RJ.A necropsy diagnosis of hypoplastic left ventricular syndrome was made in a day-old foal. The cardiac abnormalities included mitral and aortic valve atresia, patent ductus arteriosus, and a secundum atrial septal defect. The left ventricle was hypoplastic and nonfunctional. The brief survival of the foal was a consequence of left-to-right shunting through the atrial septal defect and right-to-left shunting through the patent ductus. The information is presented to demonstrate the existence of the syndrome as a congenital defect in the horse and to clarify the necropsy findings for the practiti...
Frank N, Sojka JE, Latour MA.To evaluate selected concentrations of blood lipids and lipase activities in euthyroid and hypothyroid horses deprived of feed for 96 hours. Methods: 4 healthy adult mares and 4 thyroidectomized adult mares. Methods: Horses were deprived of feed for 96 hours. Blood samples were collected at 24-hour intervals and analyzed to determine concentrations of non-esterified fatty acid (NEFA), triglyceride (TG), total cholesterol (TC), and very-low-density lipoprotein (VLDL) as well as composition of VLDL. Plasma lipase activities were measured after feed was withheld for 96 hours and 12 days after res...
Götz HJ.A case of diprosopus in a foal is described. This is only the second report of such a deformity in the equine species. Hereditary pathology and pathogenesis are discussed.
Marsella R.Autoimmune dermatopathies are not common in horses. These autoimmune diseases can be idiopathic or triggered by an antigen such as drugs, vaccines, or neoplasia. The most common one is pemphigus foliaceus, which manifests as a pustular, crusting eruption. Other more common pustular diseases should be ruled out before considering pemphigus. Vasculitis is relatively common in horses and can be triggered by a variety of antigenic stimulations. Systemic lupus and true idiopathic autoimmune vasculitis are very rare in horses. Every effort should be made to reach a final diagnosis, as the prognosis ...
Johns I.This article discusses the reported paraneoplastic syndromes (PNSs) in horses, including the possible pathogenesis, diagnostic methods, and any treatment options. The more commonly reported PNSs in horses include cancer anorexia and cachexia, fever and increased acute phase protein concentrations, and hypercalcemia and monoclonal gammopathy. As these conditions can often be more commonly diagnosed in non-neoplastic conditions, the diagnosis of a PNS and the accompanying neoplasia can be challenging. As signs of a PNS may precede signs of the underlying neoplasia, it is important that the clini...
Hain-Saunders N, Knight DR, Bruce M, Riley TV.Recent increases in community-associated Clostridioides difficile infections have highlighted the importance of monitoring toxigenic C. difficile from animal and environmental sources. We provide the complete circularized genomes of two toxigenic C. difficile strains isolated from feral horse faeces. Genome N64 (sequence type 964) consists of a single chromosome of 4,078,791 bp, while genome H251 (sequence type 963) comprises one chromosome (4,304,722 bp) and three plasmids (150,942 bp, 11,534 bp, and 9,074 bp).
Finno CJ.In the field of equine muscle disorders, many conditions have a genetic basis. Therefore, genetic testing is an important part of the diagnostic evaluation. Validated genetic tests are currently available for 5 equine muscle disorders: hyperkalemic periodic paralysis, malignant hyperthermia, glycogen branching enzyme disease, type 1 polysaccharide storage myopathy, and myosin heavy chain myopathy. These diseases should be tested for in the appropriate breeds with clinical signs of disease or as part of breeding management. Genetic testing in veterinary medicine is not regulated, and therefore,...
Rossdale PD, Jeffcott LB, Leadon DP.The development and design of a project in collaborative research which originated from a problem identified in practice, namely prematurity in the newly born foal, is described here. The project established a model of equine prematurity for the purpose of studying the diagnosis, pathogenesis and treatment of the condition. It involved practitioners and full time research workers in a number of veterinary and medical institutes.
MacNeill AL, Micheloud JF, Parvin R, Gjessing M, Airas NA, Sant'Ana FJF, Adamek M.Zoonotic poxviruses, including monkeypox virus (MPV), the causative agent for Mpox disease, have gained significant media and scientific attention due to recent outbreaks in human populations across the globe. The increase in human cases of poxvirus infection is not unexpected, as routine vaccination against smallpox (a disease caused by the poxvirus variola virus, which cross protects against other orthopoxviruses) was discontinued in the 1980s after its eradication. Large numbers of vertebrate and invertebrate species are susceptible to infection by . Clinical signs and histologic lesions ca...
