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Topic:Pathogenesis
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.
Geotrichum candidum as etiological agent of horse dermatomycosis. Fungi of the genus Geotrichum are commonly found in the environment and, in some circumstances, they may cause diseases in humans and animals. Although these fungi have been isolated from skin lesions of some animal species, their pathogenic role in horses remains uncertain. With the aim to investigate the role of Geotrichum candidum as etiological agent of dermatomycoses, a retrospective study of 64 horses presenting skin lesions and suspected to have fungal infections was carried out. For each animal, anamnestic data were recorded and fungal culture were performed using hair. Out of 64 cases...
Bovine papillomavirus E7 oncoprotein binds to p600 in naturally occurring equine sarcoids. Studies regarding the functions of the bovine papillomavirus (BPV) E7 oncoprotein in vivo are lacking and no E7-mediated mechanism underlying mesenchymal carcinogenesis is known. Here, we show that the interaction between the 600 kDa retinoblastoma protein-associated factor (p600) and BPV E7, described in vitro in cultured cells, takes place in vivo in naturally occurring equine sarcoids. In these cancers we detect the expression of E7 and p600, and demonstrate that E7 and p600 co-localize and physically interact. Furthermore, intracellular signals involved in p600 functional activity are foun...
Selective cloning, characterization, and production of the Culicoides nubeculosus salivary gland allergen repertoire associated with equine insect bite hypersensitivity. Salivary gland proteins of Culicoides spp. have been suggested to be among the main allergens inducing IgE-mediated insect bite hypersensitivity (IBH), an allergic dermatitis of the horse. The aim of our study was to identify, produce and characterize IgE-binding salivary gland proteins of Culicoides nubeculosus relevant for IBH by phage surface display technology. A cDNA library constructed with mRNA derived from C. nubeculosus salivary glands was displayed on the surface of filamentous phage M13 and enriched for clones binding serum IgE of IBH-affected horses. Ten cDNA inserts encoding putat...
Therapy of equine infectious keratitis: a review. The following article briefly discusses the pathogenesis of infectious keratitis in the horse, followed by discussion of management and pharmacological aspects to be considered when devising a therapeutic protocol for affected patients.
Analysis of the subchondral microarchitecture of the distopalmar aspect of the third metacarpal bone in racing Thoroughbreds. To determine the anisotropic characteristics of the microarchitecture of the subchondral bone (SCB) plate and trabecular bone (TBB) of the distopalmar aspect of the metacarpal condyles in horses with different stages of SCB disease. Methods: 12 third metacarpal bone pairs from racing Thoroughbreds euthanized for diverse reasons. Methods: Both metacarpi were collected from horses with SCB changes that were mild (sclerosis and focal radiolucencies; n=6) or severe (multifocal radiolucencies and articular surface defects; 6). Sample blocks of SCB plate and TBB were collected from the distopalmar a...
Expression of genes associated with inflammation induced by ex vivo exposure to lipopolysaccharide in peripheral blood leukocytes from horses with gastrointestinal disease. To investigate the effect of ex vivo exposure to lipopolysaccharide (LPS) on the expression of inflammatory genes in leukocytes from horses with gastrointestinal (Gl) disease and determine whether the pattern or magnitude of the response to LPS correlated with the type of disease and outcome. Methods: 49 horses with Gl disease and 10 healthy horses Methods: Leukocytes were isolated from blood samples and submitted to 3 protocols: immediate freezing, freezing after 4-hour incubation in medium, and freezing after 4-hour incubation in medium containing LPS. Expression of 14 genes associated with ...
The OARSI histopathology initiative – recommendations for histological assessments of osteoarthritis in the horse. Equine models of osteoarthritis (OA) have been used to investigate pathogenic pathways of OA and evaluate therapeutic candidates for naturally occurring equine OA which is a significant clinical disease in the horse. This review focuses on the macroscopic and microscopic criteria for assessing naturally occurring OA in the equine metacarpophalangeal joint as well as the osteochondral fragment-exercise model of OA in the equine middle carpal joint. Methods: A review was conducted of all published OA studies using horses and the most common macroscopic and microscopic scoring systems were summar...
Adaptation of Staphylococcus aureus to ruminant and equine hosts involves SaPI-carried variants of von Willebrand factor-binding protein. Staphylococci adapt specifically to various animal hosts by genetically determined mechanisms that are not well understood. One such adaptation involves the ability to coagulate host plasma, by which strains isolated from ruminants or horses can be differentiated from closely related human strains. Here, we report first that this differential coagulation activity is due to animal-specific alleles of the von Willebrand factor-binding protein (vWbp) gene, vwb, and second that these vwb alleles are carried by highly mobile pathogenicity islands, SaPIs. Although all Staphylococcus aureus possess c...
Meniscal translocation and deformation throughout the range of motion of the equine stifle joint: an in vitro cadaveric study. By study of the translocation and deformation of equine menisci throughout the range of motion, it may be possible to identify potential mechanical factors in the pathogenesis of injury to the cranial horn of the medial meniscus. Objective: To quantitatively document meniscal translocation and deformation using radiographic and MR imaging, and to evaluate for potential variation between the medial and lateral menisci. Methods: Radiographic markers were embedded in the periphery of the menisci in 6 cadaver stifles. Proximal-distal radiographs were taken at 15° intervals ranging from full flexi...
West Nile virus lineage 2 as a cause of zoonotic neurological disease in humans and horses in southern Africa. West Nile virus (WNV) is widely distributed in South Africa, but since a few cases of neurological disease have been reported from this region, endemic lineage 2 strains were postulated to be of low virulence. Several cases of nonfatal encephalitis in humans as well as fatal cases in a foal, dog, and ostrich chicks have, however, been associated with lineage 2 WNV in South Africa. The pathogenesis of lineage 2 WNV strains was investigated using mouse neuroinvasive experiments, gene expression experiments, and genome sequence comparisons which indicated that lineage 2 strains that are highly pa...
Horses naturally infected by Trypanosoma vivax in southern Brazil. In this study, we reported the first outbreak of the infection by Trypanosoma vivax in horses in southern Brazil, a non-endemic region where bovines have only recently been found infected by this trypanosome species. We evaluated 12 horses from a farm in southern Brazil, where four horses displayed pale mucous membranes, fever, weight loss, and swelling of abdomen, prepuce, or vulva. The diagnosis of T. vivax was confirmed in four horses by morphological parameters of trypomastigotes in blood smears and species-specific PCR. All T. vivax-infected animals showed anemia, and most showed increase...
Detection of reaginic antibodies against Faenia rectivirgula from the serum of horses affected with Recurrent Airway Obstruction by an in vitro bioassay. Reaginic antibodies, mainly of the IgE and some IgG subclasses, play an important role in the induction of type I immediate hypersensitivity reactions. These antibodies bind through their Fc fragment to high affinity receptors (FcεRI) present in the membrane of mast cells and basophils. Previously, several studies have investigated the role of reaginic antibodies in the pathogenesis of RAO. However, whereas immunological aspects of RAO have been extensively studied, the precise sequence of events is still not well understood and role of IgE in this disease still remains controversial. Therefo...
Partial sequence analysis of the L1 gene of bovine papillomavirus type 1 detected by PCR with MY09/MY11 primers in equine sarcoids in Poland. 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...
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...
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...
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...
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 ...
Histological and histochemical characterisation of the equine soft palate muscles. Dysfunction of the muscles is implicated in the pathogenesis of intermittent dorsal displacement of the soft palate (DDSP) in exercising horses. The histological features of normal equine soft palate muscles have not been previously described. Objective: To describe the histological and morphometric features of normal equine soft palate muscles. Methods: The palatinus, palatopharyngeus, levator veli palatini and tensor veli palatini muscles of 6 Thoroughbred type horses were examined histologically and histochemically to assess their general morphology, fibre-type distribution and mean fibre d...
Novel keratins identified by quantitative proteomic analysis as the major cytoskeletal proteins of equine (Equus caballus) hoof lamellar tissue. The dermo-epidermal interface that connects the equine distal phalanx to the cornified hoof wall withstands great biomechanical demands, but is also a region where structural failure often ensues as a result of laminitis. The cytoskeleton in this region maintains cell structure and facilitates intercellular adhesion, making it likely to be involved in laminitis pathogenesis, although it is poorly characterized in the equine hoof lamellae. The objective of the present study was to identify and quantify the cytoskeletal proteins present in the epidermal and dermal lamellae of the equine hoof by ...
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...
A reverse genetics system of African horse sickness virus reveals existence of primary replication. African horse sickness virus (AHSV), a member of the orbivirus genus of the family Reoviridae, is an insect-vectored pathogen of horses of concern to the equine industry. Studies on AHSV replication and pathogenesis have been hampered by the lack of reverse genetics allowing targeted mutation of viral genomes. We demonstrate that AHSV single-stranded RNA synthesized in vitro (core transcripts) is infectious and that there are distinct primary and secondary stages of the replication cycle. Transfection with a mixture of core transcripts from two different serotypes or a mixture of core transcri...
Intralesional bovine papillomavirus DNA loads reflect severity of equine sarcoid disease. Sarcoids are nonmetastasising, yet locally aggressive skin tumours that constitute the most frequent neoplasm in equids. Infection by bovine papillomaviruses types 1 and 2 (BPV-1, BPV-2) has been recognised as major causative factor in sarcoid pathogenesis, but a possible correlation of intralesional virus load with disease severity has not been established thus far. Objective: Given the pathogenic role of BPV-1 and BPV-2 in sarcoid disease, we suggest that intralesional viral DNA concentration may reflect the degree of affection. Methods: Severity of disease was addressed by recording the tum...
Post mortem survey of peripheral dental caries in 510 Swedish horses. Peripheral caries (PC) of equine teeth is a poorly described disorder that can cause serious clinical problems if it progresses. Objective: To assess the prevalence, sites and severity of PC in a population of Swedish horses. Methods: A post mortem study of 510 equine skulls was performed in 2 Swedish equine abattoirs. Results: PC only affected the cheek teeth (CT) and was present in 6.1% (31/510) of skulls. It affected mainly the peripheral cementum, and 87% of PC in the 29 affected mature horses occurred in the 3 caudal CT (Triadan 09-11). Concurrent infundibular caries involving most maxill...
The interstitial cells of Cajal of the equine gastrointestinal tract: what we know so far. Gastrointestinal motility disorders are a serious problem in both veterinary and human medicine and may represent a dysfunction of the neural, muscular or pacemaker components (interstitial cells of Cajal) of bowel control. The interstitial cells of Cajal are considered to be the pacemakers and mediators of certain forms of neurotransmission in the gastrointestinal tract. These cells have been implicated, either primarily or secondarily, in the pathogenesis of gastrointestinal disease processes in which there is a prominent element of disturbance to intestinal motility. In the horse, their inv...
Laminitis and the equine metabolic syndrome. Although much has been written about laminitis in the context of its association with inflammatory processes, recognition is growing that most cases of laminitis examined by veterinarians in private practice are those associated with pasture grazing, obesity, and insulin resistance (IR). The term 'endocrinopathic laminitis' has been adopted to classify the instances of laminitis in which the origin seems to be more strongly associated with an underlying endocrinopathy, such as either IR or the influence of corticosteroids. Results of a recent study suggest that obesity and IR represent the mos...
Hyperinsulinemic laminitis. Laminitis occurring in association with hyperinsulinemia is frequently encountered in today's equine population. New evidence suggests that hyperinsulinemia is the direct cause of this form of laminitis, rather than insulin resistance per se. The mechanism by which elevated serum insulin concentrations result in lamellar dysfunction is currently under investigation by many researchers and the use of a new insulin infusion model for investigating the pathogenesis of insulin-associated laminitis will doubtless enhance progress in this field of research. By focusing on the metabolic and vascular ...
Experimental induction of recurrent airway obstruction with inhaled fungal spores, lipopolysaccharide, and silica microspheres in horses. To evaluate experimental induction of recurrent airway obstruction (RAO) with inhaled fungal spores, lipopolysaccharide, and silica microspheres in horses. Methods: 7 horses with and 3 horses without a history of RAO. Methods: RAO-susceptible horses ranged in age from 17 to approximately 30 years, and control horses ranged in age from 7 to approximately 15 years. Pure mold cultures were derived from repeated culture of hay and identified via gene amplification and sequencing. Pulmonary function testing and bronchoalveolar lavage were performed before and after nebulization with a suspension of...
Bovine papillomavirus DNA can be detected in keratinocytes of equine sarcoid tumors. Bovine papillomavirus (BPV)-1 and -2 is linked to equine sarcoids, a commonly observed skin tumor in horses that is of considerable veterinary importance. Previous studies using in situ hybridization have detected BPV DNA only in fibroblasts and not in keratinocytes of sarcoids. In contrast, normal equine skin latently infected with BPV shows a dysplastic epithelium without dermal changes, similar to lesions induced by other papillomavirus types infecting the epithelium. The first goal of our study was to describe the epidermal and dermal characteristics of several stages in sarcoid developmen...
[Study of the correlation between the plasma viral load and protective immunity induced by the equine infectious anemia attenuated vaccine and its parental virulent strain]. The threshold hypothesis of attenuated lentiviral vaccine considers that the type of host response to infections of lentiviruses depends on the viral load. To evaluate the correlation between viral loads of the attenuated vaccine strain of equine infectious anemia virus (EIAV) and their effects to induce protective immunity, longitudinal plasma viral loads in groups of horses inoculated with either an attenuated EIAV vaccine strain (EIAV(DLV125)) or sub-lethal dose of an EIAV virulent strain (EIAV(LN40)) were compared. Similar levels of plasma viral loads ranging from 10(3)-10(5) copies/mL wer...
Immunohistochemical study of matrix metalloproteinases-2 and -9, macrophage inflammatory protein-2 and tissue inhibitors of matrix metalloproteinases-1 and -2 in normal, purulonecrotic and fungal infected equine corneas. Determine the effects of matrix metalloproteinases (MMPs)-2, -9, macrophage inflammatory protein-2 (MIP-2), tissue inhibitors of matrix metalloproteinase (TIMP)-1 and -2 by immunohistochemical expression in fungal affected and purulonecrotic corneas. Methods: Paraffin-embedded equine corneal samples; normal (n = 9), fungal affected (FA; n = 26), and purulonecrotic without fungi (PN; n = 41) were evaluated immunohistochemically for MMP-2, -9, MIP-2, TIMP-1 and -2. The number of immunoreactive inflammatory cells was counted and statistics analyzed. Western blot was performed to detect MMP-2, MMP...
