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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.
Effect of paddock vs. stall housing on 24 hour gastric pH within the proximal and ventral equine stomach. Stall housing has been suggested as a risk factor for ulcer development in the equine stomach; however, the exact pathogenesis for this has not been established. Objective: To investigate the effect of 3 environmental situations (grass paddock, stall alone or stall with adjacent companion) on pH in the proximal and the ventral stomach. Methods: Six horses with permanently implanted gastric cannulae were used in a randomised, cross-over, block design. Each horse rotated through each of three 24 h environmental situations. Horses remained on their normal diet (grass hay ad libitum and grain b.i....
Venezuelan equine encephalitis virus capsid protein inhibits nuclear import in Mammalian but not in mosquito cells. Venezuelan equine encephalitis virus (VEEV) represents a continuous public health threat in the United States. It has the ability to cause fatal disease in humans and in horses and other domestic animals. We recently demonstrated that replicating VEEV interferes with cellular transcription and uses this phenomenon as a means of downregulating a cellular antiviral response. VEEV capsid protein was found to play a critical role in this process, and its approximately 35-amino-acid-long peptide, fused with green fluorescent protein, functioned as efficiently as did the entire capsid. We detected a...
Characterization of equine arteritis virus particles and demonstration of their hemolytic activity. Equine arteritis virus (EAV), a member of the newly established family Arteriviridae, is a small, positive-stranded RNA virus. It carries two protein complexes in its envelope, gp5/M and the recently described gp2b/gp3/gp4 complex. We report here on several basic features of EAV replication in cell culture and on the protein composition of virus particles. We have also characterized gp2b, gp3, and gp4 expressed using a baculovirus system in insect cells. Finally, we provide evidence that EAV possess hemagglutinating and hemolytic activity. The hemolysis assay might be useful for determining wh...
Establishment and characterization of equine fibroblast cell lines transformed in vivo and in vitro by BPV-1: model systems for equine sarcoids. It is now widely recognized that BPV-1 and less commonly BPV-2 are the causative agents of equine sarcoids. Here we present the generation of equine cell lines harboring BPV-1 genomes and expressing viral genes. These lines have been either explanted from sarcoid biopsies or generated in vitro by transfection of primary fibroblasts with BPV-1 DNA. Previously detected BPV-1 genome variations in equine sarcoids are also found in sarcoid cell lines, and only variant BPV-1 genomes can transform equine cells. These equine cell lines are morphologically transformed, proliferate faster than parental ...
Equine laminitis: membrane type matrix metalloproteinase-1 (MMP-14) is involved in acute phase onset. Enzymatic separation at the hoof lamellar dermal-epidermal interface may play a role in the development of laminitis and characterising and locating matrix metalloproteinases (MMPs) and their inhibitors (tissue inhibitors of MMPs or TIMPs) in lamellar tissues may further understanding of pathogenesis. Objective: To clone and sequence the cDNA encoding lamellar MMP-14 and TIMP-2, and quantify their transcription in normal and laminitic tissue; and to develop antibody to locate MMP-14 in lamellar tissues. Methods: Tissue samples were obtained from an oligofructose induced model of laminitis. Tot...
Early migration of Sarcocystis neurona in ponies fed sporocysts. Sarcocystis neurona is the most important cause of equine protozoal myeloencephalitis (EPM), a neurologic disease of the horse. In the present work, the kinetics of S. neurona invasion is determined in the equine model. Six ponies were orally inoculated with 250 x 10(6) S. neurona sporocysts via nasogastric intubation and killed on days 1, 2, 3, 5, 7, and 9 postinoculation (PI). At necropsy, tissue samples were examined for S. neurona infection. The parasite was isolated from the mesenteric lymph nodes at 1, 2, and 7 days PI; the liver at 2, 5, and 7 days PI; and the lungs at 5, 7, and 9 days ...
Vaccination of sarcoid-bearing donkeys with chimeric virus-like particles of bovine papillomavirus type 1. Equine sarcoids are fibroblastic skin tumours affecting equids worldwide. While the pathogenesis is not entirely understood, infection with bovine papillomavirus (BPV) type 1 (and less commonly type 2) has been implicated as a major factor in the disease process. Sarcoids very seldom regress and in fact often recrudesce following therapy. Nothing is known about the immune response of the equine host to BPV. Given that the viral genes are expressed in sarcoids, it is reasonable to assume that vaccination of animals against the expressed viral proteins would lead to the induction of an immune re...
Platelet activation in ponies with airway inflammation. Platelet activation occurs in human obstructive airway diseases and in laboratory animal models. However, there is limited evidence that platelets may be involved in equine recurrent airway obstruction (RAO) and other inflammatory diseases. This study investigated whether platelet activation also occurred in RAO. Objective: Platelet function is altered in ponies with active RAO. This alteration can be detected ex vivo by measuring platelet adhesion. Methods: An in vitro platelet adhesion assay measuring acid phosphatase (AcP) activity colorimetrically was adapted for use with equine platelets ...
Equine coronavirus induces apoptosis in cultured cells. Equine coronavirus (ECoV) was first isolated from a diarrheic foal and was found genetically similar to group II coronaviruses. However, its pathological characteristics were not adequately investigated. In our preliminary in vitro investigation, ECoV-induced cell death was observed in bovine kidney-derived MDBK cells. Based on this finding, we investigated whether the ECoV-induced CPE was apoptosis. Following ECoV infection, MDBK cells showed morphological changes such as cell rounding and detachment from the culture surface. Moreover, syncytium formation was observed as the other type of cyt...
Analysis of ORFs 2b, 3, 4, and partial ORF5 of sequential isolates of equine arteritis virus shows genetic variation following experimental infection of horses. Samples from horses experimentally infected with the "large plaque variant (LP3A+)" of equine arteritis virus were analysed. These included 182 nasal swabs collected from day 1 to 14 post-infection (p.i.), and 21 virus isolates obtained from white blood cells of animals that showed a prolonged viraemia between days 30 to 72 p.i. In order to determine the genetic stability of the virus and particularly to characterise the genetic variants found during the prolonged viraemia, partial sequences of open reading frame 5 (ORF5) encoding glycoprotein 5 (GP5) were generated. Viruses with amino acid su...
Glanders: off to the races with Burkholderia mallei. Burkholderia mallei, the etiologic agent of the disease known as glanders, is primarily a disease affecting horses and is transmitted to humans by direct contact with infected animals. The use of B. mallei as a biological weapon has been reported and currently, there is no vaccine available for either humans or animals. Despite the history and highly infective nature of B. mallei, as well as its potential use as a bio-weapon, B. mallei research to understand the pathogenesis and the host responses to infection remains limited. Therefore, this minireview will focus on current efforts to elucida...
Equine recurrent airway obstruction and insect bite hypersensitivity: understanding the diseases and uncovering possible new therapeutic approaches. Recurrent airway obstruction (RAO) and insect bite hypersensitivity (IBH) are allergic conditions that are commonly encountered in the horse. Whilst complete allergen avoidance is an effective management strategy for both diseases, this may not be achievable in all cases and treatment options are therefore required. The inflammatory response is the main therapeutic target for glucocorticoids given to horses with RAO and severe cases of IBH, whilst the bronchodilators used in RAO primarily target airway smooth muscle. Such drugs are effective in most but not all individuals and there may be unw...
High prevalence of bovine papillomaviral DNA in the normal skin of equine sarcoid-affected and healthy horses. Bovine papillomavirus (BPV), the causative agent of papillomas in cattle, has been shown to play a major role in the pathogenesis of equine sarcoids in horses. BPV has also been detected occasionally in normal equine skin. In this study, presence and activity of BPV in normal skin and peripheral blood of 4 groups of horses were evaluated: sarcoid-affected horses, horses living in contact with sarcoid-affected horses, horses living in contact with papilloma-affected cattle and control horses. From each horse, 3 samples on 4 locations were collected: a swab of the intact skin surface and both a ...
The contribution of the synovium, synovial derived inflammatory cytokines and neuropeptides to the pathogenesis of osteoarthritis. Osteoarthritis (OA) is one of the most common and disabling chronic joint disorders affecting horses, dogs and humans. Synovial inflammation or synovitis is a frequently observed phenomenon in osteoarthritic joints and contributes to the pathogenesis of OA through formation of various catabolic and pro-inflammatory mediators altering the balance of cartilage matrix degradation and repair. Catabolic mediators produced by the inflamed synovium include pro-inflammatory cytokines, nitric oxide, prostaglandin E(2) and several neuropeptides, which further contribute to the pathogenesis of OA by incr...
Electromyographic activity of the palatinus and palatopharyngeus muscles in exercising horses. Determining the respiratory related activity of the palatinus and palatopharyngeus muscles in exercising horses is relevant because dysfunction of these muscles has been implicated in the pathogenesis of dorsal displacement of the soft palate. Objective: To determine if the palatinus and palatopharyngeus muscles have respiratory activity that increases with intensity in exercising horses. Methods: Electromyographic activity was measured in the palatinus and palatopharyngeus muscles using bipolar fine-wire electrodes while the horses completed an incremental exercise treadmill protocol. Results...
Rhodococcus equi infection in foals: the science of ‘rattles’. Infection with Rhodococcus (Corynebacterium) equi is a well-recognised condition in foals that represents a consistent and serious risk worldwide. The condition manifests itself primarily as one of pulmonary abscessation and bronchitis, hence the terminology of 'rattles' derived from its most obvious clinical sign, frequently terminal when first identified. This review addresses the clinical manifestation, bacteriology and pathogenesis of the condition together with recent developments providing knowledge of the organism in terms of virulence, epidemiology, transmission and immune responses. E...
Detection and molecular characterization of Babesia caballi and Theileria equi isolates from endemic areas of Brazil. Blood samples were collected from 487 adult horses, including 83 pregnant mares, at a slaughterhouse located in Araguari, Minas Gerais State, Brazil. For each blood sample, the packed cell volume (PCV) was determined, and Giemsa-stained smears were microscopically examined for the presence of hemoparasites. The plasma was examined by the indirect fluorescent antibody test for detection of antibodies against Babesia caballi and Theileria equi. In addition, DNA was extracted and analyzed by a multiplex real-time polymerase chain reaction (PCR), specific for B. caballi and T. equi. Products of PC...
Herpesvirus chemokine-binding glycoprotein G (gG) efficiently inhibits neutrophil chemotaxis in vitro and in vivo. Glycoprotein G (gG) of alphaherpesviruses has been described to function as a viral chemokine-binding protein (vCKBP). More recently, mutant viruses devoid of gG have been shown to result in increased virulence, but it remained unclear whether the potential of gG to serve as a vCKBP is responsible for this observation. In this study, we used equine herpesvirus type 1 (EHV-1) as a model to study the pathophysiological importance of vCKBP activity. First, in vitro chemotaxis assays studying migration of immune cells, an important function of chemokines, were established. In such assays, supernat...
Induction of laminitis by prolonged hyperinsulinaemia in clinically normal ponies. The purpose of this study was to determine the effects of prolonged administration of insulin, whilst maintaining normal glucose concentrations, on hoof lamellar integrity in vivo on healthy ponies with no known history of laminitis or insulin resistance. Nine clinically healthy, unrelated ponies were randomly allocated to either a treatment group (n =5; 5.9+/-1.7 years) or control group (n =4; 7.0+/-2.8 years). The treatment group received insulin via a euglycaemic hyperinsulinaemic clamp technique modified and prolonged for up to 72 h. Control ponies were infused with an equivalent volume of...
Cyclooxygenase-2 immunoreactivity in equine ocular squamous-cell carcinoma. Squamous-cell carcinoma (SCC) is the second most common tumor in horses, and 40%-50% may occur in ocular and adnexal structures. Cyclooxygenase (COX)-2 is an inducible enzyme responsible for the production of prostaglandins that control cell growth and the development and progression of cancer. Mechanisms responsible for the initial upregulation of COX-2 in neoplasia are unclear; prolonged sunlight exposure and mutations in the p53 gene may be possibilities. Because the etiopathogenesis of ocular SCC in horses may involve ultraviolet sunlight and p53 mutations, the purpose of this study was to...
Etiology and pathogenesis of osteochondrosis. Osteochondrosis is a common and clinically important joint disorder that occurs in human beings and in multiple animal species, most commonly pigs, horses, and dogs. This disorder is defined as a focal disturbance of enchondral ossification and is regarded as having a multifactorial etiology, with no single factor accounting for all aspects of the disease. The most commonly cited etiologic factors are heredity, rapid growth, anatomic conformation, trauma, and dietary imbalances; however, only heredity and anatomic conformation are well supported by the scientific literature. The way in which t...
Dietary fructan carbohydrate increases amine production in the equine large intestine: implications for pasture-associated laminitis. Pasture-induced laminitis in the horse is associated with the overconsumption of fermentable carbohydrate, in the form of simple sugars, fructans, or starch. The fermentation of carbohydrate in the cecum and large intestine results in the production of lactic acid and other toxins or "laminitis trigger factors." Vasoactive amines have been suggested as possible initiating factors. The aim of this study was to feed a commercially available form of fructan carbohydrate (inulin, 3 g/kg of BW per day) to normal ponies and to ponies predisposed to laminitis, to mimic a change from a basal hay diet ...
Genes and respiratory disease: a first step on a long journey. This review highlights the critical importance of phenotype definition in the understanding of the pathogenesis of respiratory disease in horses. The general approach to genetic studies is discussed and comparative studies of recurrent airway obstruction (RAO) conditions, such as asthma, described in the context of learning more about equivalent equine conditions. The availability of methods to study genetic tests have previously relied on DNA sequence knowledge from man, laboratory and domesticated animals, but recent data from the horse genome sequence are now available. This should facilita...
Mucus and the mare: how little we know. Uterine infections are a major cause of infertility, but the role of mucus in equine uterine defense is not well understood. Mucociliary currents play an important role in protecting mucous membranes, including the upper and lower respiratory tracts of mammals, and are required for feeding and oxygenation of many aquatic invertebrates. Although phagocytosis has long been considered the first line of uterine defense in the mare, there are concerns about its efficacy in the uterine lumen. Additional local defenses, such as mucociliary currents, have therefore been proposed. The uterine epitheliu...
Experimental infections with West Nile virus. West Nile virus emerged recently in North America as a serious human and animal pathogen. This review summarizes the use of experimental infections with West Nile virus in diverse vertebrate species that have been used to answer fundamental questions about the host response, pathogenesis of West Nile virus infection and virus evolution. Results: West Nile virus has an extremely broad vertebrate host range. Infection of common species of birds has defined those with high vs. low potential to serve as amplifying hosts for the virus. In general, mammals (primates, horses, companion animals) are d...
Retinal Mueller glial cells trigger the hallmark inflammatory process in autoimmune uveitis. Spontaneous equine recurrent uveitis (ERU) is an incurable autoimmune disease affecting the eye. Although retinal-autoantigen specific T-helper 1 cells have been demonstrated to trigger disease progression and relapses, the molecular processes leading to retinal degeneration and consequent blindness remain unknown. To elucidate such processes, we studied changes in the total retinal proteome of ERU-diseased horses compared to healthy controls. Severe changes in the retinal proteome were found for several markers for blood-retinal barrier breakdown and whose emergence depended upon disease seve...
Inflammatory airway disease of horses. The purpose of this consensus statement is to provide a review of current knowledge and opinions concerning inflammatory airway disease (IAD) and to help practitioners differentiate IAD from heaves (or recurrent airway obstruction; RAO) and other inflammatory respiratory diseases of horses.
Early lesions of osteochondrosis in the distal tibia of foals. Material available for research into osteochondrosis (OC) in humans tends to represent chronic lesions. Comparative studies of early lesions in young animals are, therefore, important in clarifying the pathogenesis of OC in humans. Recent studies in pigs provide strong evidence that lesions of articular OC are associated with a focal failure in the cartilage canal vascular supply to epiphyseal growth cartilage (articular-epiphyseal cartilage complex excluding the articular cartilage). The purpose of the present study was to examine histological sections from a specific predilection site for ar...
