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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.
Allopregnanolone infusion induced neurobehavioural alterations in a neonatal foal: is this a clue to the pathogenesis of neonatal maladjustment syndrome? Increased plasma progestagen concentrations have been reported in foals with neonatal maladjustment syndrome (NMS). These steroids may cross the blood-brain barrier and have dampening effects in the central nervous system. Objective: To evaluate if the infusion of a progesterone derivative (allopregnanolone) in a healthy neonatal foal would induce clinical signs compatible with NMS. Methods: A healthy neonatal foal from a healthy mare with a normal gestation (length, no complications), birth and placenta was infused with allopregnanolone to observe its neurobehavioural effects. Heparinised blo...
Fell Pony syndrome: characterization of developmental hematopoiesis failure and associated gene expression profiles. Fell Pony syndrome (FPS) is a fatal immunodeficiency that occurs in foals of the Fell Pony breed. Affected foals present with severe anemia, B cell lymphopenia, and opportunistic infections. Our objective was to conduct a prospective study of potential FPS-affected Fell Pony foals to establish clinical, immunological, and molecular parameters at birth and in the first few weeks of life. Complete blood counts, peripheral blood lymphocyte phenotyping, and serum immunoglobulin concentrations were determined for 3 FPS-affected foals, 49 unaffected foals, and 6 adult horses. In addition, cytology o...
Mycobacterium DNA detection in liver and skin of a horse with generalized sarcoidosis. Sarcoidosis is a rare equine skin disease characterized primarily by an exfoliative and granulomatous dermatitis but also presenting granulomatous inflammation of multiple systems. The current report presents the clinical and histopathological findings of sarcoidosis in a 16-year-old American Quarter Horse gelding with nested polymerase chain reaction Mycobacterium spp. DNA detection within hepatic and skin samples. Mycobacterium spp. may play a role in the pathogenesis of equine sarcoidosis as has been proposed for human sarcoidosis.
Characterization of virulent West Nile virus Kunjin strain, Australia, 2011. To determine the cause of an unprecedented outbreak of encephalitis among horses in New South Wales, Australia, in 2011, we performed genomic sequencing of viruses isolated from affected horses and mosquitoes. Results showed that most of the cases were caused by a variant West Nile virus (WNV) strain, WNV(NSW2011), that is most closely related to WNV Kunjin (WNV(KUN)), the indigenous WNV strain in Australia. Studies in mouse models for WNV pathogenesis showed that WNV(NSW2011) is substantially more neuroinvasive than the prototype WNV(KUN) strain. In WNV(NSW2011), this apparent increase in vir...
Lactobacillus equigenerosi strain Le1 invades equine epithelial cells. Lactobacillus equigenerosi strain Le1, a natural inhabitant of the equine gastrointestinal tract, survived pH 3.0 and incubation in the presence of 1.5% (wt/vol) bile salts for at least 2 h. Strain Le1 showed 8% cell surface hydrophobicity, 60% auto-aggregation, and 47% coaggregation with Clostridium difficile C6. Only 1% of the cells adhered to viable buccal epithelial cells and invaded the cells within 20 min after contact. Preincubation of strain Le1 in a buffer containing pronase prevented adhesion to viable epithelial cells. Preincubation in a pepsin buffer delayed invasion from 20 min to...
Equine insect bite hypersensitivity: what do we know? Insect bite hypersensitivity (IBH) is an allergic dermatitis of the horse caused by bites of insects of the genus Culicoides and is currently the best characterized allergic disease of horses. This article reviews knowledge of the immunopathogenesis of IBH, with a particular focus on the causative allergens. Whereas so far hardly any research has been done on the role of antigen presenting cells in the pathogenesis of IBH, recent studies suggest that IBH is characterized by an imbalance between a T helper 2 (Th2) and regulatory T cell (T(reg)) immune response, as shown both locally in the skin...
Histologic and histomorphometric evaluation of midcarpal joint defects in Thoroughbreds raised with and without early conditioning exercise. To describe and measure histologic features of midcarpal joint cartilage defects in Thoroughbreds and evaluate the influence of early conditioning exercise on defect development. Methods: 24 midcarpal joints from twelve 18-month-old Thoroughbreds. Methods: Midcarpal joints from 12 horses (6 exercised spontaneously at pasture only and 6 given additional conditioning exercise beginning at a mean age of 3 weeks were evaluated. Gross cartilage defects were assessed histologically. Third and radial carpal bones were categorized with regard to the presence or absence of calcified cartilage (CC) abno...
Inflammatory responses to induced infectious endometritis in mares resistant or susceptible to persistent endometritis. The objective of the study was to evaluate the gene expression of inflammatory cytokines (interleukin [IL]-1β, IL-6, IL-8, IL-10, tumor necrosis factor [TNF]-α, IL-1 receptor antagonist [ra] and serum amyloid A (SAA) in endometrial tissue and circulating leukocytes in response to uterine inoculation of 105 colony forming units (CFU) Escherichia coli in mares. Before inoculation, mares were classified as resistant or susceptible to persistent endometritis based on their uterine inflammatory response to infusion of 109 killed spermatozoa and histological assessment of the endometrial quality. ...
Hydrallantois in the mare–a report of five cases. Hydrallantois in the mare is a very rare condition, and clinical reports help to gather information to elucidate its pathogenesis, treatment options and prognosis. Five different cases of hydrallantois in the mare are reported in this article, all with the involvement of placentitis. The five mares were presented because of acute distention of the abdomen, dyspnoea, stiff gait and a lack of appetite. After a gradual release of the excessive amount of allantoic fluid, an abortion was induced in all five mares. The foals were either born dead or euthanized. The mares recovered quickly. One mare ...
Dynamic respiratory endoscopy of Standardbred racehorses during qualifying races. Examination of the equine upper airway during racing has not previously been documented. Objective: To describe the feasibility and appearance of the upper airways by overground respiratory endoscopic examination during racing conditions. Methods: Overground videoendoscopic examinations were performed on 46 Standardbred racehorses during qualifying races. Examined horses' speeds were recorded throughout the race with a portable GPS device. Results: The procedure did not interfere with performance as there were no significant differences in race times between races in which horses were examined...
Miscellaneous vitreous-derived IgM antibodies target numerous retinal proteins in equine recurrent uveitis. In equine recurrent uveitis (ERU), immune reactions are directed toward known antigens like S-antigen, interphotoreceptor retinoid-binding protein, and cellular retinalaldehyde-binding protein, and anti-retinal antibodies were detected in vitreous samples. The aim of this study was the investigation of intraocular immunoglobulin M (IgM) reactivities to retinal proteome. Methods: Retina was separated by one- and two-dimensional gel electrophoresis and blotted semidry on PVDF membranes. To identify intraocular IgM antibody responses to retinal tissue, blots were incubated with vitreous samples o...
Gambling on putative biomarkers of osteoarthritis and osteochondrosis by equine synovial fluid proteomics. Osteoarthritis (OA) and osteochondrosis (OC) are two of the main challenges in orthopedics, whose definitive diagnosis is usually based on radiographic/arthroscopic evidences. Their early diagnosis should allow preventive or timely therapeutic actions, which are generally precluded from the poor relationships occurring between symptomatologic and radiographic evidences. These limitations should be overcome by improving the knowledge on articular tissue metabolism and on molecular factors regulating its normal homeostasis, also identifying novel OA and OC biomarkers suitable for their earlier d...
EcPV-2 is transcriptionally active in equine SCC but only rarely detectable in swabs and semen from healthy horses. Squamous cell carcinomas (SCC) are malignant tumours arising from keratinocytes. In horses, there is increasing evidence for Equus caballus papillomavirus type 2 (EcPV-2) being causally involved in SCC development. However, only little is known regarding intralesional transcription of the virus, and sparse information on the incidence of EcPV-2 infection in healthy equids is available so far. Using RT-PCR, total mRNA from 8 EcPV-2 DNA-positive and 1 EcPV-2 negative SCC/SCC precursor lesions was screened for the presence of EcPV-2 E6 and E1 transcripts. Using PCR, we tested 193 sample specimens...
Shuni virus as cause of neurologic disease in horses. To determine which agents cause neurologic disease in horses, we conducted reverse transcription PCR on isolates from of a horse with encephalitis and 111 other horses with acute disease. Shuni virus was found in 7 horses, 5 of which had neurologic signs. Testing for lesser known viruses should be considered for horses with unexplained illness.
Absence of evidence for bornavirus infection in schizophrenia, bipolar disorder and major depressive disorder. In 1983, reports of antibodies in subjects with major depressive disorder (MDD) to an as-yet uncharacterized infectious agent associated with meningoencephalitis in horses and sheep led to molecular cloning of the genome of a novel, negative-stranded neurotropic virus, Borna disease virus (BDV). This advance has enabled the development of new diagnostic assays, including in situ hybridization, PCR and serology based on recombinant proteins. Since these assays were first implemented in 1990, more than 80 studies have reported an association between BDV and a wide range of human illnesses that i...
Vitreal IgM autoantibodies target neurofilament medium in a spontaneous model of autoimmune uveitis. Although the presence of IgG autoantibodies in the vitreous of spontaneous cases of equine recurrent uveitis (ERU) has been demonstrated, the potential role of IgM reactivities during ERU pathogenesis remains unexplored. The purpose of this study was to examine the presence of IgM autoantibodies in vitreous specimens of ERU-affected horses and to test their binding specificity to intraocularly expressed proteins. Methods: To test IgM autoantibody responses to retinal tissue, vitreous samples of eye-healthy controls and ERU patients were analyzed via two-dimensional Western blot analysis with e...
Clinical and virological outcome of an infection with the Belgian equine arteritis virus strain 08P178. Equine viral arteritis (EVA) is an infectious disease with variable clinical outcome. Outbreaks, causing important economic losses, are becoming more frequent. Currently, there is a shortage of pathogenesis studies performed with European strains. In the present study, eight seronegative ponies were experimentally inoculated with the Belgian strain of equine arteritis virus (EAV) 08P178 (EU-1 clade) and monitored daily for clinical signs of EVA. Nasopharyngeal swabs, ocular swabs, bronchoalveolar cells and blood were collected for virological and serological testing. Two ponies were euthanized...
Emergence of novel equine arteritis virus (EAV) variants during persistent infection in the stallion: origin of the 2007 French EAV outbreak was linked to an EAV strain present in the semen of a persistently infected carrier stallion. During the summer of 2007, an outbreak of equine viral arteritis (EVA) occurred in Normandy (France). After investigation, a link was suggested between an EAV carrier stallion (A) and the index premise of the outbreak. The full-length nucleotide sequence analysis of a study reference strain (F27) isolated from the lung of a foal revealed a 12,710 nucleotides EAV genome with unique molecular hallmarks in the 5'UTR leader sequence and the ORF1a sequence encoding the non-structural protein 2. The evolution of the viral population in the persistently infected Stallion A was then studied by cloning...
Advanced glycation endproducts in horses with insulin-induced laminitis. Advanced glycation endproducts (AGEs) have been implicated in the pathogenesis of cancer, inflammatory conditions and diabetic complications. An interaction of AGEs with their receptor (RAGE) results in increased release of pro-inflammatory cytokines and reactive oxygen species (ROS), causing damage to susceptible tissues. Laminitis, a debilitating foot condition of horses, occurs in association with endocrine dysfunction and the potential involvement of AGE and RAGE in the pathogenesis of the disease has not been previously investigated. Glucose transport in lamellar tissue is thought to be l...
Stifle extension results in differential tensile forces developing between abaxial and axial components of the cranial meniscotibial ligament of the equine medial meniscus: a mechanistic explanation for meniscal tear patterns. To identify potential functional-anatomical characteristics of the cranial horn attachment of the medial meniscus (MM) that may help explain the pathogenesis of the common tear patterns that have been reported. Objective: Full extension of the stifle generates a significant increase in tensile forces within the cranial meniscotibial ligament (CrMTL) of the MM, which may predispose this structure to injury. Methods: The effect of femorotibial angle (160°, 150°, 140° and 130°) on tensile forces in the axial and abaxial components of the CrMTL was examined in 6 mature cadaver stifles using an...
Relative prevalence of upper respiratory tract obstructive disorders in two breeds of harness racehorses (185 cases: 1998-2006). Two genetically and phenotypically distinct horse breeds are used for harness racing in Scandinavia: the Standardbred (SB) and Coldblooded Trotter. These racehorses have identical environmental, management and racing conditions. Therefore, this study was undertaken to identify and compare the relative prevalence of upper respiratory tract (URT) obstructive disorders in these 2 breeds. Objective: To determine whether these 2 phenotypically different breeds of harness racehorses have different predispositions for URT disorders. Methods: Retrospective study of 88 Norwegian Coldblooded Trotters (N...
Risk factors for race-associated sudden death in Thoroughbred racehorses in the UK (2000-2007). Sudden death adversely affects racehorse welfare, jockey safety and the public perception of horseracing. Objective: To describe the risk of racing-associated sudden death in Thoroughbred racehorses in the UK from 2000 to 2007, to identify whether there were risk factors uniquely associated with sudden death and to improve the understanding of the pathogenesis of racing-associated sudden death by identification of risk factors for such cases. Methods: A sudden death was defined as an acute collapse and death, in an apparently healthy Thoroughbred racehorse, during or immediately after racing, ...
Functional characterization of EUL47 in productive replication, morphogenesis and infectivity of equine herpesvirus 1. EUL47 is a major component of the tegument of equine herpesvirus 1 (EHV-1). To determine its function, we used Red/ET cloning to delete its gene (gene 13) from EHV-1 strain Ab4p inserted into a bacterial artificial chromosome (BAC), yielding Ab4pattBΔ13. We also examined the reverted virus (Ab4pattB13R). Ab4pattBΔ13 replicated in rabbit kidney (RK)-13 cells, indicating that ORF13 is dispensable for virus replication in cell culture. Its intracellular and extracellular titers were about 10- and 100-fold lower than those of the revertant and parent strains, respectively. In addition, the plaqu...
MyD88-dependent recruitment of monocytes and dendritic cells required for protection from pulmonary Burkholderia mallei infection. The Gram-negative bacterium Burkholderia mallei causes rapidly fatal illness in equines and humans when contracted by inhalation and also has the potential to be used as a bioweapon. However, little is known regarding the early innate immune responses and signaling mechanisms required to generate protection from pneumonic B. mallei infection. We showed previously that monocyte chemoattractant protein 1 (MCP-1) was a critical chemokine required for protection from pneumonic B. mallei infection. We have now extended those studies to identify key Toll-like receptor (TLR) signaling pathways, effec...
Persistent digital hyperthermia over a 48 h period does not induce laminitis in horses. Persistent digital hyperthermia, presumably due to vasodilation, occurs during the developmental and acute stages of insulin-induced laminitis. The objectives of this study were to determine if persistent digital hyperthermia is the principal pathogenic mechanism responsible for the development of laminitis. The potent vasodilator, ATP-MgCl(2) was infused continuously into the distal phalanx of the left forefoot of six Standardbred racehorses for 48 h via intra-osseous infusion to promote persistent digital hyperthermia. The right forefoot was infused with saline solution and acted as an inter...
Advanced imaging of the nervous system in the horse. Neuroimaging underwent a dramatic revolution during the past few decades due to the development of new technologies that produce exquisite images of patient morphology and function, new technologies that store and distribute information more efficiently, and research that has improved understanding of pathogenesis and effective clinical use of new imaging methods. Advanced equine neuroimaging is a specialized field with unique challenges associated with patient size, availability of equipment, using equipment designed for humans, small sample size for various diseases, and issues associated wi...
Rhodococcus equi pneumonia in the foal–part 1: pathogenesis and epidemiology. Rhodococcus equi pneumonia is a worldwide infectious disease of major concern to the equine breeding industry. The disease typically manifests in foals as pyogranulomatous bronchopneumonia, resulting in significant morbidity and mortality. Inhalation of aerosolised virulent R. equi from the environment and intracellular replication within alveolar macrophages are essential components of the pathogenesis of R. equi pneumonia in the foal. Recently documented evidence of airborne transmission between foals indicates the potential for an alternative contagious route of disease transmission. In the...
Rhodococcus equi: clinical manifestations, virulence, and immunity. Pneumonia is a major cause of disease and death in foals. Rhodococcus equi, a gram-positive facultative intracellular pathogen, is a common cause of pneumonia in foals. This article reviews the clinical manifestations of infection caused by R. equi in foals and summarizes current knowledge regarding mechanisms of virulence of, and immunity to, R. equi. A complementary consensus statement providing recommendations for the diagnosis, treatment, control, and prevention of infections caused by R. equi in foals can be found in the same issue of the Journal.
