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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.
Identification and phylogenetic analysis of Mannheimia haemolytica isolated from nasal samples of horses. The Mannheimia genus, which is part of the upper respiratory tract microbiota, harbours species that have the potential to cause progressive infections, such as haemorrhagic septicaemia and enzootic pneumonia, when the host immune system is suppressed. Among these species, Mannheimia haemolytica is considered the most pathogenic, and horses can be a host for this agent. This study aimed to investigate the occurrence of Mannheimia haemolytica in horses with and without respiratory clinical signs and to assess the potential pathogenic significance of isolates recovered from animals through serot...
Isolation of Moraxella spp. strains in horses. Two species of Moraxella were isolated from swabs obtained from two symptomatic horses suffering from conjunctivitis and rhinitis. The isolates were identified via MALDI-TOF as Moraxella osloensis and Moraxella equi respectively, with a good genus identification and a probable species identification score. The first one was also confirmed by BLAST sequence analysis with a high homology (99%). Antimicrobial susceptibility testing obtained by minimum inhibitory concentration method showed that the two isolates were sensitive to all the tested molecules. The therapeutic protocols applied had an e...
Equine herpesvirus myeloencephalopathy-associated mutations in equine herpesvirus 1 DNA polymerase confer the ability to replicate at elevated temperatures. Equine herpesvirus myeloencephalopathy (EHM), caused by equine herpesvirus type 1 (EHV-1), poses a major threat to the equine industry because of its devastating impact on animal welfare and athletic performance. A single-nucleotide polymorphism (SNP), G2254, in ORF30 (UL30), which encodes the viral DNA polymerase, has been used as a marker of neuropathogenic EHV-1 strains, although its contribution to EHM pathogenesis remains controversial. In addition, other ORF30 SNPs have been reported in association with EHM, but their functional significance is unclear. Clinical observations indicate tha...
Genetic variants of EcPV2 E6 and E7 in equine genital and oronasal squamous cell carcinoma. Since its discovery in 2008, equine papillomavirus type 2 (EcPV2) has been detected in up to 100% of equine genital and up to 40% of equine oronasal squamous cell carcinomas (SCCs). Preliminary sequence data point to the existence of EcPV2 E6 and E7 oncogene variants compared to the British reference sequence from 2008. Objective: To Identify E6 and E7 sequence variations in EcPV2-positive tumours of horses from Continental Europe and Iceland. Methods: Cross-sectional study. Methods: EcPV2 E6 and E7 were amplified from DNA of 60 EcPV2-positive SCCs/SCC precursor lesions. Amplicons were gel-pur...
Leishmania spp. infection in horses in an endemic area of canine leishmaniosis (north-western Algeria). Leishmaniosis is a parasitic disease caused by obligate intracellular protozoa of the genus Leishmania. It affects humans, canids, and rodents in endemic areas and is transmitted through the bites of infected sand flies. This study aimed to estimate the prevalence of equine leishmaniosis in horses from Tiaret Province, northwestern Algeria, an area endemic for canine leishmaniosis, and to identify the main risk factors associated with infection. The study included 75 local Barb horses and employed molecular and serological techniques for the detection of Leishmania infection. Among the sampled...
Equine Sarcoid: From BPV-Driven Oncogenesis to Host-Sustained Tumor Persistence. Equine sarcoid is the most common cutaneous neoplasm of equids and represents a distinctive model of virus-associated tumor persistence. Although bovine papillomaviruses, particularly BPV-1 and BPV-2, are recognized as the main etiological agents, viral infection alone does not fully explain the clinical heterogeneity, frequent recurrence, and limited spontaneous regression of these lesions. This review summarizes current evidence on the molecular and cellular mechanisms underlying equine sarcoid pathogenesis, with emphasis on the interaction between BPV infection, host signaling pathways, tum...
Failure of Passive Transfer in neonatal foals – a review. Failure of passive transfer (FPT) is a major contributor to morbidity and mortality in neonatal foals worldwide. Adequate ingestion and intestinal absorption of colostral immunoglobulin G (IgG) during the first hours of life are essential to ensure protection against early-life infections, such as diarrhoea and pneumonia, frequently with fatal outcome. This review summarizes current knowledge on the physiology of passive immunization, risk factors for inadequate IgG absorption, diagnostic methods, therapeutic strategies, and evidence-based preventive measures. Recent research highlights the im...
Oxidative Stress and Inflammatory Responses in Horses Naturally Infected with Theileria equi. Equine piroplasmosis, caused by the intraerythrocytic protozoan , is a globally distributed tick-borne disease characterized by persistent infection and variable clinical manifestations. Although oxidative stress has been implicated in the pathogenesis of several hemoprotozoan diseases, information regarding redox imbalance and its relationship with inflammatory responses in horses naturally infected with remains limited. This study aimed to evaluate oxidative stress, antioxidant status, inflammatory cytokines, and clinicopathological alterations in horses naturally infected with . Thirty-fiv...
Equine infectious anemia virus Mat protein serves as a Tat cofactor to facilitate viral transcription. Equine infectious anemia virus (EIAV) is a member of the genus of the family and serves as an important model for studying lentiviral pathogenesis. A novel EIAV-encoded protein, designated Mat, was previously identified in our laboratory, yet its biological functions remained unclear. Here, we demonstrate that disruption of Mat moderately reduced EIAV replication in equine monocyte-derived macrophages, and this defect was restored when Mat was supplied in . Further analyses revealed that Mat exhibits nuclear localization and enhances Tat-mediated transcriptional activation of the long termin...
Preliminary Assessment on Pathogenicity of an African Horse Sickness Virus Serotype 1 Strain in Guinea Pigs and Horses. African horse sickness (AHS), a noncontagious insect-borne disease affecting equids, is caused by the African horse sickness virus (AHSV) and is associated with extremely high morbidity and mortality. AHSV has nine distinct serotypes (AHSV-1 to AHSV-9). In a previous study, we characterized the genome and in vitro growth properties of AHSV/C, a cell-adapted derivative of an AHSV-1 strain imported into China 60 years ago, and verified its safety in mice. This study preliminarily explored the pathogenicity of AHSV/C in guinea pigs and horses (its natural host). Six groups of guinea pigs were ino...
Alphavirus madariaga-associated encephalomyelitis in equines from the Brazilian Pantanal reveals arbovirus circulation in a peri-urban environment. Alphavirus madariaga (MADV), a member of the eastern equine encephalitis virus complex, is an emerging arbovirus in South America, with limited information regarding its occurrence and molecular characterization in equine populations. This study reports the detection and genetic characterization of MADV in equines from the state of Mato Grosso, Brazil. Two horses presenting acute neurological disease with a clinical course of approximately two days were evaluated. Histopathological examination revealed nonsuppurative meningoencephalomyelitis. Molecular screening for neurotropic viruses using T...
First reported case of Parafilaria bovicola infection in a horse (Equus caballus). This study reports the infection, diagnosis and treatment of the nematode Parafilaria bovicola in a horse (Equus caballus) in France. A soft, fluctuated and non-painful subcutaneous nodule was observed under the right eye. Ultrasound revealed a mobile verminous element in a fluid cyst. A nematode was surgically extracted from the cyst and further identified as Parafilaria bovicola by sequencing of mitochondrial cytochrome c oxidase subunit 1 gene. This first report indicates that horses can be accidental hosts of P. bovicola in enzootic areas.
Antibiofilm action of ozonated sunflower oil against bacteria isolated from the uterus of mares susceptible to endometritis. This study aimed to characterize the antibiofilm action of ozone-enriched sunflower oil (O) against pathogens associated with endometritis in mares. Initially, samples from 41 mares with a history of subfertility were stored in BHI broth and 0.9% NaCl solution. The samples underwent microbial culture, identification, and sensitivity testing at LABRAPE-UFRPE, Brazil. Biofilm production was evaluated by the crystal violet method. Subsequently, biofilm-forming bacteria were subjected to the action of different concentrations of ozonated sunflower oil. Of the 21 isolates tested for biofilm produc...
Systematic establishment of approaches to the detection of equine macrophage polarization and their application in pathogenic infection. Macrophage phenotypic adaptation critically regulates inflammatory balance during infection; however, progress in equine immunology has been limited by a lack of specific tools for standardized identification. To address this gap, we established a reliable, antibody-based detection method for characterizing equine macrophage M1-like and M2-like marker profiles. After initially validating canonical marker genes via qPCR, we developed specific monoclonal antibodies targeting the differentially expressed surface proteins CD80 (M1-like) and CD163 (M2-like). These novel antibodies enabled the creat...
Circulating microRNAs as potential predictive biomarkers of equine metabolic syndrome. Equine Metabolic Syndrome (EMS) is a complex endocrine disorder characterized by insulin dysregulation (ID), and an increased risk of developing laminitis, often accompanied by generalized or regional adiposity. Despite growing awareness of EMS, early and accurate diagnosis remains challenging. In this pilot study, we investigated changes in the levels of circulating microRNAs (miRNAs) in plasma samples from horses diagnosed with EMS (n=13), compared to overweight/obese (OW/OB) non-ID horses (n=16) and healthy controls (n=16). Using a targeted OpenArray, followed by a Kruskal-Wallis and Dunn's...
Cutaneous Equine Sarcoidosis: A Case Series and Investigation Into a Potential Association With Equine Gammaherpesviruses-2 and -5 in 30 Equids. Gammaherpesviruses have been associated with granulomatous inflammation in the skin of various species. Equine sarcoidosis (idiopathic granulomatous disease) can cause granulomatous dermatitis, and its cause remains unknown. Objective: This retrospective study aimed to investigate the possible association between equine gammaherpesviruses-2 and -5 (EHV-2, -5) and cutaneous equine sarcoidosis (cES). Methods: Thirty client-owned equids. Methods: All animals had histologically and clinically confirmed cES. Signalment, geographical location and clinical features were recorded. Gram, Ziehl-Nielsen ...
Equine cyathostomins-Hidden histories. Cyathostomins (also known as small strongyles or small redworms) are ubiquitous parasites of equids. They are found in a wide range of climatic regions, and inhabit the large intestine of their hosts. While infections are often sub-clinical, clinical consequences ranging from chronic to acute, and most notably, acute larval cyathostominosis, can occur in specific circumstances. Control of cyathostomin infection is complicated by widespread drug resistance. This Chapter provides a broad review of cyathostomin biology and host-parasite relationships, and also highlights significant knowledge gap...
Complete genome of Bacillus anthracis strain ter21 from an infected zoo pony in Ternopil, Ukraine, 2021. Using rapid nanopore whole-genome sequencing, we assembled the genome of strain ter21 (5,229,480 bp), a Tsiankovskii-I group isolate cultured from a fatal case in 2021 of a pony from a zoo in Ternopil, Ukraine, identifying virulence plasmid pXO1 that encodes anthrax toxin, and pXO2.
Ulcerative dermatitis, tendinitis, tenosynovitis, and desmitis caused by chronic infection with Serratia odorifera in a racehorse. We investigated a case of severe infection in a racehorse. The horse had developed progressive lameness associated with swelling of the left tarsal region, which progressed to ulcerative dermatitis, tendinitis, tenosynovitis, and desmitis. The plantar side of the superficial digital flexor (SDF) tendon was visible through the skin ulcer, and coalescing nodules were present in the dermis. The horse was euthanized and an autopsy was performed. Grossly, in addition to the changes described above, severe edema of the soft tissues was associated with the ulcer. Microscopically, necrotizing and ulc...
Integrated transcriptomic profiling reveals oncogenic pathways and chimeric transcripts in equine sarcoid lesions with predominant BPV1 detection. Sarcoids are the most common cutaneous tumors in horses, representing up to 90% (35%-90%) of skin neoplasms. Mostly caused by Bovine Papillomavirus (BPVs) infections, sarcoids are highly resistant to therapy and prone to recurring, posing a significant threat to equine health. The aim of this study is to explore molecular pathogenetic mechanisms underlying the development of equine sarcoids, by applying transcriptomic approach. After testing samples for viral DNA, both mRNA and small RNA expression was analyzed via high-throughput Illumina sequencing comparing 12 sarcoids and 12 healthy skin s...
Exploring the role of epigenetics in the processes related to the development of endometrosis in the mare. Endometrosis is a chronic degenerative condition of the mare endometrium characterized by progressive fibrosis and glandular alterations that impair uterine function and fertility. Its pathogenesis involves persistent inflammation, the activation of myofibroblasts, and the accumulation of extracellular matrix (ECM), leading to disrupted glandular secretion and compromised maintenance of pregnancy. While histopathological studies of endometrosis are well described, the underlying molecular mechanisms remain incompletely understood. Emerging evidence highlights the crucial role of epigenetic reg...
Neuroimmune Mechanisms in Equine Asthma: Primary Inflammatory Triggers, Neuroimmune Modulation and Chronic Airway Remodelling. Equine asthma is a chronic inflammatory disease of the lower respiratory tract, primarily associated with inhalation of organic dust, microbial particles and environmental aeroantigens. Although the inflammatory and immunological mechanisms underlying equine asthma have been extensively investigated, the potential contribution of neuroimmune pathways remains poorly understood. In humans and rodent models, asthma is increasingly recognised as a disorder involving complex bidirectional interactions between the nervous and immune systems. Sensory nerve activation, neuropeptide release, autonomic ...
Vital bone and increased osteoid in equine osteochondrosis dissecans of the proximal phalanx: A controlled study indicating a mineralization deficit rather than vascular failure. Osteochondrosis and osteochondrosis dissecans (OCD) are among the most common orthopaedic disorders in young horses. Although traditionally explained by vascular failure and ischaemic necrosis, recent findings in human juvenile OCD suggest that impaired bone mineralization may play an important role. Horses are known to have relatively low circulating vitamin D metabolites, raising the question of whether insufficient mineralization contributes to equine OCD. This study investigated the bone vitality and mineralization status of osteochondrosis dissecans fragments (OCDFs) collected from the do...
Evaluation of oxidative stress in ill neonatal foals: a preliminary study. Oxidative stress both contributes to and results from sepsis pathophysiology, but its role in ill foals remains poorly characterized. Objective: Ill foals will exhibit decreased antioxidant defense activity and increased oxidative products compared with healthy foals, and these changes will be associated with higher sepsis scores, lower survival scores, and non-survival. Methods: Twenty-six foals < 14 days old: 16 hospitalized foals (11 sick non-septic, 5 septic; median age, 1.5 days; range 1-13) and 10 healthy Standardbred foals (2 days old). Nine of 16 ill foals survived to discharge...
Clinical Signs of Liver Disease in Horses. Clinical signs associated with liver disease in horses are often a reflection of underlying hepatic dysfunction but typically vague rather than pathognomonic. Many observed clinical signs are subtle or not recognizable in the early stages of liver disease and thus may appear acute in onset despite an underlying chronic condition. Clinical signs reported in horses with liver disease include hyporexia or anorexia, weight loss, changes in demeanor, hepatic encephalopathy, colic signs, icterus, photosensitization, diarrhea, clinical coagulopathies, ascites, peripheral edema, steatorrhea, pruritus,...
Genomic diversity of multidrug-resistant Rhodococcus equi: novel sequence types, pangenome architecture, and phylogenomic evolution. Rhodococcus equi is a major cause of life-threatening pneumonia in foals under 6 months of age and an opportunistic pathogen in immunocompromised humans. Although common in soil and equine farm environments, its evolutionary dynamics, virulence architecture, and pathways of antimicrobial resistance (AMR) emergence remain poorly understood. This study integrated phenotypic characterization and whole-genome sequencing of 46 R. equi isolates from horses submitted for necropsy (n = 45) and equine fecal samples (n = 1) in Kentucky between January 2022 and December 2023 to define their resistance la...
Recent Advances in Natural Products for Colitis: Mechanisms and Translational Perspectives. Colitis is a chronic relapsing inflammatory disorder characterized by persistent mucosal inflammation, epithelial barrier disruption, oxidative stress, immune dysregulation, and gut microbiota imbalance. Although current therapies have improved disease management, their long-term use is still limited by incomplete response, relapse, adverse effects, and high cost. Natural products have attracted increasing attention as promising candidates for colitis intervention because of their structural diversity, broad bioactivity, and multitarget regulatory potential. In veterinary medicine, colitis and...
Genomics in Equine MEED: Whole-Genome Sequencing and Target Mutation Identification. Multisystemic eosinophilic epitheliotropic disease (MEED) is a rare and severe equine disorder characterized by chronic eosinophilic inflammation, epithelial disruption, and multi-organ involvement, with an undefined genetic basis. We performed the high-depth (~40×) whole-genome sequencing of an affected horse and compared it to 40 control genomes. Over 6.3 million variants were identified, with moderate- and high-impact variants enriched in low-frequency categories, including rare and private variants absent from the controls. The affected horse was dominated by missense mutations, with rela...
An intronic variant in Ferredoxin Reductase (FDXR) creates a cryptic exon in Quarter Horses with Equine Juvenile Spinocerebellar Ataxia. Equine Juvenile Spinocerebellar Ataxia (EJSCA) is a novel autosomal recessive neurologic disease in Quarter Horses. Affected foals display a progressive proprioceptive ataxia by 1-5 weeks of age, leading to recumbency and necessitating euthanasia. Whole genome sequencing was performed on 7 EJSCA cases and unaffected horses that included 4 obligate carriers, 4 unaffected half or full-siblings, and 28 unrelated, unaffected control Quarter Horses. An 82 kb region of association was identified (EquCab3.0, chr11: 6963986-7045999), containing 9 candidate SNPs across four genes (FADS6, FDXR, GRIN2C a...
Growth kinetics of Taylorella equigenitalis and its survival in straw-based bedding. Taylorella equigenitalis, the causative agent of contagious equine metritis, is a fastidious bacterium with limited tolerance to extra-host conditions; however, quantitative data on its growth dynamics and survival outside the host remain scarce. This study evaluated the growth of T. equigenitalis under aerobic and microaerophilic conditions in liquid medium and its survival in wet and dry straw-based bedding under controlled laboratory conditions.Growth was assessed at 20 °C and 37 °C using real-time optical density monitoring and viable cell counts. No proliferation was observed at 20 ...
