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Topic:Disease Etiology
Disease etiology in horses refers to the study of the causes and development of diseases within equine populations. It encompasses various factors, including genetic predisposition, environmental influences, infectious agents, and nutritional imbalances, that contribute to the onset and progression of diseases in horses. Understanding disease etiology is essential for identifying risk factors and implementing preventative measures in equine health management. This topic includes research on pathogen-host interactions, the impact of management practices on disease incidence, and the role of genetic and environmental factors in disease susceptibility. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanisms, contributing factors, and implications of disease etiology in horses.
Heritability estimates of atrial fibrillation in Thoroughbred racehorses in Hong Kong and Australia. Atrial fibrillation (AF) is the most common performance-limiting arrhythmia of racehorses. A genetic contribution has been suggested in Standardbred racehorses but has not been investigated in Thoroughbreds. The objective of this study was to determine the heritability of AF in Thoroughbred racehorses. Methods: Horses racing between 2007 and 2019 in Hong Kong and Australia that had AF detected postrace via auscultation (n = 463 cases) were compared with five randomly selected racing contemporaries (n = 2,315 controls). The ASReml-R programme was used to fit an animal model to the AF data t...
Position of the midline septum of the guttural pouches in horses subjected to computed tomography. Standing computed tomographic (CT) examination of the equine guttural pouch frequently reveals deviation of the midline septum. The significance of deviation is currently unknown. The aims of this retrospective, single-centre study were to determine the prevalence of deviation of the midline septum of the guttural pouch and determine whether there was an association between the presence and degree of deviation of the septum, and guttural pouch disease. Case records were reviewed, identifying 95 horses that had undergone a standing, sedated, head CT and guttural pouch endoscopy. The presence, l...
The Bone Cartilage Interface and Osteoarthritis. This review describes results obtained with tissue from prior studies of equine and human osteoarthritis (OA). The main methods considered are scanning electron microscopy, novel methods in light microscopy and X-ray Micro-tomography. The same samples have been re-utilised in several ways. The tissues described are hyaline articular cartilage (HAC; or substitutes), with its deep layer, articular calcified cartilage (ACC), whose deep surface is resorbed in cutting cone events to allow the deposition of subchondral bone (SCB). Multiple tidemarks are normal. Turnover at the osteochondral (ACC-HAC...
Equine influenza: a comprehensive review from etiology to treatment. Influenza is an extremely contagious respiratory disease, which predominantly affects the upper respiratory tract. There are four types of influenza virus, and pigs and chickens are considered two key reservoirs of this virus. Equine influenza (EI) virus was first identified in horses in 1956, in Prague. The influenza A viruses responsible for EI are H7N7 and H3N8. Outbreaks of EI are characterized by their visible and rapid spread, and it has been possible to isolate and characterize H3N8 outbreaks in several countries. The clinical diagnosis of this disease is based on the clinical signs pre...
Genomic Association of Chronic Idiopathic Anhidrosis to a Potassium Channel Subunit in a Large Animal Model. Similar to humans, the horse relies predominantly on the evaporation of sweat from the skin surface to dissipate excess body heat. Loss of the sweat response or anhidrosis can result in life-threatening hyperthermia. Anhidrosis occurs more frequently in some breeds as well as occurs at an increased frequency among individuals with a family history, suggesting a heritable component to the pathology. Given the natural occurrence and indications of genetic components in the etiology, we utilized genomics to better understand the molecular mechanisms involved in sweat response. We performed a case...
Equine “Idiopathic” and Infundibular Caries-Related Cheek Teeth Fractures: A Long-Term Study of 486 Fractured Teeth in 300 Horses. Background: Limited objective information is available on the prevalence of non-traumatic equine cheek teeth fractures, the signalment of affected horses, and the clinical features and treatment of these fractures. Objectives: This study aims to document patterns of idiopathic and infundibular caries-related cheek teeth fractures in a referral population and evaluate associations between fracture patterns and horse age, Triadan position of affected teeth, clinical signs, and deemed necessity for treatment. Study Design: A retrospective case review. Methods: The clinical records at Edinburgh Un...
Peripheral blood basophils are the main source for early interleukin-4 secretion upon in vitro stimulation with Culicoides allergen in allergic horses. Interleukin-4 (IL-4) is a key cytokine secreted by type 2 T helper (Th2) cells that orchestrates immune responses during allergic reactions. Human and mouse studies additionally suggest that basophils have a unique role in the regulation of allergic diseases by providing initial IL-4 to drive T cell development towards the Th2 phenotype. Equine Culicoides hypersensitivity (CH) is a seasonal immunoglobulin E (IgE)-mediated allergic dermatitis in horses in response to salivary allergens from Culicoides (Cul) midges. Here, we analyzed IL-4 production in peripheral blood mononuclear cells (PBMC) o...
The Clonal Population of Trichophyton equinum from Dermatophytoses of Japanese Racehorses. Trichophyton equinum is a zoophilic dermatophyte that is frequently isolated from horse dermatophytosis and rare infections in humans. In the present study, molecular and physiological testing were performed on T. equinum isolates from dermatophytoses of Japanese racehorses to assess genotype and phenotype patterns of these strains. Comparative nucleotide sequence analysis showed that internal transcribed spacer (ITS) region sequences amplified from all Japanese isolates were 99.5% identical to T. equinum reference strains. ITS sequences amplified among the isolates were 100% (BT2) showed that...
An entry risk assessment of African horse sickness virus into the controlled area of South Africa through the legal movement of equids. South Africa is endemic for African horse sickness (AHS), an important health and trade-sensitive disease of equids. The country is zoned with movement control measures facilitating an AHS-free controlled area in the south-west. Our objective was to quantitatively establish the risk of entry of AHS virus into the AHS controlled area through the legal movement of horses. Outcomes were subcategorised to evaluate movement pathway, temporal, and spatial differences in risk. A 'no-control' scenario allowed for evaluation of the impact of control measures. Using 2019 movement and AHS case data, and ...
Clinical, pathologic, and epidemiologic features of nocardioform placentitis in the mare. Placentitis is the leading cause of infectious abortion in the horse and contributes to roughly 19% of all abortions in the United States. A type of placental infection, nocardioform placentitis (NP) is associated with gram-positive branching actinomycetes localized within the ventral body of the feto-maternal interface to create a lymphoplasmacytic mucoid lesion. While the etiology of this disease is poorly described, this placental infection continues to cause episodic abortions in addition to weak and/or growth retarded neonates. The goal of the present study was to perform a comprehensive ...
Identification and genomic characterization of emerging CRESS DNA viruses in thoroughbred horses in China. Multiple novel circular replication-associated protein (Rep)-encoding single stranded (CRESS) DNA viruses have been extensively identified in the feces of humans and animals. Here, we first detected CRESS DNA virus (named Horse-CRESS DNA-like virus, HCLV) in two fecal samples from 10 imported thoroughbred (TB) horses in the customs quarantine station in North Xinjiang province, China. Additionally, we found that this virus was not detected in local breeds (LBs) (0/41) and was found only in imported TB horses (2/73). We obtained the whole-genome sequences of four viruses (HCLV ALSK-3-4, ALSK-13...
Molecular Typing of Burkholderia mallei Isolates from Equids with Glanders, India. We collected 10 Burkholderia mallei isolates from equids in 9 districts in India during glanders outbreaks in 2013-2016. Multilocus variable-number tandem-repeat analysis showed 7 outbreak area-related genotypes. The study highlights the utility of this analysis for epidemiologically tracing of specific B. mallei isolates during outbreaks.
Circovirus in Blood of a Febrile Horse with Hepatitis. Circoviruses infect vertebrates where they can result in a wide range of disease signs or in asymptomatic infections. Using viral metagenomics we analyzed a pool of five sera from four healthy and one sick horse. Sequences from parvovirus-H, equus anellovirus, and distantly related to mammalian circoviruses were recognized. PCR identified the circovirus reads as originating from a pregnant mare with fever and hepatitis. That horse's serum was also positive by real time PCR for equine parvovirus H and negative for the flavivirus equine hepacivirus. The complete circular genome of equine circovi...
The effect of ischaemic postconditioning on mucosal integrity and function in equine jejunal ischaemia. Ischaemic postconditioning (IPoC) has been shown to ameliorate ischaemia reperfusion injury in different species and tissues. Objective: To assess the feasibility of IPoC in equine small intestinal ischaemia and to assess its effect on histomorphology, electrophysiology and paracellular permeability. Methods: Randomised in vivo experiment. Methods: Experimental jejunal ischaemia was induced for 90 min in horses under general anaesthesia. In the control group (C; n = 7), the jejunum was reperfused without further intervention. In the postconditioning group (IPoC; n = 7), reocclusion was im...
Gene expression analysis of subchondral bone, cartilage, and synovium in naturally occurring equine palmar/plantar osteochondral disease. Osteoarthritis (OA) is a disease of the entire joint but the relationship between pathological events in various joint tissues is poorly understood. We examined concurrent changes in bone, cartilage, and synovium in a naturally occurring equine model of joint degeneration. Joints (n = 64) were grossly assessed for palmar/plantar osteochondral disease (POD) in racehorses that required euthanasia for unrelated reasons and assigned a grade of 0 (n = 34), 1 (n = 17), 2 or 3 (n = 13) using a recognized grading scheme. Synovium, cartilage, and subchondral bone were collected for hist...
Association of inbreeding and regional equine leucocyte antigen homozygosity with the prevalence of insect bite hypersensitivity in Old Kladruber horse. Inbreeding depression is the reduction of performance caused by mating of close relatives. In livestock populations, inbreeding depression has been traditionally estimated by regression of phenotypes on pedigree inbreeding coefficients. This estimation can be improved by utilising genomic inbreeding coefficients. Here we estimate inbreeding depression for insect bite hypersensitivity (IBH) prevalence, the most common allergic horse disease worldwide, in Old Kladruber horse. In a deep pedigree with 3214 horses (187 genotyped), we used a generalised linear mixed model with IBH phenotype from 558...
Training related risk factors for exercise induced pulmonary haemorrhage in British National Hunt racehorses. Exercise induced pulmonary haemorrhage (EIPH) is an important condition of horses performing high intensity exercise, with reported prevalence among racehorses of up to 95%, based on the detection of blood on tracheobronchoscopy. Previously identified risk factors include age, sex, season, race type, years spent in racing and lower airway inflammation. Objective: To estimate the prevalence of EIPH in British National Hunt racehorses as indicated by two outcome measures: presence of tracheal blood on tracheobronchoscopy, and presence of moderate-large (significant) proportions of haemosideropha...
Rift Valley Fever and West Nile virus vectors in Morocco: Current situation and future anticipated scenarios. Rift Valley Fever (RVF) and West Nile virus (WNV) are two important emerging Arboviruses transmitted by Aedes and Culex mosquitoes, typically Ae. caspius, Ae. detritus and Cx. pipiens in temperate regions. In Morocco, several outbreaks of WNV (1996, 2003 and 2010), affecting horses mostly, have been reported in north-western regions resulting in the death of 55 horses and one person cumulatively. Serological evidence of WNV local circulation, performed one year after the latest outbreak, revealed WNV neutralizing bodies in 59 out of 499 tested participants (El Rhaffouli et al., 2012). The coun...
Antimicrobial resistance in clinical bacterial isolates from horses in the UK. Surveillance of antimicrobial resistance (AMR) in horses is important to aid empirical treatment decisions and highlight emerging AMR threats. Objective: To describe the AMR patterns of common groups of bacteria from clinical submissions from horses in the UK during 2018, and to determine how this varies by sample site and type of submitting veterinary practice. Methods: Prospective observational study. Methods: All data on bacterial culture and subsequent antimicrobial susceptibility testing (AST) collected in 2018 from six large equine diagnostic laboratories were included. Resistance patter...
Risk factors for laminitis and nonsurvival in acute colitis: Retrospective study of 85 hospitalized horses (2011-2019). Acute colitis is a serious cause of morbidity and death in horses. Recent studies have compared clinical features of coronavirus and salmonellosis, but no study has compared clinical features of enteric salmonellosis, coronavirus, and neorickettsiosis. Objective: To identify risk factors for laminitis and nonsurvival to discharge in horses with enteric salmonellosis, coronavirus, or neorickettsiosis. Methods: Eighty-five horses hospitalized for acute colitis from 2011 to 2019. Methods: Retrospective case series. Medical record review (2011-2019) of adult (≥2 years) horses with colitis. Pri...
Isolation of Moraxella spp. from horses with conjunctivitis in Southern Brazil. Infectious keratoconjunctivitis (IKC) is the most frequent ocular disease in livestock worldwide and is primarily caused by Moraxella bovis, M. ovis, and/or M. bovoculi. The economic impact of IKC is mainly due to ocular damage, which leads to weight loss, management difficulties, pain and discomfort, and cost of treatments. In horses, limited information is available on the association of Moraxella spp. with keratoconjunctivitis. The present report describes two cases of equine keratoconjunctivitis caused by members of the genus Moraxella. Both animals presented with lacrimation, conjunctivit...
Case-Control Study of Risk Factors for Equine Asthma in Texas. Equine asthma is a common condition in horses, for which few host-related risk factors have been identified. The objective of this study was to identify host-related risk factors for the development of equine asthma. A retrospective, case-control study was performed, utilizing horses presented to the Texas A&M University, Veterinary Medical Teaching Hospital from January 2014 December 2018. Incident cases of mild to severe equine asthma (n = 37), diagnosed clinically with cytologic support of disease were examined. For each case, two control populations were identified, including one tem...
Epidemiology of Chlamydia psittaci infections in pregnant Thoroughbred mares and foals. Late-term foal loss due to the traditional avian pathogen Chlamydia psittaci recently emerged as a threat to the Australian Thoroughbred industry. A longitudinal study of 14 stud farms was undertaken to better understand C. psittaci infection in pregnant mares and their foals by evaluating C. psittaci prevalence, equine herpesvirus-1 (EHV-1) co-infection, avian reservoirs, and potential risk factors. Mucosal swabs taken from 228 healthy pregnant mares and their foals were tested for C. psittaci and EHV-1 using species-specific qPCR assays. No foal loss was recorded due to either pathogen, and ...
Utility of cell-free DNA concentrations and illness severity scores to predict survival in critically ill neonatal foals. Plasma cell-free DNA (cfDNA) levels have been associated with disease and survival status in septic humans and dogs. To date, studies investigating cfDNA levels in association with critical illness in foals are lacking. We hypothesized that cfDNA would be detectable in the plasma of foals, that septic and sick-nonseptic foals would have significantly higher cfDNA levels compared to healthy foals, and that increased cfDNA levels would be associated with non-survival. Animals used include 80 foals of 10 days of age or less admitted to a tertiary referral center between January and July, 2020 wer...
Evaluation of buffered Trypanosoma evansi antigen and rapid serum agglutination test (BA/Te) for the detection of anti-T. evansi antibodies in horses in Brazil. Surra is an infectious disease caused by , which affects a large number of domestic and wild animal species. Infection control is based on rapid diagnosis followed by treatment of sick animals. This study aimed to evaluate a buffered antigen and rapid serum agglutination test (BA/Te) for the detection of anti- antibodies in serum samples of horses. For this purpose, 445 serum samples from horses were evaluated and the results compared with the diagnosis by CATT/. Our data show a sensitivity of 92%, specificity of 91% and a degree of agreement kappa () of 0.82 (95% CI: 0.771-0.877, < 0...
Bacterial meningitis after dental extraction in a 17-year-old horse. Dental extractions in horses may result in bacteremia, which can lead to systemic complications. Bacterial meningitis following oral cheek tooth extractions in a 17-year-old Thoroughbred gelding is described in this report. The bacterial meningitis was confirmed by histopathology. The gelding was presented for evaluation of intermittent fever, loose feces, and mild colic signs which started 5 days after cheek tooth extraction. This case illustrates a rare complication associated with oral tooth extraction in a horse and highlights the unusual presenting features of meningitis. Key clinical mes...
Gastric and Large Colon Impactions Combined With Aggressive Enteral Fluid Therapy May Predispose to Large Colon Volvulus: 4 Cases. To resolve large colon impactions, frequent enteral administration of large volumes of water (8-10 liters in a 500 kg horse) has been suggested. Furthermore, in large colon volvulus, the simultaneous presence of gastric impaction has been described as a possible predisposing factor. To describe the clinical and surgical features of horses with large colon volvulus associated with aggressive enteral fluid therapy performed to resolve an initial large colon impaction. Records of horses that underwent exploratory laparotomy at the Veterinary Teaching Hospital of Turin between 2012-2019 were revie...
