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Topic:Neurological Diseases
Neurological diseases in horses encompass a range of disorders affecting the central and peripheral nervous systems. These conditions can arise from various etiologies, including infectious agents, genetic predispositions, trauma, or metabolic imbalances. Common neurological diseases in horses include equine protozoal myeloencephalitis (EPM), equine herpesvirus myeloencephalopathy (EHM), and cervical vertebral stenotic myelopathy (CVSM), also known as wobbler syndrome. Clinical signs associated with these diseases may include ataxia, weakness, altered gait, and changes in behavior or mental status. Diagnosis typically involves a combination of clinical evaluation, imaging techniques, and laboratory testing. This page compiles peer-reviewed research studies and scholarly articles that investigate the pathophysiology, diagnostic approaches, and treatment options for neurological diseases in equine populations.
Diagnostic utility of trigeminocervical reflex and quantitative sensory testing in horses with trigeminal-mediated headshaking. Assessment of trigeminal nerve (TN) function in horses with trigeminal-mediated headshaking (TMHS) using trigeminocervical reflex (TCR) and quantitative sensory testing (QST) has not been investigated. Objective: Horses with TMHS show lower TCR and QST thresholds than controls. A subset shows left-to-right differences. Methods: Privately owned horses with TMHS (n = 12) and secondary headshaking (sHS; n = 4), from a referral hospital. Headshaking-free controls (n = 14), from the hospital's teaching herd or privately owned. Methods: Prospective case-control-study. In unsedated horses, TCR ...
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...
Mesenchymal stem cells in veterinary clinical practice: Evidence from naturally occurring diseases. Over the past two decades, the use of mesenchymal stem cells (MSCs) in veterinary medicine has expanded rapidly, although the clinical evidence remains in its early stages. This review discusses clinical studies involving client-owned animals with naturally occurring diseases in which MSCs or MSC-derived extracellular vesicles (EVs) were used as treatments. It covers musculoskeletal disorders, including osteoarthritis, tendon and ligament injuries, and bone diseases; soft-tissue and oral mucosal conditions; neurological disorders; ophthalmic diseases; and internal medicine disorders, such as i...
Horses with pituitary pars intermedia dysfunction have an altered fecal short-chain fatty acid profile. Pituitary pars intermedia dysfunction (PPID) is a prevalent endocrine disease in older horses sharing pathogenetic features with Parkinson disease, including dopaminergic neurodegeneration and α-synuclein aggregation. This study was conducted to determine whether horses with PPID exhibit changes in short-chain fatty acid (SCFA) profiles as described in Parkinson disease, providing further evidence for involvement of a microbiota-gut-brain axis in the pathogenesis of PPID. Unassigned: Prospective case-control study including 22 horses > 12 years of age. Diagnosis of PPID was based on clinical ...
An experimental multiplex PCR/RT-PCR for detection of the main viruses associated with equine neurological disease. Viral neurological infections are important causes of morbidity and mortality in horses worldwide. Herein, we describe an end-point multiplex PCR/RT-PCR for simultaneous and differential detection of major equine encephalitis-related agents: rabies virus (RABV), equine herpesvirus type 1 (EHV-1), alphaviruses [Venezuelan equine encephalitis virus (VEEV), Eastern equine encephalitis virus (EEEV), Western equine encephalitis virus (WEEV) and Madariaga virus (MADV)] and flaviviruses [West Nile virus (WNV), Saint Louis encephalitis virus (SLEV), Rocio virus (ROCV) and Japanese encephalitis virus (...
Leptomeningeal dissemination of a poorly differentiated carcinoma involving the trigeminal ganglion in a horse: a case report. Neoplastic conditions involving cranial nerves are uncommon in horses and represent a significant diagnostic challenge. Leptomeningeal dissemination is a recognized mechanism of tumor progression in aggressive neoplasms but is rarely reported in this species. A 15-year-old mixed-breed horse with a history of periocular squamous cell carcinoma treated by enucleation three years earlier developed progressive neurological signs. Initial differential diagnoses included metastatic neoplasia and equine protozoal myeloencephalitis. Due to rapid neurological deterioration, euthanasia and necropsy were...
Nucleic acid detection and molecular traceability of equine herpesvirus 1 in imported horses. Equid alphaherpesvirus 1 is a major pathogen threatening the global equine industry, causing respiratory disease, abortion, and neurological disease. Unassigned: In April 2024, during routine pathogen screening of a batch of imported quarantine horses from the Netherlands, four out of 20 nasal swab samples tested positive for EHV-1 nucleic acid. Unassigned: The affected horses exhibited only mild respiratory signs. ORF30 SNP typing at nucleotide position 2254 and Sanger sequencing confirmed that all positive samples belonged to the N752 non-neuropathogenic genotype. As virus isolation was unsu...
Hepatic encephalopathy associated with extensive hepatic diaphragmatic herniation in an adult horse. Diaphragmatic hernia in horses is a rare condition, most commonly presenting with signs of colic and, less frequently, respiratory compromise. Hepatic herniation through a diaphragmatic defect with secondary hepatic failure and encephalopathy has rarely been documented in horses. Methods: A 5-year-old Mangalarga Marchador stallion was evaluated for progressive neurological deterioration, including obtundation, head pressing, ataxia, and circling. Serum biochemistry revealed severe hepatobiliary dysfunction, characterised by increased gamma-glutamyl transferase and alkaline phosphatase activiti...
Ceratohyoidectomy for Management of Unilateral and Bilateral Temporohyoid Osteoarthropathy: Long-Term Outcome in 33 Equids. Temporohyoid osteoarthropathy is a disease affecting the temporohyoid joint in equids caused by local inflammation and/or degeneration, leading to neurological deficits ranging from mild signs that affect performance to significant, acute neurological deficits such as facial nerve paralysis or vestibular signs. Multiple surgical treatment options are available, and while treatment has historically been performed unilaterally on the side of the clinical signs, advances in diagnostic imaging have highlighted the occurrence of bilateral disease of the temporohyoid joints, warranting evaluation of...
The Transcriptomic and Proteomic Molecular Signatures of Equine Multiple-System Neuropathy (Grass Sickness). Equine grass sickness (EGS or equine dysautonomia) is a predominantly fatal multi-system neuropathy affecting grazing horses, likely caused by a neurotoxic phospholipase A2 (nPLA2) derived from a plant or microorganism. We studied neuronal tissue gene and protein expression patterns in EGS to elucidate the possible mechanisms of neurotoxicity and neurodegeneration. Tissue from the cranial cervical ganglion of eight EGS horses and six controls was examined histologically and used for transcriptomic analysis. These transcriptomic data were compared with previously published EGS-related proteomic...
Altered gene expression in the liver and small intestine of horses with equine neuroaxonal dystrophy. Equine neuroaxonal dystrophy/degenerative myeloencephalopathy (eNAD/EDM) is the second most common diagnosis of spinal ataxia in horses in the United States. The disease develops due to a combination of vitamin E deficiency and an unknown genetic risk factor(s), and there currently is no effective treatment. Objective: We performed transcriptomic profiling of the liver and small intestine of horses with and without eNAD/EDM, as both tissues are the main locations for absorption, metabolism, and delivery of vitamin E to the nervous system. Methods: Case-control exploratory study. Methods: Post...
Improving concussion assessment in jockeys: normative benchmarks and web-based tool for ImPACT interpretation. Despite horse racing's exceptionally high concussion risk, there is no jockey-specific ImPACT study. This work aimed to develop demographically adjusted, jockey-specific ImPACT norms and to evaluate complementary approaches to clinical classification. Unassigned: Retrospective baseline data from 663 Irish jockeys (2021-2024) were analyzed. Two normative methods were applied: (i) a univariate regression-based approach estimating expected scores for each cognitive domain independently, adjusting for age, sex, and education, with percentile-based classification; and (ii) a multivariate regression...
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...
Combined treatment with valacyclovir and heparin reduced the incidence of equine herpesvirus myeloencephalopathy and improved survival in naturally occurring equine herpesvirus-1 outbreaks. Describe the effects and outcomes of valacyclovir and heparin administration in equine herpesvirus-1 (EHV-1)-exposed horses. Unassigned: A multicenter retrospective study identified 111 horses naturally exposed to EHV-1 from August 2017 to March 2018. Equine herpesvirus-1 infection was confirmed via blood or nasal secretion PCR. Horses that developed neurologic signs were diagnosed with equine herpesvirus myeloencephalopathy (EHM). Clinical signs, treatment, and survival were reported. A subset of horses was treated with valacyclovir and heparin. Prophylactic medication administration was perf...
Influence of collection site on cerebrospinal fluid test results in horses with equine protozoal myeloencephalitis. Cerebrospinal fluid (CSF) analysis is a critical component in the diagnosis of equine protozoal myeloencephalitis (EPM). Test results obtained may differ based on different collection sites. Objective: Compare results of EPM-specific diagnostic tests obtained from different collections sites in EPM-affected and non-EPM affected horses. Methods: Twenty control and 7 EPM-affected horses. Methods: Prospective observational study. CSF was collected from the lumbosacral (LS) and cranial sites (atlantooccipital or C1-2) in 27 horses and EPM-specific diagnostic tests were performed. Data were summari...
Seroprevalence of Orthoflaviviruses in horses in 3 different Algerian climatic zones between 2021 and 2023. Orthoflaviviruses are etiological agents of neurological diseases in equines. Horses are susceptible to equine Tick-borne encephalitis virus (TBEV), Usutu virus (USUV), and West Nile virus (WNV), although mostly WNV has been associated with clinical disease. The aim of the present study was to estimate the prevalence of TBEV, USUV and WNV in 289 healthy horses from nine provinces of Algeria. This study was conducted between March 2021 and December 2023. Sera that tested positive, doubtful, or negative close to the doubtful threshold in the Orthoflavivirus-ELISA were further tested by the virus...
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...
Eastern equine encephalitis-104 horses (1979-2017). Eastern equine encephalitis (EEE) is a highly fatal neurologic disease of horses, but data describing clinical presentation, epidemiology, and prognostic factors are limited. Objective: Describe the clinicopathologic and epidemiologic features of horses with EEE and identify factors associated with survival. Methods: One hundred four horses diagnosed with EEE presented with signs of diffuse brain disease. Methods: Retrospective case series of horses evaluated at a Veterinary Teaching Hospital (1979-2017). Medical records were reviewed for clinical findings, diagnostic results, and outcomes. Lo...
Retrospective assessment of equine herpesvirus type 1 (EHV-1) genotype-associated clinical disease in Ontario. Equine herpesvirus type 1 (EHV-1) is an important viral pathogen in horses, associated with diverse clinical manifestations including fever, upper and lower respiratory disease, neurological signs, ocular disease, and abortion. Currently, EHV-1 variants (genotypes) are classified based on a single nucleotide polymorphism mutation of the open reading frame 30 (ORF30). Unassigned: The aim of this retrospective study was to evaluate the EHV-1 genotypes present in horses with various clinical presentations, including respiratory disease, abortion, and neurological disease, at a referral center in ...
Persistence of Sarcocystis neurona and histopathology in horses with equine protozoal myeloencephalitis. Currently, little is known about the exact role of immunopathology in equine protozoal myeloencephalitis (EPM), including the ability to persist after anti-protozoal treatment. The main objectives of this study were to determine whether is present in the CNS in horses with EPM, including previously treated cases, and to evaluate the associated histopathology and immune response. For this study, control ( = 10) and horses with EPM ( = 9) were confirmed based on our inclusion criteria. Based on our preliminary data, we classified horses with EPM and clinical signs for >6 months as...
Evaluating Protein Enrichment Methods to Improve Biomarker Discovery in Equine Cerebrospinal Fluid. Cerebrospinal fluid (CSF) is a valuable source of biomarkers for neurological diseases, but detection of low-abundance proteins is often masked by highly abundant proteins. Enrichment strategies can enhance proteomic coverage and improve biomarker discovery, yet comparative evaluations of such methods in equine CSF are limited. Objective: This study compared the ProteoMiner Small-Capacity Enrichment Kit and the PreOmics Enrich-iST Kit for their ability to deplete high-abundance proteins and enhance detection of low-abundance proteins relevant to neuropathology. Methods: Equine CSF samples were...
Case Report: Neurologic signs following rattlesnake envenomation. Rattlesnake envenomation is a common emergency in horses in California. Rattlesnakes belong to a group of venomous snakes: pit vipers. The Northern Pacific Rattlesnake (), a subspecies of the Western Rattlesnake, is the most widespread rattlesnake in California (1). A 5-year-old miniature horse mare presented for a presumed Western Rattlesnake bite. The owners found the horse the morning of presentation with severe facial swelling and the horse was housed in an area where rattlesnakes are commonly observed. The horse was reported to be normal the day prior to presentation. On blood examination...
Advanced Imaging of the Cranium and the Cervical Spine for Equine Neurologic Disease. Diagnostic imaging is essential for evaluating and managing neurologic disease in horses. Following clinical lesion, neurolocalization imaging modalities are often necessary to further characterize the disease process. However, which technology to use depends on various factors, including the patient's size, clinical signs, and the anatomic region. Current advances in imaging technology, in general, and the adaptation of different modalities for equine patients, in particular, have substantially improved our ability to evaluate the equine central nervous system. This article will summarize the...
Diagnosis and Surveillance of West Nile Virus Infection in Horses: Current Methods, Challenges, and Future Directions. West Nile virus (WNV) is a mosquito-borne flavivirus of growing importance for both human and equine health in Europe. Horses are highly susceptible to neurological disease and, because they share ecological exposure with humans, they represent valuable sentinels for detecting local viral circulation within a One Health framework. However, diagnosis of WNV infection in equines is complicated by the short and low-level viraemia, which limits the sensitivity of molecular assays, and by serological cross-reactivity with related flaviviruses and the confounding effects of vaccination. In this narr...
Cervical extradural mast cell tumour in a 2-year-old Irish Sport Horse colt. A 2-year-old Irish Sport Horse colt presented with acute, severe and rapidly progressive neurological signs, arriving recumbent to the hospital. Ante-mortem diagnostics did not reveal the cause of the recumbency, and the colt was euthanized after treatment and supportive care did not result in clinical improvement. A cranial cervical extradural mast cell tumour with eosinophilic granulomas and secondary compressive myelopathy with axonal degeneration was diagnosed on post-mortem evaluation. No other masses or clinically relevant findings were present, suggesting a primary neoplasm. Neoplasia a...
Main causes of death in aged horses in a retirement facility in California can be attributed to the digestive and musculoskeletal systems. To determine the main causes of death in aged horses residing at a retirement facility in California. Unassigned: A retrospective cross-sectional study design was utilized to evaluate signalment, medical history, and necropsy reports of horses aged 20 years or older at death and housed at a single retirement facility. All cases underwent a standard post mortem evaluation from 2010 through 2020 by the University of California-Davis William R. Pritchard Veterinary Medical Teaching Hospital. Euthanasia decisions were made by the retirement facility staff in consultation with a veterinarian. The m...
Orthoflavivirus-associated neurological disease in a UK horse. Keesjan Cornelisse and Andra-Maria Ionescu discuss the clinical presentation, investigation and diagnostic approach to a case of orthoflavivirus infection in a horse in south-west England.
Rocio virus sustained circulation in Brazil: first infection case in a horse highlights the need for enhanced arbovirus surveillance. Rocio virus (ROCV), a neurotropic arbovirus of the genus, caused Brazil’s largest encephalitis outbreak in the 1970s but has since been rarely detected. We report the first ROCV encephalitis clinical case after nearly 40 years and isolated and sequenced the virus from CNS tissue of a horse. Metatranscriptomics enabled full-genome sequencing, revealing divergence from the reference sequence at an evolutionary rate of 5.8–7.0 × 10⁻⁴, consistent with . Thirty-one non-synonymous substitutions were identified, with the envelope protein most affected. Findings indicate ROCV cryptic circula...
Updates on Seizures and Epilepsy in the Horse. The goal of this article is to provide the equine practitioners with a framework for a diagnostic algorithm for the patient presented with possible seizures/epilepsy. Using a comparative approach, a review of companion animal and human research is provided with the intention of expanding our current knowledge on seizure/epilepsy, as well as diagnostic and treatment strategies for equine patients.
Update on Idiopathic Trigeminal-Mediated Headshaking. Idiopathic trigeminal-mediated headshaking is a painful neuropathic disorder characterized by sudden, violent, predominantly vertical head movements of unknown etiology. Clinical signs may be seasonal or persistent and triggered by light, sound, exercise, or tactile nasal stimulation. The pathophysiology is multifactorial, involving abnormal trigeminal nerve excitability influenced by hormonal, environmental, and dietary factors. Treatment is challenging and typically multimodal, aiming to reduce trigeminal hypersensitivity and improve quality of life.
