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Topic:Virology
Virology in horses encompasses the study of viruses that affect equine species, including their biology, transmission, and impact on horse health. This field investigates viral pathogens that can lead to a range of diseases, from respiratory infections to neurological disorders. Common viruses affecting horses include equine influenza virus, equine herpesvirus, and West Nile virus. Understanding these viruses involves examining their genetic makeup, modes of transmission, and interactions with the equine immune system. This page compiles peer-reviewed research studies and scholarly articles that explore the epidemiology, pathogenesis, and control measures of viral infections in horses.
Evaluation of mosquito transmission of equine hepacivirus in laboratory and field studies. Equine hepacivirus (EqHV) is a hepatotropic virus, closely related to human hepatitis C virus (HCV), that can cause acute or chronic infection in horses. As with HCV, transmission is thought to occur primarily through parenteral, particularly blood-borne, routes. Vertical transmission from mare to foal has been reported but appears to be uncommon. The high seroprevalence in horse populations and the occurrence of infection in isolated horses indicate efficient horizontal transmission routes exist. One such possibility is biological or mechanical transmission by arthropods, such as mosquitoes, ...
Phylogenetic and phylogeographic analysis of equine influenza in Colombia. In 2022, Colombia experienced an outbreak of equine influenza (EI) that primarily affected competition horses. Despite the epidemiological relevance of equine influenza virus (EIV) in the country, no previous phylogenetic or phylogeographic analyses based on complete genomes have been reported. Objective: To perform phylogenetic and phylogeographic analyses of complete EIV genomes obtained from horses with clinical signs in two Colombian regions between 2020 and 2023. Methods: Molecular epidemiological study based on whole-genome sequencing and evolutionary analyses. Methods: Nasopharyngeal sa...
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...
Whole-genome characterization and phylogenetic analysis of Equine Rotavirus A isolated from Jeju Island, Korea. Equine Rotavirus A (ERVA) is a major cause of acute diarrhea in neonatal foals, leading to significant economic losses. Genetic variation and global transmission complicate disease control efforts. Objective: To analyze the complete genome of an ERVA strain from Jeju Island, Korea, and assess its genetic and phylogenetic relationships with global ERVA strains. Methods: Twenty-five fecal and swab samples were collected from diarrheic horses in Jeju during spring and summer 2025. Samples were screened using antigen testing and RT-PCR. One PCR-positive, antigen-test-positive sample was selected f...
Equine Ulcerative Genital Lesions Associated with Parapoxvirus. In 2026, a widespread outbreak of ulcerative dermatitis of unknown aetiology occurred in breeding horses in Ireland. The lesions resembled those associated with equine herpesvirus 3 (EHV3) infection, i.e., papules, vesicles, and ulcers on the penis of stallions and on the vulval and anal areas of mares. This study aimed to identify the probable causative agent. The methods applied included metagenomic sequencing of DNA, phylogenetic analysis, and real-time PCR. Metagenomic analysis directly from a penile sample confirmed the presence of equine parapoxvirus (EqPPV) DNA. Phylogenetic analysis in...
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...
First Molecular Survey of Equine Adenovirus Type 1 Infection Among Horses in Poland. Equine adenovirus type 1 (EAdV-1) infection has been recognised among horses worldwide. The virus predominantly targets respiratory tract but has also been recovered from other body systems. The objective of the study was to determine the frequency of EAdV-1 infection among selected horse populations in Poland and to estimate genetic variability within the viruses obtained. A quantitative PCR assay targeting a partial gene was used to screen 1150 nasal swabs collected from 1145 horses from 19 horse studs throughout Poland. The samples were collected opportunistically between 2012 and 2025. A ...
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...
Molecular detection of African horse sickness virus from selected areas in Ethiopia. Equines are vital to global economies and support millions of livelihoods. However, their productivity and welfare are severely hindered by infectious diseases such as African Horse Sickness, which causes major socio-economic losses in Ethiopia. A cross-sectional study was conducted from November 2022 to May 2023 to isolate and detect African horse sickness virus in equines across epidemic areas of Ethiopia. In total, 30 blood samples and 2 tissue representative specimens were aseptically collected from clinically sick and recently dead animals and transported under cold chain to the National ...
Recombinant EHV-1 Vector Expressing Immunodominant Hemagglutinin Protein of Equine Influenza Virus H3N8 (Sub-Lineage Florida Clade 2). Equine herpesvirus type 1 (EHV-1) and equine influenza virus (EIV) are major respiratory pathogens in horses, causing significant economic losses in domesticated horses. Bacterial Artificial Chromosome (BAC) technology can be used to precisely manipulate the EHV-1 genome for the development of live-attenuated vector vaccines. Earlier, our group developed a live-attenuated EHV-1 vaccine by deleting virulence-associated genes using this technology and the mutant EHV-1 has been exploited for expressing foreign gene in the current study. Specifically, in this study, a mutant EHV-1 virus expressing...
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...
Cryo-EM structure of African horse sickness virus VP2 receptor-binding protein enables nanoparticle vaccine design. African horse sickness virus (AHSV) is a lethal equine pathogen with no licensed vaccine other than vaccines containing attenuated virus, which pose safety risks. Endemic to sub-Saharan Africa, AHSV has caused epizootics in Spain and Portugal, Cyprus, Morocco, the Middle East, India and Pakistan and, most recently, Thailand. Here, we resolve the 3.11 Å cryo-EM structure of full-length VP2 from AHSV serotype 4, adopting its native triskelion architecture and shedding light on an α-helical domain anchoring the triskelion core, which is absent in other structurally characterized orbiviruses. ...
Detection of equine parapoxvirus in the stable environment during pastern dermatitis outbreak in Finland. Equine parapoxvirus (EqPPV) has emerged as a cause of recurring pastern dermatitis outbreaks in horses in Finland. First detected in 2013, EqPPV has since been associated with potentially hundreds of clinical cases and suspected zoonotic transmission. Based on serological data and field reports, EqPPV causes pastern dermatitis outbreaks in Finland every few years. This study aimed to investigate the environmental presence and plausible transmission dynamics of the virus to prepare for future outbreaks and give targeted guidelines to stable staff and veterinarians. Results: After a large-scale ...
First evidence of exposure to West Nile Virus in horses within Denmark, 2025. A nationwide serological screening of 822 horses was conducted in Autumn 2025 to investigate potential exposure to West Nile Virus (WNV) within Denmark. Serum samples were tested for antibodies against WNV, tick-borne encephalitis virus (TBEV) and Usutu virus (USUV). Four horses without any history of travel outside of Denmark, or previous vaccination against WNV, tested positive for WNV neutralising antibodies. The results support local exposure to WNV indicating that virus infected mosquitoes have been present in Denmark and underline the usefulness of horses as sentinels for the risk of hum...
Intermittent shedding dynamics of EHV-1 across biological matrices during a natural outbreak linked to international equestrian events. Equine herpesvirus type 1 (EHV-1) outbreaks associated with international equestrian events have demonstrated the capacity of this virus for rapid transboundary dissemination. However, detailed longitudinal data integrating viral shedding across multiple biological matrices within the same animals during naturally occurring outbreaks remain limited. In this study, ten horses hospitalized during a naturally occurring EHV-1 outbreak linked to an international jumping competition were monitored for 10-12 days, from which 306 nasal, ocular, urine and faecal samples were obtained and analysed by qu...
First serological evidence of circulation of equine rhinitis A virus and molecular detection of equine rhinitis B virus in horses in North Africa. Equine rhinitis A virus (ERAV) and equine rhinitis B virus (ERBV) are major respiratory pathogens of horses with a global distribution. The aim of this study was to evaluate, for the first time in Algeria, the seroprevalence of ERAV antibodies, and to investigate a wide range of equine viruses (EIV, EHV-1, EHV-4, ERAV and ERBV). A total of 298 serum samples were collected between May 2022 and October 2023, from 11 provinces. Serological analysis for the presence of ERAV was performed using the complement fixation test (CFT). Our results revealed that 16.8% (50/298) samples tested positive for ...
Viral Hepatitis. Since 2012, 2 viral causes of hepatitis have been identified in horses. Much remains to be discovered about their transmission, risk factors for clinical disease, diagnosis, and treatment approaches. Equine parvovirus-hepatitis has been identified as the cause of acute hepatic necrosis, previously known as Theiler's disease. Equine hepacivirus is recognized as a cause of chronic fibrosing hepatitis. Diagnosis relies on ruling out other causes of hepatitis and documenting infection by serum or liver polymerase chain reaction. There is no direct antiviral for either condition and treatments are ...
Evaluation of two point-of-care molecular diagnostic platforms for rapid detection of equine Hendra virus. Hendra virus (HeV) is a lethal zoonotic pathogen endemic to eastern Australia, posing significant risks to equine and human health. Rapid field detection of HeV enables timely intervention and outbreak management. This study evaluated candidate point-of-care (POC) molecular diagnostic platforms for HeV detection in equine samples: including a loop-mediated isothermal amplification (DARQ RT-LAMP) assay and real-time reverse transcription quantitative polymerase chain reaction (RT-qPCR). Comparative analytical evaluation demonstrated that RT-qPCR exhibited superior analytical sensitivity relativ...
Isolation and Identification of Emerging Equine Encephalosis Virus Serotype 6 in Israel, 2023. Equine encephalosis (EE) is an arthropod-borne viral disease resembling a mild form of African horse sickness disease, which affects all species of equids. Previously, only EEV serotype 4 (EEV-4) caused sporadic outbreaks of the disease in Israel. In the summer of 2023, EE was clinically diagnosed in horses and donkeys in Israel. For laboratory confirmation, tissue cultures were inoculated with whole-blood samples obtained from sick animals. Five EEV isolates were successfully recovered in tissue and confirmed by conventional RT-PCR and Sanger sequencing of several viral genes. BLAST analysis ...
Equine infectious anemia virus blocks interferon responses through Rev-mediated activation of the stress granule-PKR-eIF2α pathway. Type I interferons (IFNs) play a pivotal role in antiviral defence by inducing interferon-stimulated genes (ISGs) that target multiple stages of viral replication. Equine infectious anemia virus (EIAV) is an ancient lentivirus that establishes long-term asymptomatic infections in equids, suggesting its exceptional immune evasion capabilities. However, the mechanisms by which EIAV modulates IFN responses remain unclear. Here, we demonstrate that EIAV infection attenuates ISG expression at the post-transcriptional level. The viral Rev protein plays a central role by interacting with the stress g...
Equine arteritis virus Nsp10 promotes MAVS proteasomal degradation via E3 ligases Smurf1/MARCH5. Equine arteritis virus (EAV) is a positive-sense, single-stranded RNA virus that belongs to the family , which also includes porcine reproductive and respiratory syndrome virus (PRRSV). EAV is the causative agent of equine viral arteritis (EVA), an economically important systemic, reproductive, and respiratory disease of equids. EAV infection triggers host innate immunity, yet the precise strategies employed by the virus to evade immune defenses and achieve productive infection are poorly characterized. In this study, it was observed that EAV infection can induce a cellular IFN response; howev...
Possible Effects of C-Reactive Protein in the Central Nervous System During Venezuelan Equine Encephalitis Virus Infection. Venezuelan equine encephalitis virus (VEEV) is an alphavirus vectored by mosquitos. It can cause disease in equines and humans characterised by a febrile illness that may progress into encephalitis. Replication of VEEV in the central nervous system induces activation of glial cells and neurons, compromising the blood-brain barrier (BBB) and inducing a state of neuroinflammation. This inflammation can lead to symptoms such as confusion, seizures, and coma, and sustained inflammation contributes to neurodegeneration. C-reactive protein (CRP) is a biomarker that has previously been associated wit...
First confirmed report of equine coital exanthema in Uruguayan horses. Equine Coital Exanthema (ECE) is a contagious venereal disease caused by Equid alphaherpesvirus 3 (EHV‑3). Although ECE is self-limiting, it causes significant economic losses to the global equine industry due to the temporary segregation of affected mares and stallions from breeding activities. This report describes the epidemiological, clinical, histological, and molecular findings from an outbreak of ECE in Uruguayan horses. Seven days following the introduction of a stallion, five mares developed extensive papular and vesicular dermatitis in the vaginal and perineal regions. The stallion...
Integrated workflow for production and in vitro characterization of equine anti-SARS-CoV-2 hyperimmune serum with epitope mapping. This study establishes an integrated workflow linking antibody production, neutralization assessment, and epitope mapping, supporting the identification of antigenic regions recognized by polyclonal antibodies generated in vivo. The viral suspension was inactivated with β-propiolactone under biosafety level 3 (BSL-3) conditions, with no cytopathic effect or plaque formation observed, confirming loss of viral replicative capacity. The produced immunogen retained antigenic activity, as demonstrated by reactivity with IgG antibodies from vaccinated and previously infected individuals. Protein an...
Insights from healthy mares reveal that mammalian uteri harbor a diverse virome. The Earth's estimated 10 virions, primarily phages, significantly impact microbial ecosystems. Despite their abundance, viromes remain relatively understudied-particularly in domestic animals. While recent studies have described a dynamic commensal microbiome in mammalian uteri, no research has yet characterized the commensal virome in a mammalian uterus. In this study, we report for the first time the presence of a sparse, but diverse native virome in the equine uterus. The resulting virome database consists of 513 non-redundant viral genomes (> 2 kb). Taxonomic annotations revealed the...
Detection of papillomavirus DNA in uterine flushing samples from healthy mares reveals diverse genotypes with differing host ranges. A molecular study to assess the presence of some papillomaviruses was performed on 105 uterine flushing samples of healthy mares using real time quantitative polymerase chain reaction (qPCR) and digital PCR (dPCR). Bovine, equine, and ovine papillomavirus DNA was detected in 27 uterine flushing samples through dPCR (~ 25.71%); qPCR was able to detect 18 positive samples (~ 17.14%). Differences between the two molecular protocols were significant as shown by McNemar's test (p˂ 0.005). EcPV DNA was detected in 10 samples by dPCR (~ 9.52%) of uterine flushing samples. qPCR detected EcPV DN...
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 ...
Multivalent Disabled Infectious Single Animal (DISA)-DIVA vaccine for all nine serotypes of African horse sickness virus (AHSV) is broadly protective in IFNAR (-/-) mice. African horse sickness (AHS) is a highly severe, midge-borne disease of equids showing a mortality rate of > 90% in naive domestic horses. Outbreaks are caused by AHS virus (AHSV) and result in devastating economic losses in developing countries as equids play a crucial role in the agricultural industry and many households. The AHSV species encompasses nine serotypes showing no or limited cross protection, which is challenging regarding AHS vaccine development. Recently, and like bluetongue virus (BTV), the AHS Disabled Infectious Single Animal (DISA)-DIVA vaccine platform was developed...
