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.
Microbead electrochemiluminescence immunoassay for detection and identification of Venezuelan equine encephalitis virus. An electrochemiluminescence (ECL) immunoassay, incorporating chemically biotinylated and ruthenylated antibodies down-selected from a panel of monoclonal and polyclonal reagents, was developed to detect and identify Venezuelan equine encephalitis virus (VEEV). The limit of detection (LOD) of the optimized ECL assay was 10(3)pfu/ml VEEV TC-83 virus and 1 ng/ml recombinant (r) VEEV E2 protein. The LOD of the ECL assay was approximately one log unit lower than that of a sandwich enzyme-linked immunosorbent assay (ELISA) incorporating the same immunoreagents. Repetition of ECL assays over time and...
EcPV2 DNA in equine squamous cell carcinomas and normal genital and ocular mucosa. Squamous cell carcinoma (SCC) represents the most common malignant tumour of the eye and external genitals in horses. Comparable to humans, papillomaviruses (PV) have been proposed as etiological agents of cancer in horses and recently, Equine papillomavirus type 2 (EcPV2) has been identified in genital SCCs. Hitherto it had never been demonstrated in ocular SCCs. The first goal of this study was to determine the prevalence of EcPV2 DNA in tissue samples from equine genital and ocular SCCs, genital papillomas and penile intraepithelial neoplasia (PIN) lesions, using EcPV2-specific PCR. The sec...
Genetic heterogeneity and variation in viral load during equid herpesvirus-2 infection of foals. Equine herpesvirus-2 (EHV-2) infection has been implicated as a cause of a variety of clinical disorders in young horses, including upper respiratory tract disease, generalized malaise, fever, pharyngeal lymphoid hyperplasia, and lymphadenopathy. Considerable sequence heterogeneity has been demonstrated previously among EHV-2 strains, and individual horses can be concurrently infected with more than one virus strain. In this study, the temporal variation of the viral load and genomic diversity of the glycoprotein B (gB) gene of EHV-2 in the nasal secretions of a cohort of foals was characteriz...
Equus caballus major histocompatibility complex class I is an entry receptor for equine herpesvirus type 1. In this study, Equus caballus major histocompatibility complex class I (MHC-I) was identified as a cellular entry receptor for the alphaherpesvirus equine herpesvirus type 1 (EHV-1). This novel EHV-1 receptor was discovered using a cDNA library from equine macrophages. cDNAs from this EHV-1-susceptible cell type were inserted into EHV-1-resistant B78H1 murine melanoma cells, these cells were infected with an EHV-1 lacZ reporter virus, and cells that supported virus infection were identified by X-Gal (5-bromo-4-chloro-3-indolyl-beta-d-galactopyranoside) staining. Positive cells were subjected t...
A reverse genetics system of African horse sickness virus reveals existence of primary replication. African horse sickness virus (AHSV), a member of the orbivirus genus of the family Reoviridae, is an insect-vectored pathogen of horses of concern to the equine industry. Studies on AHSV replication and pathogenesis have been hampered by the lack of reverse genetics allowing targeted mutation of viral genomes. We demonstrate that AHSV single-stranded RNA synthesized in vitro (core transcripts) is infectious and that there are distinct primary and secondary stages of the replication cycle. Transfection with a mixture of core transcripts from two different serotypes or a mixture of core transcri...
Molecular investigation of the viral kinetics of equine herpesvirus-1 in blood and nasal secretions of horses after corticosteroid-induced recrudescence of latent infection. Recrudescence of latent equine herpesvirus 1 (EHV-1) with subsequent viral shedding via nasal secretions is a potential source of infection for susceptible horses and has been implicated in outbreaks occurring in closed populations. Objective: To describe the viral kinetics of reactivated EHV-1 in blood and nasal secretions from latently infected horses after administration of corticosteroids, and to study the infectious nature of reactivated EHV-1 to sentinel horses. Methods: Eight healthy horses. Methods: Four horses infected 4 months previously with EHV-1 received dexamethasone on 5 consecu...
Detection of neuropathogenic strains of Equid Herpesvirus 1 (EHV-1) associated with abortions in Germany. A single nucleotide polymorphism within EHV-1 gene ORF 30, which encodes for the viral DNA polymerase, allows the differentiation of the neuropathogenic (G2254) from non-neuropathogenic genotype (A2254). The aim of our study was to investigate the distribution of the neuropathogenic and non-neuropathogenic genotype of EHV-1 isolates associated with abortions in Germany. To determine the nucleotide sequence at the polymorphic site the amplification product of ORF 30 gene specific nested PCR was digested with restriction enzyme SalI and sequenced. Thirty-two EHV-1 isolates from six abortion outb...
REVIEW PAPER: pathology of animal models of alphavirus encephalitis. The encephalitides caused by Venezuelan (VEEV), eastern (EEEV), and western (WEEV) equine encephalitis viruses are important natural diseases of horses and humans and potential agents of biowarfare or bioterrorism. No licensed vaccines or specific therapies exist to prevent or treat human infections with VEEV, EEEV, or WEEV. Well-characterized animal models are needed to support the development of such medical countermeasures under the United States Food and Drug Administration's "Animal Rule." This review focuses on the pathological features and pathogenetic mechanisms of these alphaviral enc...
Detection and sequence analysis of equine gammaherpesviruses from horses with respiratory tract disease in Turkey. The equid herpesvirus 2 (EHV-2) and 5 (EHV-5), identified agents of respiratory infections and keratoconjunctivitis cases in some equids, comprise a high degree of antigenic heterogeneity. Prevalence and genetic characterization of EHV-2 and EHV-5 strains from Turkey were investigated in this study. A total of 73 nasal swabs and 54 blood specimens were sampled from horses with respiratory tract diseases characterized by mucopurulent nasal discharge and occasional coughing. Overall, EHV-2- and EHV-5-specific DNA amplicons were obtained from 19.2% (14/73) and 21.9% (16/73) of horses tested by mu...
Control of EHV-1 viremia and nasal shedding by commercial vaccines. Equine herpesvirus-1 is a cause of outbreaks of abortion and neurological disease. The pathogenesis of both these diseases depends on establishment of viremia. An experiment was performed to determine the protective efficacy of two commercially available vaccines used with an optimized 3-dose vaccination regime: a modified-live viral (MLV) and a high antigen load killed vaccine licensed for abortion control. The study design was a blinded, randomized challenge trial. Three groups of 8 yearling ponies received one of three treatments: MLV vaccine (Rhinomune, Boehringer Ingelheim Vetmedica, Inc....
Genomic analysis of an effective lentiviral vaccine-attenuated equine infectious anemia virus vaccine EIAV FDDV13. Chinese equine infectious anemia virus (EIAV) attenuated vaccine is the first lentiviral vaccine with a successful application. In order to understand the correlation of viral genomic mutations with viral attenuation and with induced immunoprotective properties, we analyzed the proviral genome sequences of the EIAV-attenuated vaccine strain EIAV(FDDV13) (EIAV fetal donkey dermal cell-adapted vaccine) and its highly virulent parental strain EIAV(LN40). The sequences of these strains were compared with those of the major foreign EIAV strains. The results indicated a large genetic distance betwee...
Vector competence of Culex (Melanoconion) taeniopus for equine-virulent subtype IE strains of Venezuelan equine encephalitis virus. The mosquito Culex (Melanoconion) taeniopus is a proven vector of enzootic Venezuelan equine encephalitis virus (VEEV) subtype IE in Central America. It has been shown to be highly susceptible to infection by this subtype, and conversely to be highly refractory to infection by other VEEV subtypes. During the 1990s in southern coastal Mexico, two VEE epizootics in horses were attributed to subtype IE VEEV. These outbreaks were associated with VEEV strains with an altered infection phenotype for the epizootic mosquito vector, Aedes (Ochlerotatus) taeniorhynchus. To determine the infectivity for ...
Isolation and characterisation of equine influenza viruses (H3N8) from Europe and North America from 2008 to 2009. Like other influenza A viruses, equine influenza virus undergoes antigenic drift. It is therefore essential that surveillance is carried out to ensure that recommended strains for inclusion in vaccines are kept up to date. Here we report antigenic and genetic characterisation carried out on equine influenza virus strains isolated in North America and Europe over a 2-year period from 2008 to 2009. Nasopharyngeal swabs were taken from equines showing acute clinical signs and submitted to diagnostic laboratories for testing and virus isolation in eggs. The sequence of the HA1 portion of the viral...
Immunohistochemical and molecular detection of equine herpesvirus 1 in Uruguay. Equine herpesvirus 1 (EHV-1) is a major cause of epidemic abortion, neonatal mortality, respiratory disease and neurological disorders in horses. In South America, the virus has been isolated in Brazil, Argentina and Colombia. In Chile pathological findings from one aborted foetus have been reported, and in Uruguay only serological data about EHV-1 activity have been found. Some pathological findings were reported in Uruguay several years ago, but these data have never been officially confirmed. The present work describes the relevant findings of a study of EHV-1 infections in the Uruguayan eq...
Evaluation of neutralization patterns of the five unique Argentine equine arteritis virus field strains reported. Equine viral arteritis (EVA) is a contagious viral disease that frequently causes mild or subclinical infections in adult horses. Only one EAV serotype has been described. However, there are differences in antigenicity, pathogenicity and neutralization characteristics of virus field strains. The interaction of two viral proteins, GP5 and M, is critical for infectivity and amino acid changes in the GP5 sequences have an effect on the neutralizing phenotype, regardless the effects of other viral proteins. The objective of the present study was to evaluate the neutralization phenotypes of the 5 u...
Isolation and partial sequencing of Equid herpesvirus 5 from a horse in Iceland. Horses are hosts to 2 types of gammaherpesviruses, Equid herpesvirus 2 and 5 (EHV-2 and EHV-5, respectively). Both EHV-2 and EHV-5 are common in horses in Iceland. An Icelandic EHV-5 isolate was recovered by sequential culture in primary fetal horse kidney and rabbit kidney cells. Glycoprotein B, glycoprotein H, and DNA terminase genes of the isolate were fully sequenced, and the DNA polymerase gene was partly sequenced. To date, the glycoprotein B gene of EHV-5 was the only gene that has been reported to be completely sequenced in addition to small parts of the glycoprotein H, DNA polymerase,...
OAS1 polymorphisms are associated with susceptibility to West Nile encephalitis in horses. West Nile virus, first identified within the United States in 1999, has since spread across the continental states and infected birds, humans and domestic animals, resulting in numerous deaths. Previous studies in mice identified the Oas1b gene, a member of the OAS/RNASEL innate immune system, as a determining factor for resistance to West Nile virus (WNV) infection. A recent case-control association study described mutations of human OAS1 associated with clinical susceptibility to WNV infection. Similar studies in horses, a particularly susceptible species, have been lacking, in part, because...
Intra- and interhost evolutionary dynamics of equine influenza virus. Determining the evolutionary basis of cross-species transmission and immune evasion is key to understanding the mechanisms that control the emergence of either new viruses or novel antigenic variants with pandemic potential. The hemagglutinin glycoprotein of influenza A viruses is a critical host range determinant and a major target of neutralizing antibodies. Equine influenza virus (EIV) is a significant pathogen of the horse that causes periodical outbreaks of disease even in populations with high vaccination coverage. EIV has also jumped the species barrier and emerged as a novel respirator...
Molecular epidemiology and genetic characterization of equine arteritis virus isolates associated with the 2006-2007 multi-state disease occurrence in the USA. In 2006-2007, equine viral arteritis (EVA) was confirmed for the first time in Quarter Horses in multiple states in the USA. The entire genome of an equine arteritis virus (EAV) isolate from the index premises in New Mexico was 12 731 nt in length and possessed a previously unrecorded unique 15 nt insertion in the nsp2-coding region in ORF1a and a 12 nt insertion in ORF3. Sequence analysis of additional isolates made during this disease occurrence revealed that all isolates from New Mexico, Utah, Kansas, Oklahoma and Idaho had 98.6-100.0 % (nsp2) and 97.8-100 % (ORF3) nucleotide identity and c...
Identification of cellular proteins interacting with equine infectious anemia virus S2 protein. The macrophage-tropic lentivirus, equine infectious anemia virus (EIAV), encodes the small auxiliary protein S2 from a short open reading frame that overlaps the amino terminus of env EIAV S2 is dispensable for virus replication in cultured cells but is required for disease production. S2 is approximately 7 kDa and has no overall amino acid sequence homology to other cellular or viral proteins. Therefore it is likely that S2 plays a role as an adaptor protein. To further investigate S2 function we performed a yeast-2-hybrid screen to identify cellular proteins that interact with EIAV S2. The s...
Selection of a rare neutralization-resistant variant following passive transfer of convalescent immune plasma in equine infectious anemia virus-challenged SCID horses. Vaccines preventing HIV-1 infection will likely elicit antibodies that neutralize diverse strains. However, the capacity for lentiviruses to escape broadly neutralizing antibodies (NAbs) is not completely understood, nor is it known whether NAbs alone can control heterologous infection. Here, we determined that convalescent immune plasma from a horse persistently infected with equine infectious anemia virus (EIAV) neutralized homologous virus and several envelope variants containing heterologous principal neutralizing domains (PND). Plasma was infused into young horses (foals) affected with se...
Neuropathogenic and non-neuropathogenic variants of equine herpesvirus 1 in France. Equine herpesvirus 1 (EHV-1) is a common pathogen of the horse which may induce mild respiratory distress, abortion, neonatal death and neurological disease. A single nucleotide polymorphism in the EHV-1 DNA polymerase (ORF30 A(2254) to G(2254)) has been associated with clinical signs of Equine herpes myeloencephalopathy (EHM). The aim of this work was to analyze the ORF30 genomic region among a panel of EHV-1 DNA extract in order to estimate the prevalence of the EHV-1 neuropathogenic genotype in France. Samples coming from cases associated with EHM, horses with respiratory symptoms and abort...
Cell entry of the aphthovirus equine rhinitis A virus is dependent on endosome acidification. Equine rhinitis A virus (ERAV) is genetically closely related to foot-and-mouth disease virus (FMDV), and both are now classified within the genus Aphthovirus of the family Picornaviridae. For disease security reasons, FMDV can be handled only in high-containment facilities, but these constraints do not apply to ERAV, making it an attractive alternative for the study of aphthovirus biology. Here, we show, using immunofluorescence, pharmacological agents, and dominant negative inhibitors, that ERAV entry occurs (as for FMDV) via clathrin-mediated endocytosis and acidification of early endosomes...
Opposite effects of two different strains of equine herpesvirus 1 infection on cytoskeleton composition in equine dermal ED and African green monkey kidney Vero cell lines: application of scanning cytometry and confocal-microscopy-based image analysis in a quantitative study. Viruses can reorganize the cytoskeleton and restructure the host cell transport machinery. During infection viruses use different cellular cues and signals to enlist the cytoskeleton for their mission. However, each virus specifically affects the cytoskeleton structure. Thus, the aim of our study was to investigate the cytoskeletal changes in homologous equine dermal (ED) and heterologous Vero cell lines infected with either equine herpesvirus 1 (EHV-1) strain Rac-H or Jan-E. We found that Rac-H strain disrupted actin fibers and reduced F-actin level in ED cells, whereas the virus did not infl...
Efficacy of a whole inactivated EI vaccine against a recent EIV outbreak isolate and comparative detection of virus shedding. An outbreak of H3N8 Equine Influenza virus (EIV) that occurred in vaccinated horses in Japan was caused by a genetically divergent EIV isolate of the Florida clade 1 sub-lineage. This virus subsequently entered Australia where it infected thousands of immunologically naïve horses. The objective of this study was to evaluate the ability of a non-updated whole inactivated equine influenza (EI) vaccine to protect if used in the face of an outbreak induced by a virus similar to the ones circulating in Japan and Australia in 2007. Seven naïve Welsh mountain ponies were immunised twice with the co...
Development and optimisation of a duplex real-time reverse transcription quantitative PCR assay targeting the VP7 and NS2 genes of African horse sickness virus. Nucleotide sequences of 52 South African isolates of African horse sickness virus (AHSV) collected during 2004-2005 and including viruses of all nine AHSV serotypes, were used to design and develop a duplex real-time reverse transcription quantitative PCR (RT-PCR) assay targeting the VP7 (S8) and NS2 (S9) genes of AHSV. The assay was optimized for detection of AHSV in fresh and frozen blood of naturally infected horses. Assay performance was enhanced using random hexamers rather than gene-specific primers for RT, and with denaturation of double-stranded RNA in the presence of random hexamers. ...
Complement-dependent cytotoxicity assay for differentiating West Nile virus from Japanese encephalitis virus infections in horses. A complement-dependent cytotoxicity (CDC) assay was established to measure antibodies to the West Nile virus (WNV) nonstructural protein 1 (NS1) in horses. Sera collected from a WNV-infected horse mediated lysis of WNV NS1-expressing cells in a dose-dependent manner at higher percentages than sera from a Japanese encephalitis virus (JEV)-infected horse. The percentages of specific lysis for sera diluted 1:10 to 1:80 were <19.8% (assay cutoff) for almost all of the 100 JEV-infected or uninfected horses tested, in contrast to 55 to 76% in WNV-infected horses. Experimental infection revealed t...
Glycoprotein C of equine herpesvirus 4 plays a role in viral binding to cell surface heparan sulfate. Heparan sulfate moieties of cell surface proteoglycans serve as receptors for several herpesviruses. For herpes simplex virus 1, pseudorabies virus and equine herpesvirus 1, glycoprotein C (gC) homologues have been shown to mediate the binding to cell surface heparan sulfate. However, the role of gC in equine herpesvirus 4 (EHV-4) infection has not yet been analyzed. Using pull-down assay, we first determined that EHV-4 gC as well as gB are heparin-binding glycoproteins. To study the role of gC in EHV-4 infection, we constructed a gC-deletion mutant, WA79DeltagC, where the kanamycin resistant ...
Complex interactions between the major and minor envelope proteins of equine arteritis virus determine its tropism for equine CD3+ T lymphocytes and CD14+ monocytes. Extensive cell culture passage of the virulent Bucyrus (VB) strain of equine arteritis virus (EAV) to produce the modified live virus (MLV) vaccine strain has altered its tropism for equine CD3(+) T lymphocytes and CD14(+) monocytes. The VB strain primarily infects CD14(+) monocytes and a small subpopulation of CD3(+) T lymphocytes (predominantly CD4(+) T lymphocytes), as determined by dual-color flow cytometry. In contrast, the MLV vaccine strain has a significantly reduced ability to infect CD14(+) monocytes and has lost its capability to infect CD3(+) T lymphocytes. Using a panel of five re...
Molecular and biological characterization of equine infectious anemia virus Rev. Equine infectious anemia virus (EIAV) is one of the most divergent members of the lentivirus subfamily of retroviruses and is considered a useful comparative model for molecular studies of lentivirus replication. The Rev protein of EIAV is functionally homologous with other lentiviral Revs and facilitates export of incompletely spliced viral mRNAs through a Crm1-dependent pathway. The trans- and cis-acting elements that mediate EIAV Rev function are similar to, but distinct from, the well-characterized elements in human immunodeficiency virus (HIV-1), the prototypical Rev protein. In addition,...