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Topic:Virus
The study of viral infections that affect equine species assesses the relationship between viruses and horses. Infections can lead to a range of clinical symptoms and may impact the health and performance of horses. Common equine viruses include Equine Influenza Virus, Equine Herpesvirus, and West Nile Virus, among others. Understanding the mechanisms of viral transmission, pathogenesis, and host immune responses is essential for developing effective prevention and treatment strategies. This page compiles peer-reviewed research studies and scholarly articles that explore the epidemiology, molecular biology, and clinical management of viral infections in horses.
The classification of seven serotypes of equine encephalosis virus and the prevalence of homologous antibody in horses in South Africa. Selected isolates of equine encephalosis virus were shown to have comparable viral protein profiles and to represent seven distinct serotypes, based on cross-neutralization tests. Serotype-specific virus-neutralizing antibody in serum samples from horses confirmed the widespread occurrence of infection. The distribution and prevalence of individual serotypes however, varied considerably. Localised foci with an increased seasonal seroconversion in groups of horses to a specific serotype and the detection of an ongoing low level of infection from other serotypes within the population, confirmed ...
Growth characteristics of a highly virulent, a moderately virulent, and an avirulent strain of equine arteritis virus in primary equine endothelial cells are predictive of their virulence to horses. Equine viral arteritis (EVA) is an endotheliotropic viral disease of horses caused by equine arteritis virus (EAV). Although there is only one serotype of EAV, there is marked variation in the virulence of different strains of the virus. The replication and cytopathogenicity of three well-characterized strains of EAV of different virulence to horses were compared in rabbit kidney (RK-13) and primary equine pulmonary artery endothelial cells (ECs). Viral protein expression, plaque size, and cytopathogenicity of all three viruses were similar in RK-13 cells, whereas two virulent strains of EAV w...
IgG antibody subclass response against equine herpesvirus type 4 in horses. In this study, IgG subclass responses against equine herpesvirus type 4 (EHV-4) were examined by enzyme-linked immunosorbent assay (ELISA) using a type-specific region of EHV-4 glycoprotein G (gG). ELISA using sera collected from horses experimentally infected with EHV-4 revealed that IgGa and IgGb antibodies were detected at high level, but IgGc and IgG(T) antibody responses were detected at low level or were undetectable. The IgGa antibody response reached its peak on day 10 post-infection, and then dropped. The IgGb antibody response reached its maximum level on day 12 post-infection, and t...
The role of birds in the ecology of West Nile virus in Europe and Africa. Surveys on wild birds conducted during the last two decades in Europe, notably Poland and the Czech Republic, to determine their infection rate with WN virus have revealed endemic foci of infection. Some species of seropositive birds were nonmigrators while others were hatchlings of migrating species. Persistently infected avian reservoirs are potential sources of viruses for mosquitoes that multiply in the temperate European zone in hot, wet summers. In the past, evidence for geographical circulation of WN viruses was based on antigenic analysis of strains from different countries while more ...
Discriminant and multiple regression analysis of anemia and opportunistic infection in Fell pony foals. A condition resembling acquired immunodeficiency with anemia has been described in British Fell pony foals. The pathogenesis is unknown. The present study involved 322 foals of which 164 were of Fell breed and 12 were affected. Discriminant and multiple regression analyses were used to test the results of all clinical pathology parameters from these foals for statistical association with (1) breed origin and (2) presence of disease. Only hematocrit associated significantly with presence of disease. However, significant associations were found with Fell breed origin, including serum albumin con...
Demonstration of continuously seropositive population against Borna disease virus in Misaki feral horses, a Japanese strain: a four-year follow-up study from 1998 to 2001. Borna disease virus (BDV)-specific antibodies were monitored in Misaki feral horses annually for 4 years using an electrochemiluminescence immunoassay (ECLIA). Among 130 horses examined, 35 (26.9%) with an ECLIA count above 1000 once or more were judged as BDV seropositive. Throughout the study period, p24 antibodies were more frequent than p40 antibodies in almost all positive animals. Among the 35 seropositive horses, the ECLIA count was consistently high in 12 cases. Eleven horses seroconverted from negative to positive and 7 underwent reversal. The count in the remaining 95 horses (73.1%) ...
Equid herpesvirus 1 is neurotropic in mice, but latency from which infectious virus can be reactivated does not occur. Equid herpesvirus 1 (EHV-1) is the most common cause of virus-induced abortion in horses. After primary infection the virus becomes latent predominantly in the respiratory tract lymph nodes and the genome can also be detected in the peripheral nervous system. The role of mouse as a feasible model for the establishment of latency and reactivation of EHV-1 was investigated. Intracerebral and intranasal infections of 3- and 17-day-old mice were made and virus replication was confirmed by virus isolation and detected by indirect immunofluorescence (IIF) in brain. For reactivation studies, the mice...
Prevalence of equine herpesvirus types 2 and 5 in horse populations by using type-specific PCR assays. Equineherpesvirustypes 2 and 5 (EHV-2andEHV-5)have a rather unclearpathogenicity and distribution within the equid population. In order to gain more information on the prevalence of these two viruses, type-specific PCR assays were developed to detect viral DNA in nasal specimens and in peripheral blood leukocytes (PBLs) of adult horses and foals from various regions of Europe, i.e. Sweden, Hungary and the United Kingdom. In adult horses, the prevalence of EHV-2 in PBLs was up to 68% in Sweden and 71% in the United Kingdom. EHV-2 DNA was detected in the PBLs from all the foals tested in all cou...
Isolation of Salem virus, a novel equine paramyxovirus, and assessment of its etiologic role in a disease outbreak. Salem virus (SalV) is a recently identified equine virus belonging to the family Paramyxoviridae. The only known isolate was obtained from a horse that was involved in a disease outbreak of undetermined nature and the circumstances of its isolation suggested an etiologic role. However, the experimental infection of a colostrum-deprived foal failed to reproduce the disease; only mild neutropenia and temperature elevation were recorded. An additional attempt to establish an etiological relationship with the disease was made by conducting a retrospective evaluation of the serological profiles of ...
Transient immune suppression of inapparent carriers infected with a principal neutralizing domain-deficient equine infectious anaemia virus induces neutralizing antibodies and lowers steady-state virus replication. The genetic variation of equine infectious anaemia virus (EIAV) clearly affects the antigenic properties of the viral envelope; however, effects on immunogenicity remain undefined, although widely assumed. Here, the immunogenicity is reported of a novel, neutralization-resistant, pony-isolate envelope EIAV(PV564DeltaPND) that contains a 14-residue deletion in the designated principal neutralizing domain (PND) of the gp90 protein. Two ponies inoculated with a chimeric virus, EIAV(DeltaPND), containing the EIAV(PV564DeltaPND) envelope in a reference provirus strain, remained asymptomatic through...
Transmission patterns of African horse sickness and equine encephalosis viruses in South African donkeys. African horse sickness (AHS) and equine encephalosis (EE) viruses are endemic to southern Africa. AHS virus causes severe epidemics when introduced to naive equine populations, resulting in severe restrictions on the movement of equines between AHS-positive and negative countries. Recent zoning of South Africa has created an AHS-free zone to facilitate equine movement, but the transmission dynamics of these viruses are not fully understood. Here, we present further analyses of serosurveys of donkeys in South Africa conducted in 1983-5 and in 1993-5. Age-prevalence data are used to derive estim...
Importance of M-protein C terminus as substrate antigen for serodetection of equine arteritis virus infection. Equine arteritis virus (EAV), an enveloped positive-stranded RNA virus, is the prototype of the arterivirus group. In a previous paper (A. Kheyar, S. Martin, G. St.-Laurent, P. J. Timoney, W. H. McCollum, and D. Archambault, Clin. Diagn. Lab. Immunol. 4:648-652, 1997), we have shown that the unglycosylated membrane (M) protein, which is composed of 162 amino acids (aa), is a major target of equine antibody to EAV. In order to determine the antigenic regions of the M protein, the cDNA encoding the M protein of EAV was inserted into the procaryotic expression vector pGEX-4T-1 to produce recombin...
Experimental infection of horses with West Nile virus. A total of 12 horses of different breeds and ages were infected with West Nile virus (WNV) via the bites of infected Aedes albopictus mosquitoes. Half the horses were infected with a viral isolate from the brain of a horse (BC787), and half were infected with an isolate from crow brain (NY99-6625); both were NY99 isolates. Postinfection, uninfected female Ae. albopictus fed on eight of the infected horses. In the first trial, Nt antibody titers reached >1:320, 1:20, 1:160, and 1:80 for horses 1 to 4, respectively. In the second trial, the seven horses with subclinical infections developed Nt a...
The C-terminal regions of the envelope glycoprotein gp2 of equine herpesviruses 1 and 4 are antigenically distinct. The unusual mucin-like high molecular mass (Mr) glycoprotein 2 (gp2) has only been described in the equid alphaherpesviruses, among which there is considerable antigenic cross-reactivity. Equine herpesvirus 1 (EHV-1) gp2 is cleaved into a highly glycosylated N-terminal subunit and a 42 kDa C-terminal cleavage product. In order to investigate their antigenic recognition by horses naturally infected with EHV-1 and/or equine herpesvirus 4 (EHV-4), the C-terminal cleavage product and high Mr gp2 were affinity purified. Cross-reactivity between EHV-1 and EHV-4 was observed for the high Mr gp2 using...
Borna disease: current knowledge and virus detection in France. For over two centuries, Borna disease (BD) has been described as a sporadically occurring infectious meningoencephalomyelitis affecting horses and sheep in Central Europe. Over the last decade, the BD epidemiology has been discussed. Firstly, its geographical distribution seems larger than what was previously thought. Secondly, the disease can affect a large number of warm-blooded animal species, including humans. The aetiological agent is the Boma disease virus (BDV), an enveloped, nonsegmented negative-stranded RNA virus classified in the new virus family Bornaviridae (Mononegavirales order)...
EHV-1 gene63 is not essential for in vivo replication in horses and mice, nor does it affect reactivation in the horse: short communication. The aim of this study was to investigate the role of immediate early gene (gene63) in the pathogenesis of equine herpesvirus 1 (EHV-1) acute and latent infections in equine and murine models. EHV-1 gene63 mutant virus (g63mut) along with EHV-1 (Ab4) was used for intracerebral and intranasal infection of 3 and 17-day-old mice. Both viruses were recovered at the same frequency from tissues after infection. Two Welsh ponies were infected via the intranasal route with each of the viruses. Acute infection was monitored by virus isolation from nasal swabs and peripheral blood leukocytes. Six weeks p...
Genetic analysis of Group A rotaviruses: evidence for interspecies transmission of rotavirus genes. Rotaviruses are the major cause of severe gastroenteritis in young children and animals. The rotavirus genome is composed of eleven segments of double-stranded RNA and can undergo genetic reassortment during mixed infections, leading to progeny viruses with novel or atypical phenotypes. There are numerous descriptions of rotavirus strains isolated from human and animals that share genetic and antigenic features of viruses from heterologous species. In many cases, genetic analysis by hybridization has clearly demonstrated the genetic relatedness of gene segments to those from viruses isolated f...
Identification of broadly recognized, T helper 1 lymphocyte epitopes in an equine lentivirus. Equine infectious anaemia virus (EIAV) is a horse lentivirus causing lifelong, persistent infection. During acute infection, CD8(+) cytotoxic T lymphocytes (CTL) are probably involved in terminating plasma viraemia. However, only a few EIAV CTL epitopes, restricted to fewer horse major histocompatibility complex (MHC) class I alleles, are known. As interferon-gamma (IFN-gamma)-secreting CD4(+), T helper 1 (Th1) lymphocytes promote CTL activity and help maintain memory CTL, identifying broadly recognized EIAV Th1 epitopes would contribute significantly to vaccine strategies seeking to promote s...
Recent developments in the epidemiology of virus diseases. There is continual variation in viral epidemics regarding clinical symptoms, duration and disappearance, and the emergence of new diseases. This can be observed in both human and animal diseases. This evolution of virus diseases is mainly related to three factors: aetiological agent, host and environment. As far as genetic alterations of the virus are concerned, two major mechanisms are involved: mutations such as recombination and reassortment; and selection for resistance or susceptibility. This review focuses on the epidemiology of newly emerged virus diseases in man and animals, such as ac...
Equine herpesvirus type 1 (EHV-1) myeloencephalopathy: a case report. An outbreak of neurological disease occurred in a well-managed riding school. Ataxia and paresis were observed in several horses, five of which became recumbent and were euthanized. Post-mortem analysis revealed scattered haemorrhages along the spinal cord, that were reflected by multiple haemorrhagic foci on formalin-fixed sections, with the thoracic and lumbar segments being the most affected. Pathohistologically, perivascular mononuclear cuffing and axonal swelling, especially in the white matter, were evident. Parallel to the course of disease, alterations in myelin sheets and activation o...
Cloning of the genomes of equine herpesvirus type 1 (EHV-1) strains KyA and racL11 as bacterial artificial chromosomes (BAC). The genome of equine herpesvirus type 1 (EHV-1) strain RacL11, a highly virulent isolate obtained from an aborted foal, and that of the modified live vaccine strain KyA, were cloned as bacterial artificial chromosomes (BAC) in Eseherichia coli. Mini F plasmid sequences were inserted into the viral genomes by homologous recombination instead of the gene 71 (EUS4) open reading frame after co-transfection of viral DNA and recombinant plasmid pdelta71-pHA2 into RK13 cells. After isolation of recombinant viruses by three rounds of plaque purification, viral DNA was isolated from RK13 cells infected...
Lipopeptide stimulation of MHC class I-restricted memory cytotoxic T lymphocytes from equine infectious anemia virus-infected horses. The immunogenicity of equine infectious anemia virus (EIAV) Gag and Env equine leukocyte alloantigen (ELA)-A5.1, -A9, and -A1 restricted cytotoxic T lymphocyte (CTL) epitopes synthesized on multiple antigenic peptide (MAP) system coupled to tripalmitoyl-S-glycerylcysteine (P3C) was evaluated in vitro. P3C-MAP-peptide-stimulated peripheral blood mononuclear cells (PBMCs) from horses, chronically infected with EIAV, had memory CTL (CTLm) similar to that of PBMCs stimulated with either the minimal CTL epitopes, longer peptides containing the CTL epitopes, or EIAV. The stimulated CTL lysed EIAV-in...
Increased susceptibility of peripheral blood mononuclear cells to equine herpes virus type 1 infection upon mitogen stimulation: a role of the cell cycle and of cell-to-cell transmission of the virus. Equine herpesvirus-1 (EHV-1) is an important pathogen of horses, causing abortion and nervous system disorders, even in vaccinated animals. During the cell-associated viremia, EHV-1 is carried by peripheral blood mononuclear cells (PBMC), mainly lymphocytes. In vitro, monocytes are the most important fraction of PBMC in which EHV-1 replicates, however, mitogen stimulation prior to EHV-1 infection increases the percentage of infected lymphocytes. The role of the cell cycle in viral replication and the role of cluster formation in cell-to-cell transmission of the virus were examined in mitogen-s...
Influence of equine herpesvirus type 2 infection on monocyte chemoattractant protein 1 gene transcription in equine blood mononuclear cells. Representational difference analysis (RDA) was used to compare gene expression in equine mononuclear cells either infected with equine herpesvirus-2 (EHV-2) or adsorbed with inactivated EHV-2. Seven clones identified in non-infected cells after three rounds of selective subtraction and enrichment for differentially expressed genes contained sequences homologous to equine monocyte chemoattractant protein 1 (MCP-1). This suggested that EHV-2 may down-regulate MCP-1 transcription in infected cells. These findings correlate well with similar findings described for human cytomegalovirus and support...
Functional expression and membrane fusion tropism of the envelope glycoproteins of Hendra virus. Hendra virus (HeV) is an emerging paramyxovirus first isolated from cases of severe respiratory disease that fatally affected both horses and humans. Understanding the mechanisms of host cell infection and cross-species transmission is an important step in addressing the risk posed by such emerging pathogens. We have initiated studies to characterize the biological properties of the HeV envelope glycoproteins. Recombinant vaccinia viruses encoding the HeV F and G open reading frames were generated and glycoprotein expression was verified by metabolic labeling and detection using specific antis...
Isolation and characterization of two European strains of Ehrlichia phagocytophila of equine origin. We report the isolation and partial genetic characterization of two equine strains of granulocytic Ehrlichia of the genogroup Ehrlichia phagocytophila. Frozen whole-blood samples from two Swedish horses with laboratory-verified granulocytic ehrlichiosis were inoculated into HL-60 cell cultures. Granulocytic Ehrlichia was isolated and propagated from both horses. DNA extracts from the respective strains were amplified by PCR using primers directed towards the 16S rRNA gene, the groESL heat shock operon gene, and the ank gene. The amplified gene fragments were sequenced and compared to known seq...
Equine infectious anemia virus and the ubiquitin-proteasome system. Some retroviruses contain monoubiquitinated Gag and do not bud efficiently from cells treated with proteasome inhibitors, suggesting an interaction between the ubiquitin-proteasome system and retrovirus assembly. We examined equine infectious anemia virus (EIAV) particles and found that approximately 2% of the p9(Gag) proteins are monoubiquitinated, demonstrating that this Gag protein interacts with an ubiquitinating activity. Different types of proteasome inhibitors were used to determine if proteasome inactivation affects EIAV release from chronically infected cells. Pulse-chase immunoprecip...
Budding of equine infectious anemia virus is insensitive to proteasome inhibitors. The only retrovirus protein required for the budding of virus-like particles is the Gag protein; however, recent studies of Rous sarcoma virus (RSV) and human immunodeficiency virus have suggested that modification of Gag with ubiquitin (Ub) is also required. As a consequence, the release of these viruses is reduced in the presence of proteasome inhibitors, which indirectly reduce the levels of free Ub within the cell. Here we show that the budding of equine infectious anemia virus (EIAV) from infected equine cells is largely unaffected by these drugs, although use of one inhibitor (MG-132) re...
Alphavirus replicon particles expressing the two major envelope proteins of equine arteritis virus induce high level protection against challenge with virulent virus in vaccinated horses. Replicon particles derived from a vaccine strain of Venezuelan equine encephalitis (VEE) virus were used as vectors for expression in vivo of the major envelope proteins (G(L) and M) of equine arteritis virus (EAV), both individually and in heterodimer form (G(L)/M). The immunogenicity of the different replicons was evaluated in horses, as was their ability to protectively immunize horses against intranasal and intrauterine challenge with a virulent strain of EAV (EAV KY84). Horses immunized with replicons that express both the G(L) and M proteins in heterodimer form developed neutralizing ant...
Detection of equine arteritis virus by real-time TaqMan reverse transcription-PCR assay. A one-tube real-time TaqMan reverse transcription-polymerase chain reaction (RT-PCR) assay was developed for the detection of equine arteritis virus (EAV). The test was validated using the seminal plasma and nasal secretions of infected horses that were proven to contain EAV by traditional virus isolation in rabbit kidney thirteen (RK-13) cells, as well as a variety of cell culture-propagated European and North American strains of EAV. The primers and a fluorogenic TaqMan probe were designed to amplify and detect a highly conserved region of open reading frame 7 (ORF7) of EAV. The real-time Ta...
