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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.
Epitope-blocking enzyme-linked immunosorbent assays for detection of west nile virus antibodies in domestic mammals. We evaluated the ability of epitope-blocking enzyme-linked immunosorbent assays (ELISAs) to detect West Nile virus (WNV) antibodies in domestic mammals. Sera were collected from experimentally infected horses, cats, and pigs at regular intervals and screened in ELISAs and plaque reduction neutralization tests. The diagnostic efficacies of these techniques were similar.
VP2 gene phylogenetic characterization of field isolates of African horsesickness virus serotype 7 circulating in South Africa during the time of the 1999 African horsesickness outbreak in the Western Cape. We present the first VP2-gene phylogenetic analysis of African horsesickness (AHS) viruses within a serotype. Thirteen AHSV 7 isolates were obtained from cases that occurred in South Africa during 1998-1999, and three were historical AHSV 7 isolates. The goals were to start a database of isolates of known location and time of isolation and to determine if we could identify the origin of an AHS outbreak in the surveillance area in the Western Cape. We prepared full-length cDNA copies of the VP2-genes of the isolates. Nucleic acid sequence data of a 786 bp region was used to characterize the gen...
Mapping epitopes in equine rhinitis A virus VP1 recognized by antibodies elicited in response to infection of the natural host. Equine rhinitis A virus (ERAV) is an important respiratory pathogen of horses and is of additional interest because of its close relationship and common classification with foot-and-mouth disease virus (FMDV). As is the case with FMDV, the VP1 capsid protein of ERAV has been shown to be a target of neutralizing antibodies. In FMDV VP1, such antibodies commonly recognize linear epitopes present in the betaG-betaH loop region. To map linear B cell epitopes in ERAV VP1, overlapping fragments spanning its length were expressed in Escherichia coli as glutathione S-transferase (GST) fusion proteins....
Pneumonia in weanlings. Lower respiratory tract infection is common in weanling- and suckling-aged animals. Increased susceptibility to disease in this age group can result from a delay in the establishment of a competent immune system and environmental factors, such as overcrowding, shipping, and sales. S zooepidemicus and R equi are the two most common bacterial isolates. S equi is primarily a disease of the lymph nodes and upper respiratory tract. Viral agents can compromise the natural defense mechanisms of the respiratory tract, resulting in secondary bacterial infections. The acute respiratory distress syndrome...
Formation of disulfide-linked complexes between the three minor envelope glycoproteins (GP2b, GP3, and GP4) of equine arteritis virus. Equine arteritis virus (EAV) is an enveloped, positive-stranded RNA virus belonging to the family Arteriviridae of the order NIDOVIRALES: Six transmembrane proteins have been identified in EAV particles: the nonglycosylated membrane protein M and the glycoprotein GP(5) (previously named G(L)), which occur as disulfide-bonded heterodimers and are the major viral envelope proteins; the unglycosylated small envelope protein E; and the minor glycoproteins GP(2b) (formerly designated G(S)), GP(3), and GP(4). Analysis of the appearance of the GP(2b), GP(3), and GP(4) proteins in viral particles by g...
Comparison of methods for the diagnosis of equine herpesvirus type 1 infection. The objective of the investigations was to study the occurrence of the equine herpesvirus type 1 (EHV-1) infection in aborted equine fetuses and in newborn foals and to compare the sensitivity of virus isolation, immunohistochemistry and histology in 101 cases and of fetal serology in 68 cases in the diagnosis of the infection. Out of the 93 aborted equine fetuses and 8 weak foals, 15 (14.9%) (14 fetuses and 1 foal) proved to be EHV-1 infected by immunohistochemical and 13 (12.9%) by virological investigation. Characteristic microscopic changes were seen in several organs in all cases, while i...
Experimental infection of ponies with equine influenza A2 (H3N8) virus strains of different pathogenicity elicits varying interferon and interleukin-6 responses. The production of interferon (IFN), interleukin-6 (IL-6), and tumor necrosis factor (TNF) was monitored in horses during the course of influenza A2 virus infections. The effects of two virus strains, Newmarket/2/93 and Sussex/89, were compared, of which the latter is considered the more pathogenic in terms of clinical signs. Ten naive ponies were infected with influenza A/equine/Sussex/89 and 10 with influenza A/equine/Newmarket/2/93, respectively. As expected ponies infected with Sussex/89 showed the most pronounced clinical signs but there was no notable difference in viral excretion compare...
Molecular studies on Babesia, Theileria and Hepatozoon in southern Europe. Part I. Epizootiological aspects. Molecular epizootiology of piroplasmids (Babesia spp., Theileria spp.) and Hepatozoon canis was studied in mammals from southern Europe (mainly from Spain, but also from Portugal and France). Partial amplification and sequencing of the 18s rRNA gene was used for molecular diagnosis. In some particular cases (B. ovis and B. bovis) the complete 18s rRNA gene was sequenced. Blood samples were taken from domestic animals showing clinical symptoms: 10 dogs, 10 horses, 10 cows, 9 sheep and 1 goat. In addition, DNA samples were isolated from blood of 12 healthy dogs and from spleen of 10 wild red fox...
A first full outer capsid protein sequence data-set in the Orbivirus genus (family Reoviridae): cloning, sequencing, expression and analysis of a complete set of full-length outer capsid VP2 genes of the nine African horsesickness virus serotypes. The outer capsid protein VP2 of African horsesickness virus (AHSV) is a major protective antigen. We have cloned full-length VP2 genes from the reference strains of each of the nine AHSV serotypes. Baculovirus recombinants expressing the cloned VP2 genes of serotypes 1, 2, 4, 6, 7 and 8 were constructed, confirming that they all have full open reading frames. This work completes the cloning and expression of the first full set of AHSV VP2 genes. The clones of VP2 genes of serotypes 1, 2, 5, 7 and 8 were sequenced and their amino acid sequences were deduced. Our sequencing data, together with t...
The serologic response of horses to equine arteritis virus as determined by competitive enzyme-linked immunosorbent assays (c-ELISAs) to structural and non-structural viral proteins. In an effort to further characterize the humoral immune response of horses to equine arteritis virus (EAV), direct and competitive enzyme-linked immunosorbent assays (c-ELISAs) were developed using monoclonal and polyclonal anti-sera to structural (G(L), N and M) and non-structural (nsp1) viral proteins. A nsp1-specific monoclonal antibody was produced to facilitate development of a c-ELISA to this protein. Data obtained using the various c-ELISAs confirm that the M protein is a major target of the antibody response of horses to EAV. However, none of the c-ELISAs that were developed were as se...
Neuropharmacological sequelae of persistent CNS viral infections: lessons from Borna disease virus. Borna Disease Virus (BDV) is a neurotropic RNA virus that is worldwide in distribution, causing movement and behavior disorders in a wide range of animal species. BDV has also been reported to be associated with neuropsychiatric diseases of humans by serologic study and by recovery of nucleic acid or virus from blood or brain. Natural infections of horses and sheep produce encephalitis with erratic excited behaviors, hyperkinetic movement or gait abnormalities; naturally infected cats have ataxic "staggering disease." Experimentally infected primates develop hyperactivity, aggression, disinhib...
[Laryngeal infection by Rhodococcus equi in patient with AIDS]. The Rhodococcus equi is an aerobic gram positive pleomorphic bacillus, that was isolated for the first time like a producer of bronchopneumonia in young horses. Every time more often, it is being recognized as a pathogen in humans, mainly in the immunodepressed population. We described a case, until now exceptional, of laryngeal infection by Rhodococcus equi in a patient with positive serology for the virus of the human immunodeficiency (HIV), and we reviewed some clinical and epidemiological characteristics of the infections by this germ. The treatment is riphampicine and/or erythromycin, bei...
Use of an internal standard in a closed one-tube RT-PCR for the detection of equine arteritis virus RNA with fluorescent probes. Routine detection of equine arteritis virus (EAV) can be achieved by virus isolation (VI) in cell culture, or by the amplification of viral genome by molecular methods. To simplify molecular diagnosis, a number of different Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) and RT-nested PCR (RT-nPCR) assays were compared, and a one-tube method was developed and optimised utilizing a fluorogenic probe (TaqMan). An artificial RNA template (Mimic) and associated probe were also constructed to provide in-tube validation of the RT-PCR system. To assess the utility of the RT-PCR TaqMan assay,...
Characterization of enzootic foci of Venezuelan equine encephalitis virus in western Venezuela. The distribution of the sylvatic subtype ID Venezuelan equine encephalitis (VEE) viruses in the lowland tropical forests of western Venezuela was investigated using remote sensing and geographic information system technologies. Landsat 5 Thematic Mapper satellite imagery was used to study the reflectance patterns of VEE endemic foci and to identify other locations with similar reflectance patterns. Enzootic VEE virus variants isolated during this study are the closest genetic relatives of the epizootic viruses that emerged in western Venezuela during 1992-1993. VEE virus surveillance was condu...
A recombinant envelope protein-based enzyme-linked immunosorbent assay for West Nile virus serodiagnosis. Recombinant West Nile virus envelope (E) protein was examined in enzyme-linked immunosorbent assay (ELISA) to detect antibodies elicited during West Nile virus infection. Horses (nine of 10) and humans (six of six) with confirmed West Nile virus infection had IgG and/or IgM antibodies to the E protein. Antibodies to the recombinant West Nile virus membrane and nonstructural 1 proteins were not detected in any of these sera. An E protein-based ELISA may aid in the serological diagnosis of West Nile virus infection.
Limited potential for mosquito transmission of genetically engineered, live-attenuated western equine encephalitis virus vaccine candidates. Specific mutations associated with attenuation of Venezuelan equine encephalitis (VEE) virus in rodent models were identified during efforts to develop an improved VEE vaccine. Analogous mutations were produced in full-length cDNA clones of the Cba 87 strain of western equine encephalitis (WEE) virus by site-directed mutagenesis in an attempt to develop an improved WEE vaccine. Isogenic viral strains with these mutations were recovered after transfection of baby hamster kidney cells with infectious RNA. We evaluated two of these strains (WE2102 and WE2130) for their ability to replicate in and...
The Australian paralysis tick may be the missing link in the transmission of Hendra virus from bats to horses to humans. Hendra virus is a new virus of the family Paramyxoviridae. This virus was first detected in Queensland, Australia, in 1994; although, it seems that the virus has infected fruit-eating bats (flying-foxes) for a very long time. At least 2 humans and 15 horses have been killed by this virus since it first emerged as a virus that may infect mammals other than flying-foxes. Hendra virus is thought to have moved from flying-foxes to horses, and then from horses to people. There is a reasonably strong hypothesis for horse-to-human transmission: transmission of virus via nasal discharge, saliva and/or...
Equine amplification and virulence of subtype IE Venezuelan equine encephalitis viruses isolated during the 1993 and 1996 Mexican epizootics. To assess the role of horses as amplification hosts during the 1993 and 1996 Mexican Venezuelan equine encephalitis (VEE) epizootics, we subcutaneously infected 10 horses by using four different equine isolates. Most horses showed little or no disease and low or nonexistent viremia. Neurologic disease developed in only 1 horse, and brain histopathologic examination showed meningeal lymphocytic infiltration, perivascular cuffing, and focal encephalitis. Three animals showed mild meningoencephalitis without clinical disease. Viral RNA was detected in the brain of several animals 12-14 days after...
Venezuelan equine encephalitis virus-vectored vaccines protect mice against anthrax spore challenge. Anthrax, a disease usually associated with herbivores, is caused by the bacterium Bacillus anthracis. The current vaccine licensed for human use requires a six-dose primary series and yearly boosters and causes reactogenicity in up to 30% of vaccine recipients. A minimally reactogenic vaccine requiring fewer inoculations is warranted. Venezuelan equine encephalitis (VEE) virus has been configured for use as a vaccine vector for a wide variety of immunogens. The VEE vaccine vector is composed of a self-replicating RNA (replicon) containing all of the VEE virus nonstructural genes and a multiple...
Down-regulation of MHC class I expression by equine herpesvirus-1. There is good evidence that cytotoxic T lymphocytes play an important role in the clearance of equine herpesvirus-1 (EHV1) in horses. We have demonstrated that, in common with other alphaherpesviruses, EHV1 infection can lead to dramatic down-regulation of MHC class I expression at the cell surface, a common strategy for pathogen evasion of the host immune response. This down-regulation is specific for MHC class I and does not reflect a general shut-off of host-cell protein synthesis. The use of monoclonal antibodies that recognize different MHC class I epitopes has demonstrated that the effec...
Characterization of a cytolytic strain of equine infectious anemia virus. A novel strain of equine infectious anemia virus (EIAV) called vMA-1c that rapidly and specifically killed infected equine fibroblasts (ED cells) but not other infectible cell lines was established. This strain was generated from an avirulent, noncytopathic strain of EIAV, MA-1. Studies with this new cytolytic strain of virus have permitted us to define viral parameters associated with EIAV-induced cell killing and begin to explore the mechanism. vMA-1c infection resulted in induction of rapid cell death, enhanced fusogenic activity, and increased rates of spread in equine fibroblasts compared...
Absence of viral antigens on the surface of equine herpesvirus-1-infected peripheral blood mononuclear cells: a strategy to avoid complement-mediated lysis. Equine herpesvirus-1 (EHV-1) may cause abortion in vaccination- and infection-immune horses. EHV-1-infected peripheral blood mononuclear cells (PBMCs) play an important role in virus immune evasion. The mechanisms by which infected PBMCs can avoid destruction by EHV-1-specific antibody and equine complement were examined. The majority of EHV-1-infected PBMCs (68.6 %) lacked surface expression of viral antigens and these cells were not susceptible to complement-mediated lysis. In infected PBMCs with surface expression of viral antigens, 63 % showed focal surface expression, whereas 37 % showed ...
Response of ELA-A1 horses immunized with lipopeptide containing an equine infectious anemia virus ELA-A1-restricted CTL epitope to virus challenge. Lipopeptide containing an ELA-A1-restricted cytotoxic T lymphocyte (CTL) epitope from the envelope surface unit (SU) protein of the EIAV(WSU5) strain was used to immunize three horses having the ELA-A1 haplotype. Peptide-specific ELA-A1-restricted CTL were induced in all three horses, although these were present transiently in PBMC. These horses were further immunized with lipopeptide containing the corresponding CTL epitope from the EIAV(PV) strain. Then, the three immunized horses and three non-immunized horses were challenged by intravenous inoculation with 300 TCID(50) EIAV(PV). All horses...
A comparison of the vector competence of the biting midges, Culicoides (Avaritia) bolitinos and C. (A.) imicola, for the Bryanston serotype of equine encephalosis virus. Equine encephalosis virus (EEV) is widespread and prevalent in southern Africa. In this study, the oral susceptibility of Culicoides (Avaritia) imicola Kieffer (Diptera: Ceratopogonidae) to EEV was confirmed. In addition, C. (A.) bolitinos Meiswinkel, collected in the high-lying eastern Free State, South Africa, was systemically infected with the Bryanston serotype of EEV after feeding through a membrane on artificially infected equine blood containing 4.7 log10 PFU/mL of EEV. The mean infectivity of Bryanston virus in C. bolitinos increased from 1.2 log10 PFU/midge, in midges assayed for viru...
