Topic:Equine Herpesvirus
Equine Herpesvirus (EHV) is a contagious virus that affects horses, causing a range of clinical conditions. It primarily impacts the respiratory system but can also lead to neurological disorders, abortion in pregnant mares, and neonatal foal death. The virus is transmitted through direct contact with infected horses or through contaminated surfaces and equipment. There are several strains of EHV, with Equine Herpesvirus-1 (EHV-1) and Equine Herpesvirus-4 (EHV-4) being the most commonly studied due to their prevalence and impact on equine health. EHV-1 is associated with more severe outcomes, including equine herpesvirus myeloencephalopathy (EHM). This page aggregates peer-reviewed research studies and scholarly articles that explore the epidemiology, pathogenesis, clinical manifestations, and management strategies related to Equine Herpesvirus in horses.
Equine interferons following exposure to equid herpesvirus-1 or -4. When 23 ponies were infected with equid herpesvirus-1 or -4 (EHV-1 or EHV-4), nasal shedding of interferon (IFN) correlated closely with the duration of viral excretion. Equine interferon (EqIFN) was detected in the serum only from animals infected with the EHV-1 virus, and here high levels correlated with clinical symptoms of locomotor disorder and indicated a poor prognosis. Low levels of IFN were detected in explanted mononuclear cells from ponies infected with either virus.
Haematological changes in two thoroughbred horses in training with confirmed equine herpesvirus 1 infections. An outbreak of respiratory disease among thoroughbred horses in training in Hong Kong was caused by equine herpesvirus 1 (EHV-1) subtype 1 (abortion strain). Two of the horses affected by EHV-1 were serially blood sampled over a period of several weeks and their haematological values measured. There was an increase in monocyte count in the first few days which steadily decreased in one horse, but the other had a second monocyte peak after a period of exercise, thus demonstrating the importance of not working animals in the early stages of the disease.
Identification of the gB homologues of equine herpesvirus types 1 and 4 as disulphide-linked heterodimers and their characterization using monoclonal antibodies. Equine herpesvirus types 1 and 4 (EHV-1 and EHV-4) labelled with [14C]glucosamine were purified from infected cell culture medium and profiles of their structural proteins were obtained that enabled identification of the major glycoproteins. Nine glycosylated polypeptides were identified for each virus. Preparations of the purified viruses each contained a glycoprotein which was linked by disulphide bonds, as determined by diagonal gel electrophoresis under reducing/non-reducing conditions. High Mr forms of this glycoprotein were detected for EHV-1 when the sample was not heated. The EHV-1 pro...
Identification and nucleotide sequence of a gene in equine herpesvirus 1 analogous to the herpes simplex virus gene encoding the major envelope glycoprotein gB. A gene in equine herpesvirus 1 (EHV-1; equine abortion virus) equivalent to the gB glycoprotein gene of herpes simplex virus (HSV) has been identified by DNA hybridization and nucleotide sequencing. A 4.3 kbp EHV-1 PstI-ClaI sequence (0.40 to 0.43 map units) contained an open reading frame flanked by appropriate control elements and was capable of encoding a polypeptide of 980 amino acids. This had 50 to 60% identity over a 617 amino acid conserved region with the gB gene products of HSV and three other alphaherpesviruses, and 20 to 30% identity with those of human cytomegalovirus and Epstein-...
Physical mapping of the genomic heterogeneity of isolates of equine herpesvirus 2 (equine cytomegalovirus). The BamHI, EcoRI, and HindIII physical maps of the genomes of 14 isolates of equine herpesvirus 2 (EHV 2) were determined by Southern blot analysis using DNA fragments of a previously mapped EHV 2 strain 86/67. No two isolates had identical maps for all 3 enzymes, the number of differing cleavage sites between pairs of isolates varying from 3 to 21. Overall 75 cleavage sites were mapped, of which 40 were variable. Cleavage sites occurred throughout the genome, including within the terminal repeat regions. Additionally, fragment length polymorphisms, independent of cleavage site loss or gain, w...
Equine herpes virus 1 (EHV-1) in liver, spleen, and lung as demonstrated by immunohistology and electron microscopy. Ten aborted foals, diagnosed as infected with Equine Herpes Virus 1 (EHV-1) on histopathological criteria, were examined for the presence of EHV-1 using immunohistology as the investigative instrument. The primary reagent was an antiserum specific for viral envelope glycoproteins. Immunohistology localised EHV-1 to areas of liver necrosis and to the cytoplasm of infected Kupffer cells and hepatocytes. Cytoplasmic immunolabelling was also prominent in reticular cells of the red pulp of the spleen and in intact and degenerated bronchiolar epithelium. Cytoplasmic immunolabelling was seen in morph...
Evolution of the herpes thymidine kinase: identification and comparison of the equine herpesvirus 1 thymidine kinase gene reveals similarity to a cell-encoded thymidylate kinase. We have identified the equine herpesvirus 1 (EHV-1) thymidine kinase gene (TK) by DNA-mediated transformation and by DNA sequencing. Alignment of the amino acid sequence of the EHV-1 TK with the TKs from 3 other herpesviruses revealed regions of homology, some of which correspond to the previously identified substrate binding sites, while others have as yet, no assigned function. In particular, the strict conservation of an aspartate within the proposed nucleoside binding site suggests a role in ATP binding for this residue. Comparison of 5 herpes TKs with the thymidylate kinase of yeast revea...
Molecular pathogenesis of equine coital exanthema: identification and expression of infected cell polypeptides at the restricted temperature during equine herpesvirus 3 infection. Equine herpesvirus 3 (EHV-3)-infected equine cells display a kinetics of infected cell polypeptide (ICP) synthesis at 34 degrees C that is typical of coordinate cascade gene regulation of herpesviruses. In contrast, when infected cell cultures are incubated at the restricted temperature of 39 degrees C, the shift from early (beta) gene expression to late (gamma) gene expression is perturbed, i.e., there is an accumulation of early (beta) gene products and a decrease in, or absence of, late (gamma) gene products. Some of the affected late (gamma) gene products may be glycoproteins since these I...
Analysis of the in vitro translation products of the equine herpesvirus type 1 immediate early mRNA. Equine herpesvirus type 1 (EHV-1) gene expression is coordinately regulated in an alpha, beta, gamma fashion. Viral alpha gene products include a 6.0-kb immediate early (IE) mRNA species (W. L. Gray et al., 1987, Virology 158, 79-87) and at least four closely related IE polypeptides (IEPs) (G.B. Caughman et al., 1985, Virology 145, 49-61). In this report, we describe results obtained from a series of in vitro translation experiments which were performed in an effort to characterize the IEPs and identify the mechanism by which individual IE protein species are generated. Our data indicate that ...
Isolation and characterization of monoclonal antibodies against an attenuated vaccine strain of equine herpesvirus type 1 (EHV-1). The production and differentiation of monoclonal antibodies (mabs) against the Rac-H strain of EHV-1 used as an attenuated live vaccine to prevent rhinopneumonitis and abortion is described. Seven different antigenic sites were detected by the 15 mabs produced. EHV-1 specific mabs as well as EHV-1 and -4 common mabs could be established, allowing easy typing of EHV isolates. One mab recognized the vaccine strain only. This reaction was used to investigate a possible involvement of the vaccine strain in cases of abortion. Common antigenic determinants with EHV-1,-3,-4 and BHV-1 could also be de...
Application of cloned fragments of equine herpesvirus type-1 DNA for detection of virus-specific DNA in equine tissues. Tissue specimens obtained from equine herpesvirus-1 (EHV-1), subtype 1-infected aborted foetuses were analysed for the presence of virus DNA by means of Southern blot and dot blot hybridisations. The specificity of the methods was confirmed although the sensitivity was inferior to classical techniques such as virus isolation. However, the possibility of detecting the state of the virus DNA and the ability to distinguish between subtypes were important features, and the dot blot method was shown to have potential for a rapid diagnostic test. This report demonstrates some potential practical app...
Characterization of an equine herpesvirus type 1 gene encoding a glycoprotein (gp13) with homology to herpes simplex virus glycoprotein C. The molecular structure of the equine herpesvirus type 1 (EHV-1) gene encoding glycoprotein 13 (gp13) was analyzed. The gene is contained within a 1.8-kilobase AccI-EcoRI restriction fragment mapping at map coordinates 0.136 to 0.148 in the UL region of the EHV-1 genome and is transcribed from right to left. Determination of the nucleotide sequence of the DNA fragment revealed a complete transcriptional unit composed of typical regulatory promoter elements upstream to a long open reading frame (1,404 base pairs) that encoded a 468-amino-acid primary translation product of 51 kilodaltons. The p...
Characterization of the genome of equine herpesvirus 1 subtype 2. The genome structure of equine herpesvirus 1 (EHV-1) subtype 2 was shown by electron microscopic studies and restriction endonuclease site mapping to comprise two covalently linked segments (L, 109 kbp; S, 35 kbp). The S segment contains a unique sequence (US) flanked by a substantial inverted repeat (TRS/IRS). Thus, the genome structure of EHV-1 subtype 2 is similar to that published previously for EHV-1 subtype 1, but the two subtypes differ in the occurrences of EcoRI and BamHI restriction sites. Hybridization studies using cloned EHV-1 DNA showed that the genome of EHV-1 subtype 2 is colin...
ADCC and complement-dependent lysis as immune mechanisms against EHV-1 infection in the horse. Immunity to equine herpesvirus type 1 (EHV-1) was evaluated using sera collected from yearling horses involved in a trial of a commercial vaccine. Measurement of the ability of these sera to mediate antibody-dependent cellular cytotoxicity and complement-dependent lysis revealed that these mechanisms, although potentially important in recovery from EHV-1 infection, do not play a role in protection following vaccination.
Agents of equine viral encephalomyelitis: correlation of serum and cerebrospinal fluid antibodies. A survey was conducted by testing 115 paired equine serum and cerebrospinal fluid samples by hemagglutination-inhibition for antibodies to Powassan and snowshoe hare viruses, and by virus neutralization for antibodies to equine herpesvirus type 1. Twenty-five samples were from horses with spontaneous neurological disease and the remainder from horses euthanized because of various nonneurological disorders. All sera and cerebrospinal fluids were negative for antibodies to Powassan virus. Fifty-one sera (44.3%) and 15 cerebrospinal fluids (13.0%) had antibodies to snowshoe hare virus. Ninety-eig...
The characterization of equine herpes virus-1-infected cell polypeptides recognized by equine lymphocytes. Ponies, without evidence of previous exposure to Equine herpes virus-1 (EHV-1), were experimentally infected with EHV-1 subtype 2 and investigated for lymphocyte transformation to virus-infected cell polypeptides, as shown by separation with gel electrophoresis. Animals made significant responses to Western blot fractions that corresponded to molecular weights of approximately 30,000, 40,000-45,000, 60,000-65,000, 80,000-95,000 and 100,000-140,000 MW. These molecular weight ranges correlated with the positions of major EHV-1 subtype 2 glycoproteins that were found at migration distances approx...
Propagation and quantitation of animal herpesviruses in eight cell culture systems. A comparative study was carried out to determine the relative sensitivities of eight different cell culture systems to six different herpesviruses of animals. The cells used were: OFL (ovine fetal lung), ML (mink lung), FK (ferret kidney), PTK-2 (potoroo kidney), TEK (turkey embryo kidney), ED (equine dermal), BT (bovine turbinate), and PK15 (porcine kidney). The viruses tested were: PRV (pseudorabies) of swine, CPHV (caprine herpesvirus), IBRV (infectious bovine rhinotracheitis virus), DN-599 strain of bovine herpesvirus type 4, EHV-1 (equine herpesvirus), and CHV (canine herpesvirus). On the...
[Infection with equine herpesvirus and its manifestation in the central nervous system of the horse]. Infections with EHV1 can lead to manifestation at the CNS of horses followed by encephalomyelitis and "equine stroke". Horse experiments could confirm the clinical picture and gave links to the potential pathogenesis of the disease. We also have been in the position to isolate and characterize an EHV4 virus out of the brain of a horse with CNS disorders. The two viruses carry different biological properties which obviously dominate the pathogenesis. These properties as well as experimental and field cases are described and different diagnostic tests are discussed.
Asinine herpesvirus genomes: comparison with those of the equine herpesviruses. Two previously unknown and distinct herpesviruses were isolated from donkeys. One, with the characteristics of a betaherpesvirus, was isolated from the leukocytes of an apparently healthy donkey, while the second, an alphaherpesvirus, was recovered from the nasal cavity of donkeys given high doses of corticosteroids, and caused rhinitis in two seronegative weanling donkeys when they were intranasally infected. Few, if any, restriction endonuclease fragments were shared by the donkey betaherpesvirus, equine herpesvirus 2 (EHV 2) or EHV 5, a second distinctly different equine betaherpesvirus, no...
[Preventative vaccination against EHV (equine herpesvirus) abortion]. From 1981 until 1987 we investigated the more detailed circumstances regarding a prophylactic vaccination in altogether 37 stud farms with a history of virus abortion. In 23 cases, in which Prevaccinol and/or Resequin were used, it was found that the following of vaccination schedule and necessary immunization programmes respectively, had considerable imperfections. In seven cases prophylactic vaccinations were not carried out or corresponding questionnaires were not answered. The fact that in the present data no case of virus abortion was observed, when the mare was vaccinated according to th...
Genetic restriction of cytolysis during equid herpesvirus 1 subtype 2 infection. Six Welsh Mountain pony foals were experimentally infected with a subtype 2 isolate of Equid Herpesvirus 1 (EHV-1) and subsequently examined for T cell mediated cytotoxicity against both subtypes. Cytotoxicity was not observed at 3 or 7 days after primary exposure but virus-specific, and genetically restricted, cytotoxicity of EHV-1-labelled autologous skin fibroblasts could be demonstrated 7 and 21 days after the animals were given a second exposure to live virus. Killing of subtype 2 antigen-labelled targets was more efficient than subtype 1 coated cells. This finding was paralleled by the o...
An enzyme-linked immunosorbent assay (ELISA) for measurement of antibodies against equine herpesvirus 2 in equine sera. An indirect enzyme-linked immunosorbent assay (ELISA) was developed for the detection of antibodies against equine herpesvirus type 2 (EHV-2) in equine sera. The optimal conditions of antigen concentration, and serum and conjugate dilutions were established by chequerboard titrations. When the standard ELISA test was used for titration of test sera, it was found to give titres approximately 1500 times higher than those obtained in the virus neutralization (VN) test, and a correlation coefficient of 0.815 was obtained between these two tests on 42 equine sera. All the positive serum samples by ...