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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.
Rapid detection of equine herpesvirus type-1 antigens in nasal swab specimens using an antigen capture enzyme-linked immunosorbent assay. An antigen capture enzyme-linked immunosorbent assay (ELISA) was developed for the detection of equine herpesvirus type-1 (EHV-1) antigens in nasal swab specimens. The test was designed as a solid phase, amplified sandwich assay in which an EHV-1 specific monoclonal antibody was used to capture virus antigen and polyclonal antisera used to detect antigen bound to the test plates. Eight monoclonal antibodies were tested for their ability to capture virus antigen and one was selected for routine use. The sensitivity and specificity of the ELISA was compared with that of virus isolation using swa...
The activity of (S)-1-[(3-hydroxy-2-phosphonyl methoxy) propyl] cytosine (HPMPC) against equine herpesvirus-1 (EHV-1) in cell cultures, mice and horses. The activity of the nucleotide analogue, (S)-1-[(3-hydroxy-2-phosphonyl methoxy) propyl] cytosine (HPMPC), against equine herpesvirus-1 (EHV-1) was tested in cell culture, mice and foals. The ED50 for plaque reduction was found to be 0.07 and 0.03 microgram/ml in RK-13 and EEL cells respectively. In mice, a single administration of HPMPC (20 mg/kg, s.c.) was very effective at reducing clinical signs and virus replication if given on the day before intranasal inoculation with EHV-1. Treatment on the day of infection or day 1 p.i. was less effective, but still significantly reduced clinical sign...
The pathogenicity of Ab4p, the sequenced strain of equine herpesvirus-1, in specific pathogen-free foals. The sequencing of the genome of equine herpesvirus-1 (EHV-1) is reported in Elizabeth A. R. Telford, Moira S. Watson, Kathryn McBride, and Andrew J. Davison, 1992, Virology, 189, 304-316. The sequence was derived using a plaque-purified clone of EHV-1 strain Ab4 (designated Ab4p). To ensure that Ab4p shares the pathogenic characteristics of parental Ab4 (hereafter Ab4), both were inoculated intranasally into foals, specifically free from EHV-1 and EHV-4. Clinical signs, including rectal temperature, were similar for both viruses. In addition, nasal shedding of virus was observed over a 1- to 2...
Abortion of virologically negative foetuses following experimental challenge of pregnant pony mares with equid herpesvirus 1. From 1988 to 1991, 51 pregnant pony mares were challenged intranasally or by aerosol with an isolate of EHV-1 (AB4) originally recovered from a quadriplegic mare. This resulted in 32 abortions, occurring from 9 to 29 days after infection. In 14 of the early abortions (Days 9-14), EHV-1 was not demonstrated in the foetal tissues by virus isolation or immunostaining despite no other non-viral cause for the abortion being evident. Application of the polymerase chain reaction to foetal tissues from 9 of these cases also proved negative. One of the 14 mares was destroyed immediately after abortion,...
Natural killer cells in normal horses and specific-pathogen-free foals infected with equine herpesvirus. Peripheral blood mononuclear cells (PBMC) from an adult horse and from foals demonstrated natural killer (NK)-type cytotoxicity against a range of xenogeneic and allogeneic cell targets. The human tumour cell line, Chang liver was consistently the most susceptible. Chang liver, rabbit kidney (RK-13), equine sarcoid (ES) and embryonic equine kidney (EEK) cells were more susceptible when presented to horse PBMC than monolayer cultures. Embryonic equine lung (EEL) and murine YAC-1 cells conversely, were more susceptible in a trypsinized state. Horse PBMC demonstrated higher levels of NK-type acti...
The molecular epidemiology of equine herpesvirus 1 (equine abortion virus) in Australasia 1975 to 1989. The restriction endonuclease DNA fingerprints of 57 isolates of equine herpesvirus 1 (EHV1; equine abortion virus) from abortion, perinatal foal mortalities and encephalitis from 15 epidemics that occurred in Australasia between 1975 and 1989 were examined using the enzymes Bam HI, EcoRI and Bgl II. There was a remarkable degree of uniformity in the restriction patterns; mobility differences were observed in only 14 of 52 (27%) of the fragments. Twelve of these 14 fragments were located within the repeat structures that bracket the unique short region of the genome or were located at the left ...
Epizootiological aspects of type 1 and type 4 equine herpesvirus infections among horse populations. The dissemination of equine herpesvirus types 1 (EHV-1) and 4 (EHV-4) among various horse populations in Japan was investigated through the isolation and typing of virus strains from horses with respiratory diseases. Type specific monoclonal antibody pools were used for the typing of isolates. The 42 strains of EHV-1 and 64 strains of EHV-4 were isolated from 4593 nasal swabs and/or blood plasma samples collected from 3326 horses during a period from 1979 to 1990. All the strains of EHV-1 were isolated from racehorses only and during the winter season exclusively, when the epizootic of respira...
The effects of equine rhinovirus, influenza virus and herpesvirus infection on tracheal clearance rate in horses. The response of horses exposed to three common respiratory viruses was studied by measuring tracheal mucociliary clearance rates in the trachea. Tracheal clearance rates (TCR) were determined before, during illness and following recovery in horses exposed to equine rhinovirus (ERhV-2), equine influenza virus (EIV) and equine herpesvirus (EHV-4) by means of lateral scintigraphs made following an injection of technetium-99m sulphide colloid into the tracheal lumen. In six horses exposed to ERhV-2, TCR remained within normal limits. Exposure to EIV resulted in reduced TCR in six of seven horses, ...
Characterization of the regulatory functions of the equine herpesvirus 1 immediate-early gene product. Use of the translation-inhibiting drug cycloheximide has indicated that the equine herpesvirus 1 (EHV-1) immediate-early (IE) gene, the sole EHV-1 IE gene, encodes a major viral regulatory protein since IE mRNA translation is a prerequisite for all further viral gene expression (W.L. Gray, R. P. Baumann, A. T. Robertson, G. B. Caughman, D. J. O'Callaghan, and J. Staczek, Virology 158:79-87, 1987). An EHV-1 IE gene expression vector (pSVIE) in combination with chimeric EHV-1 promoter-chloramphenicol acetyltransferase (CAT) reporter constructs was used in transient transfection assays to charact...
[Virologico-serologic studies in horses with respiratory tract diseases]. Of 1081 acute and chronically respiratory diseased as well as clinically normal horses 824 sera and 257 paired serum samples collected 1986 and 1987 were tested for antibodies against several different respiratory viruses such as influenza virus A/equi 1 and 2 (Influenza 1 a. 2), equine herpesvirus type 1/4 (EHV 1/4), mammalian reovirus type 1-3 (Reovirus 1-3), equine rhinovirus type 1 (ERV 1), equine adenovirus type 1 (EAdV 1), and equine arteritis virus (EAV). The investigations resulted in an antibody prevalence of 57.2% (Influenza 1), 59.5% (Influenza 2), 81.5% (EHV 1/4), 50.3% (Reovirus 1...
Latent equid herpesviruses 1 and 4: detection and distinction using the polymerase chain reaction and co-cultivation from lymphoid tissues. The polymerase chain reaction (PCR) and co-cultivation were used to identify the lymphoreticular system as the site of latency of equid herpesvirus I (EHV-1). Primers for PCR were designed from aligned nucleotide sequences of the glycoprotein gB genes to amplify the same region of both the EHV-1 and EHV-4 genomes. Subsequent restriction digests using specific enzymes distinguished the amplified fragments of the EHV-1 genome from those of the EHV-4 genome. Ten weeks following an experimental infection of five ponies with EHV-1, latent virus was detected by PCR and recovered by co-cultivation, p...
[The polymerase chain reaction (PCR) for the detection of DNA of equine herpesviruses 1 and 4]. Formalin-fixed and Paraplast-embedded tissue samples of 42 aborted equine fetuses were examined by polymerase chain reaction for the presence of equine herpesvirus DNA. The used set of primers was located in the glycoprotein 13 open reading frame and allowed the amplification of both EHV 1 und EHV 4. By cleaving pattern analysis after Hinf I digestion EHV 1 could be distinguished from EHV 4. In 9 of the cases investigated EHV 1-DNA was detected. This finding is in absolute context with the results of the virological investigations.
The IR3 gene of equine herpesvirus type 1: a unique gene regulated by sequences within the intron of the immediate-early gene. The complete nucleotide sequence of the inverted repeat component (IR; 12,776 bp each) of the genome of equine herpesvirus type 1 (EHV-1) has been determined. Transcription analyses have revealed that the EHV-1 IR sequence encodes at least 6 genes. In this report, we present the DNA sequence and transcriptional characterization of a gene (IR3) that maps entirely within the IR sequences. The IR3 open reading frame (ORF) is located between nucleotides (nt) 6123-6411 of the IR sequence and possesses an ORF of 95 amino acids. Interestingly, this ORF does not show homology to any known herpesvirus ...
An immunoperoxidase method applied to the diagnosis of equine herpesvirus abortion, using conventional and rapid microwave techniques. An indirect immunoperoxidase (IMP) technique was applied to cryostat and paraffin sections of liver from ten aborted equine foetuses. Equid herpesvirus type 1 (EHV-1) had been isolated from seven of them and EHV-4 from one: the remaining two were virologically negative and were not used as controls. In the eight virus-infected cases the immunostaining revealed foci of cells exhibiting a distinct brown cytoplasmic and inclusion body pigmentation. No specific signal was present in the non-infected controls. The method also was adapted for incubation in a microwave oven, which allowed the total l...
[Causes of prenatal foal loss in Switzerland]. In Switzerland during the foaling season 1988 and 1989 the cause of abortion in 60 foals was investigated. Special attention was paid to infections with equine herpesvirus 1 (EHV 1). Diagnosis were based on post-mortem, histopathological, bacteriological and immunofluorescence investigation. The results confirm data from other countries, that EHV 1 is the most prevalent viral (20%) cause of abortion, followed by various bacterial agents (12%). Other causes were umbilical torsion, twin pregnancy and malformations. In 18% of the cases the investigation of fetuses did not give any results as to t...
Diagnosis of equid herpesviruses -1 and -4 by polymerase chain reaction. The polymerase chain reaction (PCR) is a sensitive technique used to detect DNA of viral pathogens. We have applied the technique to the detection of Equid herpesviruses-1 and -4 (EHV-1 and EHV-4) DNA within nasopharyngeal swab samples from horses. Ninety-eight samples from suspected field cases and in-contact horses were analysed. The assays were conducted blind and later decoded and compared with virus isolation data. Our results indicate that PCR is a sensitive and rapid technique for the diagnosis of EHV-1 and EHV-4 infection.
Pathogenesis of equine herpesvirus-1 in specific pathogen-free foals: primary and secondary infections and reactivation. Six specific pathogen-free foals shown to be free of equine herpesvirus-1 and 4 (EHV-1 and -4) and lacking in maternally-derived antibodies were used to investigate the pathogenesis of EHV-1 in horses. Following primary intranasal inoculation with EHV-1 all foals showed signs of a mild, self-limiting upper respiratory tract infection. A leucopenia was observed, comprising both a lymphopenia and neutropenia. Virus was isolated from nasal mucus and buffy coat cells over several days during the clinical episode and after the animals became clinically normal. Notwithstanding the mildness of the cl...
Pathological findings in horses dying during an outbreak of the paralytic form of Equid herpesvirus type 1 (EHV-1) infection. In 1988 an outbreak of the paralytic form of Equid herpesvirus type 1 (EHV-1) infection occurred on a stud farm and several animals died. This provided an opportunity to perform detailed pathological investigations to gain insights into the pathogenesis of this spontaneous disease. Two paretic mares, three foals, an aborted foetus and its non-paretic dam were examined. The endotheliotropism of the virus was clearly demonstrated by the use of an indirect immunoperoxidase (IP) stain. At autopsy, evidence of viral infection was widespread in the foetus and foals, but limited or absent in the mare...
Identification and comparative sequence analysis of a gene in equine herpesvirus 1 with homology to the herpes simplex virus glycoprotein D gene. A homologue of the herpes simplex virus (HSV) glycoprotein D gene has been identified in the genome of equine herpesvirus-1 (EHV-1, equine abortion virus). An open reading frame in the middle of the short unique (US) region is capable of encoding a polypeptide of 402 amino acids that has 26% and 20% of its residues matching pseudorabies virus (PRV) gp50 and HSV-1 gD, respectively. Despite this low level of similarity, the positional identity of six cysteine residues and certain motifs, and the location of the EHV-1 gene, clearly define the EHV-1 polypeptide as one of a family of "gD-like" prot...
Clinical signs and humoral immune response in horses following equine herpesvirus type-1 infection and their susceptibility to equine herpesvirus type-4 challenge. A group of three horses was experimentally infected with equine herpesvirus type 1 (EHV-1) and showed clinical signs characterised by a biphasic febrile response, leucopenia and cell associated viraemia accompanied by virus shedding from the nasopharynx. A second exposure to the virus 18 days later resulted in the isolation of virus from the nasopharynx of one horse. This and a further group of three EHV-1 seropositive horses were subsequently infected with equine herpesvirus type 4 (EHV-4) 147 days after the initial EHV-1 infection and virus was shed from the nasopharynx in the absence of cli...
Attempts to immunoprotect adult horses, specifically pregnant mares, with commercial vaccines against clinical disease induced by equine herpesvirus-1. In a project lasting 4 years more than 300 Lipizzans, around 180 of them adults, were vaccinated systematically against Equine Herpesvirus-1 (EHV-1) and representative groups thereof were serologically controlled for their antibody responses. In part, vaccination intervals recommended on packing slips were followed, in part other intervals, implicated by intermediary results, were used. A live virus vaccine proved ineffective if humoral antibodies were present. An oil-adjuvanted vaccine proved of highest antiviral immunogenicity, but after repeated revaccinations caused severe local reactions ...
Isolation of equine herpesvirus-1 mutants in the presence of (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine: demonstration of resistance in vitro and in vivo. The compound (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine (HPMPA) had been previously shown to be highly effective in treatment of EHV-1 in a murine model for the equine disease. This paper describes the isolation of a series of mutants resistant to the drug. Resistance was demonstrated in cell culture and one mutant was tested in a murine model. The resistant mutant was pathogenic for mice; infectious virus was recovered from respiratory tissues and blood at levels similar to the parental virus. However, the mutant showed a significant degree of resistance in vivo, thus proving the viru...
Amplification and differentiation of the DNA of an abortigenic (type 1) and a respiratory (type 4) strain of equine herpesvirus by the polymerase chain reaction. Unpurified DNA derived from cultures of equine fetal kidney cells infected with either equine herpesvirus type 1 or equine herpesvirus type 4 was amplified by the polymerase chain reaction using one pair of oligonucleotide primers. Restriction endonuclease digestion of the amplified segments with PvuII, followed by electrophoresis, revealed restriction fragment length polymorphisms which enabled the two virus types to be differentiated.
The role of endothelial cell infection in the endometrium, placenta and foetus of equid herpesvirus 1 (EHV-1) abortions. One of three mares in the last trimester of pregnancy became paraplegic 7 days after experimental infection with EHV-1 and was killed 10 days after infection (d.p.i.). The other two mares aborted foetuses at 12 and 14 d.p.i. In the first mare, virus was detected by immunofluorescence (IIF) and immunoperoxidase (IP) staining in endothelial cells of the endometrium, placenta and umbilical vein, but not in any other foetal tissues. In the experimentally aborted foetuses, and in two other independent field cases of abortions, endothelial cell infection was also detected in the foetuses, both in ma...
Clinical, viral, and genetic evaluation of equine degenerative myeloencephalopathy in a family of Appaloosas. A clinical, viral, hematologic , and genetic study was conducted over a 4-year period on a family of Appaloosas with high incidence of clinical ataxia and pathologic features of equine degenerative myeloencephalopathy. Marginal to deficient serum vitamin E (alpha-tocopherol) and blood selenium values were the only other consistent antemortem abnormalities in the affected horses. Members of this family were all descendants of a clinically normal mare and were raised in 3 separate environments with variable quality of feed. All horses had access to pasture grasses. Normal chromosomal karyotypes ...
An outbreak of Equid herpesvirus abortion in New South Wales. Thirty-three of the 44 mares on a Thoroughbred stud in New South Wales aborted or lost foals within one day of birth. Gross pathological and histological changes were in keeping with Equid herpesvirus I (EHV-1) abortion. In the six foals that underwent virological examination, EHV was isolated and typed as EHV-1 by restriction endonuclease analysis. EHV-1 abortion had not occurred previously on this stud and the source of the infection was not identified.
