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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.
Rabies surveillance in the United States during 2002.
Journal of the American Veterinary Medical Association    December 24, 2003   Volume 223, Issue 12 1736-1748 doi: 10.2460/javma.2003.223.1736
Krebs JW, Wheeling JT, Childs JE.During 2002, 49 states and Puerto Rico reported 7,967 cases of rabies in nonhuman animals and 3 cases in human beings to the Centers for Disease Control and Prevention, an increase of 7.2% from the 7,436 cases in non-human animals and 1 case in a human being reported in 2001. More than 92% (7,375 cases) were in wild animals, whereas 7.4% (592) were in domestic species (compared with 93.3% in wild animals and 6.7% in domestic species in 2001). Compared with cases reported in 2001, the numbers of cases reported in 2002 increased among all major reporting groups with the exception of swine and ro...
Generation and characterization of an EICP0 null mutant of equine herpesvirus 1.
Virus research    December 9, 2003   Volume 98, Issue 2 163-172 doi: 10.1016/j.virusres.2003.09.007
Yao H, Osterrieder N, O'Callaghan DJ.The EICP0 gene (gene 63) of equine herpesvirus 1 (EHV-1) encodes an early regulatory protein that is a promiscuous trans-activator of all classes of viral genes. Bacterial artificial chromosome (BAC) technology and RecE/T cloning were employed to delete the EICP0 gene from EHV-1 strain KyA. Polymerase chain reaction, Southern blot analysis, and DNA sequencing confirmed the deletion of the EICP0 gene and its replacement with a kanamycin resistance gene in mutant KyA. Transfection of rabbit kidney cells with the EICP0 mutant genome produced infectious virus, indicating that the EICP0 gene is not...
Oral susceptibility of South African Culicoides species to live-attenuated serotype-specific vaccine strains of African horse sickness virus (AHSV).
Medical and veterinary entomology    December 4, 2003   Volume 17, Issue 4 436-447 doi: 10.1111/j.1365-2915.2003.00467.x
Paweska JT, Prinsloo S, Venter GJ.The oral susceptibility of livestock-associated South African Culicoides midges (Diptera: Ceratopogonidae) to infection with the tissue culture-attenuated vaccine strains of African horse sickness virus (AHSV) currently in use is reported. Field-collected Culicoides were fed on horse blood-virus mixtures each containing one of the seven serotype-specific vaccine strains of AHSV, namely serotypes 1, 2, 3, 4, 6, 7 and 8. The mean titres of virus in the bloodmeals for the seven vaccine strains were between 6.8 and 7.6 log10TCID50/mL. All females (n = 3262) that survived 10 days extrinsic incubati...
Intra- and intermolecular disulfide bonds of the GP2b glycoprotein of equine arteritis virus: relevance for virus assembly and infectivity.
Journal of virology    December 4, 2003   Volume 77, Issue 24 12996-13004 doi: 10.1128/jvi.77.24.12996-13004.2003
Wieringa R, De Vries AA, Post SM, Rottier PJ.Equine arteritis virus (EAV) is an enveloped, positive-strand RNA virus belonging to the family Arteriviridae of the order NIDOVIRALES: EAV virions contain six different envelope proteins. The glycoprotein GP(5) (previously named G(L)) and the unglycosylated membrane protein M are the major envelope proteins, while the glycoproteins GP(2b) (previously named G(S)), GP(3), and GP(4) are minor structural proteins. The unglycosylated small hydrophobic envelope protein E is present in virus particles in intermediate molar amounts compared to the other transmembrane proteins. The GP(5) and M protein...
Equine arteritis virus in Irish thoroughbreds.
The Veterinary record    November 25, 2003   Volume 153, Issue 18 570 
Cullinane A.No abstract available
Equine viral arteritis in a newborn foal: parallel detection of the virus by immunohistochemistry, polymerase chain reaction and virus isolation.
Journal of veterinary medicine. B, Infectious diseases and veterinary public health    November 25, 2003   Volume 50, Issue 6 270-274 doi: 10.1046/j.1439-0450.2003.00684.x
Szeredi L, Hornyák A, Dénes B, Rusvai M.A 4-days-old foal died after a short course of respiratory syndrome and fever. Large areas of the alveoli, bronchioles and bronchi were partly or completely filled by hyaline membranes. Pronounced oedema and mild interstitial pneumonia were present and, in the small muscular arteries, fibrinoid necrosis and vasculitis or perivasculitis could be seen. Vasculitis was found in several other organs, and it was most severe in the thymus. The virus was detected in the lung, kidney and spleen using virus isolation and in the lung and spleen using polymerase chain reaction. The virus was also detected...
Post-entry restriction of retroviral infections.
AIDS reviews    November 6, 2003   Volume 5, Issue 3 156-164 
Towers GJ, Goff SP.Pathogenic retroviruses have driven the evolution of several dominant-acting mechanisms able to block infection and protect the host. These are exemplified by the mouse gene Fv1, which encodes a Gag-like protein able to protect against murine leukemia virus (MLV) infection. The block is saturable, occurs after reverse transcription and is directed against the viral capsid gene. Several other mammalian species are also able to block MLV infection with the same capsid specificity. A human gene with this activity has been named Ref1. Recently, primates have been shown to restrict a variety of ret...
Screening for West Nile virus infections of susceptible animal species in Austria.
Epidemiology and infection    November 5, 2003   Volume 131, Issue 2 1023-1027 doi: 10.1017/s0950268803001031
Weissenböck H, Hubálek Z, Halouzka J, Pichlmair A, Maderner A, Fragner K, Kolodziejek J, Loupal G, Kölbl S, Nowotny N.Avian mortality and encephalomyelitis in equines are considered good indicators for West Nile virus (WNV) activity. We retrospectively tested 385 horse sera for WNV antibodies and looked for WNV nucleic acid and/or WNV antigen in paraffin embedded tissues from 12 horses with aetiologically unresolved encephalomyelitis and 102 free-living birds of different species which had been found dead. With the exception of four horses originating from eastern European countries investigated on the occasion of transit through Austria, all horse sera were negative. Nested RT-PCR of the horse tissues yielde...
Pre-infection frequencies of equine herpesvirus-1 specific, cytotoxic T lymphocytes correlate with protection against abortion following experimental infection of pregnant mares.
Veterinary immunology and immunopathology    November 1, 2003   Volume 96, Issue 3-4 207-217 doi: 10.1016/j.vetimm.2003.08.004
Kydd JH, Wattrang E, Hannant D.In general, vaccines containing inactivated equine herpesvirus-1 (EHV-1) fail to prevent abortion in pregnant mares following infection with a virulent strain of EHV-1. We have tested the hypothesis that resistance to EHV-1-induced abortion in pregnant mares is associated with high frequencies of EHV-1 specific, major histocompatibility complex (MHC) class I-restricted, cytotoxic T lymphocytes (CTL) in the circulation. To test this theory, three groups of pregnant mares were assembled with varying backgrounds of infection or vaccination in an attempt to mimic the immune status of the general p...
West Nile virus activity–United States, October 23-29, 2003.
MMWR. Morbidity and mortality weekly report    October 31, 2003   Volume 52, Issue 43 1053-1054 
This report summarizes West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m., Mountain Standard Time, October 29, 2003.
Outbreak of equine herpesvirus type 1 myeloencephalitis: new insights from virus identification by PCR and the application of an EHV-1-specific antibody detection ELISA.
The Veterinary record    October 30, 2003   Volume 153, Issue 14 417-423 doi: 10.1136/vr.153.14.417
Studdert MJ, Hartley CA, Dynon K, Sandy JR, Slocombe RF, Charles JA, Milne ME, Clarke AF, El-Hage C.Five of 10 pregnant, lactating mares, each with a foal at foot, developed neurological disease. Three of them became recumbent, developed complications and were euthanased; of the two that survived, one aborted an equine herpesvirus type 1 (EHV-1)-positive fetus 68 days after the first signs were observed in the index case and the other gave birth to a healthy foal on day 283 but remained ataxic and incontinent. The diagnosis of EHV-1 myeloencephalitis was supported by postmortem findings, PCR identification of the virus and by serological tests with an EHV-1-specific ELISA. At the time of the...
Subpopulations of equine infectious anemia virus Rev coexist in vivo and differ in phenotype.
Journal of virology    October 29, 2003   Volume 77, Issue 22 12122-12131 doi: 10.1128/jvi.77.22.12122-12131.2003
Baccam P, Thompson RJ, Li Y, Sparks WO, Belshan M, Dorman KS, Wannemuehler Y, Oaks JL, Cornette JL, Carpenter S.Lentiviruses exist in vivo as a population of related, nonidentical genotypes, commonly referred to as quasispecies. The quasispecies structure is characteristic of complex adaptive systems and contributes to the high rate of evolution in lentiviruses that confounds efforts to develop effective vaccines and antiviral therapies. Here, we describe analyses of genetic data from longitudinal studies of genetic variation in a lentivirus regulatory protein, Rev, over the course of disease in ponies experimentally infected with equine infectious anemia virus. As observed with other lentivirus data, t...
Virulent and avirulent strains of equine arteritis virus induce different quantities of TNF-alpha and other proinflammatory cytokines in alveolar and blood-derived equine macrophages.
Virology    October 14, 2003   Volume 314, Issue 2 662-670 doi: 10.1016/s0042-6822(03)00506-3
Moore BD, Balasuriya UB, Watson JL, Bosio CM, MacKay RJ, MacLachlan NJ.Equine arteritis virus (EAV) infects endothelial cells (ECs) and macrophages in horses, and many of the clinical manifestations of equine viral arteritis (EVA) reflect vascular injury. To further evaluate the potential role of EAV-induced, macrophage-derived cytokines in the pathogenesis of EVA, we infected cultured equine alveolar macrophages (AMphi), blood monocyte-derived macrophages (BMphi), and pulmonary artery ECs with either a virulent (KY84) or an avirulent (CA95) strain of EAV. EAV infection of equine AMphi, BMphi, and ECs resulted in their activation with increased transcription of g...
West Nile virus activity–United States, September 25-October 1, 2003.
MMWR. Morbidity and mortality weekly report    October 3, 2003   Volume 52, Issue 39 941 
This report summarizes West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m., Mountain Daylight Time, October 1, 2003.
Lateral transmission of equine arteritis virus among Lipizzaner stallions in South Africa.
Equine veterinary journal    October 1, 2003   Volume 35, Issue 6 596-600 doi: 10.2746/042516403775467162
Guthrie AJ, Howell PG, Hedges JF, Bosman AM, Balasuriya UB, McCollum WH, Timoney PJ, MacLachlan NJ.A serological study conducted in 1995 revealed that 7 stallions at the Lipizzaner Centre, Gauteng, South Africa, were seropositive for antibody to equine arteritis virus (EAV). A Lipizzaner stallion imported into South Africa from Yugoslavia in 1981 had previously (1988) been confirmed to be an EAV carrier. Despite being placed under life-long breeding quarantine, EAV had been transmitted between stallions at the Lipizzaner Centre. Objective: To investigate the phylogenetic relationships between the strain of EAV shed in the semen of the original carrier stallion and strains recovered from the...
Development of competitive ELISA for serodiagnosis on African horsesickness virus using baculovirus expressed VP7 and monoclonal antibody.
Journal of virological methods    September 23, 2003   Volume 113, Issue 1 13-18 doi: 10.1016/s0166-0934(03)00217-9
Kweon CH, Kwon BJ, Ko YJ, Kenichi S.VP7, the sero-group common antigen, of African horsesickness virus (AHSV-4) was expressed in insect cells by recombinant baculovirus. To develop a specific diagnostic method, monoclonal antibody (Mab) against VP7 was prepared and investigated as diagnostic reagent with the baculovirus expressed VP7. However, the Mab against VP7 of AHSV cross-reacted with Chuzan virus by the indirect immunofluorescence assay (IFA), confirming the presence of conserved domain of VP7 among Orbiviruses. This study describes two types of ELISA; Mab linked indirect (I-ELISA) and competitive-ELISA (C-ELISA) using bac...
Detection of equine arteritis virus (EAV)-specific cytotoxic CD8+ T lymphocyte precursors from EAV-infected ponies.
The Journal of general virology    September 19, 2003   Volume 84, Issue Pt 10 2745-2753 doi: 10.1099/vir.0.19144-0
Castillo-Olivares J, Tearle JP, Montesso F, Westcott D, Kydd JH, Davis-Poynter NJ, Hannant D.Equine arteritis virus (EAV) causes a systemic infection in equids with variable outcome, ranging from subclinical infections to severe disease, and also has the capacity to induce abortion in pregnant mares and persistent infections in stallions. The serum virus-neutralizing antibody response that invariably develops in the infected animal lasts for many months or years and is believed to play an important role in virus clearance. However, very little is known about cellular immunity against EAV because of a lack of methods for evaluating these immune responses. In the present study, we descr...
Surveillance results from the first West Nile virus transmission season in Florida, 2001.
The American journal of tropical medicine and hygiene    September 19, 2003   Volume 69, Issue 2 141-150 
Blackmore CG, Stark LM, Jeter WC, Oliveri RL, Brooks RG, Conti LA, Wiersma ST.After West Nile virus (WNV) was first detected in Florida in July 2001, intensive surveillance efforts over the following five months uncovered virus activity in 65 of the state's 67 counties with 1,106 wild birds, 492 horses, 194 sentinel chickens, and 12 people found infected with the virus. Thirteen of 28 mosquito isolations came from Culex mosquitoes. As seen in the northeastern United States, wild bird mortality was the most sensitive surveillance method. However, unlike the predominantly urban 1999 and 2000 epizootics, the Florida transmission foci were rural with most activity detected ...
West Nile virus activity–United States, September 4-10, 2003.
MMWR. Morbidity and mortality weekly report    September 13, 2003   Volume 52, Issue 36 870 
This report summarizes West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m., Mountain Daylight Time, September 10, 2003.
Enhancement of equine infectious anemia virus virulence by identification and removal of suboptimal nucleotides.
Virology    September 5, 2003   Volume 313, Issue 2 588-603 doi: 10.1016/s0042-6822(03)00351-9
Cook RF, Cook SJ, Berger SL, Leroux C, Ghabrial NN, Gantz M, Bolin PS, Mousel MR, Montelaro RC, Issel CJ.Pathogenicity was reportedly restored to an avirulent molecular clone of equine infectious anemia virus (EIAV) by substitution of 3' sequences from the pathogenic variant strain (EIAV(PV)). However, the incidence of disease in horses/ponies was found to be significantly lower (P = 0.016) with the chimeric clone (EIAV(UK)) than with EIAV(PV). This was attributable to 3' rather than 5' regions of the proviral genome, where EIAV(UK) differs from the consensus EIAV(PV) sequence by having a 68-bp duplication in the 3' LTR and arginine (R(103)) rather than tryptophan (W(103)) at position 103 in the ...
Epitope specificity is critical for high and moderate avidity cytotoxic T lymphocytes associated with control of viral load and clinical disease in horses with equine infectious anemia virus.
Virology    September 5, 2003   Volume 313, Issue 2 537-552 doi: 10.1016/s0042-6822(03)00344-1
Mealey RH, Zhang B, Leib SR, Littke MH, McGuire TC.Equine infectious anemia virus (EIAV) is a lentivirus that causes persistent infections in horses. We hypothesized that high-avidity CTL specific for nonvariable epitopes might be associated with low viral load and minimal disease in EIAV-infected horses. To test this hypothesis, memory CTL (CTLm) responses were analyzed in two infected horses with high plasma viral loads and recurrent disease (progressors), and in two infected horses with low-to-undetectable viral loads and mild disease (nonprogressors). High-avidity CTLm in one progressor recognized an envelope gp90 epitope, and the data doc...
Detection of equine herpesvirus-1 in the fetal membranes of aborted equine fetuses by immunohistochemical and in-situ hybridization techniques.
Journal of comparative pathology    August 19, 2003   Volume 129, Issue 2-3 147-153 doi: 10.1016/s0021-9975(03)00022-7
Szeredi L, Aupperle H, Steiger K.Formalin-fixed, paraffin wax-embedded fetal membranes from 76 cases of equine abortion were examined immunohistochemically for equine herpesvirus (EHV)-1 antigen. Of the 76 cases, 11 had been proved EHV-1-positive by diagnostic methods applied to the aborted fetuses (viral isolation in tissue culture, or immunohistochemical examination, or both). Of the 11 fetal membranes from the virus-positive animals, five gave positive results on immunohistochemical examination, and three on in-situ hybridization; the positive signals were detected in trophoblastic cells and occasionally in monocytes and e...
Model of the equine rhinitis A virus capsid: identification of a major neutralizing immunogenic site.
The Journal of general virology    August 15, 2003   Volume 84, Issue Pt 9 2365-2373 doi: 10.1099/vir.0.19232-0
Kriegshäuser G, Wutz G, Lea S, Stuart D, Skern T, Kuechler E.Mouse monoclonal antibodies (mAbs) were employed to select neutralization escape mutants of equine rhinitis A virus (ERAV). Amino acid changes in the ERAV mutants resulting in resistance to neutralization were identified in capsid protein VP1 at Lys-114, Pro-240 and Thr-241. Although the changes were located in different parts of the polypeptide chain, these mutants exhibited cross-resistance against all four mAbs employed, indicating that these residues contribute to a single immunogenic site. To explain this result, we constructed a model of the three-dimensional structure of the ERAV capsid...
Equine arteritis virus non-structural protein 1, an essential factor for viral subgenomic mRNA synthesis, interacts with the cellular transcription co-factor p100.
The Journal of general virology    August 15, 2003   Volume 84, Issue Pt 9 2317-2322 doi: 10.1099/vir.0.19297-0
Tijms MA, Snijder EJ.Non-structural protein 1 (nsp1), the N-terminal subunit of the replicase polyprotein of the arterivirus Equine arteritis virus (EAV), is essential for viral subgenomic mRNA synthesis, but fully dispensable for genome replication. However, at the molecular level, the role of nsp1 in EAV subgenomic mRNA synthesis is poorly understood. A yeast two-hybrid screen did not reveal interactions between EAV nsp1 and other viral non-structural proteins or the nucleocapsid protein, although both nsp1 and the nucleocapsid protein were found to form homomers. Subsequently, a yeast two-hybrid screen of a HeL...
Presentation and binding affinity of equine infectious anemia virus CTL envelope and matrix protein epitopes by an expressed equine classical MHC class I molecule.
Journal of immunology (Baltimore, Md. : 1950)    August 7, 2003   Volume 171, Issue 4 1984-1993 doi: 10.4049/jimmunol.171.4.1984
McGuire TC, Leib SR, Mealey RH, Fraser DG, Prieur DJ.Control of a naturally occurring lentivirus, equine infectious anemia virus (EIAV), occurs in most infected horses and involves MHC class I-restricted, virus-specific CTL. Two minimal 12-aa epitopes, Env-RW12 and Gag-GW12, were evaluated for presentation by target cells from horses with an equine lymphocyte Ag-A1 (ELA-A1) haplotype. Fifteen of 15 presented Env-RW12 to CTL, whereas 11 of 15 presented Gag-GW12. To determine whether these epitopes were presented by different molecules, MHC class I genes were identified in cDNA clones from Arabian horse A2152, which presented both epitopes. This h...
A case control study of factors and infections associated with clinically apparent respiratory disease in UK Thoroughbred racehorses.
Preventive veterinary medicine    August 6, 2003   Volume 60, Issue 1 107-132 doi: 10.1016/s0167-5877(03)00085-0
Newton JR, Wood JL, Chanter N.A matched case control study was used to determine infections and other factors associated with clinically apparent respiratory disease in young racehorses in training in the UK. A total of 170 cases, defined as horses with sudden onset coughing, nasal discharge or pyrexia, were identified and matched to 632 non-affected controls by trainer and time period. Factors examined included age, sex, time since entry into the training yard, time since last race and different infections including tracheal and nasopharyngeal (NP) bacteria and viruses. Multivariable conditional logistic regression (CLR) ...
Serologic evidence of West Nile virus infection in horses, Yucatan State, Mexico.
Emerging infectious diseases    August 2, 2003   Volume 9, Issue 7 857-859 doi: 10.3201/eid0907.030167
Loroño-Pino MA, Blitvich BJ, Farfán-Ale JA, Puerto FI, Blanco JM, Marlenee NL, Rosado-Paredes EP, García-Rejón JE, Gubler DJ, Calisher CH....Serum samples were obtained from 252 horses in the State of Yucatan, Mexico, from July to October 2002. Antibodies to West Nile virus were detected by epitope-blocking enzyme-linked immunosorbent assays in three (1.2%) horses and confirmed by plaque reduction neutralization test. We report the first West Nile virus activity in the State of Yucatan.
Serologic evidence of West Nile virus infection in horses, Coahuila State, Mexico.
Emerging infectious diseases    August 2, 2003   Volume 9, Issue 7 853-856 doi: 10.3201/eid0907.030166
Blitvich BJ, Fernandez-Salas I, Contreras-Cordero JF, Marlenee NL, Gonzalez-Rojas JI, Komar N, Gubler DJ, Calisher CH, Beaty BJ.Serum samples were obtained from 24 horses in the State of Coahuila, Mexico, in December 2002. Antibodies to West Nile virus were detected by epitope-blocking enzyme-linked immunosorbent assay and confirmed by plaque reduction neutralization test in 15 (62.5%) horses. We report the first West Nile virus activity in northern Mexico.
Pathogenicity of a Venezuelan equine encephalomyelitis serotype IE virus isolate for ponies.
The American journal of tropical medicine and hygiene    July 24, 2003   Volume 68, Issue 4 485-494 
Sahu SP, Pedersen DD, Jenny AL, Schmitt BJ, Alstad AD.The enzootic or endemic strains of Venezuelan equine encephalomyelitis (VEE) virus (ID, IE, IF, and II-VI) are considered avirulent. In 1993 and 1996, outbreaks of encephalitis occurred in the horse populations in the Chiapas and Oaxaca provinces of Mexico, respectively. In both instances, enzootic VEE virus subserotype IE was isolated from brain tissues of dead horses. The present study investigated the pathogenicity of the Chiapas viral isolate (NVSL VEE IE 93-42124) in ponies. Three ponies were inoculated intradermally with 4, 5, and 6 logs, respectively, of the NVSL VEE IE 93-42124 viral i...
Transmission of eastern equine encephalomyelitis virus in central Alabama.
The American journal of tropical medicine and hygiene    July 24, 2003   Volume 68, Issue 4 495-500 
Cupp EW, Klingler K, Hassan HK, Viguers LM, Unnasch TR.A site near Tuskegee, Alabama was examined for vector activity of eastern equine encephalomyelitis (EEE) virus in 2001. More than 23,000 mosquitoes representing 8 genera and 34 species were collected during a 21-week period, and five species, Culiseta melanura, Aedes vexans, Coquillettidia perturbans, Culex erraticus, and Uranotaenia sapphirina, were examined for the presence of virus using a nested reverse transcriptase-polymerase chain reaction for EEE virus. Each species was infected at various times of the mosquito season (May-September) with different minimum infection rates (MIRs). Culis...
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