Outbreak of Neurologic Disease Caused by Equine Herpesvirus-1 at a University Equestrian Center

University Equine Veterinary Services, Findlay, OH 45840, USA.
Journal of Veterinary Internal Medicine (Impact Factor: 1.88). 01/2007; 21(1):157-65. DOI: 10.1892/0891-6640(2007)21[157:OONDCB]2.0.CO;2
Source: PubMed


Equine herpesvirus type 1 (EHV-1) infection causes neurologic disease in horses. However, risk factors for the disease and long-term prognosis are poorly characterized.
There are identifiable risk factors for equine herpes-1 myeloencephalopathy.
The entire population of 135 horses housed within the equestrian facility.
A descriptive study investigated the clinical, serologic, virologic, and management aspects of an outbreak of EHV-1 myeloencephalopathy.
Out of 135 horses at the facility, 117 displayed signs of EHV-1 infection. Forty-six horses developed neurologic deficits characterized by symmetrical hind limb ataxia and weakness. Twelve horses that developed neurologic deficits became recumbent and did not survive. The development of severe neurologic deficits during the outbreak was associated with the presence of residual deficits at the 6-month examination. Within 1 year of the outbreak onset, all horses that survived had returned to an exercise level comparable to that experienced before the outbreak. Factors associated with the development of neurologic disease included age of > 5 years, location in the south or arena stall areas, and highest rectal temperature on day 3 or later of the febrile period.
Being > 5 years of age, having had a rectal temperature of > 103.5 degrees F, and highest rectal temperature occurring on or after the 3rd day of the febrile period were the factors most predictive of the development of neurologic disease and death. Data obtained during this outbreak substantiate previous findings relating to clinical aspects and diagnosis of EHV-1 myeloencephalopathy. The prophylactic and therapeutic use of acyclovir during this outbreak is described.

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Available from: Stephen M Reed, Mar 09, 2014
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    • "Rabbit kidney cells (RK-13, American Type Culture Collection (ATCC) CCL- 37, Manassas, VA) and Madin-Darby bovine kidney cells (MDBK; ATCC CCL-22) were grown in Eagle's Minimal Essential Medium (EMEM; Life Technologies, Carlsbad, CA) supplemented with 10% FBS and 100 U/ml penicillin–streptomycin. The EHV-1 virus that was used in this study was a well-characterized, neuropathogenic strain, known as T953 strain or Findlay Strain, which was isolated from a nasopharyngeal swab from a horse suffering from EHV-1 neurologic disease at the Veterinary Medical Teaching Hospital, University of Findlay, Ohio in 2003 (Henninger et al., 2007). To prepare working virus stocks, EECs were infected with EHV-1 strain at a multiplicity of infection (MOI) of 0.1 and the viruses were harvested when 100% cytopathic effect (CPE) was evident. "
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    ABSTRACT: Equine herpesvirus-1 (EHV-1) is one of the most common and important respiratory viral pathogens of horses. EHV-1 in horses replicates initially in the respiratory epithelium and then spreads systematically to endothelial cells lining the small blood vessels in the uterus and spinal cord, and highly pathogenic virus strains can produce aborted fetuses or myeloencephalopathy. Like other herpes viruses, EHV-1 employs a variety of mechanisms for immune evasion. Some herpes viruses down-regulate the type-I interferon (IFN) response to infection, but such activity has not been described for EHV-1. Here, in an in vitro system utilizing an established equine endothelial cell line, we studied the temporal effect on IFN-β responses following infection with the neuropathogenic T953 strain of EHV-1. Results show that after an early induction of IFN-β, the virus actively shut down further production of IFN-β and this was correlated with expression of the viral late genes. Expression of the IFN response factor viperin, a marker of host cell type-I IFN responses, was also suppressed by T953 virus infection. EHV-1-mediated suppression of host type-I IFN responses may play an important role in EHV-1 pathogenesis and the mechanism of this, presumably involving a viral late gene product, warrants investigation. Copyright © 2015 Elsevier B.V. All rights reserved.
    Veterinary Immunology and Immunopathology 08/2015; DOI:10.1016/j.vetimm.2015.07.015 · 1.54 Impact Factor
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    • "The body temperature was measured during sampling from clinically affected equines. Previous studies on naturally occurring outbreaks of EHM indicated that fever occurs days before the onset of neurological signs, but is often absent during the neurological disorders (Henninger et al., 2007). Gryspeerdt et al. (2011) also reported rapid occurrence of ataxia and paralysis immediately after the disappearance of fever. "
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    ABSTRACT: Although equine herpesvirus myeloencephalopathy (EHM) is a sporadic and relatively uncommon manifestation of equine herpesvirus-1 (EHV-1), it has the potential for causing devastating outbreaks in horses. Up till now, there were no reported EHM outbreaks in donkeys and mules. This study describes the isolation and molecular characterization of EHV-1 from clinically EHM-affected horses (n = 6), mules (n = 3) and donkeys (n = 82) in Ethiopia during outbreaks from May 2011 to December 2013. The incidence of EHM cases was higher from April to mid-June. EHM in donkeys was more severe and death without clinical signs of paralysis, and recumbency was frequently observed. The main age of affected equines ranged from 7 to 10 years (n = 51; 56.0%), and females (n = 58; 63.7%) were more affected than males. The incidence of neuropathogenic (D752 ) and non-neuropathogenic (N752 ) variants of EHV-1 from EHM-affected equines in Ethiopia was assessed by sequencing the DNA polymerase gene (ORF30) of the EHV-1 isolates. The results indicated that from the total of 91 clinically affected equines, 90 (98.9%) of them had an ORF30 D752 genotype. An ORF30 N752 variant was only found in one donkey. Analysis of ORF68 as grouping marker for geographical differences showed that the Ethiopian EHV-1 isolates belong to geographical group 4. Due to the fatal nature of EHV-1 in donkeys, it would be interesting to examine the pathogenesis of EHM in this species. At present, there is no vaccine available in Ethiopia, and therefore, outbreaks of EHV-1 should be controlled by proper management adaptations. In addition, it is important to test the efficacy of the commercial vaccines not only in horses, but also in donkeys and mules. © 2015 Blackwell Verlag GmbH.
    Transboundary and Emerging Diseases 05/2015; DOI:10.1111/tbed.12377 · 2.94 Impact Factor
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    • "The efficacy of acyclovir for the resolution of EHM is difficult to assess because of the many confounding factors typically present in an outbreak situation. Nevertheless, in one EHM outbreak, the administration of acyclovir appeared to be associated with decreased severity of disease and increased survival (Henninger et al. 2007). However, other researchers have reported poor bioavailability of acyclovir in the horse and variable serum time profiles of the drug (Wilkins et al. 2005). "
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    ABSTRACT: Abstract Equid herpesvirus (EHV) type 1 is a common pathogen of horses with worldwide distribution. Although severe tracheobronchitis has been described in some field outbreaks of EHV-1 respiratory disease, many EHV-1 infections occur asymptomatically or are accompanied only by signs of mild respiratory disease. However, EHV-1 infection can also result in outcomes other than respiratory disease such as abortion, neonatal death or neurological disease. This review provides an overview of the diagnosis, treatment and prognosis for EHV-1 associated diseases, with an emphasis on neurological presentations of EHV-1 infection. Pathogenesis and epidemiology of EHV-1 associated diseases are described in an accompanying paper (Dunowska 2014).
    New Zealand veterinary journal 03/2014; 62(4). DOI:10.1080/00480169.2014.899945 · 1.26 Impact Factor
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