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: 2.22). 01/2007; 21(1):157-65. DOI: 10.1892/0891-6640(2007)21[157:OONDCB]2.0.CO;2
Source: PubMed

ABSTRACT 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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    • "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 · 3.12 Impact Factor
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    • "Nucleosidic antiviral drugs have been used to treat human herpesviral infections since the 1970s, and have been tested and applied for limited applications in veterinary species, including for HV infections (Rollinson et al., 1988; Wilkins et al., 2003; van der Meulen et al., 2006; Henninger et al., 2007). However, widespread clinical use of antiviral drugs is not common in veterinary medicine (Kahn et al., 2005). "
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    ABSTRACT: Bovine herpesvirus 1 (BHV-1) infection is widespread and causes a variety of diseases. Although similar in many respects to the human immune response to human herpesvirus 1, the differences in the bovine virus proteins, immune system components and strategies, physiology, and lifestyle mean the bovine immune response to BHV-1 is unique. The innate immune system initially responds to infection, and primes a balanced adaptive immune response. Cell-mediated immunity, including cytotoxic T lymphocyte killing of infected cells, is critical to recovery from infection. Humoral immunity, including neutralizing antibody and antibody-dependent cell-mediated cytotoxicity, is important to prevention or control of (re-)infection. BHV-1 immune evasion strategies include suppression of major histocompatibility complex presentation of viral antigen, helper T-cell killing, and latency. Immune suppression caused by the virus potentiates secondary infections and contributes to the costly bovine respiratory disease complex. Vaccination against BHV-1 is widely practiced. The many vaccines reported include replicating and non-replicating, conventional and genetically engineered, as well as marker and non-marker preparations. Current development focuses on delivery of major BHV-1 glycoproteins to elicit a balanced, protective immune response, while excluding serologic markers and virulence or other undesirable factors. In North America, vaccines are used to prevent or reduce clinical signs, whereas in some European Union countries marker vaccines have been employed in the eradication of BHV-1 disease.
    Animal Health Research Reviews 06/2013; 14(1):103-123. DOI:10.1017/S1466252313000054
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    • "doi:10.1016/j.jevs.2011.12.006 Europe is of major concern to the equine veterinarians and equine industry, because the affected horses get paralyzed or other neurological symptoms are seen in them, resulting in deads [3] [7] [8]. Molecular analysis of open reading frame (ORF30) indicated that a single-nucleotide substitution of guanine (G) for adenine (A) at position 2254 in the viral DNA polymerase gene (encoded by ORF30) is found to be strongly associated with neurological disease in horses [4,5,9-13]. "
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    ABSTRACT: There has been an increase in outbreaks of neuropathogenic equine herpesvirus-1 (EHV-1) in the United States and Europe. However, the presence and frequency of neuropathogenic EHV-1 in Turkish horses are not known at present. This study aimed to investigate the frequency of EHV-1 and neuropathogenic strains of EHV-1 in the Marmara Region of Turkey. Samples were analyzed for the presence of EHV-1 and neuropathogenic EHV-1 by real-time PCR TaqMan probe assays. Overall detection rate of EHV-1 was 45.5% (51 of 112). The detection rates were 70.5% (24 of 34) in aborted fetuses, 53.3% (8 of 15) in neonatal deads, 66.6% (4 of 6) in foals, 40% (2 of 5) in dead mares, and 25% (13 of 52) in living mares. Overall detection rate of neuropathogenic EHV-1 was 7.8% (4 of 51), and the real-time PCR results were confirmed by sequencing. Neuropathogenic strains of EHV-1 were detected in the brain and lung of two mares with neurological disease but without a history of abortion, in the brain of a foal that died of respiratory disorder, and in the nasal swab from a mare with a history of abortion. On histopathology, nonpurulent meningoencephalitis, hemorrhages, and vasculitis were seen in the brain. In conclusion, results of this study indicated, for the first time, that the neuropathogenic EHV-1 is circulating in the Marmara Region of Turkey. The results of this study also show that the current risk for non-neuropathogenic strains is high, whereas risk for the neuropathogenic EHV-1-G2254 strain seems to be low. As outbreaks of EHV-1 continue in the Marmara region of Turkey, surveillance for neuropathogenic EHV-1 genotype should be maintained.
    Journal of Equine Veterinary Science 09/2012; 32(9). DOI:10.1016/j.jevs.2011.12.006 · 0.89 Impact Factor
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