Quantitative molecular viral loads in 7 horses with naturally occurring equine herpesvirus‐1 infection. (30th December 2014)

• Record Type: Journal Article
• Authors: Estell, K. E.; Dawson, D. R.; Magdesian, K. G.; Swain, E.; Laing, S. T.; Siso, S.; Mapes, S.; Pusterla, N.
• Is Part Of: Equine veterinary journal. Volume 47:Number 6(2015:Nov.)
• Page Start: 689
• Page End: 693
• Publication Date: 2014-12-30
• Subjects: Horses -- Diseases -- Periodicals; 636.108905
• DOI: 10.1111/evj.12351
• Languages: English
• ISSNs: 0425-1644

Abstract

<abstract abstract-type="main"> <title>Summary</title> <sec id="evj12351-sec-0001" sec-type="section"> <title>Reasons for performing study</title> <p>Data associating quantitative viral load with severity, clinical signs and survival in equine herpesvirus‐1 myeloencephalopathy (EHM) have not been reported.</p> </sec> <sec id="evj12351-sec-0002" sec-type="section"> <title>Objectives</title> <p>To report the clinical signs, treatment, and temporal progression of viral loads in 7 horses with naturally occurring EHM and to examine the association of these factors with survival.</p> </sec> <sec id="evj12351-sec-0003" sec-type="section"> <title>Study design</title> <p>Retrospective case series.</p> </sec> <sec id="evj12351-sec-0004" sec-type="section"> <title>Methods</title> <p>The population included 7 horses with EHM presented to the University of California, Davis William R. Pritchard Veterinary Medical Teaching Hospital from May to September 2011. Horses were graded using a neurological grading scale. Daily quantitative PCR was performed on nasal secretions and whole blood. Treatment, survival, outcome and histopathology were reported.</p> </sec> <sec id="evj12351-sec-0005" sec-type="section"> <title>Results</title> <p>At presentation, one horse was neurological <italic>grade 5/5</italic>, 3 were <italic>grade 4/5</italic> and 3 were <italic>grade 3/5</italic>. All were treated with anti‐inflammatory drugs, valacyclovir and management in a sling if necessary. All were infected with equine herpesvirus‐1 of DNA polymerase D<sub>752</sub> genotype. Peak viral load in nasal secretions and blood of 5 survivors ranged from 6.9 × 10<sup>3</sup> to 2.81 × 10<sup>5</sup> (median 5.11 × 10<sup>4</sup>) and from 143 to 4340 <italic>gB</italic> gene copies/million eukaryotic cells (median 3146), respectively. The 2 nonsurvivors presented with <italic>grade 3/5</italic> neurological signs and progressed to encephalopathy. Peak viral load was higher in nonsurvivors, with levels in nasal secretions of 1.9 × 10<sup>9</sup> and 2.2 × 10<sup>9</sup> and in blood of 2.05 × 10<sup>4</sup> and 1.02 × 10<sup>5</sup><italic>gB</italic> gene copies/million eukaryotic cells. Case fatality was 2/7.</p> </sec> <sec id="evj12351-sec-0006" sec-type="section"> <title>Conclusions</title> <p>Nonsurvivors had viral loads 1000‐fold higher in nasal secretions and 10‐fold higher in blood than survivors. There was no relationship between severity of clinical signs at presentation and survival. Thus, encephalopathy and high viral load were negatively associated with survival in this population. Further research should be performed to determine whether high viral loads are associated with encephalopathy and poor prognosis.</p> <p> <bold>The Summary is available in Chinese – see</bold> <ext-link ext-link-type="uri" xlink:href="http://onlinelibrary.wiley.com/doi/10.1111/evj.12351/suppinfo" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink">Supporting information</ext-link>.</p> </sec> </abstract>