title: Quantitative molecular viral loads in 7 horses with naturally occurring equine herpesvirus-1 infection.
abstract: BACKGROUND
  Data associating quantitative viral load with severity, clinical signs and survival in equine herpesvirus-1 myeloencephalopathy (EHM) have not been reported.
  
  
  OBJECTIVE
  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.
  
  
  METHODS
  Retrospective case series.
  
  
  METHODS
  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.
  
  
  RESULTS
  At presentation, one horse was neurological grade 5/5, 3 were grade 4/5 and 3 were grade 3/5. 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 D752 genotype. Peak viral load in nasal secretions and blood of 5 survivors ranged from 6.9 × 10(3) to 2.81 × 10(5) (median 5.11 × 10(4) ) and from 143 to 4340 gB gene copies/million eukaryotic cells (median 3146), respectively. The 2 nonsurvivors presented with grade 3/5 neurological signs and progressed to encephalopathy. Peak viral load was higher in nonsurvivors, with levels in nasal secretions of 1.9 × 10(9) and 2.2 × 10(9) and in blood of 2.05 × 10(4) and 1.02 × 10(5) gB gene copies/million eukaryotic cells. Case fatality was 2/7.
  
  
  CONCLUSIONS
  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. The Summary is available in Chinese - see Supporting information.
authors.affiliation: William R. Pritchard Veterinary Medical Teaching Hospital, University of California, Davis, USA.
authors.forename: K E
authors.initials: KE
authors.lastname: Estell
authors.affiliation: William R. Pritchard Veterinary Medical Teaching Hospital, University of California, Davis, USA.
authors.forename: D R
authors.initials: DR
authors.lastname: Dawson
authors.affiliation: William R. Pritchard Veterinary Medical Teaching Hospital, University of California, Davis, USA.
authors.forename: K G
authors.initials: KG
authors.lastname: Magdesian
authors.affiliation: William R. Pritchard Veterinary Medical Teaching Hospital, University of California, Davis, USA.
authors.forename: E
authors.initials: E
authors.lastname: Swain
authors.affiliation: William R. Pritchard Veterinary Medical Teaching Hospital, University of California, Davis, USA.
authors.forename: S T
authors.initials: ST
authors.lastname: Laing
authors.affiliation: William R. Pritchard Veterinary Medical Teaching Hospital, University of California, Davis, USA.
authors.forename: S
authors.initials: S
authors.lastname: Siso
authors.affiliation: William R. Pritchard Veterinary Medical Teaching Hospital, University of California, Davis, USA.
authors.forename: S
authors.initials: S
authors.lastname: Mapes
authors.affiliation: William R. Pritchard Veterinary Medical Teaching Hospital, University of California, Davis, USA.
authors.forename: N
authors.initials: N
authors.lastname: Pusterla
mesh_terms: D000818:Animals; D005260:Female; D006566:Herpesviridae Infections / Q000662:veterinary* / Q000821:virology; D004861:Herpesvirus 1, Equid; D006734:Horse Diseases / Q000097:blood / Q000821:virology*; D006736:Horses; D008297:Male; D012189:Retrospective Studies; D019562:Viral Load / Q000662:veterinary*
keywords: equine herpes virus-1; equine herpesvirus-1 myeloencephalopathy; horse; neurological disease; quantitative PCR