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Frequency of molecular detection of equine herpesvirus-4 in nasal secretions of 3028 horses with upper airway infection
  1. N. Pusterla, DVM1,
  2. F. Bain, DVM2,
  3. K. James, MPH1,
  4. S. Mapes, MS1,
  5. K. Kenelty, MS1,
  6. D. C. Barnett, DVM2,
  7. E. Gaughan, DVM2,
  8. B. Craig, DVM2,
  9. D. E. Chappell, DVM2 and
  10. W. Vaala, DVM2
  1. 1Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA
  2. 2Merck Animal Health, Summit, New Jersey, USA
  1. E-mail for correspondence: npusterla{at}

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Equine herpesvirus-4 (EHV-4) is a double-stranded DNA virus that belongs together with the closely related EHV-1 to the α-herpesvirus group (Slater 2014). EHV-4 is considered one of the leading respiratory viruses associated with upper airway infections. EHV-4 is enzootic in most horse populations and the majority of horses show serological evidence of exposure to this virus (Crabb and others 1995, Van Maanen 2002). Most clinically infected horses are less than three years of age with the majority of affected horses being less than one year of age (Pusterla and others 2011). Following a short incubation period, infected horses develop fever, lethargy, anorexia, mandibular lymphadenopathy and profuse serous nasal discharge that later becomes mucopurulent. A dry cough secondary to rhinotracheitis is occasionally observed, but is not a consistent feature of the disease. A diagnosis of EHV-4 infection is supported by the laboratory detection of EHV-4 by quantitative PCR (qPCR, Pusterla and others 2005). Alternatively, a recent EHV-4 infection can be supported via the serological testing of an acute and convalescent serum sample documenting a significant increase in titres. Contemporary information on the frequency of EHV-4 detection and prevalence factors associated with EHV-4 is sparse (Cardwell and others 2013, Carlson and others 2013, Aharonson-Raz and others 2014, Badenhorst and others 2015). Therefore, the goal of this study was to determine the frequency of EHV-4 shedding and prevalence factors in 3028 horses with acute onset of fever and/or respiratory signs.

Horses with acute onset of fever (T ≥101.5°F) and/or respiratory signs presented to equine primary care providers across the USA were enrolled in this study from September 2012 to May 2016. Nasal secretions were collected using two 6″ rayon-tipped swabs (Puritan Medical Products, Guilford, Maine, USA). Veterinarians were asked to collect nasal secretions according to the following protocol: each …

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