• Open Access

Absence of Equid Herpesvirus-1 Reactivation and Viremia in Hospitalized Critically Ill Horses


  • This work was performed at the William R. Pritchard Veterinary Teaching Hospital at the University of California, Davis and the Veterinary Teaching Hospital at Michigan State University in East Lansing, MI. The abstract was presented at the 2008 ACVIM Forum in San Antonio, TX.

Corresponding author: E. A. Carr, Department of Large Animal Clinical Sciences, D202 Veterinary Medical Center, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48823; e-mail: carreliz@cvm.msu.edu.


Background: Equid herpesvirus-1 (EHV-1) reactivation and shedding can occur in latently infected, asymptomatic animals. Risk factors for reactivation include stress and illness. The risk of asymptomatic shedding in hospitalized, critically ill horses with acute abdominal disease is unknown. This information is important to assess the need for additional biosecurity protocols to prevent spread of EHV-1 in hospitalized critically ill horses with acute abdominal disorders.

Objectives: To determine the frequency of reactivation and nasal shedding of EHV-1 in hospitalized critically ill horses.

Animals: One hundred twenty-four client-owned horses admitted to the Veterinary Teaching Hospital with acute abdominal disorders were included in the study.

Methods: Cross-sectional study examining the risk of reactivation of EHV-1 in horses admitted with acute, severe, gastrointestinal disease. Whole blood and nasal secretions were collected throughout hospitalization. In addition, mandibular lymph nodes were collected from 9 study horses and 26 other Michigan horses. All samples were tested for the presence of EHV-1 nucleic acid by real-time PCR assays targeting the glycoprotein B gene and the polymerase (ORF 30) gene.

Results: One hundred and twenty-four horses met the inclusion criteria. None of the samples were positive for EHV-1 DNA.

Conclusion and Clinical Importance: These results suggest that nasal shedding and viremia of EHV-1 in hospitalized critically ill horses with acute abdominal disorder is extremely rare. Implementation of additional biosecurity protocols to limit aerosol spread of EHV-1 among horses with acute abdominal disease and other hospitalized horses is not necessary.