Nasal Shedding of Equid Herpesvirus Type 1 and Type 4 in Hospitalized, Febrile Horses

The objective of this study was to determine the prevalence of shedding of equid herpesvirus 1 (EHV-1) or EHV-4 in nasal swab samples from any febrile, hospitalized horses during a 1-year period. It was hypothesized that some fevers in horses are associated with viral replication following recrudescence of latent virus or following a horizontal viral infection prior to or during admission to a referral hospital. During the observational period, nasal swab samples were collected from 64 febrile and 10 nonfebrile hospitalized horses. Routine DNA extraction was performed, and a validated quantitative polymerase chain reaction (qPCR) assay was used to detect and quantify genomic EHV-1 and -4 DNA. Genomic DNA of EHV-4 was detected in the nasal swab specimen of 1 of 64 febrile horses. EHV-1 DNA was not detected in any of the febrile horses. Samples from all nonfebrile horses were negative for both viruses. Considering the known association between fever and shedding of EHV-1 and EHV-4, we anticipated finding a higher percentage of PCR-positive samples from febrile patients. Fevers detected were likely a result of active disease processes for which the horses were hospitalized; concurrent other diseases appeared not to affect viral recrudescence. Further studies are warranted to examine frequency and factors of EHV latency and reactivation.