The number of equine herpesvirus type-1 (EHV-1) infections caused by the neuropathogenic form of the virus has been steadily increasing over the past 51 years, report researchers from the University of Kentucky.

Clinical observations suggest that neuropathogenic strains of EHV-1 (i.e., strains of EHV-1 with a single mutation in the gene that encodes the enzyme called DNA polymerase) have become more prevalent. These infections result in significant economic losses for equine industries worldwide.

To see if there was any truth to this apparent trend, Udeni B. R. Balasuriya, BVSc, MS, PhD, an associate professor of virology at the Gluck Equine Research Center in Lexington, Ky., and colleagues analyzed 426 archived isolates of EHV-1 collected from aborted equine fetuses between 1951 and 2006.

They found that not only is the neuropathogenic strain of the virus becoming increasingly common, but that it really isn’t all that new. Even some of the EHV-1 isolates collected from fetuses aborted in the 1950s were the neuropathogenic strain