Equine herpesvirus type-1(EHV-1) is a complex virus known for inducing various forms of disease in horses. In recent years, the number of cases of neurological disease caused by this virus has increased. While there are a number of possible sources for this recent surge, this project set out to determine if a genotypic shift in the latent population of the virus in favor of the neuropathogenic form of EHV-1 is the basis for the recent increase in frequency of EHV-1 neurologic disease. To ascertain if such a shift has in fact occurred, 450 EHV-1 isolates were obtained from fetal tissues resulting from single, sporadic cases of abortion in Thoroughbred broodmares in central Kentucky. Furthermore, the isolates utilized were from different decades (1951-2006) to determine if the genotypic shift was time-related. The isolates were propagated in cell culture, purified and the viral DNA isolated. Real-time allelic discrimination PCR analysis was performed on the DNA samples to identify the genotype of EHV-1. Statistical analysis of the PCR data indicates that the latent mutant population does appear to be increasing. Therefore, the recent increase in the number of outbreaks of EHV-1 neurological disease will most likely continue unless measures are devised to curtail further spread of the pathogen.