Molecular Detection of Equine Adenovirus 1 in Nasal Swabs from Horses in the Republic of Korea

Equine adenovirus 1 (EAdV-1) can cause upper respiratory disease in horses and has been reported worldwide. In this study, and for the first time in Korea, the prevalence of EAdV-1 in equine nasal swabs was investigated using a PCR to identify potential risk factors and examine the genetic diversity of its DNA sequences by a comparison with foreign strains. Nasal swabs collected from 359 horses reared at Korea Racing Authority facilities were tested using an EAdV-1 hexon-specific PCR and the associations between EAdV-1 infection and sex, age, region, breed, and activity were analyzed. Five samples (1.4%, 5/359) tested positive for EAdV-1; however, no statistically significant differences were observed with respect to any variable. Among the five EAdV-1-positive horses, a co-infection with equine influenza, equine herpesvirus 1 and 4, or Streptococcus equi was not detected; however, clinical respiratory signs were observed in one. Phylogenetic analyses based on partial EAdV-1 hexon gene sequences revealed that the Korean EAdV-1 isolates shared approximately 98.8–100% similarity among each other and with foreign strains. Three Korean isolates shared high similarity with strains from Australia and India and the remaining two isolates were separate in phylogenetic analyses. These findings highlight the molecular prevalence and genetic diversity of EAdV-1 in horses in Korea.