Epidemiology and risk factors of equine parvovirus-hepatitis, hepacivirus, Pegivirus caballi, and Pegivirus equi in horses from the Southern United States

Over the past decade, newly identified equine hepatotropic flavi- and parvoviruses, such as equine parvovirus-hepatitis (EqPV-H) and equine hepacivirus (EqHV), have generated considerable scientific and clinical interest. Pegiviruses, including Pegivirus (P.) caballi and P. equi, are also recognized and known to frequently cause persistent infections. However, comprehensive epidemiological data in the United States remain limited. This study analyzed 1195 equine serum samples collected from university-owned horses and diagnostic submissions across Alabama, Georgia, and Texas. Quantitative PCR assays were conducted to detect EqPV-H, EqHV, P. caballi, and P. equi. EqPV-H was the most prevalent virus, detected in 19.3 % (231/1195) of samples, significantly higher than EqHV at 5.6 % (67/1195) and pegiviruses (P. caballi and P. equi combined) at 1.8 % (22/1195). EqPV-H-positive horses also exhibited significantly higher viral loads compared to animals positive for EqHV or pegiviruses. Demographic analysis revealed that EqPV-H-positive horses were significantly older, and male horses had 1.62 times the odds of infection compared to females. Breed-specific associations were also identified: Tennessee Walking Horses had higher odds of EqPV-H positivity (OR = 2.46), while Quarter Horses (OR = 4.16) and Thoroughbreds (OR = 9.64) showed increased odds of testing positive for EqHV. Viral sequences identified in this study were similar to the reported ones in the United States and other regions. This largest molecular survey highlights the widespread distribution of EqPV-H and EqHV in horses in the United States and underscores the importance of continued surveillance, particularly in high-risk breeds and settings. The data provides a foundation for developing preventive strategies and understanding of the epidemiology and potential clinical impact of these important equine viruses.