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

Overview

• This study investigated the prevalence and risk factors of several equine viruses, specifically equine parvovirus-hepatitis (EqPV-H), equine hepacivirus (EqHV), and pegiviruses (Pegivirus caballi and Pegivirus equi), in horses from the Southern United States.
• The researchers conducted a large molecular survey to understand how widespread these viruses are and identify demographic and breed-related risk factors for infection.

Background and Purpose

• In the past decade, newly identified equine viruses such as EqPV-H (a parvovirus) and EqHV (a hepacivirus) have become a focus due to their impact on horse liver health (hepatotropic viruses).
• Pegiviruses, including P. caballi and P. equi, are known to cause persistent infections in horses, but detailed epidemiological data in the United States has been limited.
• The study aimed to fill this gap by assessing the prevalence of these viruses and analyzing risk factors related to infection in a large sample of horses from Alabama, Georgia, and Texas.

Methods

• A total of 1,195 equine serum samples were collected from university-owned horses and diagnostic submissions spanning three states in the Southern U.S.
• Quantitative PCR (qPCR) assays were used to detect and quantify viral genetic material from EqPV-H, EqHV, P. caballi, and P. equi in the serum samples.
• Demographic data (age, sex, breed) were analyzed to identify associations with viral infections.

Key Findings: Prevalence of Viruses

• EqPV-H was the most prevalent virus detected, appearing in 19.3% of samples (231 out of 1,195), indicating widespread presence in the horse population.
• EqHV was detected in 5.6% (67/1,195) of samples, significantly lower than EqPV-H.
• Combined prevalence of pegiviruses (P. caballi and P. equi) was 1.8% (22/1,195), the lowest among the viruses studied.
• EqPV-H-positive horses showed significantly higher viral loads compared to horses positive for EqHV or pegiviruses, suggesting more active or robust infection.

Risk Factors and Demographic Associations

• Age: Horses positive for EqPV-H tended to be significantly older, indicating a possible cumulative risk or increased susceptibility with age.
• Sex: Male horses had a 1.62-fold higher chance (odds ratio) of being infected with EqPV-H compared to females, suggesting sex-dependent factors in susceptibility.
• Breed:
  • Tennessee Walking Horses had increased odds (OR = 2.46) of EqPV-H infection.
  • Quarter Horses (OR = 4.16) and Thoroughbreds (OR = 9.64) showed significantly higher odds of EqHV infection.

Genetic and Molecular Insights

• Sequencing of viral genomes showed high similarity to previously reported strains in the U.S. and other global regions, indicating stable and widespread viral lineages.
• This genetic data supports the reliability of the qPCR detection and points to established viral circulation rather than novel emerging variants.

Implications and Conclusions

• This is the largest molecular survey to date assessing EqPV-H, EqHV, and pegiviruses in horses from the Southern United States.
• The study highlights the widespread distribution of EqPV-H and EqHV, especially in certain breeds and older male horses, indicating the importance of targeted monitoring.
• Findings underscore the need for continued surveillance and epidemiological tracking to develop effective prevention and control measures.
• The research provides foundational data that can aid veterinarians and researchers in understanding how these viruses might impact equine health and inform vaccine or management strategies.