Detection of equine parapoxvirus in the stable environment during pastern dermatitis outbreak in Finland.

Overview

• This study investigated the presence and spread of equine parapoxvirus (EqPPV) in stable environments during outbreaks of pastern dermatitis in horses in Finland.
• Research identified environmental contamination by the virus and suggested multiple indirect transmission routes, highlighting the need for improved hygiene and surveillance to prevent recurring outbreaks.

Background and Context

• Equine parapoxvirus (EqPPV) was first detected in Finland in 2013 and has since been linked to recurring outbreaks of pastern dermatitis, an inflammatory skin disease affecting horses, particularly on their lower limbs (pastern area).
• These outbreaks occur every few years, causing clinical disease in potentially hundreds of horses and posing a suspected zoonotic risk (potential transmission from horses to humans).
• Understanding how the virus persists and spreads in the stable environment is crucial for developing targeted control measures and guidelines for stable staff and veterinarians.

Objectives of the Study

• To assess whether EqPPV DNA could be detected in the stable environment during and after outbreaks.
• To explore the possible transmission dynamics of EqPPV, including indirect routes through contaminated surfaces or materials.
• To provide data that could inform preventative practices and outbreak management in equine facilities.

Methods

• Following a significant EqPPV outbreak in winter 2021-2022 affecting hundreds of horses, PCR testing was routinely performed on suspected cases from April 2022 to May 2025.
• Samples were collected from 25 trotting horses in 20 different stables during this period.
• Environmental sampling involved 161 specimens taken from six stables with active cases (case stables) and two stables without recent outbreaks (control stables).
• Samples included:
  • Grooming tools
  • Stall infrastructure (e.g., walls, feeding troughs)
  • Bedding material
  • Items handled by humans (e.g., equipment, clothing)
  • Hands of stable personnel

Key Findings

• From April 2022 to January 2025, no EqPPV cases were detected, but a new outbreak began early in 2025.
• Between February and May 2025, 80% (8 out of 10) of Finnish trotting stables submitting diagnostic samples tested positive for EqPPV DNA.
• Environmental contamination was widespread in affected stables:
  • EqPPV DNA was detected on grooming equipment, in stall environments, bedding, human-handled materials, and on personnel’s hands.
  • 83.3% (5 of 6) of case stables had environmental samples positive for EqPPV DNA.
  • 17.4% (24 of 138) of all environmental samples collected tested positive.
• Control stables did not show such widespread environmental contamination, suggesting environmental presence strongly correlates with outbreaks.

Implications and Conclusions

• The widespread detection of EqPPV DNA in both horses and their environment during outbreaks suggests multiple indirect transmission routes beyond direct horse-to-horse contact.
• The presence of viral DNA on shared equipment and human hands underscores the role humans and fomites may play in spreading the virus within stables.
• These findings explain how EqPPV outbreaks can recur and persist within equine populations over years.
• Ongoing surveillance and early hygiene interventions (e.g., cleaning shared equipment, handwashing protocols for stable staff) are critical to preventing and minimizing future outbreaks.
• The study provides strong evidence for stable managers and veterinarians to implement strict biosecurity practices to reduce EqPPV transmission risks.