Equine dermatitis outbreak associated with parapoxvirus

Area of Science:

• Veterinary Virology
• Dermatology
• Epidemiology

Background:

• Parapoxviruses (PPV) are known to cause zoonotic skin lesions.
• Equine Parapoxvirus (EqPPV) was previously identified in humans and horses.
• A significant pustulo-vesicular pastern dermatitis outbreak occurred in Finnish horses.

Purpose of the Study:

• Analyze the 2021-2022 EqPPV outbreak in Finland.
• Identify the causative agent and describe clinical signs.
• Investigate risk factors and potential zoonotic transmission.

Main Methods:

• Epidemiological survey of affected and control stables.
• Identification of EqPPV using a novel diagnostic PCR.
• Genome sequencing of the virus from clinical samples.
• Histopathological examination of skin lesions.

Main Results:

• EqPPV was identified as the probable cause of the outbreak.
• Co-infections with pathogenic bacteria were observed.
• A highly sensitive EqPPV-specific PCR was developed.
• Minimal genetic variation was found between historical and recent EqPPV strains.
• Racehorses were identified as the primary risk factor.
• Clinical dermatitis affected about one-third of horses in outbreak stables.
• Human skin lesions were reported, suggesting zoonotic potential.

Conclusions:

• EqPPV is the causative agent of the large-scale Finnish horse dermatitis outbreak.
• The virus exhibits low genetic variability and potential zoonotic transmission.
• Racehorse ownership is a significant risk factor.
• Improved diagnostics and preparedness are needed for future outbreaks.