Antibody responses to equine parapoxvirus reveal a re-emerging pattern.
Abstract: Parapoxviruses (PPV) cause skin and mucous membrane signs to several animal species and humans worldwide. Equine parapoxvirus (EqPPV) was first detected in a sick horse in Finland in 2013. It is potentially zoonotic, and a similar virus has been detected in humans in the USA. In winter 2021–2022, EqPPV caused a large-scale pastern dermatitis epidemic in racehorses all over Finland. Field reports suggest that similar epidemics of unverified cause have also occurred in 2015 and 2019. The aim of this study was to develop a serological test and study the immune response, seroprevalence, and history of the virus utilizing serum samples from clinical cases and archived horse samples (2012–2022). A recombinant protein-based immunofluorescent assay was established using envelope proteins B2L and F1L. EqPPV induced a fast immune response within a few days from the onset of the clinical signs. Two horses that were additionally tested a year after the disease still had similar IgG titers as a year prior. Seroprevalence peaks coincided with reported outbreaks in 2015 and 2022 (yearly variation: 1.8–14.6% [B2L] and 3.6–16.7% [F1L]). The results suggest that EqPPV is a re-emerging pathogen that has a potential to cause large epidemics, bringing a need for more studies and preparedness. The online version contains supplementary material available at 10.1186/s12917-026-05314-0.
Publication Date: 2026-01-24 PubMed ID: 41580677PubMed Central: PMC12911042DOI: 10.1186/s12917-026-05314-0Google Scholar: Lookup
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- Journal Article
Summary
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Overview
- This study focuses on the equine parapoxvirus (EqPPV), a virus affecting horses and potentially transmissible to humans.
- Researchers developed a test to detect antibodies against EqPPV and examined how common the virus is and how horses’ immune systems respond to it over time.
Background on Equine Parapoxvirus (EqPPV)
- Parapoxviruses (PPV) are a group of viruses causing skin and mucous membrane infections in various animals and humans worldwide.
- EqPPV was first identified in a sick horse in Finland in 2013.
- This virus is potentially zoonotic, meaning it can spread from horses to humans; a related virus has been found in humans in the USA.
- In the winter of 2021–2022, EqPPV led to a widespread outbreak of pastern dermatitis (a skin condition affecting the lower legs) in racehorses across Finland.
- Similar but unconfirmed outbreaks were reported in Finland in 2015 and 2019.
Objectives of the Study
- To develop a serological test (a blood test) for detecting antibodies against EqPPV, indicating past or present infection.
- To study the immune response of horses to EqPPV by measuring antibodies.
- To determine the seroprevalence (how widespread the infection is within horse populations) and track the history of the virus using archived serum samples collected from 2012 to 2022.
Methods
- The researchers created an immunofluorescent assay, a laboratory test that uses fluorescent markers to detect antibodies specific to EqPPV envelope proteins, B2L and F1L.
- Serum samples came from both recent clinical cases and archived samples from horses dating back to 2012.
Key Findings
- EqPPV triggers a rapid immune response, with antibody levels rising within a few days of the start of clinical signs.
- In two horses tested one year after recovering from the disease, antibody levels (IgG titers) remained similar to the levels measured during the initial infection, suggesting a long-lasting immune response.
- Peaks in EqPPV antibody prevalence in horse populations matched known outbreak years, specifically 2015 and 2022.
- Yearly seroprevalence estimates varied between:
- 1.8% to 14.6% when using the B2L protein for detection.
- 3.6% to 16.7% when using the F1L protein for detection.
- These findings support the idea that EqPPV is a re-emerging virus capable of causing significant outbreaks among horses.
Implications
- EqPPV should be considered an important pathogen with potential to cause widespread disease in horses, impacting animal health and potentially human health due to zoonotic risk.
- There is a need for ongoing surveillance and preparedness to manage future outbreaks of EqPPV.
- Further research is necessary to better understand the virus, its transmission, and long-term immunity in horses.
Additional Information
- Supplementary material related to the study is available online at the provided journal link (doi:10.1186/s12917-026-05314-0).
Cite This Article
APA
Pettersson J, Levanov L, Tervo S, Hautala K, Aaltonen K, Utriainen M, Kareinen L, Gadd T, Sironen T, Vapalahti O, Kinnunen PM.
(2026).
Antibody responses to equine parapoxvirus reveal a re-emerging pattern.
BMC Vet Res, 22(1), 111.
https://doi.org/10.1186/s12917-026-05314-0 Publication
Researcher Affiliations
- Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, Agnes Sjöbergin Katu 2, 00790, Helsinki, Finland. jenni.pettersson@helsinki.fi.
- Department of Virology, Faculty of Medicine, University of Helsinki, Haartmaninkatu 3, 00290, Helsinki, Finland. jenni.pettersson@helsinki.fi.
- Department of Virology, Faculty of Medicine, University of Helsinki, Haartmaninkatu 3, 00290, Helsinki, Finland.
- Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, Agnes Sjöbergin Katu 2, 00790, Helsinki, Finland.
- Department of Virology, Faculty of Medicine, University of Helsinki, Haartmaninkatu 3, 00290, Helsinki, Finland.
- Institute of Biomedicine, Faculty of Medicine, University of Turku and University Hospital of Turku, Kiinamyllynkatu 10, 20520, Turku, Finland.
- Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, Agnes Sjöbergin Katu 2, 00790, Helsinki, Finland.
- Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, Agnes Sjöbergin Katu 2, 00790, Helsinki, Finland.
- Department of Virology, Faculty of Medicine, University of Helsinki, Haartmaninkatu 3, 00290, Helsinki, Finland.
- Department of Virology, Faculty of Medicine, University of Helsinki, Haartmaninkatu 3, 00290, Helsinki, Finland.
- Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, Agnes Sjöbergin Katu 2, 00790, Helsinki, Finland.
- Finnish Food Authority, Mustialankatu 3, 00790, Helsinki, Finland.
- Finnish Food Authority, Mustialankatu 3, 00790, Helsinki, Finland.
- Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, Agnes Sjöbergin Katu 2, 00790, Helsinki, Finland.
- Department of Virology, Faculty of Medicine, University of Helsinki, Haartmaninkatu 3, 00290, Helsinki, Finland.
- Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, Agnes Sjöbergin Katu 2, 00790, Helsinki, Finland.
- Department of Virology, Faculty of Medicine, University of Helsinki, Haartmaninkatu 3, 00290, Helsinki, Finland.
- Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, Agnes Sjöbergin Katu 2, 00790, Helsinki, Finland.
Conflict of Interest Statement
Declarations. Ethics approval and consent to participate: This study relied on samples collected during routine diagnostics within a non-experimental clinical veterinary setting. Hence, no ethical approval was required (European Union directive 2010/63/EU and the national act 497/2013). Samples from horses suffering from pastern dermatitis were originally taken by veterinarians for diagnostic purposes. Archived samples are routinely taken and stored by Finnish Food Authority and were not collected for the purpose of this study. Consent for publication: Not applicable. Competing interests: Besides holding the title of Associate Professor (Docent) of University of Helsinki, PMK is an employee of MSD Animal Health. The EqPPV studies were initiated before her joining the company. Other authors have nothing to declare.
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