FREE SHIPPING over $40
OVER 10000 FIVE-STAR REVIEWS
5% OFF ALL SUBSCRIPTIONS
100% HAPPINESS GUARANTEE
Analyze Diet
0
Viruses2026; 18(8); 852; doi: 10.3390/v18080852

Equine Ulcerative Genital Lesions Associated with Parapoxvirus.

Abstract: In 2026, a widespread outbreak of ulcerative dermatitis of unknown aetiology occurred in breeding horses in Ireland. The lesions resembled those associated with equine herpesvirus 3 (EHV3) infection, i.e., papules, vesicles, and ulcers on the penis of stallions and on the vulval and anal areas of mares. This study aimed to identify the probable causative agent. The methods applied included metagenomic sequencing of DNA, phylogenetic analysis, and real-time PCR. Metagenomic analysis directly from a penile sample confirmed the presence of equine parapoxvirus (EqPPV) DNA. Phylogenetic analysis indicated that it clustered closely with EqPPV first identified in Finland in 2013 from a horse with proliferative dermatitis, and associated with outbreaks of pastern dermatitis in trotting racehorses in 2021/2022. Comparison of the amino acid sequences of the DNA polymerase gene showed that the EqPPVs from Finland and Ireland share 99% identity in contrast to 76-80% with other members of the parapoxvirus genus. A specific PCR test for EqPPV, adapted from that developed in Finland, successfully identified viral DNA in samples from 22 of 25 suspect cases that tested negative for EHV3. In conclusion, this study is the first documented outbreak of genital lesions in breeding horses associated with EqPPV.
Get Full Text
Publication Date: 2026-08-04 PubMed ID: 42655670PubMed Central: PMC13517367DOI: 10.3390/v18080852Google Scholar: Lookup
The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
LinkedInCopy
  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Overview

  • Researchers investigated an outbreak of ulcerative genital lesions in breeding horses in Ireland in 2026.
  • The study identified equine parapoxvirus (EqPPV) as the probable causative agent, marking the first documented association of EqPPV with genital lesions in horses.

Background

  • In early 2026, breeding horses in Ireland experienced a widespread outbreak of ulcerative dermatitis affecting genital areas.
  • Lesions presented included papules, vesicles, and ulcers typical of equine herpesvirus 3 (EHV3) infections but tested negative for EHV3, necessitating further investigation.

Study Objective

  • To identify the causative agent responsible for the ulcerative genital lesions observed in horses during the outbreak.

Methods

  • Sample Collection:
    • Penile and other lesion samples were collected from affected horses.
  • Metagenomic Sequencing:
    • Direct DNA sequencing was performed on penile lesion samples to identify viral genetic material without prior knowledge of the pathogen.
  • Phylogenetic Analysis:
    • Genetic sequences obtained were compared to known viruses to determine evolutionary relationships.
  • Real-time PCR:
    • A PCR test specific to equine parapoxvirus (EqPPV), adapted from a Finnish protocol, was used to detect the virus in clinical samples.

Key Findings

  • Detection of EqPPV DNA:
    • Metagenomic sequencing confirmed the presence of equine parapoxvirus DNA in one of the penile lesion samples.
  • Phylogenetic Relationships:
    • The Irish EqPPV strain clustered closely with an EqPPV strain first identified in Finland in 2013.
    • The Finnish strain was previously linked to proliferative dermatitis in a horse and outbreaks of pastern dermatitis in trotting racehorses in 2021 and 2022.
  • Genetic Similarity:
    • Comparison of the DNA polymerase gene showed 99% amino acid sequence identity between the Irish and Finnish EqPPV strains.
    • Other parapoxvirus genus members shared only 76-80% identity with these strains, indicating the Irish and Finnish viruses form a closely related group.
  • Diagnostic PCR Results:
    • The adapted EqPPV-specific PCR detected viral DNA in 22 out of 25 suspect cases which had tested negative for EHV3.

Conclusions and Implications

  • This is the first documented outbreak associating equine genital ulcerative lesions with equine parapoxvirus infection.
  • EqPPV may be an emerging or underrecognized cause of ulcerative genital disease in horses, expanding the understanding of equine parapoxvirus pathogenicity beyond previously reported dermatitis cases.
  • The diagnostic PCR test adapted from the Finnish study provides a useful tool for identifying EqPPV in clinical cases, especially when herpesvirus infections are ruled out.
  • Phylogenetic data suggest that the Irish outbreak virus is closely related to the Finnish strain, indicating possible geographic spread or common origins of the virus in Europe.
  • Veterinarians and researchers should consider EqPPV as a differential diagnosis in cases of genital ulcers in horses and apply appropriate diagnostic testing.

Cite This Article

APA
Cullinane A, Garvey M, Collins D, Lyons R, Nelly M, Grimes A. (2026). Equine Ulcerative Genital Lesions Associated with Parapoxvirus. Viruses, 18(8), 852. https://doi.org/10.3390/v18080852

Publication

Viruses
ISSN: 1999-4915
NlmUniqueID: 101509722
Country: Switzerland
Language: English
Volume: 18
Issue: 8
PII: 852

Researcher Affiliations

Cullinane, Ann
  • Virology Unit, Irish Equine Centre, Johnstown, Naas, County Kildare, W91 RH93, Ireland.
Garvey, Marie
  • Virology Unit, Irish Equine Centre, Johnstown, Naas, County Kildare, W91 RH93, Ireland.
Collins, Donald
  • The Phoenix Equine Ltd., Grey Abbey Road, Kildare Town, County Kildare, R51 YW50, Ireland.
Lyons, Rachel
  • Virology Unit, Irish Equine Centre, Johnstown, Naas, County Kildare, W91 RH93, Ireland.
Nelly, Maura
  • Virology Unit, Irish Equine Centre, Johnstown, Naas, County Kildare, W91 RH93, Ireland.
Grimes, Adam
  • Virology Unit, Irish Equine Centre, Johnstown, Naas, County Kildare, W91 RH93, Ireland.

MeSH Terms

  • Animals
  • Horses
  • Horse Diseases / virology
  • Horse Diseases / epidemiology
  • Horse Diseases / pathology
  • Phylogeny
  • Female
  • Poxviridae Infections / veterinary
  • Poxviridae Infections / virology
  • Poxviridae Infections / epidemiology
  • Poxviridae Infections / pathology
  • Parapoxvirus / genetics
  • Parapoxvirus / classification
  • Parapoxvirus / isolation & purification
  • Disease Outbreaks / veterinary
  • Male
  • DNA, Viral / genetics
  • Ireland / epidemiology
  • Penis / virology
  • Penis / pathology
  • Ulcer / veterinary
  • Ulcer / virology

Conflict of Interest Statement

Dr. Donald Collins is affiliated with The Phoenix Equine Limited, an equine veterinary practice. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

References

This article includes 28 references
  1. McInnes CJ, Damon IK, Smith GL, McFadden G, Isaacs SN, Roper RL, Evans DH, Damaso CR, Carulei O, Wise LM. ICTV Virus Taxonomy Profile: Poxviridae 2023. J. Gen. Virol. 2023;104:001849.
    doi: 10.1099/jgv.0.001849pmc: PMC12447285pubmed: 37195882google scholar: lookup
  2. Brum MC, Anjos BL, Nogueira CE, Amaral LA, Weiblen R, Flores EF. An outbreak of orthopoxvirus-associated disease in horses in southern Brazil. J. Vet. Diagn. Investig. 2010;22:143–147.
    doi: 10.1177/104063871002200132pubmed: 20093706google scholar: lookup
  3. Fenner F, Wittek R, Dumbell K. The Orthopoxviruses. .
  4. Mclntyre R. Virus papular dermatitis of the horse. Am. J. Vet. Res. 1949;10:229–232.
  5. Tulman ER, Delhon G, Afonso CL, Lu Z, Zsak L, Sandybaev NT, Kerembekova UZ, Zaitsev VL, Kutish GF, Rock DL. Genome of Horsepox Virus. J. Virol. 2006;80:9244–9258.
    doi: 10.1128/jvi.00945-06pmc: PMC1563943pubmed: 16940536google scholar: lookup
  6. Airas N, Hautaniemi M, Syrjä P, Knuuttila A, Putkuri N, Coulter L, McInnes CJ, Vapalahti O, Huovilainen A, Kinnunen PM. Infection with Possible Novel Parapoxvirus in Horse, Finland, 2013. Emerg. Infect. Dis. 2016;22:1242–1245.
    doi: 10.3201/eid2207.151636pmc: PMC4918186pubmed: 27315302google scholar: lookup
  7. Osadebe LU, Manthiram K, McCollum AM, Li Y, Emerson GL, Gallardo-Romero NF, Doty JB, Wilkins K, Zhao H, Drew CP. Novel poxvirus infection in 2 patients from the United States. Clin. Infect. Dis. 2015;60:195–202.
    doi: 10.1093/cid/ciu790pmc: PMC5854477pubmed: 25301210google scholar: lookup
  8. Virtanen J, Hautala K, Utriainen M, Dutra L, Eskola K, Airas N, Uusitalo R, Ahvenainen E, Smura T, Sironen T. Equine dermatitis outbreak associated with parapoxvirus. J. Gen. Virol. 2023;104:001940.
    doi: 10.1099/jgv.0.001940pubmed: 38117290google scholar: lookup
  9. Pettersson J, Levanov L, Tervo S, Hautala K, Aaltonen K, Utriainen M, Kareinen L, Gadd T, Sironen T, Vapalahti O. Antibody responses to equine parapoxvirus reveal a re-emerging pattern. BMC Vet. Res. 2026;22:111.
    doi: 10.1186/s12917-026-05314-0pmc: PMC12911042pubmed: 41580677google scholar: lookup
  10. International Collating Centre Equine Disease Surveillance. [(accessed on 12 June 2026)]. Available online: https://equinesurveillance.org/iccview.
  11. Li K, Cappelletti E, Dessaix C, Ciosek J, Robyn E, Johnson L, AbouEl Ela NH, Arias X, Adelson DL, Raudsepp T. Fully Phased Telomere-to-Telomere Assemblies for Thoroughbred Horse and Donkey Haplotypes derived from a Mule Illumi-nate the Peculiar Evolution of Equid Centromeres. bioRxiv 2026.
    doi: 10.64898/2026.02.26.707634pmc: PMC13119311pubmed: 42051287google scholar: lookup
  12. Virtanen J, Hautaniemi M, Dutra L, Plyusnin I, Hautala K, Smura T, Vapalahti O, Sironen T, Kant R, Kinnunen PM. Partial Genome Characterization of Novel Parapoxvirus in Horse, Finland. Emerg. Infect. Dis. 2023;29:1941–1944.
    doi: 10.3201/eid2909.230049pmc: PMC10461679pubmed: 37610155google scholar: lookup
  13. Kumar S, Stecher G, Tamura K. MEGA7: Molecular Evolutionary Genetics Analysis Version 7.0 for Bigger Datasets. Mol. Biol. Evol. 2016;33:1870–1874.
    doi: 10.1093/molbev/msw054pmc: PMC8210823pubmed: 27004904google scholar: lookup
  14. Li Y, Meyer H, Zhao H, Damon IK. GC content-based pan-pox universal PCR assays for poxvirus detection. J. Clin. Microbiol. 2010;48:268–276.
    doi: 10.1128/jcm.01697-09pmc: PMC2812294pubmed: 19906902google scholar: lookup
  15. National Center for Biotechnology Information (NCBI) Nucleotide BLAST. [(accessed on 5 June 2026)]; Available online: https://blast.ncbi.nlm.nih.gov/Blast.cgi.
  16. Le S.Q., Gascuel O.. An Improved General Amino Acid Replacement Matrix. Mol. Biol. Evol. 2008;25:1307–1320.
    doi: 10.1093/molbev/msn067pubmed: 18367465google scholar: lookup
  17. Uprety T., Sreenivasan C.C., Hause B.M., Li G., Odemuyiwa S.O., Locke S., Morgan J., Zeng L., Gilsenan W.F., Slovis N.. Identification of a Ruminant Origin Group B Rotavirus Associated with Diarrhea Outbreaks in Foals. Viruses 2021;13:1330.
    doi: 10.3390/v13071330pmc: PMC8310321pubmed: 34372536google scholar: lookup
  18. Jones S.E.. Papillomaviruses in equids: A decade of discovery and more to come?. Equine Vet. Educ. 2022;34:236–240.
    doi: 10.1111/eve.13506google scholar: lookup
  19. Sypsa V., Mameletzis I., Tsiodras S.. Transmission potential of human monkeypox in mass gatherings. Open Forum Infect Dis. 2022;9:11.
    doi: 10.1093/ofid/ofac501pmc: PMC9620358pubmed: 36340738google scholar: lookup
  20. Moeller R.B., Jr., Crossley B., Adaska J.M., Hsia G., Kahn R., Blanchard P.C.. Parapoxviral vulvovaginitis in Holstein cows. J. Vet. Diagn. Investig. 2018;30:464–467.
    doi: 10.1177/1040638718758829pmc: PMC6505816pubmed: 29429402google scholar: lookup
  21. Vissani M.A., Damiani A.M., Barrandeguy M.E.. Equine Coital Exanthema: New Insights on the Knowledge and Leading Perspectives for Treatment and Prevention. Pathogens 2021;10:1055.
    doi: 10.3390/pathogens10081055pmc: PMC8398825pubmed: 34451519google scholar: lookup
  22. Vissani M.A., Perglione C.O., Zabal O., Alvarez G., Thiry E., Barrandeguy M., Parreño V.. Topical Ganciclovir Reduces Viral Excretion in Mares with Equine Coital Exanthema. J. Equine Vet. Sci. 2020;94:103199.
    doi: 10.1016/j.jevs.2020.103199pubmed: 33077066google scholar: lookup
  23. Lunn D.P., Burgess B.A., Dorman D.C., Goehring L.S., Gross P., Osterrieder K., Pusterla N., Soboll Hussey G.. Updated ACVIM consensus statement on equine herpesvirus-1. J. Vet. Intern. Med. 2024;38:1290–1299.
    doi: 10.1111/jvim.17047pmc: PMC11099706pubmed: 38497217google scholar: lookup
  24. Spyrou V., Valiakos G.. Orf virus infection in sheep or goats. Vet. Microbiol. 2015;181:178–182.
    doi: 10.1016/j.vetmic.2015.08.010pubmed: 26315771google scholar: lookup
  25. Schmidt F.I., Bleck C.K.E., Mercer J.. Poxvirus host cell entry. Curr. Opin. Virol. 2012;2:20–27.
    doi: 10.1016/j.coviro.2011.11.007pubmed: 22440962google scholar: lookup
  26. Gallina L., Scagliarini A.. Virucidal efficacy of common disinfectants against orf virus. Vet. Rec. 2010;166:725–726.
    doi: 10.1136/vr.c3001pubmed: 20525950google scholar: lookup
  27. Eggers M., Eickmann M., Zorn J.. Rapid and Effective Virucidal Activity of Povidone-Iodine Products Against Middle East Respiratory Syndrome Coronavirus (MERS-CoV) and Modified Vaccinia Virus Ankara (MVA). Infect. Dis. Ther. 2015;4:491–501.
    doi: 10.1007/s40121-015-0091-9pmc: PMC4675768pubmed: 26416214google scholar: lookup
  28. Tervo S., Aaltonen K., Hautala K., Utriainen M., Pennström L., Sironen T., Kinnunen P.M., Pettersson J.. Detection of equine parapoxvirus in the stable environment during pastern dermatitis outbreak in Finland. Acta Vet. Scand. 2026.
    doi: 10.1186/s13028-026-00870-9pubmed: 42380996google scholar: lookup

Citations

This article has been cited 0 times.
Subscribe to our newsletter
Join 106,643 horse owners like you who receive our email updates on horse health and nutrition.