new information on a potentially zoonotic equine dermatitis outbreak and a novel parapoxvirus
10 january 2024
a research team in university of helsinki, finland, has studied the nature and risk factors of an infectious pastern dermatitis outbreak among racehorses in finland and identified the likely cause. the research, published in journal of general virology, hopes to enable better preparedness, diagnostics and guidelines for future outbreaks.
during the outbreak, which occurred in the winter of 2021-2022, hundreds of racehorses all over finland were suffering from pustulo-vesicular pastern dermatitis, which later presented with serous or purulent excretion. the infection was painful, and some horses became lame even when in walk.
most of the skin samples taken from sick horses were positive for a novel equine parapoxvirus by pcr-test. in addition, several species of animal and human pathogenic bacteria were identified. the lack of equine parapoxvirus findings in healthy control horses together with clinical signs and pathological findings in the affected horses indicate, for the first time, that equine parapoxvirus was the cause of this large epidemic. due to this, a diagnostic pcr-test was set up to prepare for future epidemics.
based on an epidemiological survey, the most significant risk factor was having racehorses. around 60% of the respondents from infected stables estimated that the disease came from a racecourse. a farrier’s visit, the introduction of a new horse and visiting another stable or a clinic were also suspected sources of transmission. around one third of the horses in infected stables became sick and the incubation time was estimated to be three days. clinical signs typically lasted for 2-3 weeks, and the most common treatments were resin, honey, and/or antibiotic ointments. most (73%) reported that local treatment sufficed, but horses were also treated with systemic antibiotics in one third of the stables. only one in ten stables treated horses with pain medication.
a few cases of skin lesions were also reported in humans that were in contact with infected horses, but as no samples were acquired, we were unable to verify the cause of the lesions. as at least three out of five previously known parapoxviruses are known to infect humans and a very similar virus has previously been found in humans in united states, it is important to recognize that this disease is potentially zoonotic. hence, protective measures should be used when treating infected horses. further studies are important to estimate the potential occupational health hazard.
the university of helsinki will continue to study transmission routes, verify zoonotic potential of the disease, and develop diagnostics in collaboration with finnish food authority and hus diagnostic center.
notes for editors
the full paper 'equine dermatitis outbreak associated with parapoxvirus' by virtanen j, hautala k, utriainen m, dutra l, eskola k, airas n, uusitalo r, ahvenainen e, smura t, sironen t, vapalahti o, kant r, virtala amk, kinnunen pm is published in journal of general virology at the following:
doi: doi.org/10.1099/jgv.0.001940
url: https://www.microbiologyresearch.org/content/journal/jgv/10.1099/jgv.0.001940
we warmly thank the horse and stable owners, veterinarians and other survey respondents for taking part in the study. we also thank the funders: niemi foundation, finnish foundation of veterinary research, the erkki rajakoski fund of hippos finland, the finnish veterinary foundation, sakari alhopuro foundation, and orion research foundation.
further information:
veterinarian, veterinary specialist in infectious diseases, katja hautala, [email protected]
postdoctoral researcher, jenni virtanen, [email protected]
associate professor in emerging infectious diseases, tarja sironen, [email protected]
scientific papers based on the research:
virtanen j, hautala k, utriainen m, dutra l, eskola k, airas n, uusitalo r, ahvenainen e, smura t, sironen t, vapalahti o, kant r, virtala amk, kinnunen pm. equine dermatitis outbreak associated with parapoxvirus. journal of general virology. 2023. 10.1099/jgv.0.001940. (in press)
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. emerging infectious diseases. 2023;29(9):1941-1944. 10.3201/eid2909.230049.
earlier studies on the topic:
1st finding of equine parapoxvirus in a horse
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. emerging infectious diseases. 2016. jul;22(7):1242-5. 10.3201/eid2207.151636.
finding of a similar virus in humans:
osadebe lu, manthiram k, mccollum am, li y, emerson gl, gallardo-romero nf, et al. novel poxvirus infection in 2 patients from the united states. clinical infectious diseases. 2015;60(2):195-202.
image: istock/evrymmnt.
