Equine dermatitis outbreak associated with parapoxvirus

Equine dermatitis outbreak associated with parapoxvirus
J Gen Virol. 2023 Dec;104(12). doi: 10.1099/jgv.0.001940.
Authors
Jenni Virtanen 1 2 , Katja Hautala 1 , Mira Utriainen 2 , Lara Dutra 2 , Katarina Eskola 3 4 , Niina Airas 1 , Ruut Uusitalo 1 2 5 , Ella Ahvenainen 2 , Teemu Smura 2 , Tarja Sironen 1 2 , Olli Vapalahti 1 2 , Ravi Kant 1 2 , Anna-Maija K Virtala 1 , Paula M Kinnunen 1
Affiliations

1 Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland.
2 Department of Virology, Faculty of Medicine, University of Helsinki, Helsinki, Finland.
3 Department of Equine and Small Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland.
4 Animal Health and Welfare Department, Finnish Food Authority, Helsinki, Finland.
5 Department of Geosciences and Geography, Faculty of Science, University of Helsinki, Helsinki, Finland.

PMID: 38117290
DOI: 10.1099/jgv.0.001940

Abstract

Parapoxviruses (PPV) cause skin and mucous membrane lesions in several animal species, and of the five recognized PPVs, at least three are zoonotic. Equine PPV (EqPPV) is the sixth one initially described in humans in the United States and later in a severely sick horse in Finland in 2013-2015. In 2021-2022, a large-scale pustulo-vesicular pastern dermatitis outbreak occurred in horses all over Finland. This study aimed at analysing the outbreak, identifying and describing the causative agent, describing clinical signs, and searching for risk factors. EqPPV was identified as a probable causative agent and co-infections with several potentially pathogenic and zoonotic bacteria were observed. Histopathologically, suppurative and ulcerative dermatitis was diagnosed. Due to the lack of specific tests for this virus, we developed a novel diagnostic EqPPV-PCR with sensitivity of 10 copies/reaction. Based on a large proportion of the genome sequenced directly from clinical samples, very little variation was detected between the sequences of the case from 2013 and the cases from 2021 to 2022. Based on an epidemiological survey, the main risk factor for pastern dermatitis was having racehorses. Approximately one third of the horses at each affected stable got clinical dermatitis, manifesting as severe skin lesions. Skin lesions were also occasionally reported in humans, indicating potential zoonotic transmission. Case stables commonly reported attendance at race events before acquiring the disease. Survey also identified differences in practises between case and control stables. Taken together, these results enable a better preparedness, diagnostics, and guidelines for future outbreaks.

Keywords: One Health; PCR; epidemiology; histopathology; poxvirus; sequencing.