First detection of a cervidpoxvirus in Europe-disease occurrence in semi-domesticated Eurasian tundra reindeer (Rangifer tarandus tarandus) in Norway and Sweden.

UNLABELLED: Globally, there are six millions of Rangifer spp., including both wild and semi-domesticated populations. Reindeer herding with Eurasian tundra reindeer (Rangifer tarandus tarandus) is central to the Fennoscandian Sámi people. Commencing in 2018, a novel disease presenting with periorbital lesions was reported in reindeer in multiple locations in Norway and Sweden, as individual cases and outbreaks. Lesions were also seen on the genitals, nostrils, and ears of affected reindeer, in combination with lethargy. Necropsy findings included lesions with crusts on the eyelids, vulva, and anus, along with moderately swollen lymph nodes, liver, and spleen. Histological examination of the eyelid lesions showed a disrupted epidermis with necrotic squamous epithelium and inflammation. Shotgun sequencing of samples from outbreaks yielded a partial draft genome of a virus related to Deerpox virus W-848-83 (currently known as Cervidpoxvirus muledeerpox) in genus Cervidpoxvirus. Cervidpoxviruses have previously only been detected in Capreolinae in North America. An in-house qPCR targeting the cervidpoxvirus virion core protein gene was designed and showed the presence of viral-specific DNA in multiple organs, with the highest load in skin lesions. RNAscope in situ hybridization detected viral transcripts in the epithelium of the eye lesions. Transmission electron microscopy analysis revealed the presence of intracytoplasmic poxvirus-like particles with characteristic morphology within the lesions. In vitro infection in Madin-Darby bovine kidney epithelial cells demonstrated cytopathic effect. It is unknown whether the emergence of this disease in semi-domesticated reindeer in Norway and Sweden is due to ecosystem changes facilitating altered disease dynamics, or if the virus has been recently introduced.

IMPORTANCE: This study documents the first detection of a Cervidpoxvirus in Europe, causing disease in semi-domesticated reindeer in Norway and Sweden. It identifies the causative agent and describes the disease characteristics of this previously unknown condition in reindeer, advancing our understanding of how this virus impacts reindeer health and welfare. Given the cultural and ecological importance of reindeer herding in Fennoscandia, understanding this disease is crucial for safeguarding the livelihoods of Sámi communities. Additionally, the study raises important questions about the role of ecosystem changes, climate-driven insect dynamics, and potential reservoir hosts in facilitating disease outbreaks. These findings underscore the broader implications of environmental change on animal health and highlight the need for continued research to mitigate risks posed by emerging infectious diseases (EIDs).