First Detection of Bluetongue Virus Type 3 in Poland in 2024-A Case Study in European Bison (Bison bonasus)

Since the emergence of serotype BTV-3, another bluetongue virus, in fall 2023, this variant has been causing great losses in livestock farming in Europe. The virus spreads faster than the epidemic BTV-8, which appeared on the continent nine years earlier. This study describes the first case of BTV-3 in Poland detected in a European bison (Bison bonasus) in Poland's Wolin National Park, approximately 15 km from the German-Polish border. The animal suffered from a severe and fatal hemorrhagic disease. The symptoms included respiratory problems, bloody diarrhea, and rapidly progressive cachexia. In addition to the virus's confirmation as BTV-3 and the presence of the infecting agent in the blood and spleen of the animal, the virus was also detected in one pool of blood-fed Culicoides punctatus caught near the bison enclosure two weeks after the death of the bison. This is the first detection of BTV-3 in C. punctatus, which suggests vector competency for this serotype. Phylogenetic analysis based on segment 2 of the virus revealed the homology of the Polish isolate to the BTV-3 strains circulating in the Netherlands, Germany, and Portugal, and slightly lower similarity to the BTV-3 strains detected in sheep in Sardinia (Italy) in 2018 and in Tunisia in November 2016. A retrospective serosurvey of the exposure to BTV in thirteen other European bison populations distributed over the country indicated that the observed case at the Wolin National Park was the first BTV-3 to be detected in Poland.