Genome characterization of two bluetongue virus serotype 5 strains isolated from white-tailed deer: first detected cases in Florida after 19 years

Hemorrhagic disease caused by bluetongue virus (BTV) significantly impacts Florida’s deer farming industry each year. In 2022, we investigated mortality events in white-tailed deer on two separate farms. Necropsies were performed on affected animals, and tissues were subjected to RT-qPCR screening and molecular diagnostics, confirming BTV infection. Virus isolation in C6/36 cell culture and whole-genome sequencing identified BTV serotype 5 (BTV-5) infection in both fawns—the first cases reported in Florida since 2003. Our analyses further reveal that key serotype-defining genome segments (2 and 6) remained conserved, while other segments exhibited evidence of reassortment with co-circulating BTV strains in the region. This suggests that BTV-5 may have persisted undetected at low levels, undergoing genetic exchange with co-circulating strains. These findings highlight the need for improved surveillance programs to monitor genetic changes and mitigate impacts on deer and other ruminants in Florida.