Speaker
Description
Heartland virus (HRTV) is an emerging tick-borne bunyavirus associated with severe febrile illness that has caused >60 cases across the southeastern and midwestern US since its discovery in 2009. Little is known about the transmission ecology and phylodynamics of HRTV and only 13 unique complete HRTV genomes exist in the literature (3 of which were generated by our group). Since our group first detected and isolated HRTV from Amblyomma americanum in 2019 at two sites (5 km apart) in central Georgia, we have conducted continuous longitudinal sampling. Pooled samples of ticks from the field were crushed, RNA was extracted, HRTV qRT-PCR was performed and positive pools underwent multiplex amplicon sequencing using a newly-developed assay. A total of 30,300 lone star ticks were collected and tested from 2018-2023. In total, nine pools of ticks tested positive for HRTV (2019: 3 pools, 2021: 1 pool, 2022: 2 pools, 2023: 3 pools) across the three sites including the two sites in central GA and a new site in western GA. We generated 9 complete HRTV genome sequences, which were more closely related to each other than others in the literature; they shared 88.4-100% nucleotide identity across the three genome segments. The sequence from western GA in 2023 (~160 km away from the central GA sites) was the most distantly related. In the sequences from the central sites (8), the L and S segments assort differently with genomes from site 1 in 2019 clustering with genomes from site 2 in varying years across segments. This is the first comparison of HRTV genetic diversity over time and space, and our initial findings suggest 1) a stable focus of HRTV in central GA with evidence circulation across the state and 2) potential reassortment or mixing of viruses through hosts/vectors between the central sites across time.
