Co-feeding transmission of Heartland virus between the North American tick, <i>Amblyomma americanum</i> (Acari: Ixodidae), and the invasive East Asian tick, <i>Haemaphysalis longicornis</i> (Acari: Ixodidae)

Haemaphysalis longicornis Neumann is an invasive tick species from East Asia with a rapidly expanding geographic range in the United States. In a laboratory setting, H. longicornis has been shown to support transovarial transmission of Heartland virus (HRTV; genus Bandavirus), an emerging tick-borne pathogen responsible for human disease in the southern and midwestern United States. The native Amblyomma americanum (L.) is the primary known vector of HRTV, and field surveillance studies have documented co-feeding of H. longicornis and A. americanum on shared hosts, raising questions about the potential for interspecies viral transmission. To investigate whether H. longicornis can acquire HRTV through co-feeding with infected A. americanum, we used a mouse model in which HRTV-infected A. americanum nymphs were co-fed with uninfected H. longicornis larvae or nymphs and screened recipient ticks using q-RT-PCR. HRTV RNA was detected in H. longicornis collected from multiple mice, demonstrating interspecies co-feeding transmission of HRTV. Mouse blood samples were consistently negative for HRTV RNA, while some skin biopsies from tick feeding sites were positive for the virus, indicating nonviremic co-feeding transmission. These findings provide the first experimental evidence that H. longicornis can acquire HRTV RNA through co-feeding with A. americanum and could contribute to its maintenance in nature, even in the absence of a known vertebrate reservoir host for HRTV.