UCSF

Ticks are increasingly important vectors of human and agricultural diseases. While many studies have focused on tick-borne bacteria, far less is known about tick-associated viruses and their roles in public health or tick physiology. To address this, I investigated patterns of bacterial and viral communities across two field populations of western black-legged ticks (Ixodes pacificus). In addition to commonly found tick-associated microbes, I discovered 11 novel RNA viruses from Rhabdoviridae, Chuviridae, Picornaviridae, Phenuiviridae, Reoviridae, Solemovidiae, Narnaviridae and 2 highly divergent RNA viruses lacking sequence similarity to any known viral families. I also unexpectedly identified numerous virus-like transcripts that are likely encoded by tick genomic DNA, and which are distinct from known endogenous viral element-mediated immunity pathways in invertebrates. Together, my work reveals that I. pacificus ticks carry a greater diversity of viruses than previously appreciated, in some cases resulting in evolutionarily acquired virus-like transcripts. These findings highlight how pervasive and intimate tick–virus interactions are, with major implications for both the fundamental biology and vectorial capacity of I. pacificus ticks.