Lizard feeding enhances Ixodes pacificus vector competency

A vector’s susceptibility and ability to transmit a pathogen— termed vector competency—determines disease outcomes, yet the ecological factors influencing tick vector competency remain largely unknown. Ixodes pacificus , the vector of Borrelia burgdorferi ( Bb ) in the western U.S., feeds on rodents, birds, and lizards. While rodents and birds are reservoirs for Bb and infect juvenile ticks, lizards are Bb- refractory. Despite I. pacificus feeding on a range of hosts, it is undetermined how larval host bloodmeal identity affects future nymphal vector competency. We experimentally evaluate the influence of larval host bloodmeal on Bb acquisition by nymphal I. pacificus . Larval I. pacificus were fed on either lizards or mice and after molting, nymphs were fed on Bb- infected mice. We found that lizard-fed larvae were significantly more likely to become infected with Bb during their next bloodmeal than mouse-fed larvae. We also conducted the first RNA-seq analysis on whole-bodied I. pacificus and found significant upregulation of antioxidants and antimicrobial peptides in the lizard-fed group. Our results indicate that the lizard bloodmeal significantly alters vector competency and gene regulation in ticks, highlighting the importance of host bloodmeal identity in disease transmission and upends prior notions about the role of lizards in Lyme disease transmission. ### Competing Interest Statement The authors have declared no competing interest.