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 tick vector of Borrelia burgdorferi (Bb) in the
western U.S., feeds on rodents, birds, and lizards. Unlike rodents and
birds which are reservoirs for Bb and infect juvenile ticks, lizards are
refractory to Bb and cannot infect feeding ticks. Additionally, the
lizard bloodmeal contains borreliacidal properties, clearing previously
infected feeding ticks of their Bb infection. Despite I. pacificus
feeding on a range of hosts, it is undetermined how the host identity of
the larval bloodmeal 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 tick 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 vector-borne disease transmission and upends prior notions
about the role of lizards in Lyme disease community ecology.