Vector-borne pathogens are increasingly recognized to interact with the vector’s microbiome, influencing disease transmission dynamics. However, the processes that regulate the formation and development of the microbiome are largely unexplored for most tick species, an important and emerging group of disease vectors. It is not known how much of the tick microbiome is acquired through vertical transmission vs. horizontally from the environment or interactions with bloodmeal sources. Lyme disease, a zoonotic disease, is the most prevalent vector-borne disease in the Northern Hemisphere. Diversity of the vector (tick) microbiome can impact pathogen transmission, yet the biotic and abiotic factors that drive microbiome diversity are largely unresolved, especially under natural, field conditions. We describe the microbiome of Ixodes pacificus ticks, the vector for Lyme disease in the western United States using 16S rRNA amplicon-based next-generation sequencing. We evaluated the microbiome diversity in this tick species across life stages, host blood meal source, and infection status.
Results/Conclusions
We found a decrease in both species richness and evenness as the tick matures from larva to adult. There was a strong impact of host blood meal on tick microbiome species richness and composition. Western fence lizards, a host that is refractory to the Lyme disease pathogen, significantly reduces microbiome diversity in ticks relative to ticks that feed on a mammalian host. Our analysis found that that lower microbiome diversity is positively associated with pathogen transmission in wild-type ticks. Furthermore, laboratory-reared nymph microbiome diversity was found to be compositionally distinct and significantly depauperate relative to field-collected nymphs. These results provide strong evidence that ticks acquire a significant portion of their microbiome through exposure to their environment despite a loss of overall diversity through life stages. Loss of microbial diversity is at least in part due to elimination of microbial diversity with bloodmeal feeding but other factors may also play a role. These results highlight unique patterns in the microbial community of I. pacificus that is distinct from studies conducted in other tick species. Host blood meal-driven reduction of tick microbiome diversity may have lifelong repercussions on I. pacificus vector competency and ultimately disease dynamics.