Temporal and spatial dynamics of the internal microbial community of an important disease vector, the blacklegged tick (Ixodes scapularis )
The blacklegged tick (Ixodes scapularis) is an important disease vector in the United States. Although its role as a vector of Borrelia burgdorferi, the agent of Lyme disease, has been known since the late 1970’s, recent discoveries of its transmission of other pathogens suggest that our understanding of the range of pathogens this species can vector and the complexity of its internal microbial community is limited. The goal of this dissertation was to explore the spatial and temporal determinants of the internal microbial community composition of the blacklegged tick. Using molecular pathogen detection techniques and spatial analyses, I have contributed to the growing body of literature that does not support the “dilution effect” for pathogens vectored by this tick. Additionally, using high-throughput DNA sequencing of the 16S rRNA gene, I have provided the first assessment of the internal bacterial community structure across all developmental stages of this tick species. I found Rickettsia to be the relatively abundant bacterial genus across life stages, decreasing as development progressed, with the exception of adult females. Many of the non-Rickettsia bacterial genera found in these samples include species associated with soil, water, and plants, suggesting environmental acquisition while off-host. I explored the influence of tick sex and host bloodmeal source on the tick microbiome and found a decrease in bacterial diversity from field-collected nymphs through feeding, bloodmeal digestion, and molt. This is suggestive of a loss of bacterial operational taxonomic units after the blood meal and throughout digestion. This also suggests that the increase in bacterial diversity that I found previously in adult males is likely maintained through continual exposure to the field environment. Bacterial taxonomic heterogeneity was observed across individual tick samples and a significant relationship was found across three site locations. No clear relationship emerged between the internal bacterial community composition and infection with three important tick-borne pathogens.
Zolnik, Christine Patricia, "Temporal and spatial dynamics of the internal microbial community of an important disease vector, the blacklegged tick (Ixodes scapularis )" (2015). ETD Collection for Fordham University. AAI3727413.