Similar microbiome compositions of nymphal blacklegged ticks (Ixodes scapularis) infected and uninfected with Borrelia burgdorferi in Delaware

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University of Delaware
Pathogens can be influenced by their host's microbiome, and this can have consequences for pathogen dynamics. Therefore, characterizing the microbiome of hosts, particularly vectors, may help explain pathogen transmission patterns and facilitate the development of novel transmission-blocking approaches. Borrelia burgdorferi is a bacterium that is transmitted by blacklegged ticks (Ixodes scapularis) in the eastern and upper midwestern United States and causes Lyme disease in humans. Borrelia burgdorferi has been hypothesized to be susceptible to exclusion from the midgut of blacklegged ticks by other bacteria, however, blacklegged tick microbiomes have not been characterized across the entire geographical range of the tick. Here we compare the microbiomes of nymphal blacklegged ticks infected and uninfected with B. burgdorferi collected at three sites across Delaware, a highincidence state for Lyme disease. Infected and uninfected ticks did not differ in alpha diversity of their microbiomes and had similar microbiome compositions after removing B. burgdorferi from the analysis. Tick microbiomes varied among sampling locations in terms of both alpha and beta diversity, demonstrating that the tick microbiome can differ over small spatial scales. We also found at least one tick infected with the emerging pathogen B. miyamotoi. We compare our results to the growing literature of blacklegged tick microbiome studies and suggest that there is currently only limited evidence that tick microbiomes consistently influence the probability of ticks being infected with B. burgdorferi in nature.
Lyme disease, Microbial ecology, Tick microbiome, Nymphal blacklegged ticks