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

Authors: CASEY, TYLER - University Of Delaware; SHIFFLETT, SCARLETT - University Of Delaware; KENNEDY, ASHLEY - State Of Delaware Division Of Fish & Wildlife; Maestas, Lauren; ELLIS, VICENZO - University Of Delaware

Submitted to: Journal of Vector Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2023
Publication Date: 1/30/2024
Citation: Casey, T., Shifflett, S.A., Kennedy, A., Maestas, L.P., Ellis, V.A. 2024. Similar microbiome compositions of nymphal black-legged ticks (Ixodes scapularis) infected and uninfected with Borrelia burgdorferi in Delaware. Parasitology Research. https://doi.org/10.1016/j.ttbdis.2023.102139.
DOI: https://doi.org/10.1016/j.ttbdis.2023.102139

Interpretive Summary: Pathogens can be influenced by their host’s internal fauna, and this can have consequences for pathogen dynamics. Therefore, characterizing the microbiome or internal fauna of hosts, and particularly pathogen transmitting organisms, may help explain pathogen transmission patterns and facilitate the development of novel transmission-blocking approaches. Borrelia burgdorferi is a bacterium that is transmitted by black-legged ticks (Ixodes scapularis) in the northeastern and upper midwestern United States and causes Lyme disease in humans. B. burgdorferi has been hypothesized to be susceptible to exclusion from the gut of black-legged ticks by other bacteria, however, black-legged tick microbiomes have not been characterized across the entire geographical range of the tick. Here we compare the microbiomes of nymphal black-legged ticks infected and uninfected with B. burgdorferi at three sites across Delaware, a high-incidence state for Lyme disease. Infected and uninfected ticks did not differ in 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 diversity and change in diversity between infected and uninfected ticks, demonstrating that the tick microbiome can differ over very small spatial scales. We also found at least one tick infected with the emerging pathogen B. miyamotoi, adding Delaware to the geographic distribution of that pathogen. We compare our results to the growing literature of black-legged tick microbiome studies and suggest that there is currently only limited evidence that tick microbiomes influence the probability of ticks being infected with B. burgdorferi in nature.

Technical Abstract: Pathogens can be influenced by their host’s microbiome, and this can have consequences for pathogen dynamics. Therefore, characterizing the microbiome of hosts, and 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 black-legged ticks (Ixodes scapularis) in the northeastern and upper midwestern United States and causes Lyme disease in humans. B. burgdorferi has been hypothesized to be susceptible to exclusion from the midgut of black-legged ticks by other bacteria, however, black-legged tick microbiomes have not been characterized across the entire geographical range of the tick. Here we compare the microbiomes of nymphal black-legged ticks infected and uninfected with B. burgdorferi at three sites across Delaware, a high-incidence 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 very small spatial scales. We also found at least one tick infected with the emerging pathogen B. miyamotoi, adding Delaware to the geographic distribution of that pathogen. We compare our results to the growing literature of black-legged tick microbiome studies and suggest that there is currently only limited evidence that tick microbiomes influence the probability of ticks being infected with B. burgdorferi in nature.