Ixodes scapularismicrobiome correlates with life stage, not the presence of human pathogens, in ticks submitted for diagnostic testing

Abstract

Ticks are globally distributed arthropods and a public health concern due to the many human pathogens they carry and transmit, including the causative agent of Lyme disease, Borrelia burgdorferi. As tick species’ ranges increase, so do the number of reported tick related illnesses. The microbiome is a critical part of understanding arthropod biology, and the microbiome of pathogen vectors may provide critical insight into disease transmission and management. Yet we lack a comprehensive understanding of the microbiome of wild ticks, including what effect the presence of multiple tick-borne pathogens (TBPs) has on the microbiome. In this study we chose samples based on life stage (adult or nymph) and which TBPs were present. We used DNA from previously extracted Ixodes scapularis ticks that tested positive for zero, one, two or three common TBPs (B. burgdorferi, B. miyamotoi, Anaplasma phagocytophilum, Babesia microti). We produced 16S rRNA amplicon data for the whole tick microbiome and compared samples across TBPs status, single vs multiple coinfections, and life stages. Focusing on samples with a single TBP, we found no significant differences in microbiome diversity in ticks that were infected with B. burgdorferi and ticks with no TBPs. When comparing multiple TBPs, we found no significant difference in both alpha and beta diversity between ticks with a single TBP and ticks with multiple TBPs. Removal of TBPs from the microbiome did not alter alpha or beta diversity results. Life stage significantly correlated to variation in beta diversity and nymphs had higher alpha diversity than adult ticks. Rickettsia, a common tick endosymbiont, was the most abundant genus. This study confirms that the wild tick microbiome is highly influenced by life stage and much less by the presence of human pathogenic bacteria.

The bacterial biome of ticks and their wildlife hosts at the urban–wildland interface

“…In comparison, tick samples showed a less diverse bacterial composition. This is likely to be due to the dominance of endosymbiont bacteria in the tick microbiome, which has been demonstrated in previous studies of the same tick species as identified in the present study [17, 18], and in tick species globally [66, 67]. The overall lack of similarity in bacterial communities between sample types observed in the present work has been reported in previous studies on small mammals and their vectors (ticks and fleas), indicating the complexity of microbial assemblages inhabiting these biological niches [65, 68, 69].…”

Ecological and evolutionary perspectives on tick-borne pathogen co-infections

“…B. burgdorferi , B. miyamotoi , A. phagocytophilum and B. microti ) was compared with that of uninfected ticks. In the study by Gil et al. (2020) no significant differences were found in the alpha- and beta-diversity indices of the tick microbiome under single or co-infections with any of the pathogens tested ( Gil et al., 2020 ).…”

“…The nature of the relationship between pathogen co-infection and vector microbiome composition remains unclear. The association between microbiome composition and co-infections in ticks submitted for diagnostic testing was recently assessed ( Gil et al., 2020 ). The microbiome of whole I. scapularis nymphs and adults that tested positive for one, two or three tick-borne pathogens (i.e.…”

Exploring the Individual Bacterial Microbiota of Questing Ixodes ricinus Nymphs

“…Out of these, 60,149 reads were assigned to ticks or eukaryotic organisms and were further discarded. As nymphal ticks are low biomass arthropods [ 75 , 76 ], the number of generated reads may be low on average, and variations in the read numbers can thus exist among samples. Moreover, such low biomass samples can be critically impacted by contamination originating from the various kits used to produce amplicons [ 77 ].…”