Concordance of bacterial communities of two tick species and blood of their shared rodent host

Abstract

High-throughput sequencing is revealing that most macro-organisms house diverse microbial communities. Of particular interest are disease vectors whose microbiome could potentially affect pathogen transmission and vector competence. We investigated bacterial community composition and diversity of the ticks Dermacentor variabilis (n = 68) and Ixodes scapularis (n = 15) and blood of their shared rodent host, Peromyscus leucopus (n = 45) to quantify bacterial diversity and concordance. The 16S rRNA gene was amplified from genomic DNA from field-collected tick and rodent blood samples, and 454 pyrosequencing was used to elucidate their bacterial communities. After quality control, over 300 000 sequences were obtained and classified into 118 operational taxonomic units (OTUs, clustered at 97% similarity). Analysis of rarefied communities revealed that the most abundant OTUs were tick species-specific endosymbionts, Francisella and Rickettsia, and the commonly flea-associated bacterium Bartonella in rodent blood. An Arsenophonus and additional Francisella endosymbiont were also present in D. variabilis samples. Rickettsia was found in both tick species but not in rodent blood, suggesting that it is not transmitted during feeding. Bartonella was present in larvae and nymphs of both tick species, even those scored as unengorged. Relatively, few OTUs (e.g. Bartonella, Lactobacillus) were found in all sample types. Overall, bacterial communities from each sample type were significantly different and highly structured, independent of their dominant OTUs. Our results point to complex microbial assemblages inhabiting ticks and host blood including infectious agents, tick-specific endosymbionts and environmental bacteria that could potentially affect arthropod-vectored disease dynamics.

Tick microbiome and pathogen acquisition altered by host blood meal

“…This simple life history and feeding strategy provides an ideal system to investigate the natural drivers of microbiome diversity and its effect on pathogen transmission in a disease vector. A previous study did not find a correlation between host blood meal and Ixodes scapularis microbiomes (Rynkiewicz et al, 2015), yet Ixodes pacificus, the focal tick of this study, has a distinct natural history (Lane and Loye, 1989;Eisen et al, 2001). As a generalist, I. pacificus feeds on numerous vertebrate species that may be pathogen reservoirs, but the primary blood meal host for juvenile I. pacificus is the western fence lizard, Sceloporus occidentalis, a Borrelia-refractory host (Lane and Quistad, 1998;Kuo et al, 2000).…”

“…But it remains unclear what factors drive natural variation of the tick microbiome and whether such variation would affect pathogen transmission in the wild and therefore regulate disease risk. Prior field studies have identified microbiome differences by tick species (Hawlena et al, 2013), sex (Williams-Newkirk et al, 2014;Zhang et al, 2014) and region (Carpi et al, 2011;van Treuren et al, 2015) but have not found correlations with host blood or the immediate environment (Hawlena et al, 2013;Rynkiewicz et al, 2015).…”

Effects of temperature on bacterial microbiome composition in Ixodes scapularis ticks

“…In addition, they carry numerous endosymbionts and commensals, which may provide nutrient supplements to the tick and also affect vector competence (reviewed in (Narasimhan & Fikrig, ; Bonnet et al., ; Clay & Fuqua, )). Studies have reported that the tick microbial community is variable depending on several factors such as source of host blood meal (Rynkiewicz, Hemmerich, Rusch, Fuqua, & Clay, ), feeding status (Menchaca et al., ; Swei & Kwan, ; Zhang et al., ), tick species, life stage, gender, and geographical origin (Carpi et al., ; Van Treuren et al., ; Williams‐Newkirk, Rowe, Mixson‐Hayden, & Dasch, ). However, very few studies have focused on the tick microbiome differences based on environmental conditions such as seasons of collection (Lalzar, Harrus, Mumcuoglu, & Gottlieb, ) or the immediate environment (Menchaca et al., ).…”

Molecular detection of Bartonella henselae in 11 Ixodes ricinus ticks extracted from a single cat

“…Here, vertical transmission of Bartonella spp. might be the explanation for presence of bacteria, if those larvae did not have an undetected blood meal [30]. Furthermore, B. henselae was detected in eggs from female ticks which were fed with infected blood but no Bartonella DNA was amplified from the larvae eclosed from those eggs [14].…”