Abstract
BackgroundTicks are regarded as the most relevant vectors of disease-causing pathogens in domestic and wild animals. The cattle tick, Rhipicephalus (Boophilus) microplus, hinders livestock production in tropical and subtropical parts of the world where it is endemic. Tick microbiomes remain largely unexplored. The objective of this study was to explore the R. microplus microbiome by applying the bacterial 16S tag-encoded FLX-titanium amplicon pyrosequencing (bTEFAP) technique to characterize its bacterial diversity. Pyrosequencing was performed on adult males and females, eggs, and gut and ovary tissues from adult females derived from samples of R. microplus collected during outbreaks in southern Texas.ResultsRaw data from bTEFAP were screened and trimmed based upon quality scores and binned into individual sample collections. Bacteria identified to the species level include Staphylococcus aureus, Staphylococcus chromogenes, Streptococcus dysgalactiae, Staphylococcus sciuri, Serratia marcescens, Corynebacterium glutamicum, and Finegoldia magna. One hundred twenty-one bacterial genera were detected in all the life stages and tissues sampled. The total number of genera identified by tick sample comprised: 53 in adult males, 61 in adult females, 11 in gut tissue, 7 in ovarian tissue, and 54 in the eggs. Notable genera detected in the cattle tick include Wolbachia, Coxiella, and Borrelia. The molecular approach applied in this study allowed us to assess the relative abundance of the microbiota associated with R. microplus.ConclusionsThis report represents the first survey of the bacteriome in the cattle tick using non-culture based molecular approaches. Comparisons of our results with previous bacterial surveys provide an indication of geographic variation in the assemblages of bacteria associated with R. microplus. Additional reports on the identification of new bacterial species maintained in nature by R. microplus that may be pathogenic to its vertebrate hosts are expected as our understanding of its microbiota expands. Increased awareness of the role R. microplus can play in the transmission of pathogenic bacteria will enhance our ability to mitigate its economic impact on animal agriculture globally. This recognition should be included as part of analyses to assess the risk for re-invasion of areas like the United States of America where R. microplus was eradicated.
Highlights
Ticks are regarded as the most relevant vectors of disease-causing pathogens in domestic and wild animals
Estimated richness and diversity of bacterial communities The application of bacterial 16S tag-encoded FLX-titanium amplicon pyrosequencing (bTEFAP) reported here enabled us to explore the genome of bacterial symbionts, i.e. the microbiome, living inside and outside the cattle tick R. microplus as a means to initiate the characterization of the microbiota associated with this tick species of economic significance in animal agriculture worldwide
Results are presented at the 1, 3, and 5% dissimilarity levels, attention is focused on Operational Taxonomic Unit (OTU) at 5% dissimilarity since it has been reported that reasonable genus-level richness can be achieved using that degree of discrimination [22]
Summary
Ticks are regarded as the most relevant vectors of disease-causing pathogens in domestic and wild animals. Ticks are considered to be second only to mosquitoes as worldwide vectors of human diseases, but they are regarded as the most relevant vectors of disease-causing pathogens in domestic and wild animals [1]. The vector competency of R. microplus for A. marginale suggests that other microbial associations with this tick host may exist. Seminal studies by Smith and Kilbourne at the end of the 19th century demonstrating that Rhipicephalus annulatus transmitted B. bigemina triggered research on other microorganisms harbored by ticks [3,4]. Our understanding of ticks as vectors of infectious agents has advanced to the point where some tick-borne bacterial diseases are considered an emerging infectious threat globally [5,6]. Species related to pathogenic bacteria were detected and identified in ticks before their effect on human health was fully determined [8]; but our knowledge of bacterial communities in ticks beyond pathogenic species is limited, even though the association between non-pathogenic bacteria and ticks was documented at the beginning of the 20th century [9]
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