New tools, new tick-borne diseases?

Exploring the bacteriome in anthropophilic ticks: To investigate the vectors for diagnosis

OBJECTIVE

The aim of this study was to characterize the bacterial microbiome of hard ticks with affinity to bite humans in La Rioja (North of Spain).

METHODS

A total of 88 adult ticks (22 Rhipicephalus sanguineus sensu lato, 27 Haemaphysalis punctata, 30 Dermacentor marginatus and 9 Ixodes ricinus) and 120 I. ricinus nymphs (CRETAV collection, La Rioja, Spain), representing the main anthropophilic species in our environment, were subjected to a metagenomic analysis of the V3-V4 region of the 16S rRNA gene using an Illumina MiSeq platform. Data obtained with Greengenes database were refined with BLAST. Four groups of samples were defined, according to the four tick species.

RESULTS

Proteobacteria was the predominant phylum observed in all groups. Gammaproteobacteria was the most abundant class, followed by Alphaproteobacteria for R. sanguineus, H. punctata and D. marginatus but the relative abundance of reads for these classes was reversed for I. ricinus. This tick species showed more than 46% reads corresponding to 'not assigned' OTUs (Greengenes), and >97% of them corresponded to 'Candidatus Midichloriaceae' using BLAST. Within Rickettsiales, 'Candidatus Midichloria', Rickettsia, Ehrlichia, 'Candidatus Neoehrlichia' and Wolbachia were detected. I. ricinus was the most alpha-diverse species. Regarding beta-diversity, I. ricinus and H. punctata samples grouped according to their tick species but microbial communities of some R. sanguineus and D. marginatus specimens clustered together.

CONCLUSIONS

The metagenomics approach seems useful to discover the spectrum of tick-related bacteria. More studies are needed to identify and differentiate bacterial species, and to improve the knowledge of tick-borne diseases in Spain.

Neglected aspects of tick-borne rickettsioses

Rickettsioses are among the oldest known infectious diseases. In spite of this, and of the extensive research carried out, many aspects of the biology and epidemiology of tick-borne rickettsiae are far from being completely understood. Their association with arthropod vectors, the importance of vertebrates as reservoirs, the rarity of clinical signs in animals, or the interactions of pathogenic species with rickettsial endosymbionts and with the host intracellular environment, are only some examples. Moreover, new rickettsiae are continuously being discovered. In this review, we focus on the ‘neglected’ aspects of tick-borne rickettsioses and on the gaps in knowledge, which could help to explain why these infections are still emerging and re-emerging threats worldwide.

The Challenges and Advances in Diagnosis of Vector-Borne Diseases: Where Do We Stand?

Vector-borne diseases (VBD) are of major importance to human and animal health. In recent years, VBD have been emerging or re-emerging in many geographical areas, alarming new disease threats and economic losses. The precise diagnosis of many of these diseases still remains a major challenge because of the lack of comprehensive data available on accurate and reliable diagnostic methods. Here, we conducted a systematic and in-depth review of the former, current, and upcoming techniques employed for the diagnosis of VBD.