Abstract
BackgroundTicks participate as arthropod vectors in the transmission of pathogenic microorganisms to humans. Several tick-borne infections have reemerged, along with newly described agents of unexplored pathogenicity. In an attempt to expand current information on tick-associated bacteria and protozoans, we performed a cross-sectional screening of ticks, using next-generation sequencing. Ticks seeking hosts and infesting domestic animals were collected in four provinces across the Aegean, Mediterranean and Central Anatolia regions of Turkey and analyzed by commonly used procedures and platforms.ResultsTwo hundred and eighty ticks comprising 10 species were evaluated in 40 pools. Contigs from tick-associated microorganisms were detected in 22 (55%) questing and 4 feeding (10%) tick pools, with multiple microorganisms identified in 12 pools. Rickettsia 16S ribosomal RNA gene, gltA, sca1 and ompA sequences were present in 7 pools (17.5%), comprising feeding Haemaphysalis parva and questing/hunting Rhipicephalus bursa, Rhipicephalus sanguineus (sensu lato) and Hyalomma marginatum specimens. A near-complete genome and conjugative plasmid of a Rickettsia hoogstraalii strain could be characterized in questing Ha. parva. Coxiella-like endosymbionts were identified in pools of questing (12/40) as well as feeding (4/40) ticks of the genera Rhipicephalus, Haemaphysalis and Hyalomma. Francisella-like endosymbionts were also detected in 22.5% (9/40) of the pools that comprise hunting Hyalomma ticks in 8 pools. Coxiella-like and Francisella-like endosymbionts formed phylogenetically distinct clusters associated with their tick hosts. Borrelia turcica was characterized in 5% (2/40) of the pools, comprising hunting Hyalomma aegyptium ticks. Co-infection of Coxiella-like endosymbiont and Babesia was noted in a questing R. sanguineus (s.l.) specimen. Furthermore, protozoan 18S rRNA gene sequences were detected in 4 pools of questing/hunting ticks (10%) and identified as Babesia ovis, Hemolivia mauritanica, Babesia and Theileria spp.ConclusionsOur metagenomic approach enabled identification of diverse pathogenic and non-pathogenic microorganisms in questing and feeding ticks in Anatolia.
Highlights
Ticks participate as arthropod vectors in the transmission of pathogenic microorganisms to humans
Tick-borne infections of humans are of zoonotic origin, with pathogens maintained in natural cycles involving tick vectors and animal hosts [3]
The Francisella-like endosymbionts (FLE) sequences formed phylogenetically distinct clusters associated with their tick hosts, suggesting differential evolutionary patterns in various hosts and ecological niches (Fig. 3)
Summary
Ticks participate as arthropod vectors in the transmission of pathogenic microorganisms to humans. Several tick-borne infections have reemerged, along with newly described agents of unexplored pathogenicity. Ticks (class Arachnida, subclass Acari) are the most significant arthropod vectors, along with mosquitoes, participating in the transmission of pathogens to humans [1]. A diverse group of infectious agents including viruses, bacteria and protozoans can be transmitted by ticks, surpassing most arthropods in terms of vector potential [2]. Tick-borne infections of humans are of zoonotic origin, with pathogens maintained in natural cycles involving tick vectors and animal hosts [3]. The past decades have witnessed the emergence and resurgence of several tick-borne infections with considerable impact on human and animal welfare [1, 5]. A deeper understanding of the epidemiology and potential public health threats of tick-borne infections rely on effective surveillance programmes to identify circulating pathogens in vectors and reliable diagnosis of vertebrate infections
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