Tick-host-pathogen Interactions

Approximately 10% of the 900 known tick species are of significant veterinary or medical importance. Besides causing direct damage associated with blood feeding and in some cases through the excretion of toxins with their saliva, the main relevance of ticks lies in the wide variety of pathogens that they can transmit, including viruses, bacteria, protozoa and helminths. Most tick-borne pathogens (TBPs) are transmitted with tick saliva, with few notable exceptions such as Hepatozoon canis, where infection occurs through oral ingestion of ticks infected with oocysts. The ability of a tick species to acquire, maintain and transmit a certain pathogen is referred to as vector competence, and this depends on several factors, including tick host preferences, duration of attachment, the pathogen’s ability to cross (epithelial) barriers raised by tick tissues, molecular events at the tick-host, host-pathogen and tick-pathogen interfaces, interactions between pathogens and the tick microbiome and the availability of tick saliva components that facilitate infection of the host. The elucidation of factors resulting in vector competence and tick-host-pathogen interactions broadens our understanding of these complex systems and exposes paradigms for controlling and preventing tick-borne diseases. Although our understanding of tick-host-pathogen interactions remain limited, advances in this field are facilitated by the increasing number of available genomic resources, including metabolomic, transcriptomic and proteomic datasets of various ticks and TBPs, and the recently published genome sequence assembly for Ixodes scapularis, an important vector of Borrelia burgdorferi and Anaplasma phagocytophilum in North America. Together with tools such as tick cell lines and the widespread adaptation of RNA interference (RNAi) to study tick gene function, this has opened possibilities to study pathogen infection and transmission by ticks in greater detail.

This Research Topic provides an overview of known molecular tick-host-pathogen interactions for a number of TBPs and highlights how this knowledge can contribute to novel control and prevention strategies for tick-borne diseases.