Ticks and Host Immunity – New Strategies for Controlling Ticks and Tick-Borne Pathogens

The WHO informs that vector-borne diseases account for more than 17% of all infectious diseases of humans. Similarly, among the 117 diseases of animals listed by the OIE, 20 of them are transmitted by vectors. Ticks are second to mosquitoes as vectors of disease and, with almost 900 species world-wide, they are known to parasitize mammals, birds, reptiles, and amphibians. In many cases, there is a balance between host health and tick parasitism which appears to be due to co-evolution. The appearance of blood-feeding arthropods during evolution, therefore, represents a formidable selective pressure on defensive responses of vertebrate hosts. Furthermore, akin to helminths, ticks spend up to weeks on a single host, a phenomenon that entails dealing with many levels of their host’s immune system. In spite of this fact, hematophagous ectoparasites are not often employed as models to understand immune responses in the skin, their target organ. With the global migration of humans including their livestock and companion animals, incidental tick infestations have spread to susceptible hosts thereby transmitting diseases and causing production losses. The latter is due to an imbalance between the incidental host and the tick resulting from an ineffectual immune response and in some cases, paralysis and respiratory failure. Furthermore, several studies show that wildlife living in degraded habitats present with increased tick loads compared with those that they would present in their intact natural habitats. Stress negatively affects immunity in humans and in animals; thus the consequences of environmental stressors potentially create opportunities for amplifying transmission of tick-borne pathogens.

Building on decades of research on ticks and the more recent applications of novel omics, many researchers have attempted to decipher these tick-host interactions. This interface is characterized by very complex immunological interactions as the ticks require a host blood meal for the perpetuation of their life cycle. These interactions govern tick development and tick-host specificity since the parasite’s evasion mechanisms are complementary to the defense mechanisms mounted by hosts. Tick feeding is known to induce host immune regulatory and effector pathways involving antibodies, complement, antigen-presenting cells, and T lymphocytes. However, the constant conceptual advances in Immunology warrant an equally constant re-evaluation of knowledge about the tick-host interface. The balance between acquired resistance and immune modulation in tick hosts continues to inspire researchers to explore these dynamics to develop effective tick control measures to protect susceptible hosts.

This Research Topic will focus further on the tick-host interface, adaptations to different hosts and how these insights can inform the development of successful vaccines and other sustainable technologies for controlling ticks. It will also identify the gaps in knowledge that need to be addressed in order to better address issues in tick control. We welcome the submission of Original Research articles, Reviews, Methods and Perspectives focusing on the following subtopics:

• Tick immune evasion
• Local and systemic host responses to ticks mechanisms and outcomes of local and systemic responses of hosts to tick bites and saliva
• Genetic factors associated with host immunity
• Factors of host physiology and immunity which impact tick-host specificity
• Immuno-physiology of physical skin characteristics upon responses to ticks including hair follicles, odor, and odorants
• Impact of skin microbiota on immune responses to ticks
• Tick immunity and pathogen transmission
• Host and immune impacts on vectorial competence of ticks
• Immuno-pharmacological aspects of tick saliva
• Host immunity aspects associated with the development of rational vaccines and other sustainable control strategies for ticks and tick-borne pathogens