The tick and I: Parasite‐host interactions between ticks and humans

Abstract

Summary Ticks, particularly hard ticks (Ixodidae), which are among the most important vectors of dangerous infectious agents, feed on their hosts for extended periods of time. With this lifestyle, numerous adaptations have evolved in ticks and their hosts, the pharmacological importance of which is increasingly being recognized. Many bioactive substances in tick saliva are being considered as the basis of new drugs. For example, components of tick cement can be developed into tissue adhesives or wound closures. Analgesic and antipruritic salivary components inhibit histamine or bradykinin, while other tick‐derived molecules bind opioid or cannabinoid receptors. Tick saliva inhibits the extrinsic, intrinsic, or common pathway of blood coagulation with implications for the treatment of thromboembolic diseases. It contains vasodilating substances and affects wound healing. The broad spectrum of immunomodulatory and immunosuppressive effects of tick saliva, such as inhibition of chemokines or cellular immune responses, allows development of drugs against inflammation in autoimmune diseases and/or infections. Finally, modern vaccines against ticks can curb the spread of serious infections. The medical importance of the complex tick‐host interactions is increasingly being recognized and translated into first clinical applications. Using selected examples, an overview of the mutual adaptations of ticks and hosts is given here, focusing on their significance to medical advance.

Ulcerating plaque and lymphadenopathy in tularemia

“…Important reservoirs for human infections include various small mammals such as rodents, but also other wild and domestic animals, as well as arthropods such as ticks or horseflies. 2,4,[7][8][9] Cutaneous infection occurs via skin lesions after contact with infected animals or carcasses, 10 but can also occur after arthropod bites. 1,3,[7][8][9] Depending on the husbandry, infection through domestic animals is possible in principle, though it is the exception.…”

“…2,4,[7][8][9] Cutaneous infection occurs via skin lesions after contact with infected animals or carcasses, 10 but can also occur after arthropod bites. 1,3,[7][8][9] Depending on the husbandry, infection through domestic animals is possible in principle, though it is the exception. In the case presented, the lack of contact with wild animals, the localization on the scapula and the recreational history suggest transmission by arthropods.…”

Iripin-1, a new anti-inflammatory tick serpin, inhibits leukocyte recruitment in vivo while altering the levels of chemokines and adhesion molecules

“…Ixodes ricinus (Acari: Ixodidae) is a European tick species that transmits several animal and human pathogens, including tick-borne encephalitis virus and Borrelia burgdorferi sensu lato ( 9 ). It is a highly specialized obligate ectoparasite whose three active developmental stages (larva, nymph, adult female) must blood feed on different hosts in order to molt or lay eggs ( 10 ). The insertion of the tick hypostome and two chelicerae into skin triggers the host’s hemostatic and inflammatory response ( 10 ).…”

“…It is a highly specialized obligate ectoparasite whose three active developmental stages (larva, nymph, adult female) must blood feed on different hosts in order to molt or lay eggs ( 10 ). The insertion of the tick hypostome and two chelicerae into skin triggers the host’s hemostatic and inflammatory response ( 10 ). In reaction to skin integrity disruption and presence of foreign antigens, resident cells in the vicinity of the tick attachment site, such as keratinocytes, fibroblasts, mast cells, macrophages, and dendritic cells, start producing pro-inflammatory cytokines and chemokines ( 11 ).…”

“…Ticks must suppress inflammation accompanied by itch and pain so that they could feed uninterruptedly on a host for several days ( 10 ). For this reason, ticks secrete saliva, containing anti-inflammatory and immunomodulatory molecules, into the wound ( 20 , 21 ).…”