The skin as interface in the transmission of arthropod-borne pathogens

Animal skin separates the inner world of the body from the largely hostile outside world and is actively involved in the defence against microbes. However, the skin is no perfect defence barrier and many microorganisms have managed to live on or within the skin as harmless passengers or as disease-causing pathogens. Microbes have evolved numerous strategies that allow them to gain access to the layers underneath the epidermis where they either multiply within the dermis or move to distant destinations within the body for replication. A number of viruses, bacteria and parasites use arthropod vectors, like ticks or mosquitoes, to deliver them into the dermis while taking their blood meal. Within the dermis, successful pathogens subvert the function of a variety of skin resident cells or cells of the innate immune system that rush to the site of infection. In this review several interactions with cells of the skin by medically relevant vector-borne pathogens are discussed to highlight the different ways in which these pathogens have come to survive within the skin and to usurp the defence mechanisms of the host for their own ends.