Tick – Borrelia interactions: burden or benefit?

Abstract

A key factor in the success of parasites is the ability to move between hosts. Some parasites make use of an intermediate arthropod host to move between their primary hosts. Several examples exist where such parasites manipulate their intermediate host to enhance their transmission, but examples for ticks are scarce. In this chapter, we describe how Borrelia burgdorferi sensu lato, the causative agent of Lyme borreliosis, is associated with changes in the behaviour, physiology and survival of Ixodes ticks. Such changes can lead to more effective host finding for the tick and better colonisation of new hosts by Borrelia. We discuss how these changes may lead to an increased transmission (risk) of Borrelia. A next-generation matrix approach is applied to model potential effects of increased tick survival on the basic reproduction number R0 of Borrelia. Using this approach, we show that Borrelia-associated increased survival of ticks can have a profound effect on the circulation of spirochaetes, and hence on Lyme borreliosis risk. Future studies would ideally resolve the mechanisms behind the described changes, and establish experimentally whether Borrelia can enhance its circulation between hosts.