Climate change has driven significant northward expansion of Ixodes ricinus (the sheep tick, which transmits Lyme disease and tick-borne encephalitis) and Dermacentor reticulatus (the marsh tick) across Europe and North America. Regions such as Scandinavia, Canada, and northern Russia are experiencing unprecedented tick population growth, and tick-borne disease incidence is rising correspondingly. The expansion of the tick into previously cold regions creates new human-parasite relationships in countries with literary traditions that had not previously had to accommodate the tick's intimate menace.

The expanding tick has become, in the early twenty-first century, a figure for the biological consequences of climate change in the same way that the expanding mosquito has. Scandinavian, Canadian, and northern European writers have begun to incorporate the tick and tick-borne disease into their work as markers of a changing environmental reality. The intimate horror of the tick — which buries its head in human skin and must be carefully extracted while still alive — gives it a particularly strong literary charge as a figure for the parasite's claim on the human body, and its spreading range makes it an increasingly global literary subject.