Tick-borne pathogens, transmission rates and climate change.

Ticks are parasites that expend most of their life cycles off the host. Most important parts of the tick life cycle are directly dependent upon climate. There exist some concerns about the effects of the forecasted climate change on the geographical distribution of ticks. As tick life cycle dynamics would also be affected, the transmission of tick-borne pathogens could also be transformed by climate trends. Tick cycles are the result of complex interactions between climate, hosts populations, landscape characteristics, and the fine modulation of the populations of every partner involved, and not a simple, straightforward correlation between abundance and climate. The understanding of the climate niche used by different tick species may help in the search of clues towards a clarification of the expected effects of climate changes on the reported tick range shift. Populations of ticks occupying different portions of a wide geographical range may use different "portions" of the climate envelope, therefore resulting in misinterpretations from modeling results. Some advances can be foreseen in the complex task of modeling tick-host-pathogen interactions.