[Frontiers in Bioscience 14, 2674-2687, January 1, 2009]
Tick-borne pathogens, transmission rates and climate change

Agustin Estrada-Pena

Department of Parasitology, Veterinary Faculty, Miguel Servet 177, 50013-Zaragoza, Spain

TABLE OF CONTENTS

1. Abstract
2. Introduction
3. Climate and climate niche of ticks
3.1. The framework of climate and ticks distribution
3.2. The concept of climate niche
3.3. Tick populations and adaptations to local conditions
3.4.Predictions derived from climate matching models
3.5. Reports about range shift in tick distribution
3.6. Distribution versus abundance: other effects of climate conditions on tick populations
4. The transmission of pathogens: harmonized contacts between hosts and vectors.
4.1. Generalities
4.2. Lyme borreliosis
4.3. Climate and masting: are they markers of Lyme borreliosis rates?
4.4. Tick-borne encephalitis
4.5. Crimean-Congo hemorrhagic fever
4.6. Other tick-borne diseases
5. Summary and Perspective
6. References

1. ABSTRACT

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.