Tick-borne pathogens, transmission rates and climate change

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.

Determinants of tick-borne encephalitis in counties of southern Germany, 2001-2008

“…With one exception (spring warming) the results are broadly in line with previous research, highlighting the range of factors influencing TBE transmission dynamics and thus infection potential in humans [33,34,38]. The fact that the factor "year" had to be included in the model constitutes a failure of the model.…”

Geographic Variation in the Relationship between Human Lyme Disease Incidence and Density of Infected Host-Seeking Ixodes scapularis Nymphs in the Eastern United States

“…As for the fragmentation and weather variables, we are unaware of work that has directly tested whether they could impact human contact with vectors or transmission rates, but weather has been hypothesized to impact transmission. 34 Furthermore, the direction of the relationship between fragmentation and DIN compared with fragmentation and human incidence is conflicting, 17 suggesting that fragmentation could act directly on incidence through some unexplained mechanism. Thus, we incorporated weather and fragmentation variables from a hypothesis-generating standpoint.…”

Estimated Incidence of Erythema Migrans in Five Regions of France and Ecological Correlations with Environmental Characteristics

“…Several epidemiological studies conducted in Europe have considered the effect of climate characteristics (such as precipitation, temperature, climate change) on LB risk (EstradaPena et al 2006, Estrada-Pena 2009a, Jaenson et al 2009, Jaenson and Lindgren 2011. But environmental variables have been studied by considering their effects solely on the density of infected ticks and not on the risk of human disease (Estrada-Pena 2009b, Halos et al 2010, Richter and Matuschka 2011.…”