In a new paper published in April in the journal of Ecology and Evolution, Gilbert, Aungier, and Tomkins write about how ticks from cooler climates tend to venture into new territory when it is cool while ticks from warmer climates go questing when the temperature is higher. What this means for a world with a changing climate is that many tick populations could become more active around a month earlier than usual.
This adaptation essentially extends the tick season and increasies our risk of exposure to Lyme disease and other tick borne infections. In Europe it is the Ixodes ricinus tick which primarily spreads Lyme disease, by transmitting Borrelia burgdorferi sensu lato. Ixodes ricinus was the focus of this latest research where Gilbert and colleagues looked at the questing behaviour of ticks, i.e. their attempts to find a new host.
Hungry Tick Seeks Host for Cool Time and Blood Meal
The scientists collected I. ricinus ticks from northeast Scotland, North Wales, South England, and central France, covering a range of different latitudes and climates. They then carefully controlled the temperature in which the ticks lived in the laboratory, increasing the temperature by 1 degree Celsius per day from 6 degrees to 15 degrees. Five times a day during the increase in temperature they monitored the number of ticks questing to find a new host.
From theese measurements the researchers estimated the likelihood of ticks seeking out a new host in the new conditions that would arise with future climate change. Ticks from a cooler climate did indeed quest more at lower temperatures than ticks from warmer regions and this association was significant. Because the ticks were able to adapt to the temperature changes in the laboratory the researchers projected that as the global temperature rises this may allow ticks to begin questing a month earlier than is typical, extending Lyme disease season.
When is Tick Season?
Although this research only looked at a single tick species, Ixodes ricinus, it may be presumed that Ixodes scapularis, the main vector for Lyme disease in North America, would display similar adaptive behaviours. As such, instead of April to October being the usual tick season, and June seeing 80% of Lyme disease cases, it may be that more people get Lyme disease earlier in the year after being bitten as early as March. So, perhaps as the temperature rises it’s wise to start using that tick repellent a little earlier and checking for ticks all year round.
Gilbert L, Aungier J, Tomkins JL. Climate of origin affects tick (Ixodes ricinus) host-seeking behavior in response to temperature: implications for resilience to climate change? Ecol Evol. 2014 Apr;4(7):1186-98. doi: 10.1002/ece3.1014. Epub 2014 Mar 10.