By Erin Frick, Cary Institute of Ecosystem Studies
Warmer months are drawing to a close, but it’s not time to let down our guard against ticks.
Climate change is making many regions around the world warmer and wetter. In the northeastern United States, tick habitat is expanding as temperatures rise. Ticks are moving to new places, and they are bringing new diseases with them. The threat of getting sick from one or multiple tick-borne diseases is increasing as a result.
Richard Ostfeld, a disease ecologist at Cary Institute of Ecosystem Studies in Millbrook, NY, is a leading expert on the ecology of ticks and the diseases they carry. Ostfeld explains, “Our records from 25 years of data from Dutchess County, NY, show that ticks are emerging earlier each year. With autumn temperatures on the rise, the season of high tick risk is expanding on both ends. This means we should be on the lookout for ticks earlier and later in the year.”
Ticks are hardy creatures that can withstand a wide range of temperatures. As long as there is a sufficient degree of moisture in the environment, ticks will persist. “Contrary to popular belief, ticks are not killed off with the first frost,” says Ostfeld. “Even on mild winter days, ticks can emerge from a state of dormancy and seek blood meals.”
One project in Ostfeld’s active research portfolio is a five-year study looking at the effects of climate change on blacklegged ticks—the primary vector for diseases like Lyme disease, anaplasmosis, babesiosis and Powassan virus. The work, funded by the US Department of Defense’s Strategic Environmental Research and Development Program (SERDP), focuses on three field sites located on U.S. military bases: West Point in southern New York, Fort Drum in northern New York and Camp Lejeune in coastal North Carolina. Each base is situated at a different latitude, with distinct climate conditions. Researchers are monitoring tick survival, reproduction and feeding behavior—along with climate data—at each site.
Ticks have three life stages: larva, nymph and adult. Ticks take one blood meal at each life stage. At each field site, researchers annually deploy fed and unfed ticks of each life stage in outdoor “tick containers,” which consist of soil and leaf litter inside a fine-mesh fabric that ticks cannot penetrate.
Ticks representing the different life stages are deployed at a specific time of year, mirroring the timing of when that life stage is most active in nature: nymphs in spring, larvae in late summer and adults in the fall.
For the unfed ticks, researchers are monitoring survival and feeding activity. For the fed ticks, they are also looking at survival and molting success—the ability of larval and nymphal ticks to transition from one life stage to the next—as well as egg-laying success among adult females.
Data on the microclimate of the tick containers, including temperature and humidity, is recorded. By exposing ticks of all life stages to ambient conditions at three distinct latitudes, researchers are gaining insight into the impacts of different climatic conditions on ticks.
Ostfeld concludes, “Data from this project will inform forecasting models to help us predict tick-borne disease emergence within changing climatic conditions. If we can identify where ticks are spreading and what diseases they are carrying, we can fine-tune public messaging and prepare local health officials so that they may better diagnose and treat cases. For now, on the individual level, remaining vigilant against ticks year-round is key to preventing illness.”
For more information, visit caryinstitute.org. █